rear end shift
 

I have an 87 TII. When I am driving on the freeway I can feel the rear of the car shifting between two different positions as something is lose. Does anyone have any idea what this might be?

It is very common for the front diff mount to break. Look up at the subframe from underneath, where it dips down. Mount is located there. Pry up on the diff to see if the nose moves.

After installing a new or used front differential mount, look into installing a pinion snubber.

coxxoc: Pinion Snubber Install

(NOTE: This is not an alternative for the front differential mount. They both must be installed and in working order for the pinion snubber to operate properly.)

Thanks for the information. Right now I am replacing the clutch. The drive shaft and exhaust are removed so it should be easy to check the diff mounts and possibly install a pinion snubber. I have never installed new diff mounts. Is it a tough job?

Whether you're replacing the front differential mount or the rear differential mounts, you'll still have to drop (or at least lower) the rear subframe. Dropping the whole differential is necessary when replacing the rear differential mounts. If you're good with your hands and only have to replace the front differential mount... Then you won't have to drop the differential.

Here's a front differential mount replacement write-up. (With pics)-> https://www.rx7club.com/2nd-generation-specific-1986-1992-17/front-differential-mount-replacement-write-up-pics-574592/

rear end problem
 

Hello again. I checked the front differential mount and there is no evidence that it is damaged in any way. The rubber looks good but I did not take it off. I pryed up on the diff with a screw driver as suggested and it seems solid. I thought I'd give a little more history on this situation since it may help. The original differential was replaced with a used one about five years ago and that is when this problem started. I have taken the car on some long rides like from LA to Montery and it doesn't seem to be hurting anything but it is very annoying. What happens is the rear end shifts between two positions when you turn the wheel very slightly. When the rear end shifts to the left a chattering sound can be heard. When it shifts back to the right the sound goes away. If I have to take the sub frame down to fix this now would probably be the time to it since I already have the exhaust and driveshaft off the vehicle. Any suggestions or advice would be greatly appreciated.

You might as well drop the whole rear subframe and differential. That way you can inspect EVERYTHING on the rear. Especially inspect the rear differential mounts and mounting studs that are attached to the car.

It sounds as though one of the mounts is broken. The front is common, but if it isn't (this is very surprising!) that only leads to the two rear diff mounts or possibly the bolts. A thorough inspection of the diff, subframe and all the links is what is needed. Make sure to check the big bushings on the trailing arms, and the lateral links (maybe the bolts are missing!).

Thanks again. I won't be able to start on this for a few days so I will let you know how it goes in about five days. Hopefully I will be able to show pictures of the project. I am still new to this site and I haven't figured out how to upload pictures (won't accept mine because they are too large).

Hello again,

It has been a lot longer than I thought getting back on this project. I started taking the rear subframe off and I noticed that the two nuts securing the front diff mount to the subframe were LOOSE. I'll bet that this is problem. Now I'm trying to figure out the easiest way to tighten them. They are very difficult to get at which is probably why the guy who put the new differential in didn't get it right. Thanks again for your help. I would have never found this on my own.

You may have to take the exhaust off( y pipe at least).. take the subframe bolt off the driver's side and undo the shock.Undo the lateral link(link from subframe to car)
remove the caliper off the subframe.(DR side)
loosen the other subframe bolt (pass side)
pry the driver's side down and you can see the Front diff nuts on the subframe.2 17mm nuts
you can get a 12 inch extension and impact in there..ZAAAPPPP..done.

^ Exactly how I did it.