Goldfinger911

iTrader: (24)

I have searched and found several different answers to this question....

I did a T56>TH400 conversion a couple months ago. Everything went very well. I had a custom driveline made to the proper length, a torque converter built with the proper spacer, a SFI flexplate from Hughes (with the proper holes so the converter bolts lined up perfectly too) I didnt skimp anywhere. I installed the Th400 with a 1" spacer between my 6-speed crossmember and the mounting surface of the TH400. I have a vibration/resononance when the car gets past 60mph or so; on the gas or coasting. My pinion angle is -1.5 degrees.

My questions are:

What angle should the driveshaft be with respect to the output shaft of the TH400? Zero degrees? so effectively a straight line from the output shaft down the drive shaft?

Is a 1" spacer enough? I have found people claiming anywhere between no spacer when using a Silverado 2500 mount (which is the same size as the Energy mount I have) to a spacer size up to 3" !!

Has anyone cured any vibration with changing the spacer size and aligning the tranny output shaft to the drive shaft?

Thanks in advance.

Goldfinger911

iTrader: (24)

Hmmm... Well with the help of Google... I found this:

http://home.flash.net/~ivc1/cobra/irsvibes.html

Anyone ever go through this problem/solution? This is for an IRS, but I think the principle is the same.

veee8

iTrader: (40)

I have the Spohn spacer and Poly mount, zero problems with the setup. First crossmember was a GM T56, then the Midwest chassis, and no problems doing this.

Goldfinger911

iTrader: (24)

I was just looking at the Spohn spacer on their web page. It looks like it is larger than 1 inch. Any chance you could measure it? Or do you remember the dimensions?
Thanks man.

6LTRiceater

I set my pinion angle at 2.5 deg. 1.5 deg doesn't sound like enough.

Do you have adjustable LCA's?

Goldfinger911

iTrader: (24)

I do not have adjustable LCA's. However, I am running a Moser 9" with relocation brackets welded on that have two hole positions. I have BMR boxed LCA's.

So, 2.5* down on the pinion. I am curious about the angle from the trans output shaft to drive shaft. I appears that these two settings need to equal zero, or close to it. (+2.5 and -2.5) ??

veee8

iTrader: (40)

1.5" thick spacer, and a standard energy suspension poly mount

6LTRiceater

I think it's a reasonable assumption. I never really worried about the trans output angle, to be honest, but it should end up close to what the pinion angle is.

BMR Tech2

iTrader: (5)

Take a look at this video. It sounds like your pinion angle is off a little.

http://www.bmrtvonline.com/video_detail.php?mId=3788

code4

iTrader: (30)

I had the same exact thing happen. Someone said that having poly engine mounts & tranny mount will cause a vibration. It didn't make any sense to me but I went to napa & got a soft rubber tranny mount. It fixed it!

I have seen others post here that poly mounts work good for them. IDK, but in my case this absolutely was the problem.

WYATT318MOPAR

iTrader: (28)

My car does the same thing so don't feel bad I have determined it to just be the nature of the cars setup. I have changed my pinion angle several times seems to be the best at around 2* neg on the rearend. I am running poly motor and trans with a chome moly driveshaft, have thought several times about trying a normal rubber mount on the trans to solve the problem. Also have the sphon block on a T56 crossmember have thought about welding the block to the crossmember also

MY99TAWS6

iTrader: (3)

Briing this thread back..

So what was the deal ?Should the trans and driveshaft yoke be basically zero?
We shimmed mine up using bmr crossmember and think just t56 trans mount. It took fair bit of shims to get things inline. I am fighting some vibration issues and still have few things to check and try.
Driveshaft was rebalanced. Will double check pinion angle at rear with the bmr video. Think might have it wrong.Also looking into putting rubber sheet spacers under the crossmember since torque arm is mounted to it on my 4l80swap. Another reason for the original posters question..so do I want trans to front yoke level and zero.

Goldfinger911

iTrader: (24)

You do want the least amount of angle between the yoke and driveshaft, yes. However, on our cars, more important that the yoke to driveshaft angle, is the fact that the rear of the TH400 is spaced properly so that you are not preloading the motormounts. This can cause vibration and drastically shorten the life of the mounts (which are a bitch to change with headers). You want to mount the tranny such that the motor mounts are floating in the middle essentially.

If you are using a 6-speed crossmember with a TH400, you will need 1"-1.2" spacer. I used a piece of steel square tube that I cut and drilled to fit between the tranny and the tranny mount.

The angle to measure carefully and set accurately is the pinion angle at the other end of the driveshaft. This may take some playing with to get it right.

Lastly, are you using a poly tranny mount? If so, you may feel a little more vibration that if using a rubber one. I use an Energy Susp one and have a slight vibration on decel.

Adam Gambuzza

Do you have a part number or year / make / model? I went to NAPA yesterday and they needed more info. I just did a TH400 swap and I'm getting a bad vibration too.