pinion angle and caltracs

reera · 08-31-2009, 08:55 AM

Hey guys. I've got a question about what you set your pinion angle at when using caltracs. My car is a 71 Pont. Ventura (Pontiac's version of a Nova) with caltracs bars, split leaf mono springs and Calvert's Rancho shocks. It's a 9" tire car set up just like a stocker with a mild 350 bracket motor, with even an old stocker camshaft. I've tried the bars on both holes at different preloads, all shock settings, all tire pressures and still can't seem to get what seems like tire chatter out of it, right after the initial hit. I footbrake the car, stab the throttle, the car jumps like it wants to leave, and then the rear starts shaking (only for a short time). The front end is free, with Afco lightweight bushings, Koni SPA-1 shocks, and Moroso springs. It does get the front off the ground, but it is just a hop before it starts shaking. I normally try to use 1/4 turn of preload in the bars as Calvert suggested, but just for kicks, I put a full turn in one time and it was a totally different car. The front hiked up waaayyy better but it still got to shaking slightly. That led me to believe that the full turn of preload wasn't letting the pinion kick up as much on the launch and that I may have a pinion angle problem. Also with that much preload, I may be "pushing" more downward pinion angle into the rear end. It presently has about 2 1/2 degrees down versus the driveshaft angle. What do you all suggest?

Thanks,
Ryan W.
W316 ET Bracket

Chad E532 · 08-31-2009, 09:36 AM

I had a similar problem on my bracket wannabe stocker 77 Camaro. I talked with Travis at Cal Tracs and he told me it was due to lack or rear shock travel. He suggested having the car setup with 1.5"-2" of exposed shock shaft when the car is at rest. I had to add 2" shock extenders for my QA1 shocks to get me in the correct shaft exposed and it did take away the car "bucking" off the line. Also, I have a theory that the 1/4 turn of preload would be fine at a national event prepared track but at the local bracket tracks I am running a full turn of preload to get the car to work correctly.

Chad

sixty8 · 09-03-2009, 11:05 PM

Travis answered my question earlier this week about the recommended pinion angle with Caltracs - "-2 ot -4 degrees down in relationship to the output shaft of the transmission not the driveshaft".

reera · 09-04-2009, 06:01 AM

Quote:

Originally Posted by sixty8

Travis answered my question earlier this week about the recommended pinion angle with Caltracs - "-2 ot -4 degrees down in relationship to the output shaft of the transmission not the driveshaft".

Thanks to all who responded. I talked to Travis @ Calvert a couple days ago and he told me the somewhat the same thing. He said to measure the output of the transmission angle and the pinion angle and add them together. Should add up to -2 to -4 degrees. He said most transmissions are angled -1 to -2 degrees so your pinion would only need maybe -1 to -2 degrees. Got it set per his instructions. Going to give it a shot tommorrow.

Thanks again,
Ryan

08-31-2009, 08:55 AM	#1
reera Junior Member Join Date: Jul 2007 Posts: 50 Likes: 3 Liked 31 Times in 6 Posts	pinion angle and caltracs Hey guys. I've got a question about what you set your pinion angle at when using caltracs. My car is a 71 Pont. Ventura (Pontiac's version of a Nova) with caltracs bars, split leaf mono springs and Calvert's Rancho shocks. It's a 9" tire car set up just like a stocker with a mild 350 bracket motor, with even an old stocker camshaft. I've tried the bars on both holes at different preloads, all shock settings, all tire pressures and still can't seem to get what seems like tire chatter out of it, right after the initial hit. I footbrake the car, stab the throttle, the car jumps like it wants to leave, and then the rear starts shaking (only for a short time). The front end is free, with Afco lightweight bushings, Koni SPA-1 shocks, and Moroso springs. It does get the front off the ground, but it is just a hop before it starts shaking. I normally try to use 1/4 turn of preload in the bars as Calvert suggested, but just for kicks, I put a full turn in one time and it was a totally different car. The front hiked up waaayyy better but it still got to shaking slightly. That led me to believe that the full turn of preload wasn't letting the pinion kick up as much on the launch and that I may have a pinion angle problem. Also with that much preload, I may be "pushing" more downward pinion angle into the rear end. It presently has about 2 1/2 degrees down versus the driveshaft angle. What do you all suggest? Thanks, Ryan W. W316 ET Bracket Last edited by reera; 08-31-2009 at 12:49 PM.

08-31-2009, 09:36 AM	#2
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 5 Liked 54 Times in 7 Posts	Re: pinion angle and caltracs I had a similar problem on my bracket wannabe stocker 77 Camaro. I talked with Travis at Cal Tracs and he told me it was due to lack or rear shock travel. He suggested having the car setup with 1.5"-2" of exposed shock shaft when the car is at rest. I had to add 2" shock extenders for my QA1 shocks to get me in the correct shaft exposed and it did take away the car "bucking" off the line. Also, I have a theory that the 1/4 turn of preload would be fine at a national event prepared track but at the local bracket tracks I am running a full turn of preload to get the car to work correctly. Chad

09-03-2009, 11:05 PM	#3
sixty8 Junior Member Join Date: Sep 2007 Posts: 14 Likes: 0 Liked 0 Times in 0 Posts	Re: pinion angle and caltracs Travis answered my question earlier this week about the recommended pinion angle with Caltracs - "-2 ot -4 degrees down in relationship to the output shaft of the transmission not the driveshaft".