[chuckybob]

So a few hours and a few hundred miles after buying my van, heard a LOUD THUMP THUMP THUMP THUMP on the highway. Pulled off. Wheels looked fine, some play in the CV so I towed it home from there.

After inspection, there's A LOT of play on the passenger side CV where it meets the front diff, and play matches the sound, so I'm thinking the needle bearing in the front diff blew out. This seems to be a very common failure point for AWD.

Front end rebuild is in order. While I'm pulling everything out, is there either a heavy duty rebuild kit or a front diff swap that improves reliability?

 

[tungtide]

I have a cast iron front diff. Mine came out of a Chevy Envoy. Some guys find them in manual shift blazers. They are a little difficult to find, but they are out there. I also had a limited slip locker built for Mine, for a little added traction. The Envoy. One was not a direct bolt in but. By borrowing a few parts from the original aluminum diff it all works

 

[tungtide]

A pic of the beginning. Side by side shiny aluminum vs dirty cast. Had to change front yolk, shifting diaphragm was removed, new seals paint few other parts then it bolted in place.

 

[markmitch]

Wow, any chance of a write-up on this: I would love to do this swap. Did the new diff have a vacuum or electric lock out like the S-10 diff? What year envoy did yours come from?

 

[tungtide]

I think the envoy was a 96. Bought from a guy who. Cruises junk yards so not sure. At the time he had two one was from a blazer for 300 clams and the other from an envoy. 200 clams (if I. remember right ) the envoy had a vacuumed diaphragm on it and as stated needed parts from the Astro diff. The envoy had a two piece axel housing where the Astro has a one piece. Mark I thought I did a write up when I did this, because that’s where I found the pics. But I live in a zone non computerized zone so I may have not. Anyway then I sent it to Jeff in Georgia and had him install an LSD locker and go through it. In the end I have 900 ish dollars in it. Some of you guys could do it cheaper I just don’t know enough about the special LSD lockers for these smaller diffs. Mike at Journey has done several. He would know more than I would. Getting long winded mark ill pm ya.

 

[markmitch]

First year of the Envoy was 2006.

 

[tungtide]

Goes to show ya how much I know. Guess it must have been a 2006. As stated bought from a private seller. Maybe he was enjoying my ignorance. Have decided to start looking for another one.

 

[sixsix]

Wiki says:
The GMC Envoy is a mid-size SUV, manufactured and marketed by General Motors for model years 1998-2009 over two generations.

 

[chuckybob]

A pic of the beginning. Side by side shiny aluminum vs dirty cast. Had to change front yolk, shifting diaphragm was removed, new seals paint few other parts then it bolted in place.

Did changing the front yoke require resetting preload?

 

[tungtide]

Can’t answer honestly as I had Jeff from Georgia do everything as he was installing the limited slip option. Jeff is one of two guys in us that manufacture lsd for the 7.2 front diffs. I got this lead from Mike at Journey off road. Since then I have lost contact with Jeff. My phone died and all numbers were lost.

 

[chuckybob]

Tungtide, thanks for the pics. They were a huge help in understanding the swap. After agonizing over the potential swap and reviewing threads here and on the S10 forums, looks like:

• "Simple" swap is only possible for GT4 RPO option (3.73:1 differential)
• Front driveshaft yolk must be swapped to Astro/Safari/Bravada model
• Vacuum diaphragm must be removed from s10 differential
• Axle tube must be swapped to Astro/Safari/Bravada model - This will remove front locker option but improves reliability
• Differential mount from Astro/Safari/Bravada model must be kept, or will cause premature wear due to incorrect mounting angle
• Worn engine mounts may prevent install, clearance with oil pan may be an issue
• Second-gen S10 differential case with ZR2 4x4 Manual option is always cast iron, others vary

Questions:

• Bushing from Astro/Safari/Bravada model must be maintained?
• Compatible 3.73 iron diff case available on other models/years? Would be great to just swap in an LSD. Looks like maybe Envoy? Front differential
• Am I missing anything here? What's going to bite my butt if I attempt this?
• Is there anyone here with hands-on experience with this swap or maybe a build thread that I missed?