i have an 87 iroc with 81k on it but it sat for a few years and was probably beaten on pretty hard before that point.

i put in a 86 tpi, and put in new throwout and pilot bearing. new clutch, pressure plate.

i also repacked the front wheel bearings and threw on some new pads.

when i get up to 60 mph the vibration starts. i feel it in the stick and in my seat and then the whole car starts to vibrate. nothing changes when i push the clutch in, still same vibes. and i dont feel any vibes shifting up to 60mph at any rpm, just strong steady pulls though each gear up to 3-4000rpms. then i hit 60-65 and it starts in, and stays about the same frequency up through 85-90 and thats as fast as i have taken this car since i put it together. they dont get stronger they just seems to happen faster.

my tires have been balanced and the rims are good, no bends or flat spots.

i have herd bad u joints in my cutlass and felt the same vibration (not as bad) but thats an auto and the shift from park to drive i herd the clunk. with the stick i cant hear that drop.

i was reading on here that the drive shaft can be put in 180 degrees and that will mess it up? its never happened to me before, thought they just went in... and also clips that hold the caps on? never seen those on any 80's GM ive worked on. the caps just seemed to slide on and off.

anyhow, any pointers for diag. or if the u joint/s a good place to start then ill do that.

**ALSO, the 86 tpi was an auto, i put in the pilot bearing and hooked everything up the way it stated in the book. There isnt anything i should have been particularly aware of when i was installing the flywheel was there? it lined up with the dowel on the crank then tighten everthing down right? there is no way to put it on backwards?

there were no major internal or external balancing differences between the 86-87 motors, just the roller cam right?

 

Do u have poly trans mount if so remove it a get the stock rubber mount i had alot of vibration with my t5 around highway speeds as well so i tryed everything replaced u joints cleaned the driveshaft of any grease grime an oil checke if the counter weight was on still but all in all just had to change the poly mount to rubber an it smoothed the vibration right out

 

It's the stock style mount, I crawled under the car last night to remove the trailer hitch that the previous owner put on and got a chance to check it out.

Looks like the rear one was replaced before because it says Japan on the caps. And I have roughly 1/16th inch movement on one of the axis. Any movement is bad I'm assuming that bad.

 

that's leading you to the driveline, tire/wheel assys. or rear axle. Usually the first two. And since you just changed something, you now know it's between the trans. and driveline somehow.

It's possible for a u-joint to be installed incorrectly and a slight offset correct the issue but it's a band-aid fix that really isn't correct.

Normal stuff. Potentially not original parts to the car.

Usually, it's driveline angles.
Lower the crossmember by shimming it away from the floor, drive it and see if that fixes it. A thinner mount may be an answer. An adjustable torque arm to set pinion angle is a more costly and more flexible option.

To answer your flywheel / crank questions, nothing at the bottom end is different between 86 and 87. Just the roller cam provisions at the valley of the block.

Curiosity - how thick is the mount? Any pics of the hitch?

Totally normal. The axles are retained with c-clips inside the differential carrier assembly.

 

Happened to me and I rebuilt my entire rear end because of it. It was my drums, someone painted them while they were against a wall and the paint ran down. Was off .010. If you have drums throw them on a tire balancer.

 

cant hurt

 

I don't know if these pics will show up but this is where I am seeing the movement. Right between where the zurk fitting and cap is... Is there a "proper" way to bolt the drive to the diff? Or is it self centering?

And its a rear disc setup.

 

You missing the cap and bearings off that ujoint?
Cause thatll do it!

 

Make sure your tires are all balance before you even think about changing or rebuilding the drivetrain. Had a similiar problem on my Acura TL a few months ago - figured out it tossed some weights and once redone was smooth as silk.

 

Well I picked this car up to fix up and sell so rebuilding the drive terrain probably isn't going to happen. I work at a dealership so I've balanced the tires a couple times already. I'm going to do the u joints and hopefully that does it.

The caps are there on the diff end, but I don't know how centered it is. Or if it self centers?

How common of an issue is it on these cars that the rear ends give a vibration at 60+?

 

I pulled the drive shaft and the front joint is very nimble and moves with ease but the rear one is pretty stiff on the axis that is pressed into the drive shaft. Seems like it should be pretty free moving but I got new ones. I just picked up some new ones I'm going to put in tomorrow.

I noticed that the ones I got have C clips, is there any particular way I should but them in?

 

The old u joint was missing the c clips on the part that ties into to diff. Soo with new joints and the clips properly installed, and the joint centered up properly I should have fixed the problem. Still need to get her back on the ground to drive her but that will come soon enough. Updates when that happenss.

 

isnt 87 also the first year for 1pc RMS?

 

<--- Look


I've put 3 manual transmissions in behind an original numbers matching 1986 engine.

Now you get to pick between the following two:

or

or both.