Hi,

i've recently converted my car from A4 to M6. since then, the car not anymore what can be called "streetable" under the 2200 rpm line with very bad "vibrations" that you can feel strongly with the shifter shaking in the car.

My problem is : i dont really know if this problem has happen since the conversion or it is engine related and the auto + converter helped not to feel it before.

My setup is :

stock shortblock
LE2 heads + LE1.5 cam
LT / 52 holley / 30 SVO

since i've my M6, i've used :

* stock new M6
* Mc Leod 7500 clutch
* RAM flywheel

just in case , it is not engine related , i've different questions :

1) can the RAM aluminum flywheel too light for this setup and be the cause ?
2) i've seen posts about special position to bolt the pressure plate to the flywheel. I have just bolt it without having look if there was any. can it be the pb ?
3) i've seen people talking about pressure plate bolts. I didn't have the stock ones so use some aftermarkets bolts that have threads on their whole lengh. maybe it can has caused a misalignment ?

Any idea would be appreciate. if engine related also what to check ? (would be great before having to take the trans out) MAF ?

Thanks for help.

Pierre

 

1. did you put in a pilot bearing in the back of the crank?
2. The flywheel on an LT1 needs to be balanced.... i dont know if you after market one is or not

 

yes i've put a pilot bearing

the flywheel has been balanced same as the auto flexplate

 

I don't believe the flywheel being to light would be the problem. Do you have the T56 crossmember and all the other mounts tightened completely?

 

hello jtarp : yes T56 crossmember everything is tight well.

i forgot : when i did the conversion, i didn't had the right mount for the torque arm (though it would be same), so we made one by ourself to have the torque arm on the gear box. can it be a problem too ?

 

two more thoughts
1. you sure on the quality of the tranny? maybe its bent imput shaft of something the previous owner didnt tell you


2. the tq arm mount should be fine, i just did the identical thing yesterday with mine. I accidentally got an auto tq arm mount from my t56... had to cut cut, bend grind and drill it to work, but its does.

 

the tranny was new from the shop . never had any oil in it.

thanks for the info for the mount. one thing less to worry

 

I thought pressure plate bolts were shoulder bolts used to center the plate on the flywheel. I'd check the simplest things first...replace 'em with the correct ones.

 

The LE1.5 cam should be plenty streetable and idle well at 950-1000 without any significant vibration

If you're sure that the flywheel was matched to the flexplate (you have a stock bottom end, I'm assuming?)
I'd check for loose bolts; specifically the flywheel.

Did you also switch to poly motor/trans mounts?
Are you running a base tune set up for that cam and those injectors?

 

i've not changed to poly mounts. Still original ones.

I've also thinkong about that loose bolts.

i will take the tranny off when possible to check.