To update everyone. After a Yank 4L80e C5 transmission conversion I had horrific vibration....in park....and when driving!

So.....I pulled the setup. Sent the Drive Shaft Shop drive shaft back to check for balance....it was fine.

Sent the rear bellhousing, Rear torque tube bearing carrier, rear flex plate, converter, transmission bellhousing and transmission pump back to Precision Industries (Terri made all the parts for the conversion). Everything checked out as far as alignment of the components and the torque converter balance was fine.

I also eliminated the "two piece" Yank torque tube.(it was .150 out of round) I shortened a new torque tube and mounted the complete setup as GM designed it.

I also replaced both rubber drive shaft couplers with new GM units. All bearings were changed, I also checked for straightness of the torgue tube input splined shaft....all checked good...

Quess what.........I still have horiffic vibration....

I have replaced and checked all the parts that I can...all components have been checked..........

I am at a loss.......I dont know what to do....I am ready to hang up this whole project after a year and 12,000 dollars later...

I am running poly engine mounts... evrything else....(engine and engine flexplate are the same as when I ran the 4L60e and didnt have a problem.

Any ideas?

tom

 

Torque converter???

Never mind, I see you checked that.

 

Just for the hell of it I am going to unbolt the converter from the flex plate and then run it to see if I get vibration.

I have to pull the trans and the torque tube to unbolt it as this conversion the access hole is on top of the bell housing.....not the bottom!

This would eliminate the torque converter as the problem!

Tom

 

Man, I really gotta feel your frustration on this one Tom Best of luck.

 

For what it's worth: I don't know what our C5s use for U-joints, but I've concluded that I once caused myself such a mysterious vibration problem by over-tightening the U-joint U-bolts when reinstalling a drive shaft. This prevented the needle bearings in the U-joints from turning freely - binding, actually.

 

We don't have U-joints in the driveshaft ... we have a "torque tube" with a propeller shaft inside. The only "flex" are the two rubber "guibo" installed at the ends of the shaft,

 

Two thoughts ....

First, this seems stupid, but are you sure the engine doesn't have a misfire ?? Don't know how long the project took you, but if the engine sat for a while, maybe a plug fouled, or an injector gummed up ?????

Only other thought is .... could the poly mounts somehow be "distorting" the alignment of the engine with the drivetrain ??? Can you loosen them, or put the OEM mounts back in and see if that eliminates, or at least changes, the vibration ???

I'm just throwing out ideas .... seems like you've covered a lot of the bases already.

 

What about loosening the collar on the torque tube (where it connects to the engine), and manually rotate the wheels to let the shaft self-align. then re-tighten the collar. Just a thought.

HTH.

Good Luck

 

I would go back to the TC....send it to someone other than Yank to verify...I suggest FTI in FL, they will tell you if it is OK. Reason I say this is having dealt with similar issues with Yank...send it back, they claim nothing wrong & still charge $250 to cut & inspect & then send it to FTI & find the snout welded on out of round, etc. Just a thought.

 

I think I read in the manual that they index the flex plate to the converter and check the vibration to find the optomum location, but that is for fine tuning. I would say check the TC at an independent vendor also.

Good luck and be sure to let us all know what you find.

Mike V

 

I did some more trial and error today...pulling the unit in and out.

I do think the poly mounts are transmitting vibration throught the car. Not really an alignment problem.

I did have the converter check by Precision Industries. This is who made the converter .....not mike. I trust Terri...at Precision. He said it was fine. He did "polish" the hub.

I bolted the setup in the car without the driveshaft in .....but everything else was installed. There was some vibration but minimal. When I put the driveshaft in ..not hooked to the converter the vibration was definately more noticable. When I put my hand on the torque tube at 3000-6000 rpm with the driveshaft in I didnt feel excessive vibration......

Engine mounts...making things feel worse than they are?

I think I may replace the driveshaft with a GM unit...although not as strong it will be less mass rotating around....I need to find a late model with the billet ends ...not the cast early style units!

Ideas?

Tom