I've been having constant traction issues lately and have tried about everything in the book (pinion angle related). I recently tried setting my pinion angle as shown by Rossler (measure output shaft angle of tranny and set rear in relation to it) and I couldn't get it to -2 degrees WTF?

So I measured the torque arm mounting flange on the rear (that bigass bracket that bolts to the housing) and I measured the angle of the pinion yoke. Guess what. The bracket was not built/positioned correctly by moser. There is a good 5-degree difference between the two which keeps my pinion angle in the positive 2 or so range and I don't want to thread the bottom heim joint out any further w/o risking any damage to it under launch (too many threads act as a stress riser) <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />

I talked to Steve spohn about this and have a resolution...I'm going to remove the bracket and shim the top with a washer or 2 so that the correct geometry is restored (pinion parallel to the TA mounting flange)...then I'll reset the pinion angle <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Just a heads up <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />

<small>[ November 07, 2002, 11:09 AM: Message edited by: Fireball ]</small>

 

Great info and timely too. I'm finishing a 94 Z28 with an LS1. The chassis I bought had a 9" in it with an Spohn torque arm. Just got through installing a new pinion yoke on it for a 1350 joint.

Anyway was under it last night checking angle with the method you mention and it looked close to -2 degrees. However that was only due to the fact that I had lowered the front mounting at the G-load brace by 1/2" (to gain exhaust clearance for a custom 3.5" Y), thus having a similar effect to your washer.

Thanks for the tip.

 

Ok after closer inspection they were 7 degrees apart <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

I shimmed out the bottom 2 mounts with 3 3/4" washers each and now they are within 2 degrees of each other. Was able to set pinion angle at -2 <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

I'm curious to know how many people have tried the Rossler(tranny tail shaft/rear pinion relation) method vs the driveshaft/pinion flange method and what were the results...??

 

based on how a universal joint works...the rossler method is the ONLY CORRECT WAY to measure pinion angle IMO

Basically you want the pinion centerline to be parallel with the transmission output shaft centerline at full load. With aftermarket suspension components. figure a 2-3 degree rotation upward of the pinion angle under load so to counterbalance this you want a static -2 degree pinion angle.

Measuring the difference between the pinion and driveshaft has one inherent flaw. its assuming the pinion centerline is coaxial with the transmission centerline. This may or may not be true with a factory 10-bolt but I KNOW its not true with a 9" ford with its lower pinion position relative to the ring gear. That is, if you set the angle between the DS and the pinion to -2 you could very well have a 6 degree difference or more between the DS and transmission which will result in different effective speeds at each end of the driveshaft. this imbalance shows up as horrific driveline-induced vibration

Maybe this makes some sense <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

ok, after closer inspection...the bigass bracket to bolt the TA to the rear is what is built incorrectly. The 3 studs they bolt to are square to the pinion centerline (within 1/2 degree) . This kinda only leaves the bracket to be the culprit. it appears that it was built about 7 degrees off of being square. Maybe the welder had a few too many brewski's that day <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

I'm going to do something to tackle this issue this evening...when I figure it out, I'll repost <img border="0" alt="[chug]" title="" src="graemlins/gr_chug.gif" />

 

if you've got a camera, could you snap a few pics of how everything is off? I've got a 9" coming in soon.

Thanks

 

solution...

since the bracket was what was off by 7 degrees, I laid it across to flats in a 12-ton press and pushed it down a millimeter or so (to bow it in some). then I heated the area with oxy-acetelene until HOT and quenched the area to releve any residual stresses.

Now its within 2 degrees which I can tune in with an adj TA.

 

did moser ever find out about this problem?

(curious because im 2 weeks away from ordering my 9 inch) and now im getting worried

 

ttttt

 

Mine was fine, I bought it back in march.

 

i hope everything is fine because i just ordered one yesterday