It is too early on a Sunday morning for my brain to wrap around all the writeups. So hopefully I can get a straight answer from someone who has done this. I have driveshaft noise, and I am pretty sure it is pinion angle. The tail of my transmission is facing downward at 5 degrees. What angle should my rearend be facing? Up or down, and how many degrees? Not for high performance drag racing, but for just driving on the streets. If you know about this stuff, I would appreciate drag settings as well. Using leaf springs, Cal-Tracs, and I have the options of raising the trans with spacers and/or using shims on the rear end (I have 2 degree shims). I can also tighten the Cal-Tracs to adjust the rear. Currently set with ZERO preload, but was humming with 1-1/2 to 2 turns preloaded.
Scott, I welded my perches to the axle with -2° (pointing down) as per all my "car buds", supposedly to counteract the spring wrap on acceleration. Unfortunately, they had no experience with Cal-Trac's, which don't require it. My tailshaft is also -5° (down) so I ended up buying a set of 6° steel wedge shims from here to put under the axle to tilt the pinion back up. This gives me a 1° misalignment which is within the acceptable range. No vibration or noise at all... Russ
a leaf spring car usually needs 4-6* of negative pinion angle to fight leaf spring wrap up. 4 link and ladder bar cars can get awt with almost none 0-2*
Have a coffee (or some wine, if it's not too early), then take your time and read this!! http://www.carcraft.com/howto/91758/index.html
If my memory serves me correct, I run 4 degrees down. Anything over this and the driveline vibrates. I run just a small amount of preload on the drivers side bar (1/2 turn) The other side is set with to no load, but no slack. I also run the bottom hole on the bars. On my last outing it pulled a 1.40 60 ft. Hope this helps.
The Cal-Tracs virtually eliminate leaf-spring wrap, so I can stay within closer tolerance. No coffee for me (or wine, way too early!) but took a break, had breakfast, my sodas kicked in. And I let things settle in my head a bit. Correct me if I am wrong. If I want 2 degrees pinion angle, and my tailshaft is facing down at 5 degrees, then I need the pinion to face down 3 degrees. Right?
Blown chimed in while I was typing, so my 3 degrees down sounds about right Thanks for the specifics on the CalTrac settings.
i have ran cal -tracs with a chevy2 i ran it at 0 but it sez you need to have between 3 and 5 deg. difference between the driveshaft and the pinion ,mine was i think 3 down on driveshaft and 0 on the pinion .....it worked great on my street car with bf goodrich drag radials ,pulled 1.50 60fts with a 355 sbc and a glide
Setting the pinion angle is actually a phrase for setting the torque line. The torque line on any car is where if you drew a line flat from the rear of the pinion out to the tires, Where this line intersected the tires would be the torque line. Normally on a leaf spring car this line will be behind the tires a small amount, (down pinion angle). But upon acceleration as the pinion tries to climb the ring gear the line moves under the center of the contact patch of the tire. This is optional pinion angle. Next time you watch a car leave the line watch the wrinkle in the tire. The end of the crease is where the torque line is at. If the crease is not in the middle of the contact patch then which ever way it needs to move to be centered is what the rear needs to be moved. If the crease ends in front of the patch then it needs more pinion angle, If it goes behind then it needs less. As always this is just my opinion others may vary.
Neat! Never put all those variables together to see how they interact... If I ever get back to the track, I will have the wife video recored it and see how this works. I just took the preload off and the pinion fell to 3.5 degrees. I left the preload off until track day, then I will try it at zero and then 1/2 turn driver side like yours is set up. Waiting for the neighbors to wake up before I start it up and take it for a test drive.
good to here that the vibration is gone with the caltracks unloaded. if your motor is 5 degrees down then the pinion angle needs to be pointed 3 degrees up, not down. it will move up when you accelerate to 5 degrees. when you preload with the cal tracks it pushes the angle futher down and doesnt allow it to wrap up when you accelerate.
Well, I finally got out on the freeway testing out my MSD box, and I noticed that there was still a little harmonic vibration, so I installed a set of 2 degree shims to bring it up to about 1 degree total angle. That actually cleared it all up. Got to 70 and it vibrated just as much as it does at 15. CalTracs are unloaded so if I want to pick up a degree or 2 at the track, I can preload them a bit. But for highway and street drivng, the current setup seems to be optimum.
