Pinion angle

[TimR]

Certainly not a racecar at a portly 4000pounds with me in it, but after I could do no better than 2.60 60 foot times on my street tires, I decided I better do something about it. First thing was to look at the traction bars that move the upper arm point higher (I like this style because you can't see it without going underneath) and support the rear diff to prevent it from rolling at high load.

Anyway, after installation I have -6 driveline angle, and +5 on the rear diff so thats -1 while sitting still in my garage. I understand these cars like -2 (so you are at 0 when under full load going down the track) but I'm thinking the poly bushings that came with my arms will help prevent it from moving around..in fact, after installation is pretty obvious the rear diff is much more stable in position than it was before, so hoping we can shave some time off those horrible 60 foot times. Next step would be drag radials.....

I have heard of several methods for determining pinion angle, I used the flat face of the tranny aft end with the driveshaft removed and the u-joint cup flat face on the diff. I don't have adjustable arms either, so there really isn't any adjustment other then shimming the tranny or backing off all the rear suspension bolts and then retorquing under load (its in the buick manual, believe it or not!).

I plan on doing a written evaluation of the edelbrock arms on the BPG forum, hopefully get the experience down soon...they aren't as bolt on as some believe!!LOL

Any thoughts???

Thanks
Tim

[Jeff Hart]

Hey Tim, Check your e-mail, some shy away from this subject because there are so many opinions. I will just tell you what worked for me. I will post on this when I check on my records and give credit to those who have helped me.

[70455ht]

I was wondering if there is any more info of the pinion angle discussion. I put "no hop" bars on my GS and they seem to change the pinion angle upward quite a bit - maybe too much. The car doesn't seeem to hop but it doesn't seem to hook up that much either. Are the south side bars much better for this purpose and what is a good pinion angle to have for racing purposes and wher to measure this! My car seems to pull dramatically to the right when I get on it hard. I have boxed lower control arms. Any suggestions?

Carl

[Jeff Hart]

Hi Carl, do have adjustable upper control arms? Also did you preload the passenger side upper control arm? Pinion angle should be a little more negative for a street car and a little less for a "less flexible" race chassis. What exactly is your combination and I will do what I can to help. If you don't get the GSX-tra, I can get you an excellent article written by a very reputable racer on this subject.

[Kerry s.]

Hi Guys,

Jeff......I think this is the article you are referring to....go here http://www.buickperformance.com/Pinion.htm

Hope this helps...... :)

[Jeff Hart]

Thanks Kerry, that is it, and it worked for me! In fact I think it explained why I exploded a 12-bolt ring and pinion a few years ago at the Nationals, I had way too much pinion angle.:)

[Kerry s.]

Glad to help out.......:TU:

[70455ht]

Jeff,

My rear suspension has stock upper and lower control arms with the no hop bars added in. I have air bags on each side. I am running a 12 bolt rear end with 3.91 gears. How do you preload the upper control arm? I think I better check the pinion angle out fast. I am getting some vibration over about 60 mph and increases in intensity as the speed goes up. I put in an aluminum driveshaft (used) to fit the 12 vs 10 bolt. It was suppose to have been balanced. I will rotate it 180 deg. to see if that helps.

Thanks for the article guys. You people are all right. Nice to meet people that are so helpful.