Replace front diff?

[6716]

This would be a totally elective repair. Truck runs fine.

Challenge is the diff has never held oil for long, lately I get 48 hours before it's empty again. Replaced seals, no joy.

4wd sometimes engages, but given the lack of diff oil I don't dare run it long. Actuator works and has been replaced, transfer case mechanism seems to work.

I don't understand what causes the 4wd to engage or not. For some recent work I had to back up an unpaved slope and I got 4wd. I was pointed down when I tried to engage it. Times I have been on flat ground I have not gotten it to engage.

Other than the diff and intermediate shaft I don't know what it would be at this point. And even if I did solve it, I'd want a diff that holds oil.

I don't feel like buying a new truck right now, and even if the diff replacement is spendy (I'll do the work) it's still less than I new used truck I'd get to maintain anyway.

Also steering rack could use replacement as well so two birds on one repair.

Any diff recommendations?

 

[Mooseman]

All diffs from all years will work however the 02 had case leak issues. You'll find replacement methods in the FAQs.

I wouldn't run it too much with no oil since the spider gears are continuously spinning with the left wheel even with the 4x4 set to 2wd and the disconnect disconnected. It shouldn't be shifting into 4hi unless you have it on auto. If you aren't replacing it for a while, I would pull the axle shafts and drive shaft until you do.

Good used diffs should be plentiful in yards. Just make sure you get the same gearing as yours. Check the fluid level and condition before removing and that is spins freely.

 

[TJBaker57]

I will add that even in 2Hi not only are the spider gears turning as Mooseman states, the intermediate shaft and the front driveshaft (and thus the ring gear/carrier) is almost certainly spinning as well.

On my 2002 at 65 mph my intermediate shaft spins up to 1200 rpm in the reverse direction and the front propshaft is also spinning though I cannot recall a value at the moment. Once fully warmed up the intermediate shaft comes down to about 700 rpm, still in the reverse direction.

One might ask how I know this. I wanted to quantify what is happening in the front axle disconnect at speed when the vehicle is shifted to any non-2Hi mode. So I developed some PIDs/equations to do just that.

 

[JayArr]

TJ knows more about Envoy PIDs than the engineers in Detroit!

I've had mine out, it's not the worst job I've ever had to do. If the steering rack is already out it becomes easier. If you're doing the rack do the two steel lines from the pump that go to it that rust out at the top of the strut tower. You need to pull front half shafts so think about ball joints and bushings too. You may be surprised at how much more you like driving it if you tighten up the front end suspension and steering.

4WD has gotten me out of a couple of jambs so I wouldn't abandon it.