When I start the car it is noisy/grindy/vibrating in the rear. When the car gets warmed up the noise goes away or after you drive it a little. This is my first RWD car so idk much about them yet. I was thinking I might just need to change the diff fluid?

Another thing I noticed was that it's really rough ride in the back and it makes a clanking sound when going over a speed bump.

 

If its a vert then the rear camber links are likely going out. As for the grinding, does it only grind when you drive it? Im guessing that it is and if I was you I would give a fluid change a try. And if it has a limited slip diff make sure you use the lsd additive for it. Easiest way to check is to jack up the rear of the car and spin one wheel and if the other spins the same way you mostlikly have an lsd.

 

Thanks for the help. It's an 88 vert, which means it has the 3.9 trans and no lsd I believe. I'll try that trick though to find out for sure. I attempted to change the fluid, but I couldn't get the darn plug out, so I'll have to wait. Is the trans from the 88 vert a sought after piece or is it garbage in the first place? The gears seem to be so far apart and fifth is practically useless IMO.

I'll also take a look at the rear camber links then, thanks again.

 

I'd check the diff oil for metal first. If you can't get the plug out yourself, take it to a shop and have them put it on a lift. It's much easier to get leverage on stubborn plugs that way.

The diff and transmission are two separate things. The 3.9 final drive is determined by the diff, and the transmission itself is basically the exact same one found in all NA FCs. The 5th gear ratios only changed slightly between series, and not enough for you to notice if you changed it out. 5th gear isn't for acceleration anyway; just highway cruising.

 

Wow, I didn't know the diff is what contained the final drive ratio. Sorry for the confusion. The car goes in for inspection on Wednesday so i'm going to have them loosen the plugs on the trans and the diff. I know this has probably been covered, but can I change to the turbo 2 diff? Or will that not bolt up to the NA drivetrain? I am looking for a diff that allows the car to drift, yet mostly stock since it's my daily driver too. Is the 4.3 a lot quicker acceleration? My friend has an NA, but his is a coupe not a vert and it just seems quicker than mine, is this why?

 

You can't easily bolt in a 4.1 TII LSD. The diff flange is different, so you would need a custom driveshaft to retain the NA transmission too. 4.1 NA LSDs however will swap in directly.

The only car to get a 4.3 LSD was the S5 GTUs model, which is semi-rare. Your friend probably just has the 4.1 open diff or LSD found in all other manual coupes. But combine that with 2-300 lbs of less weight, and you end up with 1-2 sec faster 0-60 times. Weight changes significantly affect how fast NAs get off the line due to their lack of torque.

 

^^Thanks again rotaryrocket, you always have constructive and helpful posts for me.