front diff ?

[ak diesel driver]

So I've been having a slight vibration while driving down the hwy and it felt like it was in 4wd. Floor shifter is in 2wd when I'm getting this vibration. So I crawled under the truck today and checked out all the ujoints, hubs, etc, NADA everything was good. While I had the frontend up I could turn either wheel independently from the other. I put the Tcase in nuetral and discovered I couldn't turn the front driveshaft. So I jacked up the frontend again and with the Tcase in nuetral if I rotated the driveshaft the front tires were solidly connected to the driveshaft. To further check this out I pulled the TLA and could still turn the wheels with the driveshaft. It appears the diff is at the very least sticking in the engaged position if not stuck in the engaged position all the time. Anyone ever hear of this before?

 

[NVW]

A few instances lately I've had the same thing happen. I just thought the transfer case wasn't disengaging. I'm in deep snow and it's cold.

 

[ak diesel driver]

the first time I noticed it it was the same here, cold. today was 35* above, and I was checking it out in my brothers heated garage.

 

[NVW]

My guess is if you grabbed the driveshaft it would stop turning.

 

[ak diesel driver]

My guess is if you grabbed the driveshaft it would stop turning.

Don't understand that comment Leo. The driveshaft is solidly connected to the front wheels all the time like whatever slides in the diff is sticking

 

[NVW]

Is it solid to both wheels? Or just the driver side? From my understanding the TLA engages the pass side to the diff.

If it's solid to both then likely the locking mechanism must be sticking.

 

[ak diesel driver]

I assumed it was both but I only checked pass side.

 

[NVW]

I'm not sure which axle is constantly connected to the diff, I thought it was the drivers side. The TLA then connects the other axle.

 

[6.2 turbo]

When the transfer case is in neutral,the front and rear shafts will be locked together.

 

[ak diesel driver]

I'm not sure which axle is constantly connected to the diff, I thought it was the drivers side. The TLA then connects the other axle.

pass side is the constantly connected side. Talked to a guy I know that has a driveline shop and he said the 1/2ton diff failed regularly but the 3/4ton diffs lasted quite a bit longer. he said the vibration was coming from the bearing going out on the drivers side of the diff and that you should be able to grab hold of the cv shaft where it comes out of the diff and wiggle it pretty easily if it's bad. I tried that from the wheel well but it felt pretty solid so I'm not sure what's up with mine.

 

[bison]

I replaced the pass side half on one of mine a number of years ago Les
The driverside is the one in constant engagement
The passide has a splined collar with a springloaded shiftfork and pin that engages trough the actator that wheelshaft with the pumpkin.

 

[ak diesel driver]

if so what's causing the disengaging issue?

 

[bison]

I dunno,..here i'm thinking out loud. Could it be the disengagement spring broke or a stuck collar or shiftpin?
Did the actuator flew appart?
The dr shaft is held steady by a needle bearing towards the pumpkin.
Did that bearing gave up the ghost making the shaft run out of center were it engages the splines on the collar?,...it might prevent the collar to slide back on the shaft and it could explain the vibration you feel.

Sounds like you got to dig the axle housing half outa there to find out, but i would pull the actuator first.

 

[THEFERMANATOR]

The drivers side is constantly engaged, and the passenger side axle is a 2 piece with a slip collar on it for enagagement. If the front axle is unlocked at the disconnect, the spider gears in the diff allow the axles to rotate without the driveshaft spinning. With it in 2 wheel drive, you should be able to rotate the driveshaft by hand. And yes, many(not all) new process transfer cases lock the front and rear diveshafts together when it is in neutral. Put the transfer case in 2 wheel drive and jack up the front passenger side tire. If the driveshaft spins when you turn it the axle disconnect is engaged. It is not uncommon for the axle disconnect to get froze up if you don't regularly use 4X4. GM used dry film lubricant in the front diff fluid(this is why it is green and looks milky) to help prevent the front axle disconnect and ring gear from rusting when the 4X4 doesn't get used much, but it is always a good idea to engage it every month for just a mile or so to keep everything lubricated and unfrozen. Also there is a chance that the return spring for the axle disconnect has broke in which case it will stay enagaged. It is possible to remove the passenger side axle tube and service the disconenct portion seperate of the compelete diff. Remove the passenger side axle shaft, remove teh 2 bolts that hold the passenger side axle tube to the mount, and then remove the bolts tha tatatch teh passenegr side axle tube to the diff. Watch out for parts falling out when you do this because if it is froze up the spring will shoot out when you pull the tube off.

 

[ak diesel driver]

thought I'd update this. My TLA quit working shortly after this and the frontend disengaged so I have been driving it ever since without 4x4. Today I upgraded to an electric actuator which works great, downside is my 4x4 issues are back. Looks like I need to rebuild the front diff or replace it.

 

[3500GMC]

3.73?

 

[ak diesel driver]

so it looks like I might get lucky on this one. turns out a large shim broke into pieces and the rest of my diff seems tight. and yes 3:73

 

[Big T]

Nice catch! Good luck on the repair.

 

[bison]

I wonder what caused that spacer to break?

 

[ak diesel driver]

I don't know but talking to a driveline guy I know he said there was some updated parts available for it