When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello everyone! Looking for some help. I have a 1969 442 original 4-speed car that I recently swapped out for a new Tremec TKX from Silver Sport. After installation I had vibration on the highway. I measured the pinion angle with the stock crossmember at the front of the engine and back of the transmission and it was about 5.5* which my understanding is a bit steep. I was able to modify the tunnel and add some shims to trans mount but the best I can get is 4* and I set the rear diff pinion angle to match (no more vibration). However, now if someone is in the back seat the driveline will hit the floor on bumps. I'm not sure of the best way to address this issue.
Questions:
Has anyone else had this pinion angle issue with the TKX? How did you fix it?
Should I put in a taller trans tunnel? In order to do that, I would have to cut through one of the floor supports that is right above the trans u-joint (this is where it is hitting), will that will cause any issues?
The other option I was considering was getting a stiffer rear coil spring or switching to coilovers. Currently suspension is all new UMI and at stock ride height. traditional coil springs and shocks also from UMI.
Your problem is familiar. When I installed a Viper 6-speed (before the days of kits) I had problems with transmission angle.
The Viper is taller than your 5-speed, so I had to cut out the front tunnel to get a better transmission angle (-2.25°).
When I had the raised transmission in place, the driveshaft hit the floor reinforcement brace.
I cut out the brace as you can see in this picture, a shadow of it is left on both sides of the U-joint.
To maintain structural floor support, I rolled a piece of 6 x 1/4 plate into a U-shape. I had it welded to the floor support, so it would carry the floor load. You can see it on the left side of this picture, taken before everything was welded.
I drilled and tapped three holes on each side on the bottom of the U and made a shorter, matching U that I could bolt on to form a front driveshaft loop.
I installed adjustable upper control arms to get the driveshaft angles OK at both ends.
I still had an area where the driveshaft hit when I took out the rear springs (to simulate maximum compression). That area was just behind the new driveshaft loop. The welder suggested the fix.
He heated the sheet metal in that area to red and jacked a piece of 4" pipe up from below to stretch the metal enough that my 3.5" driveshaft would clear.
Gary
Last edited by VC455; September 3rd, 2023 at 05:48 PM.
Reason: added transmission angle
I don't think anyone would guess the work involved, looking at the interior today. Virtually the only hint is that the stick is 3" back from the Muncie position.
Wow! That is great work Gary! Thanks for the reply. Mine is not that far off and I rarely have people in the backseat but it just bothers me. I'm thinking of ordering new springs from Eaton that have a higher spring rate and 1 inch taller. Right now I have UMI factory height springs in the rear. If that doesn't work I will probably go the same route as you did. The floor support was the only thing I was worried about but it sounds like your solution worked so that makes me feel better about it.
The kit maker (Silver Sport) should have some input on this problem as well.
They can't pretend ignorance because you don't drive a Chevelle--A-bodies shared underpinnings across car lines.
Let us know if they have a good solution.
And we love pictures on this site. Make a post in The Newbie Forum to introduce yourself and put in pictures of your car, so we can all admire it.
One of the great things about this site is that no matter what your question, a verifiable expert will jump in with a solution--even if it has nothing to do with cars!
September 3rd, 2023, 02:48 PM
