I have 04 suburban that has issues when I try to turn at a slow speed. Trouble on both sides but left is worse. Feels like rear wheels are locked up. After it started my front diff went out so I thought that was the problem but after replacing front diff problem persists. Truck is awd has 3.73 gear ratio. I know I need to try changing fluids to the new recommended fluids. What other things should I check if fluid change doesn't fix isuues?

Sounds like there may be a problem with the transfer case. A little research shows me the awd transfer case was a borg-warner unit that used planetary gears to split the torque and there have been problems with it. I suggest you have that checked out before driving it much if at all. Not only do you have a safety issue but you will have undue tire wear and risk losing another differential.

Thanks. I will tear it down and check it out. Several threads I had read stated that the fluid was a big part of the problem but then again it does have over 200k miles on it.

A question: I'm not aware of an AWD version of the Suburban for 2004. Is this AWD or 4WD? This would change troubleshooting somewhat.

I didn't realize it was awd either until I changed out the front diff. It only has a 4-lo option on the dash as well as traction control. I just pulled rear diff pan and the spider gears look good. It was definitely ready for a fluid change. After I posted yesterday, I drove a short distance to the pharmacy and had traction control, abs, and brake lights all come on. Any suggestions?

It is definitely AWD. I didn't know until I replaced the front diff last week. I have pulled the plate from the rear diff and changed the fluids. Spider gears are in great shape but it definitely needed the change. Drove it yesterday and this morning and the traction control, abs, and brake lights all came on at the same time. Any suggestions?

I will also let you know that this problem started about two weeks before my front differential went out. Was driving home when the gears shattered in the front diff but was able to drive it on home about five miles. My front diff doesn't have any electrical connections or an actuator. It only has a vent hose on top. I am not sure that the current problem, which was my original problem, caused my front diff to shatter it'* gears or not but definitely would like to solve before I ruin another one.

I pulled ABS and VSES-ECAS fuses just to check and make sure that wasn't the issue since the warning lights were on.

Making super duper sure as this is an unusual config in my mind: No Auto4WD/2HI/4HI/4LO switches on the dash? . . . and a little vertical unusable storage pocket between the far-left dash vent and the gauges? Or maybe a 3-button combination in the same place?

If it is a 3-button, which is indicated with a little light?

This is good news.

This combination strikes me as ABS sensors having issues. The car uses the ABS sensors for traction control as well. I'd check all four including wiring.

Makes sense. It was bound up for two weeks of driving then the weakest link failed under the ongoing stress.

This is why I am being really super duper certain you have AWD and not part-time 4WD. 4WD if locked in 4HI (whether indicated or not) will do everything you describe. The assumption here is that surfaces are slippery when engaged so no binding issues and the driver will disengage it when the slip goes away. Often the rear-most universal joint will give out before anything else due to the ongoing bind condition and the fact that the rear universal joint on the rear driveshaft does the most flexing of the four of them and gets the most dirt/water/salt/mud/deer/weeds/hits/etc. of all of them. In these models the cause is commonly the switch and sometimes the TCCM, both of which are much less expensive than hard parts.

Anyways, if this is not 4WD and is AWD after all, this would be explained by the planetary set in the transfer case being locked up like garagerog mentioned earlier. This would essentially be acting like a part-time 4WD in 4HI with no ability to unlock the front axle. I think this would also be an expensive repair.

Amazing to me that this worked at all. With no slip detected at the wheels the TC would stay in open-front/back mode and either not move you at all or only a little. That you were able to still drive it tells me that yes the front diff was shot but still had enough meat left on whatever was left to help the center differential keep the car moving.

This would confirm AWD.

As above, I bet it did.

My money would be on that rear universal joint this time around. Let'* hope we don't get there.

the light on the selector switch on the dash is on AWD. I can hear the transfer case shift in and out of 4wd when I select it. The truck would act like traction control was kicking in when going around sharp turns in the road, I go around a lot of them in my line of work. It would only do it on occasion and didn't matter if the road was dry or wet.
If it were an anti-lock braking issue, wouldn't it stop when I unhook the fuse for it? I have unhooked ABS in other vehicles and it would solve the issues. I should probably also mention that this is my first time working on drive train issues. I normally work under the hood but I follow direction well and learn fast. Can I unhook the tccm and see if that helps before I replace it or do I need to replace it to find out and where is it located. I don't have my owner'* manual but I can download it if I need to.