Mama JJ is on the road with our 5ver toy hauler. Last night she engaged four wheel drive in order to get the camper into a campsite. This morning she drove for about 2 hours at 65-70 mpg still in four wheel drive high. http://www.dieselplace.com/forum/smileys/Confused.gif She didn't realize the truck wouldn't disengage the 4x4 when she turned it off.


Tranny temp was 190, engine temp 200. http://www.dieselplace.com/forum/smileys/Geek.gif She was towing without overdrive engaged since she is in the foothills of Georgia. Last week I changed to transynd in the tranny and transfer case. Probably a good thing that I did.


Since she has the truck I don't have access to my owners manual. My concern is how fast can she drive in 4x4, and can/should we tow in four wheel drive? Any damage? http://www.dieselplace.com/forum/smileys/Ouch.gifShe commented that it was pulling hills with ease and she was passing semi-trucks. She's towing a 17k lb toy hauler. Geesh! Gotta slow Mama JJ down! http://www.dieselplace.com/forum/smileys/HiHi.gif

4x4 on hard dry roads is tough on the transfer case and should be avoided. The front and back wheels fight each other. Loaded, the loads on the trasfer case are even higher from the tongue weight.

Speed isn't a problem, the case will handle highway speeds just fine in 4x4. I have a stretch of hard packed dirt/gravel road I pull down every once in a while. I'm in 4x4 most of the way to keep from spinning. Going about 40-45.

Check the transfer case and axles and make sure she didn't scorch the fluids.

To answer you question, use 4x4 when you have to because of bad traction only.

Just my opinion and experience for what it's worth.http://www.dieselplace.com/forum/smileys/Big Smile.gif

I wouldn't drive in 4 wheel drive on the pavement or any hardpack. Anything soft or muddy and you should be OK. I always turn it on once I hit anything soft (Sand, Mud, Etc.). I've even let air out of the tires and ran them down to 25psi when in the sand. I'm sure some of the guys that do truck pulls will chime in. I'd think their trucks would have it roughest when competeing.

Thanks for the quick replies. http://www.dieselplace.com/forum/smileys/Clap.gif Just got off the phone with Mama JJ and all is well in 2wd up in the Georgia foothills.


Fingers, how do the front/rear wheels fight each other? I posted a similar question on the 2004.5 forum regarding whether the front and rear axles actually turn at different ratios in 4wd? If they do, why would GM give you a 4x4 that you can engage below 40mph? Would seem like a recipe for disaster. http://www.dieselplace.com/forum/smileys/Dead.gif I've read posts where guys that race their trucks in 4wd rip up their front suspensions quite a bit doing it. Should be interesting to see what they have to say.


This does pose an interesting question though. http://www.dieselplace.com/forum/smileys/Question.gif Mama JJ didn't even notice she was in 4wd until she saw the dash indicator light. She commented that the D/A was ripping through the foothills of Georgia with minimal effort pulling 17k lbs at 65-70 mph. http://www.dieselplace.com/forum/smileys/Rock On.gif Does operating in 4x4 put that much mo' power to the wheels versus 2wd? Good discussion! As always I really appreciate everyones input. JJ http://www.dieselplace.com/forum/smileys/Hug.gif

Fingers, how do the front/rear wheels fight each other? I posted a similar question on the 2004.5 forum regarding whether the front and rear axles actually turn at different ratios in 4wd?

There is no differential in the transfer case. Any difference in tire size front to rear must be taken up by skidding a tire somewhere. When you go around a bend, the front tires take a different path from the rear, and again, a tire has to skid. All this skidding loads up the drivetrain.

Fingers, appreciate your input on both threads. JJ http://www.dieselplace.com/forum/smileys/Clap.gif

JJs DuMax, If your willing to try, Have her put it in 4 wheel drive and while running straight, gas it. That's how we noticed it was in 4x mode. Got a hum under accelleration.

Tranny temp was 190, engine temp 200. http://www.dieselplace.com/forum/smileys/Geek.gif She was towing without overdrive engaged since she is in the foothills of Georgia. Last week I changed to transynd in the tranny and transfer case. Probably a good thing that I did. http://www.dieselplace.com/forum/smileys/HiHi.gif


Only thing is, you do not know Tcase temps which could have been a bit hot. High speed in 4WD on hard paverment will heat things up in Tcase a bit for sure.

When we get back to J'ville I'll change the tcase to synthetic. I'm running 75w140 synthetic in the rear, but am thinking I should run the regular weight in the front since there isn't as much weight involved.


Thanks for the reply. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

When we get back to J'ville I'll change the tcase to synthetic. I'm running 75w140 synthetic in the rear, but am thinking I should run the regular weight in the front since there isn't as much weight involved.


Thanks for the reply. JJ http://www.dieselplace.com/forum/smileys/Big Smile.gif

GM does not recommand 75w 140 for front axle and only recommands 75w90 if truck will see temps below about -12F regularly. Currently, I use 75w90 in rear axle (Dino oil) and 80w90 in front myself. There is little need for 140 weight oil in rear axle unless you tow in extreme temps and/or heavy load on long grades in warm weather regularly as the rear axle is pretty beefy to begin with.

Stay with 75w90 in the front. If you go heavier the front axles may not engage in 4x4. The "hubs" are in the front diff.

Let us know what condition the transfer case oil is in. I'm curious.

runnin it in 4 high shouldnt give it anymore power.


if you wanna see how much the tires can fight each other, sometime put it in 4 hi or low and turn the steering all the way to the left or right and hold it. if you mash the peddle, it will feel like the front of the truck just got picked up off the ground. this is a good way to test the 4 wheel drive of a used truck when considering buying. the more it feels like it is getting picked up, the better.


just my two cents...

runnin it in 4 high shouldnt give it anymore power.


Actually it will because they will not have the same rolling radius on both axles even if they have same gears and tires. There will be a difference, no matter how small, which will add drag and driveline wrap up along with stress/heat to Tcase bearings.

you can run at top speed in 4HI and not hurt a thing... in a straight line, turn and you bind the T case, which is why your wife couldn't get it back into 2WD. If you have a handy jack lift one of the front tires off the ground which will relieve bind, if not, back up on soft ground and blip throttle a bit when you shift into D, this should also relieve bind. Believe it or not but more torque goes to front in 4WD, thats why 208 T cases made strange noises in AWD, stretched chain jumping sprockets, put into 4 hi or lo lock and noise goes away

WHOOPS... wrong case.... 208 is aluminum part time case, meant 203 case