skinny z

I had originally started this thread in the Tech/General Engine section. Thought I'd repost it in the transmission and drivetrain forum. Someone may find it useful.

It's been a long time however it looks as thought the vibration issue has been resolved.
Unintentionally no less.
For the record, EVERYTHING in the drivetrain has been removed, replaced or rebuilt at least once. Check out the 'vibration' thread in the Tech/General Engine forum for the list.

https://www.thirdgen.org/forums/tech...vibration.html

I've been driving with this problem for a few seasons and had resigned to myself to accepting that this is how the car is going to be.
Recently I had a 700R4 3-4 clutch go away. This trans with the TCI Street Fighter convertor helped the car to it's first sub 13 second pass.
I found a low mileage 700R4 from a forum member, did a quick shift kit, basic mod procedure and installed it with same convertor. Now it only took 4 quarter mile passes to cook this transmission ( that's another story ) however, the vibration is GONE. I have only 1st and 2nd gears to test with but I can say at all previous test rpm's, there is no longer the ' harmonic vibration' that was painfully obvious before.
I can come to two different conclusions. Two previous 700's ( I'm on my third ) and 3 different convertors all combined to produce the vibration. This I find unlikely.
Or the relationship between the flexplate and the convertor had a stacked up tolerance with respect to balance ( and I have been using a new SFI flexplate and new TCI convertors as well as an engine balance). After the latest installation, the convertor and flexplate were bolted together not using the previous index marks. Now it's smooth as silk.
After investigating further and going through the GM manual, I've come across a chapter titled " Flywheel Assembly/Torque Convertor Clutch Vibration Test Procedure ".
Who knew?
The test describes checking for vibration in park or neutral, decoupling the torque convertor, rotating it 120 degrees and hooking it up again. Check for the vibration and repeat the procedure if the vibration is the same or worse. Looks like when I reinstalled this latest trans and convertor I inadvertantly came across the best connection.
It was a long time coming. And expensive too although I must say I've collected and installed a lot a top quality parts along the way.

skinny z

A little follow up to the story.
Having learned a lesson regarding indexing components during disassembly, I was smart enough to mark the torque converter/flexplate relationship in preparation for the latest transmission install. This trans was a servicable unit that I put on the shelf during the vibration testing because I thought that it might have been damaged in some way.
Reassembly with the index marks and the vibration is still history.
That sure was a lot a work for nothing.

kenbob

Is this the same for manual transmission cars with a clutch also is the drive shaft clocked as well. sorry having issues after new engine mounts and tranny mount engine rubber trans poly

Aviator857

Interesting how easy it is to get out of balance. When I rebuilt my transmission years ago I discovered at some point before I owned it (or even maybe new?) it had been assembled with the trans dip stick flange between the engine and the trans. My transmission builder said it didn't do good things to it to have been out of alignment all those years. Oddly it didn't vibrate.

skinny z

There's no such test/repair procedure in the GM manual for manual transmissions as there is for automatics. At least not that I could find.
Somewhere in this forum is a thread about the poly transmission mounts and vibrations. Various conclusions were drawn with some saying the vibration went away when the mount was converted back to rubber.

Tootie Pang

iTrader: (2)

There is no indexing. Usually what happens is people put shorter gears in the back and then their factory driveshaft spins beyond what it is balanced for and they get the vibration.

kenbob

So I tested the theory that the polymount from energy suspension was made out of spec. Off of the car it's almost exactly the same but mounted the gap between the trans and crossmember is much bigger I believe that the top plate that preloaded the polymount doesn't allow it to compress like the factory rubber mount. The factory style rubber mount for my car sits at 1 3/4 inch mounted the polymount was a little bit over 2 1/4 inch so it raised the tail shaft by over a half an inch this completely messing up my driveline angle and causing a severe vibration. If I had an adjustable torque arm I could line everything up and be fine but since I'm using a stock one I went back to a factory rubber that I bonded with windo-weld urethane it works fantastic and has taken away the vibration. Although I will hold onto the polymount for when I get an adjustable torque arm. Thanks everyone for your help, time, and insight. Also I did reclock the driveshaft to see if it helped and it did a little.

84 z28

Adjustable torque arm doesnt fix everything, I have been through 3 different driveshafts and 2 different rear ends and the poly mount still picks up on vibrations. The energy suspension mount was by far the worst, I now use the prothane mount which is better but still picks up vibrations. If I ever feel froggy I'm going to try what skinny z has tried with the convertor over the winter

DaveyDug

iTrader: (3)

I left the preload plate out when I installed my ES poly mount because I saw how it was going to affect driveline angle. It works beautifully with no vibration whatsoever.

kenbob

Well I have installed every single 1LE part made except for the Corvette front brakes my car was a weird factory special order 36mm front away bar and 24mm rear with a 9-bolt posi. So it came with a WS6 option but ordered with 15 inch honeycomb style wheels. I have the aluminum driveshaft but it needs new U-joints and a balance and it's hard to find anyone to even touch an aluminum driveshaft. I know less rotating mass is less vibration so I can't wait to install that final part. My car was a 86 LB9 t.p.i auto now it's a stealth ram T5 with a 3.70 gear 9-bolt

kenbob

So important information here after talking to the representative at the energy suspension company apparently most of us have purchased the wrong mount if it says GM transmission mount and 1108 it's the wrong one this is for older cars and trucks they have a specific mount for 82-92 Camaro/firebirds it's part number 3.1142R it is specifically made to not transfer vibration and is the correct height

kenbob

Find this one it says GM trans mount 3.1142R

SbFormula

From summit racing site. (Ignore the G it's for black color). Information was confirmed to this date by catalog look-up. The 1108 and 1142 are the same height. They differ in stiffness only:
Q:

what different mount heights for the stiffest flexible GM trans mounts for road course race cars?

Asked by STEPHEN on December 02, 2018
A:Hi Stephen. 3.1142G is the softest version of our GM transmission mount. It uses a 60 Shore A durometer, with a compressed height of 1-15/16". We offer an identical, stiffer mount, which instead uses a 70 Shore A durometer, 3.1108G. The last option we offer is a 70 Shore A mount with a compressed height of 1.625", part # 3.1158G. Give us a call at 888-913-6374 for more information. Thank you.

Energy Suspension Answer - December 03, 2018