Stock torque arm, aftermarket torque arm... same vibrartion, everything is tight.

I was thinking maybe both transmissions have a bad tailshaft bushing or something... how would I check that

How are the rotors? If they have bad corrosion, pieces of the vane in the fronts can rust off, and pieces along the edge can flake off making them oob. Because of their rather small diameter, they won't show vibration until high speeds. Also check the back side of the front rotors to be sure nothing is stuck in the cooling vents that could cause it to be oob.

The rear are a single solid rotor, iirc. But they should be inspected for excessive rusting/flaking along the edges.

Another thing, check the clutch friction disk to be sure it has not lost a chunk of lining.

If one or more wheels were repaired, I would swap on another set of wheels & tires. You don't know if they are oob from welding, and balancing may not eliminate the oob at high speeds, although it will feel balanced at lower highway speeds.

Doesn't sound like an issue with the trans. Did you check the u-joints, driveshaft play, pull the driveshaft and spin the rear to see if the brakes are grabbing unevenly. See if you can have someone follow you on the highway and watch your rear wheels at 70 mph to see if there is any wobble at all. Are the rotors/wheels seating themself all the way on the axle flange? If there is any rust buildup on the flange the rotors might not seat all the way making it uneven. Definitely try swapping wheels/tires with someone if possible to help eliminate wheel/tire/balancing without spending too much time or money.

who wants to swap wheels with me? :O I also removed the whole rear to have it rebuilt... so i put the rotors back on also. but I should check the brakes

It ain't rotors unless they aren't seated right, and you'd know that by now. Rotate front to rear and see if it changes. If it does you found it if it does not you likley elimiated wheels/tires.

Here, this chart is great.
http://www.tirerack.com/images/tires/vibechart.pdf

I put 2 new tires on the back, balanced them and checked them. Same vibration. so I rotated the tires, checked all 4 again, all good... same vibration

Then tires/wheels are not the issue. Move on to axle runout/bearing play and driveshaft/u-joints.

Have you checked to make sure the rear is square in the car? With all the work you've done, maybe the rear is not located properly under the car and is causing a bind in the driveline at speed? Measure from the center of the front wheels to the center of the rear wheels. Should be equal from side to side or very close. This is a long shot and there would have to be a pretty big difference to cause the problem, but ?????

Chris

new bearings, same vibration. 2 diff driveshaft, same vib. put 2 new u joints in my steel driveshaft that was balanced, same vibe....

axel runout?

I'm out of ideas. But I sure am interested in knowing the cause and solution to this problem!

One last thought....

I once had a similar problem on a chevy monza. Balanced and re-balanced the tires, but a high speed vibration would not go away. Turns out that one of the tires was not round. I noticed it when the car was jacked up one day and I spun a wheel and I could see the out of round. Balanced, but out of round. Replaced the tire and the problem was solved.

Ok, now I'm out of ideas......

You'd likely see that on the balancer and that fact he rotated tires and no change eliminates tires.

and I replaced 2 tires and had them on the back. so that eliminated tires... next week im bringing it in to do inner and outer tie rods (they lock nuts are ceased, could not align it)... so im going to check the axles

check for play tailshaft bushing to yoke @ rear of transmision.

when trans replaced, the trans wasn't hung from input shaft was it? possible slightly bent input shaft?not likely though.

also check to make sure locating pins in back of block are through the trans, if pushed into block can cause trans to be off-center(then the input shaft will be forced to ride @ a slight angle to engine,tearing up pilot bearing and possible clutch disc to pressure plate contact in nuetral

^^also good

A little heat doesn't help that?

they were bad... I dont like heating up suspension parts :) haha. my uncle owns a garage so I get parts cheap. Im just going to get new ones.

my thought right now is something in the axles or possibly a tailshaft bushing... maybe they were bad in both transmissions

sounds in the area of driveline angle / pinion angle / rear end centered. If its getting worse when the clutch is disengaging / or disengaged then your on the coast side of the gear.

you said your pinion angle is at -2, so thats good but if the rear end isnt centered, do you have an adjustable pan hard bar?

also what s.j. sleeper said about the yoke

I have an adj panhard bar and I centered the rear using that pendulum method as best as I could. that didnt change the vibration at all. Like i said the vibration is BAD when the clutch is DISENGAGED (Pedal in).

Im going nuts, I seriously like replaced everything... :( I hope its the tail shaft bushing or an axle thats kinda bad, I Just want to find the culprit!

like i said before.... check the locating pins on trans, possible input shaft/trans alignment or tailshaft bushing.

if you just want to eliminate a possibility, and feel like driving down to hamilton, you can throw my oem wheels on and see if it helps........

Unless you are actully looking for an out of round, I doubt you will notice 3/8" run out. And the guys balancing the tires probably wouldn't notice either. Its not obvious until something is held near the tire as it spins to see the gap change.

keep on looking, the problem will be found eventually.

Do you have access to a roadforce balancer?? Might want to try to road force balance your tires, it will tell you where to put each tire on the car to get the least amount of vibration. It measures tire/rim runout and will tell you if a tire has too much runout as well...might want to give that a shot mayybe help reduce the vibration.

I have a similar problem at higher speeds, vibration is much worse when you put the clutch in because it doesn't have the engine to absorb the vibrations anymore. Wouldn't this problem be centered around the driveshaft/tailshaft bushing area because if it had to do with the wheels it wouldn't get worse with the clutch disengaged?

His problem is not tire balance. He replaced 2, no change. He rotated, no change. He's very likely got a drive line issue

My 10 years in the business says otherwise, but maybe I did a better job than others. So maybe. But rotation would have highlighted that in an instant as the vibration would have changed.

i roadforced all tires, no issues. its driveline.