angles on driveshaft / u-Joints stock leafsprings with caltracs

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Buschi340

Buschi340

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Hi,
never adjusted this before. Can you guide me how and where to measure. And what angle is where the optimum? Can I expect movements at the pinion upwards with those caltracs? ( dragstrip a few times a year with Slicks - 12.xx second manual car ) I read a lot in the net but it is kinda contrversy. especially with caltracs. tranny should show up from ground or driveshaft angle? and pinion down 3 degrees from driveshaft angle? Seems me stupid german Needs a step by step instruction.. :)
 
The angle stuff is a little complicated, but here's what I know. The main goal is that the trans angle match or run parallel when the vehicle/suspension is under load. I think most people would say 2* down on the trans tail is about standard. But anywhere from 1*-3* is acceptable. You want to measure with the car at full weight on the ground on a level surface. Whatever you measure their is opposite of what the rear should be at under load. (So 1*-3* loaded)

To reiterate, if your trans is 2* down, the pinion should be 2* up under load so that the u-joint angles match and are parallel. This is where you're gonna prevent wear, reduce friction and keep from breaking stuff.

Here's the rub with leaf spring suspensions. The stuff I've read says rear leafs allow 6-7* of pinion travel from unloaded to load depending on suspension and age. And talking to caltracs guys they say 3-5* of travel based on wear and how firm you have your caltracs set.

So if your trans was 2* down, your goal would be 2* up pinion when loaded. So assuming 5* with good leafs and caltracs, you'd want to be sitting 3* down at the pinion on the ground, so that it would "wind up" 5* as predicted and sit at 2*up loaded...

Clear as Mud?!

Joe
 
Like so

IMG_8510.PNG
 
clear as mud. Yes. hahahaha.

ok, first i check if I have to bring the tranny down. otherwise i would never get a straight line under load.
i'll take your numbers for caltracs and assume 4° travel because the stress at a race is much more than on the street. fu**ing angles, i already had Problems in School with that sh**** :)
Those numbers of maximum travel on the pinion can only be a guess right? I mean there is no way to measure 100%
 
Yeah, no way to measure under load or actually measure pinion wrap up that I can think of... but I'm a hack!!! Mines 3* down trans, 2*down pinion at rest with shims...

I snagged some 2* shims and played the install and drive "is it quieter" game... I also tried them in/out at the track to see if I picked up and no change either... but I'm mostly street car, occasional track like you.

Good luck!
Joe
 
ok, thanks a lot. Will start today bringing the tranny in Position and measure pinion where i am. Now it sounds easier than all those Internet reading :) 3° down tranny, 2° down pinion.

guess. If i jack up those assumed 5° travel on the pinion ( simulating load ) I should achieve equal angles on both sides of the drive shaft... right?
 
Buschi340 said:
ok, thanks a lot. Will start today bringing the tranny in Position and measure pinion where i am. Now it sounds easier than all those Internet reading :) 3° down tranny, 2° down pinion.

guess. If i jack up those assumed 5° travel on the pinion ( simulating load ) I should achieve equal angles on both sides of the drive shaft... right?
Click to expand...

Whether the drive shaft has equal angles isn't what all the "pinion angle" web sites are saying, although it might be one way to check. What they do say is that when the rear end is under load (acceleration) the pinion should rise up at which point the eng/trans drive line and the pinion center line will be parallel. It's really hard to tell how much a particular pinion (rear suspension) will rise and that's why there procedures to "dial it in":

"" Checking to see if you have got it correct:
If there is no vibration under normal operating conditions then the angles are correct.
If there is vibration under acceleration, you need to add more downward pinion angle preload. If the opposite occurs, the vibrations tends to decrease or disappear under acceleration, you need to reduce the downward angle preload.

If the vibration steadily increases with driveshaft speed (either accelerating or decelerating) the symptom is primarily the result of a driveshaft imbalance or yoke runout. Sometimes this yoke runout problem can be improved by rotating the U-joint 180-degrees in the rear end differential yoke.

Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem.""


You can also look here:

Determining Engine and Pinion Angle

Drive Shaft Harmonics

Setting Pinion Angle | Hotrod Hotline

That's why they make "angle shims". The factory had engineers and test facilities to "dial it in" perfectly so that new cars have no vibration in the drive line. Us Hot Rodders have to do it in steps and the angle shims let you get it perfect because you never really know exactly how much your pinion will rise. You also need to realize that the pinion will rise different amounts (to some degree) depending on whether you're launching off the line (drag racing), casually leaving a stop sign in town or stomping into passing gear at 55MPH.

Treblig
 
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