Tomulrich

Well I finally finished my 4L80e C5 conversion. I am using a Drive Shaft Shop Driveshaft with the BMW replacement rubber bushings front and rear. I replaced all the bearings ...using RPM's rebuild kit.

I have horrible/ untolerable vibration over 2200rpm. You can feel the vibration with the car on jack stands and no wheels on it.....in Park.

The driveshaft does have a metal weight on it...so I assume it is balanced?????

The converter is a Precision industries 5 clutch unit. It also has a weight on it......the only thing spinning is the drivehsaft and the torque converter.....

On the 4L80e Conversion the transmission and rear differential is solidly mounted to the rear cradle........I know you would feel for vibration through the car ....but I wouldnt expect to feel as much as I do.....

Anyone had problems with larger diameter(3") driveshaft from Drive Shaft Shop??

I quess the only way to know if it is the driveshaft is to pull the transmission and Torque converter and run the car on the jack stands......if the vibration goes away....then it either the converter or the fact that the trans and differential is solidly mounted to the cradle.....


Am I missing something here? Please help..

roythomas

glad you have it back !!! sounds like you got figured out with pulling out will give you a idea !!!

STEALTH 99 C5

Tom , I hate to say it like this , You should've went with an RPM conversion in the first place , and you wouldn't have all these problems . My RPM 4L80E conversion ( running a Driveshaft Shop piece ) has performed like it came that way from GM . Sorry to hear of your setbacks . Hope you get it squared away soon . Maybe it's the within the Yank system somewhere , the Driveshaft shop does excellent work , never heard of anyone having a problem with them .

ajg1915

Is the vibration constant after 2200 RPM or is it only at that spot ?

Tomulrich

Its constant after 2200 rpm...raises with rpm. If I had known it was going to be this much custom work and head aches I would have kept the 4l60E the car.

Its either the drive shaft or torque converter. I will need to pull everything out and see if I have vibration with the TT/ driveshaft.

Thanks for the advice

Tomulrich

stealth

What differential mount are you using? One of my concerns are the Yank system mounts the trans and diff to the cradle which transmits vibration through the car....but It shouldnt be as much as I am feeling.....because other cars have trans solidly mounted....something is off....

Thanks guys

0rodney@rpmtransmissions

Tom I suggest unbolting the converter and push it back away from the drive plate then start it up. This will give you an idea where the vibration is for sure.

Tomulrich

This morning I unbolted the transmission and differential (keep in mind this setup bolts to the cradle) from the cradle the vibration is better but I can still feel it....its definately something out of balance in the driveshaft or converter.....it is just pronounced when everything is bolted into the cradle.

Next step is to remove the trans/TT and unbolt the converter.....this will isolate the driveshaft.....I should get the answer....Driveshaft assembly or the converter. .....

Major PIA the converter the flexplate access hole is throught the bellhousing is on top with this conversion...I have to pull everything to unbolt the converter to isolate the driveshaft...

Tom

ajg1915

Yeah sometimes being first into doing something is not the best. I have learned to follow the crowd after some of my previous experiences.

Keep us posted of your progress, hope you get it all figured out.

Tomulrich

I took the TT apart and noticed the BMW rubber couplers were rubbing the inside of the TT. Something is either vibrating or the Couplers are expanding under RPM

Tom

ajg1915

It sounds like the torque tube case is not wide enough internally or your shaft is out of round. The tolerance is like .004. Take a look at the service manual.

STEALTH 99 C5

That's why I went with the best the first time around , RPM . I know how technical Rodney is and had no reservations whatsoever when he said he wanted to build a 4L80E conversion for my car .

0rodney@rpmtransmissions

Easy stinger Thanks for the props but lets stay on topic and help Tom get his problem figured out.

ajg1915

It's never good to be a pioneer doing these conversions as I have learned first hand, from my own experiences.

BTW, RPM does do a great job.

Tom,

Have you contacted Yank about your problems ?

Tomulrich

Yes ...mike at Yank said I needed to keep the small 55mm driveshaft in the torque tube. He said he has spent alot of $$ on larger driveshafts and they all vibrate due to not having the "clutch/flywheel in the automatics to stabilize the front bearing" I am not sure what this means...but I know peple who are running the larger diameter driveshafts with no vibration.....

I am clueless as to why this is happening.

ECS thinks it the 2 piece torque tube....but when bolted together it doesnt move.....the shaft spins freely and alignment is perfect...so I am not sure how this effects / causes the problem I am having.
The tube is the stock unit so the diameter is the same as stock vette ....how could the rubber bushings be rubbing in 3 areas ..the areas of smaller diameter not the larges diameter of the rubber coupling.......how is this physically possible.....even if things were aout of alignment the largest portion of the rubber couplers should have been rubbing also.....

its easy to blame a new design.....but I need some more info to confirm this...and so far none of the explinations can explain what is occuring....

please keep the posts coming....I need help on this one.....I am ready to scrap the whole project.

Thanks Tom

ajg1915

It would sure help if you could post up some pictures of the problem.

Also, the torque tube supports not only the engine but the drive train as well.

I figure it must be flexing where they are joined together.

Skunkworks

Purely speculation on my part... but with torque tube no longer rigid or one solid piece. Is it possible that torque tube is no longer true or straight? It takes a very large a surface (bearing or collar) to ensure no misalignments and especially as power goes up. What I'm getting at is if carrier (torque tube) is just slightly off in relation to drive shaft, with that much length, failure can be expected (first indication being vibration).

This is purely from memory based on pics you posted up some time ago.


Mike

Tomulrich

appreciate the replys and posts
The TT is bolted together and cannot flex as the bolts that old it together are shoulder bolts and are the exact size of the holes they go trough....the unit cannot flex.

when I check TT measurements there seems to be no out of alignment issues....this still wouldnt cause the couplers to rub on the smaller diameter of the rubber couplers and not the larger diameter portion.

There would need to be some serious TT alignment problems to cause problems..

I will post some pictures later tonight or in the AM
Keep the help coming

Tom

Tomulrich

Not ecs......but RPM in pevious post...sorry