I have a 1990 IROC it used to have a 700r4 i swapped a T5 in. It was running really well but developed a problem in the last year or so.

When I am driving down the road at just about any speed say 30mph in 5th gear and let off the gas sharply there is a clunk in the driveline. I think it comes from the tranny but you know how that is -- it could be coming from anywhere. Same for 3rd, 4th or 5th gears.

mods or upgrades are
- tubular LCA and panhard
- new bushings on all rear suspension
- UMI torque arm relocator
- new clutch kit
- flywheel shaved
- recent trans mount

tranny does not grind between gears, no problems shifting

the clunk can come in any gear as soon as you back off the gas.

it used to be I could idle in 1st gear no gas, and the car would drive well, now it clunks and bucks

basically drives like crap.

 

Sounds like broken tranny mount. The rubber part that connects the tranny to the crossmember.

 

tried that. replaced tranny mount a few weeks back.

it did improve some minor vibration issues but did not fix "clunk"

some more detail, I use a UMI tq arm relocator. This is one stout piece of gear. Separates the tq arm from tranny using 1/4 inch steel bracing. I have a poly mount in the tq arm mount for the UMI brace.

The UMI piece isolates the tranny from the tq arm so the only load on the mount is upstream from the engine. I thought this would make the clunk go away. It made a noticeable difference I definitely recommend this upgrade. But did not make the clunk go away.

 

does it sound like a noise from the transmission or more towards the rear of the car in the pinion area?

 

id check universal joints

 

Could it be the top of the torque arm hitting the trans tunnnel where it mounts to the diff on top? I know some have had trouble with this before on lowered cars. Just thinking out loud.

 

well I was driving down the road and heard a metal clank noise something hit the pavement. I went back and see it is the metal spacer the sits in the torque arm bracket for the UMI torque arm relocation brace. It fell out.

I don't understand how this can happen there are six bolts holding the metal brace that sandwiches the poly bushing (that the tq arm slips into) against the verical brace of the arm.

I assume the bushing is not the right one for this UMI relocator. This would explain the noise in the tranny.

I will fix this and update this thread with results.

 

Just a general FYI: At one point UMI recommended an OE rubber trans mount to lessen vibrations. I may have missed it on their site, but the following is from Ryan a while back:

Hello,

What we were trying to say was we found the polyurethane mounts such as the Energy Suspension or Prothane ones to offer vibrations. When in installed with our tunnel mounted torque arm the vibrations seem to increase and we do not recommend using these two items together on a street car. For a street car we do recommend the stock rubber transmission bushing.

We do not have any issues with this set-up and never had a complaint. It sounds like just a small issue with a easy fix.

Hope that helps,
Ryan

JamesC