Sad front differential??

[Gdsmith07]

There’s probably some junk rigs out at the city pit I might be able to Score a front diff to swap for now I’ll have to go and see. I was wanting to re-gear for lower gears since im running bigger tires with a little old 4.8 and a leveling kit (that’s how I bought it) so maybe this is just the push to get that done before I do the coil over swap.

 

[Erickk120]

The 8.25 is not the strongest ifs diff, so I wouldn't be surprised, give the pinion yoke a spin with the axles disengaged, and without the drive shaft, if you feel any rough spots, or anything not smooth it will probably be your problem. A pitted bearing will do the popping like a bad cv axle, or at least I've seen it before.

 

[Matthew Jeschke]

Make sure you do as recommended... This will isolate problem so you know it's either front diff or transfer case. It only take a few minutes to remove the driveshaft. You can just undo the diff yoke and set it down. Then support the front end on axel stands and spin the diff by hand you can tell a LOT from doing that... If you don't want to get under the car to spin it, then take a tire off and spin the hub.

Check the driveshaft universal joint while you're at it.

Disconnect front driveshaft at front diff. Jack frontend off the ground and turn diff by the yoke. You'll feel it if the front diff is screwed up. You replaced the front diff pinion seal? How many miles ago was that? Use a new crush washer? Set lash correctly?

FYI~ There's also an encoder motor to switch between 2HI, 4HI, & AWD. They do go bad. That's on the side of the transfer case. The transfer case computer takes reading from your panel and applies it to that motor. To check it, listen as somebody switches between the modes. It'll have gear grinding noise if it is bad.

There's a second motor on the front diff to lock the passenger side axel in when you engage 4wd. You might try and actuate that manually with a 12v source

Do you know if anybody rebuilt the front diff at any point? There's some spacers that have to get setup on the passenger side, as well as pilot bearing to hold the passenger side driveshaft up. Likely not the problem but worth noting if somebody had tried to rebuild it. Somebody tried to rebuild mine and did it all wrong, parts were floating around and beat up in the axle tube.

 

[Matthew Jeschke]

The 8.25 is not the strongest ifs diff, so I wouldn't be surprised, give the pinion yoke a spin with the axles disengaged, and without the drive shaft, if you feel any rough spots, or anything not smooth it will probably be your problem. A pitted bearing will do the popping like a bad cv axle, or at least I've seen it before.

I believe when I rebuilt my front diff (minus carrier) the axel bearings were needle bearings. Would make for a HELL of a mess if some of those needles are missing. It would run but really rattle bad and make all kinds of fuss. Might be worth checking... it's a bit more work but you can pull the driver side half axel out of the housing without having to dismantle it all. Not the story with the passenger side...

 

[Gdsmith07]

Make sure you do as recommended... This will isolate problem so you know it's either front diff or transfer case. It only take a few minutes to remove the driveshaft. You can just undo the diff yoke and set it down. Then support the front end on axel stands and spin the diff by hand you can tell a LOT from doing that... If you don't want to get under the car to spin it, then take a tire off and spin the hub.

Check the driveshaft universal joint while you're at it.



FYI~ There's also an encoder motor to switch between 2HI, 4HI, & AWD. They do go bad. That's on the side of the transfer case. The transfer case computer takes reading from your panel and applies it to that motor. To check it, listen as somebody switches between the modes. It'll have gear grinding noise if it is bad.

There's a second motor on the front diff to lock the passenger side axel in when you engage 4wd. You might try and actuate that manually with a 12v source

Do you know if anybody rebuilt the front diff at any point? There's some spacers that have to get setup on the passenger side, as well as pilot bearing to hold the passenger side driveshaft up. Likely not the problem but worth noting if somebody had tried to rebuild it. Somebody tried to rebuild mine and did it all wrong, parts were floating around and beat up in the axle tube.

I’ll definitely be getting it back up in the air and disconnecting the drive shaft to spin the pinion. Ill report back once I get it done. Maybe I’ll be able to get to it tomorrow but it’s looking like more of a Monday project.

I replaced all the U joints about 6-8 months ago. There’s always a possibility one could have gone bad again. But I had always experience U joints as a *pop or *slap when they began to go out or even a vibration. This is a dragging feeling.

I will give the engagement motors a look but i can feel the front differential engaging with power it just feels like it’s dragging tremendously more than it should and also has almost a howl to it as you speed up.

I do not know if anyone rebuilt the front differential. The PO was not the best of Wrencher and gave up on it when it needed tierods.

I also replaced the drivers side Axel seal, I just popped the shaft out pulled the seal and set a new one. Haven’t had a leak since. I’m now more concerned that maybe I screwed the adjustment tabs I’ve read about or maybe the shaft bearings have gone bad.

I get a continuous *click or *tap even when in 2WD. I have replaced the CV axels, both, twice just because I thought maybe the whacked out front end was throwing the cv axels apart. I’ve since rebuilt the entire front end. Brand new steering and suspension. However I just installed the second set of cv axels and still have a *tap or *click

Today I was doing a final alignment on it, and again noticed that the drivers side wheel, when in 2WD and the front end off the ground, felt like it took maybe slightly more force to Rotate the assembly.

I have another new Cv Axel sitting around I was going to throw it in the drivers side and see if maybe I had just put in two new bad cv shafts. But I’ll get it in the air to see about spinning the pinion.

Everything feels forward of the cab nothings form center or in the floors which is why I was thinking differential as opposed to T-Case.

I was thinking of re-gearing the axels anyways. Maybe a bad form diff is just going to be my excuse to do it sooner rather than later.

 

[Matthew Jeschke]

Yeah hard to say. Seems you've done your homework. I'd ventures problem is inside the housing with all you've done. If you pull the driver side CV axel then you can also check the half shaft / output bearing. That half axel pops right out... whatever you do though... DO NOT pop out the passenger side. The spacers will fall into the housing.

 

[PatDTN]

I apologize in advance for not reading this entire thread so hate me if this has already been mentioned. I saw that you're running larger tires. Are all four tires in the same state of wear? Are the tire pressures the same? When I bought my '09 Tahoe the tires were badly mismatched. I didn't know a lot about the vehicle and put it in auto 4wd mode. It immediately started lurching and doing crazy stuff. The tires would have been reporting a different speed at each wheel and thus 4wd was needed according to the computer. New tires fixed the whole issue.

 

[MassHoe04]

I apologize in advance for not reading this entire thread so hate me if this has already been mentioned. I saw that you're running larger tires. Are all four tires in the same state of wear? Are the tire pressures the same? When I bought my '09 Tahoe the tires were badly mismatched. I didn't know a lot about the vehicle and put it in auto 4wd mode. It immediately started lurching and doing crazy stuff. The tires would have been reporting a different speed at each wheel and thus 4wd was needed according to the computer. New tires fixed the whole issue.

Just looking to see if any additional clues surface by asking this...

Your condition never triggered an ABS code?

If wheel speeds were off more than what the programmed system parameters allow, I would think it would trip an ABS light/code(s) pretty quickly.

If not, I would be asking this as a follow-up...
If the ABS threw no codes and ABS system was OK with the speeds it saw at the wheels, why would the computer that controls 4WD (assuming it also relies on wheel speed information to be within certain tolerances... does it?) not be OK with the detected wheel speeds?

Just trying to apply some logic to test out some theories on what might be happening, what triggers it and how the system responds.

Sometimes logic seems to have nothing to do with anything, but I am curious to learn new things.

 

[Gdsmith07]

I apologize in advance for not reading this entire thread so hate me if this has already been mentioned. I saw that you're running larger tires. Are all four tires in the same state of wear? Are the tire pressures the same? When I bought my '09 Tahoe the tires were badly mismatched. I didn't know a lot about the vehicle and put it in auto 4wd mode. It immediately started lurching and doing crazy stuff. The tires would have been reporting a different speed at each wheel and thus 4wd was needed according to the computer. New tires fixed the whole issue.

My tires need replaced, I wouldn’t say they’re “trash” but they could
Be replaced for sure. Where I am there is no balancing machine so I couldn’t tell you if they’re out of balance but what I can tell you is there is no speed limit on the roads that do exist that is above 40MPH and with the amount of road wash and potholes im
Usually doing 25 and under so I’ve always been under the assumption that I’ve even doing low enough speeds for wheel balance to not make a drastic effect to performance. That may be an entirely wrong thought idk. But I don’t have a way to baalnce the tires. The tires I was going to order I was also going to order a new set of rims and have them shipped balanced.

My 4 other 4WD/AWD vehicles here have no issues and I’ve never balanced the tires on either of them including new tires I’ve put on.

But I’ll be able to rile
Tires out as well here shortly. Unfortunately there is no normal
Tire shop to go to everything has to be flown/shipped in.

 

[Gdsmith07]

Just looking to see if any additional clues surface by asking this...

Your condition never triggered an ABS code?

If wheel speeds were off more than what the programmed system parameters allow, I would think it would trip an ABS light/code(s) pretty quickly.

If not, I would be asking this as a follow-up...
If the ABS threw no codes and ABS system was OK with the speeds it saw at the wheels, why would the computer that controls 4WD (assuming it also relies on wheel speed information to be within certain tolerances... does it?) not be OK with the detected wheel speeds?

Just trying to apply some logic to test out some theories on what might be happening, what triggers it and how the system responds.

Sometimes logic seems to have nothing to do with anything, but I am curious to learn new things.

Never threw an ABS sensor.

When I initially bought the vehicle I had an ABS light on. That was do to a cut or broken wire at the wheel hub sensor on the drivers side.

The bolts for the brake line/Abs wiring were missing and so the brackets were loosed which I figured was due to someone at some point swapping a hub out and not correctly fastening everything back together which o concluded probably
Caused the broken ABS line.

When I rebuilt the front end I went ahead and put new MOOG wheel Hubs in. Figured if I was already that far into the extra money on the new wheel bearings/hubs was worth the peace of mind.