Extreme Traction-Control Test

Extreme Traction Control Test

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To complement the autocross, we also conducted an extreme traction-control test that examined how well the trucks could recover from a loss of grip. We placed the trucks’ right and left wheels on different surfaces with different amounts of friction — dry asphalt and wet basalt tile on a steep, 20 percent grade — to create a “split-mu” condition. Wet basalt has a coefficient of friction similar to a snow-covered road. This caused the trucks to slip to one side because the tires couldn’t gain traction equally. We parked each truck on the asphalt and basalt and attempted to drive off in two-wheel drive with traction control enabled.

Traction control cuts engine power when it senses wheel slip, allowing the slipping wheel or wheels to slow enough for the rubber to once again grip the driving surface. It may also use the truck’s antilock braking system to brake the wheel that’s spinning, allowing the wheel on the other side to grip. Because most full-size pickups are rear-wheel drive but have the bulk of their weight positioned in the front half of the vehicle, they can lose traction more easily than other vehicles, particularly in icy conditions.

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The Ford F-150 and Toyota Tundra performed best. They were the only trucks to make it off the slippery surface without having to stop and engage four-wheel drive. The F-150’s traction was superior to the Tundra’s. While the F-150’s wheels did slip, the truck was able to cut throttle smoothly and apply selective braking until grip was restored and it was able to climb the basalt. The Tundra cut throttle too, but very aggressively. It took pushing the accelerator all the way to the floor to keep throttle up while the Tundra slowly crawled off the pad. Both the Tundra and F-150 had rear limited-slip differentials. They were also the heaviest trucks we tested, which likely helped.

The Chevrolet Silverado and GMC Sierra both had locking mechanical rear differentials that engaged automatically when wheel slip hit a certain rpm. While both pickups performed excellently in the autocross, they were challenged by the wet surface and fishtailed backward as power was applied. We had to put both trucks into 4-High to get off the basalt.

The Dodge Ram 1500 also required the use of 4-High to escape the split-mu surface, but like the F-150 and Tundra it has a rear limited-slip differential. To us, this was proof that extra weight and, particularly, excellent anti-slip logic can make a big difference getting a truck out of slick conditions.


The Nissan Titan was the most challenged by this test. When its electronic-locking rear differential wasn’t engaged (which only happens in four-wheel drive) the rear diff operated as an open differential, meaning there was no way to shift power or lock up the slipping wheel. The engine quickly hit close to the redline as the Titan slipped backward and struggled to figure out a way off the hill before we cut power and engaged four-wheel drive to escape.

Another traction-control test we conducted involved driving the trucks straight up a wet jenite surface without stopping. Wet jenite has a coefficient of friction similar to an icy road. Almost all the trucks were able to make it up the jenite as long as forward momentum was maintained at 10 mph or more. Again, the Nissan Titan was the most challenged by this test; it required backing off the jenite and using 4-High.

Next: Squat Test

Comments

This test was ridiculous.... The titan had a locking rear differential which would have walked the test with ease compare to the others. Who would drive in the snow and ice without 4 wheel drive?

Completely illogical results.

Your traction test was joke. I sell Sierras and I've seen this same test done with the same trucks, except the Chevy, and the Siearra with the Eaton locing diff put them all to shame. The Ford (2008 ), Dodge, Tundra(2007) and Titan were used. The trick was to drive up a ramp that one side was rollers like whats used for unloading and the other side dry. Not one of these trucks except the GMC could get up this even in 4wd! I also dont understand how the GMC and Chevy return such different numbers when there the same truck.

@Jacel: Thanks for your feedback. As we said in the video, all the trucks could make it up the hill in 4WD. We also talked about the e-locker on the Titan, which is only usable in 4WD. The point of this test was to find out which truck had the best traction control in 2WD. As we say, this was an extreme test.

@Chris: This test (with this particular result) took place at GM's Proving Grounds. There were GM staff on hand that watched. When GM repeated the same test with the same exact trucks we used after the Shootout, they saw the same results.

I Found this article to be interesting and well conducted however I have to take exception on this particular test. It's commonly acknowledged that a mechanical locker is the most sure way to clear this type of obstacle, simulated or on a back-wood trail. I have witnessed tests of this type and observed very different results on roller wheel incline tests, twist ditch test, as well a on sand and mud. Here is a link to a video that compares trucks with open differential that cannot climb a roller hill at all(due to a lack of traction control) and a truck with a mechanical locker(the same G80 locker used in the Silverado and Sierra in your test): http://www.youtube.com/watch?v=q-rQTHMVAuw
At first glance your test results mystified me until i watched the article's supplemental video again and noticed the G80 locker in the GM trucks is indeed working, however the wheel with traction is also spinning. It's apparent that the drivers of these trucks are not using the locker correctly. As illustrated in your test, conventional brake activated traction control requires a lead foot to spin the wheel with traction. Lockers however do not require this, and with a powerful motor and the traction of only one rear tire, a truck can simply burnout in place, instead of going up the hill. An off-roader can attest that this scenario requires gradual use of the throttle as to not break traction. Another aspect to consider, although unrelated to the simulation at hand, is that brake activated traction control can produce brake fade with prolonged use which can be very undesirable once you've gotten to the top of a slippery hill and need to descend back down.

Bingo!

I've had Ford, Dodge, and GM trucks. I'd take the mechanical locker any day. The GM vehicles failed because the driver still thought he was at Milan. These types of obstacles are about traction management, not going fast. Limit the throttle so you don't slip the high-mu wheel and the truck will climb right up the hill. Take a look at the G80 youtube videos or try it yourself. This will be especially true in this high-torque vehicle configuration. When you have a lot of power you had better know how to management.

Ford, Dodge, Toyota do well because they "idiot" proof the vehicle and drastically retard the throttle when you experience wheel slip. That works great until you pull out on to a slippery road and need to accelerate only to sit there with a retarded throttle watching that snow plow fill up your rear view mirror.

Send your drivers to training and then try it again.

@Yankee: Thanks for the feedback. I'll respond that the split-mu starts were not full throttle and certainly not a drag start. Enough accelerator was applied to stop the trucks from slipping backward against gravity and additional throttle was applied to start climbing up the hill. The GM trucks slipped. The Ford and Toyota didn't. You'll have to take my word that GM repeated the same test with the same results.

Mike,

With all due respect you don't seem to understand traction management yourself based on the arguement you're trying to make. If the wheel is spinning as your video clearly shows it is not being driven properly. The driver needed to reduce the throttle until the wheel slip stopped and then use light throttle. Once you spin a tire on any vehicle the coefficient of friction drops rapidly just like a drag car that breaks loose at the green.

What you're really testing here is if the vehicles traction systems can bias enough torque to the single high-mu wheel to drive the vehicle up the grade. What you're asking us to believe is that the only vehicle that can fully lock and bias 100% of the torque couldn't make it up and that's absurd when the brake based systems that bias 50-60% could. I'm guessing the GM folks present weren't anymore familiar with this than your staff since I doubt they expected they would need to trian your drivers. Bottom line, if you drive properly and manage the throttle the mechanical locker and electronic locker will win every time over a brake based system.

I also agree with the comment on the Nissan. Who among us with 4x4 would not turn it on and activate the locker under these conditions. You talk repeatedly about making the test real world, but missed that mark by a long shot.

Out of curiosity what type of formal evaluation driving training does your test crew have for on and off-road evaluation?


@Yankee: I've written about the G80 since 2002: http://www.pickuptrucks.com/html/stories/eaton/page1.html.

You're probably aware that if you want the G80 to engage, there's got to be ~100 rpm difference between the wheels. Throttle is necessary to hit that threshold. Which way are you suggesting I should have driven the truck up the hill? Little throttle and too much slip or adding enough accelerator to get the G80 to engage?

With all due respect, your statement that this is a driver training issue strikes me as arrogant - especially from a customer perspective. How many GM truck buyers are taken to a split-mu pad and given formal training before they drive their pickup home?

I've been to two racing schools and an off-road school with Land Rover. The rest of my experience is almost 14 years participating in various ride and drives and using my own vehicles.

Mike,

It takes very little throttle to generate a 100 RPM delta. Have you ever tried it by hand on the G80 displays at a GM dealer? As a drag racer when you spin a wheel coming off the line and torque to the right do you stay on throttle? NO! You get off the gas until you hook back up and then accelerate again. No where in this video do you back off the throttle to allow the tire to regain traction. In fact as the video cuts out you can see the vehicle start to move up the hills.

You still don't address why a vehicle that biases 100% of the
torque doesn't make it up a split-mu grade that a system with only a partial bias does. Please explain that.

@Yankee: I can't explain it except to say, again, that GM engineers took the trucks from us after the test, repeated it and had the same results. I assume they "know how to drive" the truck. You can believe me or not.

@Yankee: I'll post another piece of video this morning of the Sierra in this test.

Stupid test. Doesnt prove a thing. Go drive a Titan. I bet you buy one, if you do.

are the GM fanbois mad? face it guys, the others have stepped up their game, and, in an unbiased test, the results are only surprising to you. the roller test that you keep referrencing is clearly a GM backed test, hardly independent. also, if you actually watch it, you will notice that the trucks in the roller test do not have traction control on. this is obvious because the wheels, even with a limited slip, are alowed to just spin at free will. and, that test doesn't even use the newest model pickups(you know the ones that have been changed/upgraded, like in this test).
and, this isn't meant to be a realistic test, its meant to be a measure of traction and the traction control system. these tests are performed for people who are interested in knowing which truck is the best, which one they should get. when you have the fanboi goggles on, ofcourse the tests aren't performed to your liking.

fact is, this is an independent test at GMs proving grounds.

BTW, the G80 "locker" is a joke, and is always one of the first drivetrain pieces replaced by anyone looking to do some off-roading. give me the more predictable limited slip or selectable locker instead of this 'on when it feels like it' "locker".

This test is kind of pointless since not every truck is using the exact same tire. You're testing the tires traction, not just the truck.

We have a blacktop driveway at work, with a big incline. My 2007 Silverado with the locking rear always has issues pulling out. Tons of tire spin, fishtailing, rear end hop while turning onto the main road.

But at least both rear tires turn. A friend has a 2007 Titan, and we got it stuck in a small ditch. Only one rear tire turned, we had to pull it out with my truck. For fun, I backed into the same ditch, both tires pulled me out without a problem.

Ry_Trapp0 ,

You're correct that any of us that do any significant off-roading replace the G80. Is there an OEM locker out that that we don't?

The Detroit Locker is generally regarded as king of the off-road hill and it's made by the same company that makes the G80, recognition that you want a different set-up for a daily driver vs off-road.

Do you really think that Ford/Toyota's BTC is better? You're kidding yourself if you do. Have you ever seen how useless BTC becomes once the rotors are wet or have a stone stuck in them?

Bottom line is still that a vehicle that transfers 100% of the engine torque to the high-grip wheel (aka Titan or GM) will perform better than a BTC at 50% of the torque if driven properly with a realistic test.

This test really isn't for real world conditions. If you have a truck that is in deep mud, sand, or snow and is about to get stuck the last thing you want is for the engine to reduce power and start braking some of the wheels. You want as many tires spinning as possible to keep you moving foward and to clean your tires so they can continue to gain traction. Take each of these trucks through a mud pit or 2 feet of snow. The trucks with the lockers will make it out, the others won't.

Real world testing this is not. The Titan, especially the PRO-4X tested, has 4 wheel ABLS (Active Brake Limited Slip) that works quite well. Problem is, it's not very effective at WOT because the engine will easily overpower the brakes in that case. Driven properly, any and all these trucks should have climbed that hill in 2WD. Also, the Titans locker not only has to be used in 4WD, it must be in 4LO to engage.

During this test, it appears to me that the F-150 slid sideways off the white part of the hill (the white portion) and only then did it gain traction. Did you notice this, Mike?

I, for one, am glad to see the test -- regardless of the results. I appreciate the video! I really do believe that if you're in the market for new truck, to drive them all. People who sit at their computers and nit-pick the results probably have too much time on their hands. I don't necessarily agree with the winner, but appreciate the results nonetheless. You might notice that another popular truck magazine did a joint-review with these guys and came out with nearly the same results (with the F-150 on top). I would never own a Ford, but it's interesting nonetheless.

I would just like to know why any would life of the throttle of a vehicle that is clearly making forward progress, especially if you know you're gonna get stuck. I too noticed that the F-150 slide sideways and gained traction as did the Tundra and so did the Silverado and Sierra. The only difference is that the DRIVER let of the throttle instead of the computer. Once the computer senses slippage it reduceds throttle and then adds if back as traction is gained. Your driver didn't do this. What throttle was used? Part throttle, half throttle, WOT, braked throttle? Does look like the same was used on all trucks.

I would also like to know which truck was tested first. It looks like the right side of the test site was dry for the F-150, and then wet on the Silverado which would prove to be more challenging for any unweighted pickup. You can clearly see the Sierra lock its diff. and start to move up the hill then the driver stops, is this the same result the GM had? You also state that "we had to cut power...switch to four high" to make it up the hill. This is demostrated by the video of the Ram and the Titan. What's the deal with Sierra that starts at the bottom of the ramp, goes all the way, and never stops? If you watch closely you can see the G80 lock as soon as it "sees that 100 rpm" difference.

This test was a very interesting test to see regardless of my opinion of truck. I am a supporter of the toyota BUT i do think the GM trucks G80 locker was used improperly, too much throttle given. Also the driver did stop the GM vehicle when it got traction. The ford did slide off the slick surface and then gained traction but i still think it did just as good as the toyota considering both got off in 2WD. I do think that if done properly most of the trucks could make it up the hill in 2WD except the Titan. I thought the Titan had a limited slip differential but this tests proves it doesn't. I agree with not using the locker because that would require engaging 4Low. Also for all you people not getting why they did 2WD, they did it to see if the truck COULD make it up in 2WD, in real world if you did NOT have 4WD then your stuck with 2WD and its nice to see which trucks can make it up with only 2WD and which NEED 4WD, however the GM trucks should have made it up in 2WD.

As someone has already mentioned the biggest flaw in this test as well as on any other off road truck tests IMO is tires. Tires make ALL the difference. It's not really important which particular tire is used but that the SAME tire is used on all trucks. My Tundra came with the factory BFG Rugged Trails and these tires were very poor performers off road and not great on road either, when I changed over to Bridgestone Revos it was like a different truck, I could now drive in in 2WD in conditions and terrain that required 4WD with the BFG Rugged Trails. I can't see how you could conduct an accurate traction or off road test when right off the bat certain vehicles would have an advantage if they may be using a particular tire that has inherently better traction than other tires used.

the chevy and the gmc are also pushing the big powerful 6.2liter engine unlike he ford with a puny 5.4 liter

What a bunch of sour grapes! "Oh, it's the driver." "Oh, it's the tires." "Oh, it's the test." Hogwash! Your favorite truck has a limited slip that doesn't limit slip, or in GM's case, a so called locker that doesn't lock. This was the most revealing test of all of them, because it showed the traction aids everyone is paying for are nearly useless, and flawed. The test is simple and elagant. The differential just has to prove it can transfer torque to the wheel with the highest coefficient of friction, and none of them did. It was mainly the traction control system, a cheap bandaid no less, that saved the day. If you don't mind creeping ahead at a crawl, and you don't get the brakes wet or overheated, it's bettern than nothing. What I got out of this test, is get a true manual locker if you want dependable traction. That must be why they are becoming available on more and more trucks as options.

Thank you for doing this test. It was a real eye opener, and a great learning tool. I hope to see it again in all future tests.

What a bunch of sour grapes! "Oh, it's the driver." "Oh, it's the tires." "Oh, it's the test." Hogwash! Your favorite truck has a limited slip that doesn't limit slip, or in GM's case, a so called locker that doesn't lock. This was the most revealing test of all of them, because it showed the traction aids everyone is paying for are nearly useless, and flawed. The test is simple and elagant. The differential just has to prove it can transfer torque to the wheel with the highest coefficient of friction, and none of them did. It was mainly the traction control system, a cheap bandaid no less, that saved the day. If you don't mind creeping ahead at a crawl, and you don't get the brakes wet or overheated, it's bettern than nothing. What I got out of this test, is get a true manual locker if you want dependable traction. That must be why they are becoming available on more and more trucks as options.

Thank you for doing this test. It was a real eye opener, and a great learning tool. I hope to see it again in all future tests.

What a bunch of sour grapes! "Oh, it's the driver." "Oh, it's the tires." "Oh, it's the test." Hogwash! Your favorite truck has a limited slip that doesn't limit slip, or in GM's case, a so called locker that doesn't lock. This was the most revealing test of all of them, because it showed the traction aids everyone is paying for are nearly useless, and flawed. The test is simple and elagant. The differential just has to prove it can transfer torque to the wheel with the highest coefficient of friction, and none of them did. It was mainly the traction control system, a cheap bandaid no less, that saved the day. If you don't mind creeping ahead at a crawl, and you don't get the brakes wet or overheated, it's bettern than nothing. What I got out of this test, is get a true manual locker if you want dependable traction. That must be why they are becoming available on more and more trucks as options.

Thank you for doing this test. It was a real eye opener, and a great learning tool. I hope to see it again in all future tests.

Wow... this test was absolute junk... nowhere near a good test of traction control... I mean, for one thing, you said it yourself - you're testing the bloody trucks in 2wd... now, i dont' know about you guys, but if I'm expecting slick conditions, i engage 4x4 right away.

I'm a proud owner of a 1990 Nissan Pathfinder w/ the factory LSD, and that old gal has never let me down, ever.

Hahaha Government motor corp couldnt even pass the test on there own test grounds!!! Ive seen the same test with the rollers thats states above. Difference is, this is a third party test, people who have nothing to gain by saying one vehical is better than the other. The roller test was conducted by GM, no duhh there going to try and make them selves look good and make there biggest rivals, f-150, tundra, and ram look bad! Use your brains! Ha

I understand both sides of theses arguments, regarding different tires vs traction control vs locking differentials on the pickups. I think those who are most vehement, on either side, are missing the point. They conducted a test, and clearly explained what the parameters are: One tire is on the slick surface, the other tire is on pavement. The vehicles are all in 2wd. The throttle is depressed to whatever amount of power allows the vehicle to climb the hill.

The Ford and Toyota, with the tires and option packages they showed up with, climbed the hill. The Dodge, Chevy, GMC, and Nissan, with the tires and option packages they tested did not. That's all it proves. Leave the rest. Could a different driver have made it up by feathering the throttle on the GMC or Chevy? Maybe. I happen to think so. But that wasn't the test. If the Dodge had been equipped with different tires it may have climbed the grade. If this, then that. Maybe. But the point is, if you go buy those vehicles, and put them through these conditions, you will get the same results. That's why they documented what they did, and their results. It's a stock to stock comparison with driving parameters as listed.

My rock crawler happens to run ARB air lockers front and rear. It is effectively unstoppable. Both axles even steer. But it is absurd to compare that vehicle to these trucks. It isn't apples to apples. Comparing a Tundra to a Silverado as they leave the showroom floor is. And if you drive a Silverado up to a hill with basalt tiles on one side and asphalt on the other, with a stream trickling down only the tile side, stop at the bottom and hit the gas, it won't climb it in 2wd. The Tundra will. That's all.

If you don't think this comparison is useful to you, then ignore it. But don't complain about not having the same tires on all of the rigs. That's what the comparison is about! How do the OEMs equip their vehicles as they come compared to one another? The devil just might be in the details. If an OEM puts on tires with markedly reduced traction compared to others, that's still useful information. However, it's probable that the tires are all approximately equal-without a comparison of the static and dynamic coefficients of friction for each tire, we cannot know. But we can compare the "driving up a basalt tile hill with water running down it" ability of stock vehicles with those option packages. I'm still going to buy a Dodge, most likely. They're all nice vehicles.

I'm curious as to which gear the Chevy and GMC are in while being used in 2WD. I am assuming you put them in low. In the Chevy, if the vehicle is put into the lowest gear then the locking mechanical differential disengages automatically.

Regarding Zach's comments: It's totally irrelevant to think of this as a "stock to stock" comparison. They clearly state in the video that this is a test of the effectiveness of the TRACTION CONTROL in these vehicles. Further, the title of this article is "Extreme Traction-Control Test".

This is not about stock to stock, it's about which truck has the most effective traction control. To test that, you have to use the same tires, period.

Also, to make claim that it's "probable" that all of the tires are similar in performance is plain ignorance. Clearly visible in this video are the following tires:

Chev Bridgestone Dueler A/T
Ram Goodyear Wrangler HP
Titan BFGoodrich Rugged Trail T/A

So they've got all-terrain tires mixed with sport all-seasons? This is hardly a test for traction control. Yes, it's a stock to stock test, but it's absolutely not a test of the traction control nor a test of the truck's capabilities. This test is a function of tire traction, and nothing more.

Also, I realize this is old, but it's important for anyone else reading these comments to be actually informed, instead of remaining ignorant.

Oops, I meant Jeffrey's comments, not Zach's.

This test proves one more thing, the average Joe and even reader of this website is not an engineer. When they don't like the results of the test, or worse, don't even understand the test, they complain the test is bad, when it is really their "favorite" truck that is coming up short.

Now we even have someone complaining that they should all have the same tires, no less. Most people don't have the luxury of junking brand new tires on their newly purchased truck just to match the test results. Secondly, that's why the engineers created a test with very different friction materials for each tire, to take the tires out of the equation.

This is the probably best test in the entire shootout, and I hope to see it in the future. Most of the other information in the shootout I can dredge up in the car mags.

I keep my sierra with gov lock. It's gotten me and plenty of limited slip vehicles through sand, mud, and its fun doing donuts too. There is trick to engaging the gov lock too. It takes a certain amount of wheelslip to engage lift off the throttle it locks and back on the gas. Do any off-roading and you will figure it out quick. The flex test that gmc did is the test that needs to be done on trucks. I go to the mountains and engage auto-trac. Who's going to be driving through mountains in snow or ice in 2wd. Be surprised how many vehicles I had to pull out of a ditch my lawnmower could of made it through. 1front wheel and 1 rear wheel spins. Got to love limited slips got one in my woods truck f150 4x4 and that exactly what it does is slip with just slight to moderate flexing but it a cheap beater so can't complain too much.

this test was pretty poor. I am a dodge guy but I know trucks very well. My sister could have driven the chevy or gmc up that ramp! the driver floored it so that even when the locker locked up all it did was spin both the tire on the "ice" and the one on the road. Simply getting into the throttle enough to lock the diff, then letting out of it and slowly accelerating would have pulled those GMs up the ramp slick. As for the dodge, I'm disappointed its traction control wouldn't brake the spinning tire better giving more traction to the one on pavement. riding the brake a little would have got you up the ramp though. Race school wont help you here bud...takes real world experience.

While this test and article are very old, it is important to leave this comment so that anyone reading in the future can understand just how broken this test was.

The purpose of the test was to assess which truck can move torque best from side to side. This assessment is nearly impossible to do without using identical tires on each truck, since tires have more to do with traction than any other piece of the truck.

Even if we write that off as an unavoidable variable, the GOLD STANDARD in side to side torque transfer, meaning 100% transfer, is a locking differential. The two GM pickups had G80 locking differentials. These differentials are very good at doing what they are designed to do - when a difference of about 100rpm between two wheels on the same axle is created, the differential will lock in place and both wheels will now turn at the same rate. The G80 will remain locked until the truck moves faster than about 20 mph at which point it will unlock. The G80 is a low speed traction device. Serious off roaders do not like the G80 because they do not understand how it works, they pound the throttle, create very high rpm wheel spin and then when the G80 locks it is not locking at a low RPM wheel speed difference (say 300 rpm on one side vs 400 rpm on the other side), it is locking at a *very* high RPM (say 3000 rpm vs 3100 rpm), the huge amount of torque present at high RPMs can cause the entire differential to explode when it locks upon detecting a wheel speed difference.

That said *NONE* of those condition were occurring here. If you also watch the supplemental video of this test http://www.youtube.com/watch?v=RZBtOSuG0xo you will see that Mike Levin either did not understand how this differential worked (very possible) or he purposefully biased the test (also possible). You can see that the G80 worked exactly as intended in the video, but the driver pounded the accelerator to ensure that too much torque was being delivered to the single rear tire with traction for it to grip. This is exactly what happens when someone does a burnout at a drag strip. The driver then stopped the truck (which leaves the G80 locked), engaged 4wd, and then pulled out of the spot - ironically with the G80 doing all of the work as 4wd would do nothing here with an entire side of the vehicle on the rollers.

In other words, Mike Levin either did not understand the test he conducted, or purposefully misrepresented the test since he showed that once lower throttle was applied to the GM trucks with a locked G80 they pulled out with no trouble.

How anyone could argue with a straight face that a traction control system in an F150 functions superior to a locked differential in transferring torque to the wheel with traction is a question for the ages. The likely answer, of course, is that Mike Levin used this test (and others) to help get his current job with Ford.

Between 1:17 and 1:21 the GMC is shown to start up the hill in 2 wheel drive, then the driver stops the truck. At 2:20 to 2:26 the Chevy is shown to do the same thing as it has the same G80 differential. Why are the trucks stopped once they start going up the hill? Just curious.



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