A question on setting pinion angle
Thread Starter
Racer
Joined: Sep 2004
Posts: 469
Likes: 81
From: Saint Marys Pennsylvania
A question on setting pinion angle
I just installed an ls3 and a tremec 5-spd. in my 61 with a c-4 rear suspension. From what I have read about pinion angle I should tilt the trans. down about 3-5 degrees and the rear end up 3-5 degrees. But the car doesn't sit level to start with. Do I need to level the frame to do this. Any help would be greatly appreciated. Thanks, Bob
Melting Slicks
Joined: Jul 2000
Posts: 2,097
Likes: 99
From: Boston MA
You don't care how level the frame is. You only care about the transmission angle and the pinion angle vis a vis the same thing. Make sure you're measuring them against the same thing (the horizon or the frame) so that you can compare those 2 angles to each other. You do want those two angles to be as small as possible and as close to each other as possible. But with a C1, you'll be around 3 - 5 degrees. Try to get it closer to 3 than 5. There's some discussion that you don't want the 2 angles to be identical. You want them to be slightly different. Not a lot. Just a little. If they are the same, some harmonics could happen. If they are way off, that condition strains the U-joints. You're right in spending some time with this. Otherwise you'll get nasty vibrations over 50 mph and you'll go through a lot of U-joints.
Safety Car
Joined: Nov 2002
Posts: 4,459
Likes: 1,293
From: minneola fl
You don't care how level the frame is. You only care about the transmission angle and the pinion angle vis a vis the same thing. Make sure you're measuring them against the same thing (the horizon or the frame) so that you can compare those 2 angles to each other. You do want those two angles to be as small as possible and as close to each other as possible. But with a C1, you'll be around 3 - 5 degrees. Try to get it closer to 3 than 5. There's some discussion that you don't want the 2 angles to be identical. You want them to be slightly different. Not a lot. Just a little. If they are the same, some harmonics could happen. If they are way off, that condition strains the U-joints. You're right in spending some time with this. Otherwise you'll get nasty vibrations over 50 mph and you'll go through a lot of U-joints.
All of the cars that I've done have been in the 2 to 4 range, and haven't had any vibration or harmonics as a result. Good luck!!Mike Coletta
Thread Starter
Racer
Joined: Sep 2004
Posts: 469
Likes: 81
From: Saint Marys Pennsylvania
Thanks for the help guys. so what you are saying is if my frame is angled down 2.5 degrees towards the front and I want to angle the engine down 3 degrees, I would angle the engine down 5.5 degrees and angle the diff. up 5.5 degrees. Bob
Melting Slicks
Joined: Jul 2000
Posts: 2,097
Likes: 99
From: Boston MA
You'd do the 5.5 degrees if you were measuring against the floor.
Le Mans Master
Joined: Nov 2000
Posts: 7,246
Likes: 21
From: Going too fast over the hill. Iowa
The diff pinion and the trans output shaft are what you actually want to measure against, but they are encased in their respective assemblies. The angle that the ujoint is deflected between the driveshaft and the shafts connected to the yokes should be greater than 1 degree and hopefully less than 3 degrees. They should also be equal on a car like a c2 Corvette
with captive assemblies but done with the suspension fully loaded on C1 (live axle assembly) Corvettes. I would assume a full tank of gas in a C1 would compensate for the rear spring compression added by 2 average passengers. Also, there are additional considerations if you are drag racing the live axle cars.
I made small fixtures for my 66 to measure against the face of the pinion yoke and the face of the trans yoke, assuming the faces were 90 degrees to the diff shaft and trans shaft.
IMO ignore the frame and the horizon and everything else not parallel to the trans output shaft and pinion shaft.
PS here's a site with explanations: http://www.hotrodhotline.com/md/html..._harmonics.php
with captive assemblies but done with the suspension fully loaded on C1 (live axle assembly) Corvettes. I would assume a full tank of gas in a C1 would compensate for the rear spring compression added by 2 average passengers. Also, there are additional considerations if you are drag racing the live axle cars.
I made small fixtures for my 66 to measure against the face of the pinion yoke and the face of the trans yoke, assuming the faces were 90 degrees to the diff shaft and trans shaft.
IMO ignore the frame and the horizon and everything else not parallel to the trans output shaft and pinion shaft.
PS here's a site with explanations: http://www.hotrodhotline.com/md/html..._harmonics.php
Last edited by magicv8; Jul 10, 2009 at 05:48 PM. Reason: added PS
