pinion angle help please

Reply Subscribe

Thread Tools

Search this Thread

Jan 16, 2015 | 10:27 PM

crispytoast

Thread Starter

Staging Lane

iTrader: (17)

Joined: Jan 2008

Posts: 98

Likes: 0

pinion angle help please

I installed a quick performance 9", the tq arm mount that came with the housing has adjustable hiem joints on it so i adjusted them to obtain a -2 pinion angle and all was well until I installed a bmr tq arm relocation transmision crossmember and poly tq arm bushing. I have put the tq arm on all but 2 of the holes on the crossmember and obtained pinion angles of between 1 and -8 and can not seem to get rid of very harsh vibrations at speeds of 75+mph. Any of you have any suggestions? The quietest it has been is when the pinion angle was around -4, is that too much?

Jan 17, 2015 | 10:03 AM

guppymech

12 Second Club

iTrader: (7)

Joined: Jan 2010

Posts: 1,621

Likes: 3

From: Chicagoland

You want the centerlines of the trans yoke and rear pinion yoke parallel. See this tech article at Hurst Driveline, they have a couple other related articles too.
http://www.hurst-drivelines.com/?p=640

I don't know about the BMR TA relo trans mount but my UMI one positioned the trans 3/8 inch lower than the stock trans xmbr. I measured the difference from the trans to the chassis and shimmed the trans mount up to correct the difference with the UMI mount. Don't assume the trans is positioned the same with the BMR xmbr as with the stock xmbr.

Jan 17, 2015 | 11:36 AM

01ssreda4

TECH Senior Member

iTrader: (96)

Joined: Aug 2007

Posts: 24,241

Likes: 89

From: Turnin' Wrenches Infractions: 005

Quote:

Originally Posted by guppymech

You want the centerlines of the trans yoke and rear pinion yoke parallel.

This is the simplest way to put it!

Jan 17, 2015 | 12:07 PM

Bob@BruteSpeed

LS1Tech Sponsor

iTrader: (16)

Joined: Mar 2003

Posts: 21,020

Likes: 35

From: Roanoke, IN

Have you checked to see if you need a longer driveshaft? The nine inch rear in these cars typically require a one inch longer driveshaft, and having one that is an inch too short can create the driveline vibrations you are experiencing. Bob

__________________
ATI ProCharger and Moser Sales 260 672-2076

PM's disabled, please e-mail me
E-mail: brutespeed@gmail.com ob@brutespeed.com
https://brutespeed.com/ Link to website

Jan 17, 2015 | 03:16 PM

BigDB

TECH Enthusiast

Joined: Jun 2006

Posts: 594

Likes: 0

From: Enid, OK

Measure before getting a driveshaft. I went off the recommendation of 1 inch longer and had one made and now I need it shortened. Iv got maybe an 1/8 inch before the yoke bottoms out in the trans when installed

Jan 17, 2015 | 07:20 PM

guppymech

12 Second Club

iTrader: (7)

Joined: Jan 2010

Posts: 1,621

Likes: 3

From: Chicagoland

I referenced the wrong tech tip in my earlier post, this is the correct one.
http://www.hurst-drivelines.com/wp-c...roc_111606.pdf

Jan 18, 2015 | 09:34 AM

crispytoast

Thread Starter

Staging Lane

iTrader: (17)

Joined: Jan 2008

Posts: 98

Likes: 0

Yeah I had a new drive shaft made when I put the 9" in. Today I am going to put the stock crossmember back in and measure distiance between garage floor and a point on the tailshaft on the trans. Then put the bmr crossmember back in and shim appropriate. That has to be it because I didn't have any problems until I put that relocation crossmember in.