4WD and steering

[Shdwdrgn]

No, not that I've noticed? Here's what happened in the parking lot... I pulled straight into a parking space, then when I went to leave, I started backing out and turning my wheel to turn back into the lane. I just had my foot lightly on the gas to pull out, but as soon as I started to turn the wheel, the truck came to a stop, and I had to rev up my engine a few hundred rpm higher to get it to start rolling again. I think this is what gets me about the situation... I can understand the front axle binding up if I try to make a really tight turn in 4WD. I'm used to that. But this has always happened in my TB even when I'm making very gentle turns. If I turn the wheel at all while moving slowly, I have to press the gas harder to keep moving, or I come to a quick stop. Once I get up to road speeds (20mph or so?) then I seem to have no trouble making turns.

[v7guy]

I can imagine the specific scenario Bill mentioned as being pretty much the only scenario where you don't risk slamming things into gear. I hadn't considered it before, but it makes sense.

Jeff, I think the problem you're most likely seeing is that your using 4WD when you shouldn't be. The tires aren't slipping like they need to while turned in 4WD and it's binding up the drivetrain... the comment that it starts just as you starts turning reinforces my thoughts on it. The motor needs to deliver more torque to either make the tires slip or break the weakest link in the drivetrain.

Regardless of how much the wheels are turned if you're turning you are changing the radius that the tires move on in relation to each other, and if the rubber of the tire has good grip it's not gonna want to slip until there's enough torque to make it do so. Hence the heavy load on the engine, the reduced rpms and then the eventual application of more throttle to deliver enough torque to make the tire slip.

Keep in mind we aren't saying the tire needs to slip even an 1/8th of a revolution. It just needs to slip a smidge to keep things from binding up.


Also keep in mind that you have no trouble at higher speeds because you have momentum on your side that lets the tire slip the little bit it needs to.

[HARDTRAILZ]

I wonder if it could have something to do with all the issues you previously related with the ABS system. You have had some issues no one else had to deal with since your gear swap. I am fairly certain that if this was a common issue, it would have been mentioned or addressed previously.

Several of us have swapped diffs and gears and use 4x4 on and off road with out this kind of issue. I would say it is something odd in your truck or is common and you are not used to it.

[navigator]

Your issue sounds just like when my traction control kicks in. When taking off on a slick surface the traction control will kick in and you have to rev it pretty good or turn off the traction control. When I am moving down a slick muddy road, I don't notice the traction control loss of power as much as when I am going slow or taking off.

I can't recall if the earlier models have traction control or if it is just the later models.
Do you get a flashing traction control light on the top left side of your dash when it happens?

[The Roadie]

I think this is what gets me about the situation... I can understand the front axle binding up if I try to make a really tight turn in 4WD. I'm used to that. But this has always happened in my TB even when I'm making very gentle turns. If I turn the wheel at all while moving slowly, I have to press the gas harder to keep moving, or I come to a quick stop. Once I get up to road speeds (20mph or so?) then I seem to have no trouble making turns.

If you have ANY driveline binding in 2WD mode, then I think that can only happen if you have two failures at the same time. The disconnect is connected when it shouldn't be. And either 1) the TC clutches are engaged when they shouldn't be, or 2) Your front diff carrier/spider gears are frozen together and turning your front axle into a always-locked assembly.

Should be easy to diagnose if you get the vehicle into the air.

[Shdwdrgn]

v7guy - the problems I'm seeing are only when I'm using 4WD on snow/ice, so there should be no concern about tire slippage.

hardtrailz - I haven't had any problems with my ABS since the GM guy used his techII and changed my tire size in the abs system. However this 'problem' has nothing to do with the gear change, it is something I have noticed every since I bought the truck. The first time I backed out of my driveway into fresh snow, I thought I was having transmission problems again (the tranny was actually replaced shortly after I bought the truck). It has that same sensation like you should still be going when the transmission is slipping, except you can still feel the torque on the vehicle.

navigator - I do not have traction control, and I haven't noticed any lights flashing on the dash when it happens (not that I'm paying attention to the dash at the time...). Its hard to remember exactly what happens, or when it happens, because this does not occur every time. I can't just back out of my drive into snow and have it consistently occur. In fact, backing out this morning in 4WD there were no problems at all. I've had it happen on fresh deep snow and hard-packed snow. I'm pretty sure it happens much more often while reversing than moving forward, but I only notice it when I'm already moving and get this sudden sense of losing all power. It usually only happens when I first take off after being parked, so maybe it has something to do with snow getting packed into the drivetrain, and then when I try to move my steering wheel it binds up?

roadie - This only happens in 4WD, never in 2WD.

When I tore apart the front end to replace my diff, I did not see any wear on the drivetrain. The front axles felt nicely flexible at the U-joints and there was no damage to the boots (they actually looked rather new, so the previous owner may have replaced them?).

Sorry if it feels like I keep changing my story... its just hard to remember exactly what happens *because* it doesn't happen all the time. The more I think about it, the more it seems like the idea of snow getting packed in sounds plausible. It does seem like this usually happens when we've had fresh deep snow or when there's a lot of slush on the road, so maybe its just that simple. I really don't know...