I just completed the LSD swap into a 3.9 and then went back and read the instructions on the USMB. Ended up doing everything right but noticed it doesn't say to pull the outer bearing races for the axle stubs. Have people being doing this or have you'll been getting away with mis-matching the 3.7 bearings with the 3.9 outer races?

As far as I know, and I have done about 6 of these conversions, the race and bearings are the same. I have never had a problem with any of the conversions.

Cool, thats kind what I thought, but I was just checking. I was taught that bearings break in / wear differently even if they are same, so if you mix match bearings and races your run a chance of destroying the bearings.

 

As far as I know, and I have done about 6 of these conversions, the race and bearings are the same. I have never had a problem with any of the conversions.

It is generally advised that you use the races/shims and chunk from the same differential. It might be worth the $ to have a driveline shop make sure the lash is OK unless you're handy with Prussian Blue (I'm not).

It is generally advised that you use the races/shims and chunk from the same differential. It might be worth the $ to have a driveline shop make sure the lash is OK unless you're handy with Prussian Blue (I'm not).

Yes, actually I use all the shims off the 3.90 and just swap the ring gear to the LSD unit. I've never had trouble with the lash since I'm using that same ring and pinion gear set. I have prussian bluing and know how to set that lash, but have never had to.