My son just replaced the front diff in his 2000 zr2 with one from a 98 blazer, and his actuator. He was complaining the truck seems to jump around and pull to one side when he puts it into 4x4. I went for a ride with him and when he put it into 4x4 i could hear the front end clunking and the truck jumping, mainly to the right. Also, it would not come out of 4x4 until we backed up a bit then gunned it going forward. It the banged back into 2 wheel drive. Lucky were on an icey street and not bare pavement. To me it seems like the front diff is not the same gear ratio as the rear. He says he checked the diff serial numbers and they came back as the same ratio as the rear. Anybody have any comments or suggestions........Needd help asap.

 

ZR2 differentials are different than non ZR2. Among other things, they have a larger ring gear. Look on your glove box door for a white sticker that has a bunch of 3 character codes, (RPO codes). The sticker tells every option that your Blazer came with originally. Post all codes that start with the letter "G" (or post a picture of the sticker) and we can tell what axle ratio you had originally.

 

Sounds like the front diff has the wrong gear ratio, 3.73's are stock in ZR2's and fairly rare in non-ZR2's.




You should not use 4wd at all until you get it sorted out or you risk serious damage to the transfer case and or diff.