can someone give us beginers a walk thru on the correct way to check and adjust the pinion angle////what do you need to do it thanks ps is 1 1/2- what we want???thanks again pete
You'll need to get a magnetic protractor to do this. You can get them at Sears or Harbour Freight. They're less than $10. Next you'll want to put the car on a flat, level surface in order to do this the easiest and best. And obviously you'll need room to get under there. The rear tires must not be suspended but as they would be on the ground and under load. You'll also need adj. upper control arms on the rearend to be able to pivot the rearend up and/or down. For stock cars, -1 to -1.5 is probalby near stock. I've been told that on race cars, -3 to -4 is what you're looking for. This is because the rearend is going to want to wrap itself in the upward direction upon launch. Your goal here is to create a straight line between the transmission, driveshaft, and rearend when under hard acceleration. The u-joints take care of things when this is not lined up. Anyway, once the car is up, place the protractor on the rear snout of the transmission. Record the measurement. Next take a measurement on the rearend. You can use the pinion yolk. Record the measurement. Now you can add the two together. Generally you should find that the transmission is 0 or slightly positive. The rearend will therefore be slightly negative. Adding the two will get you your -1 to -4 pinion angle. To adjust, you'll loosen the jamb nuts on the upper adjustable control arms and lengthen or shorten the control arm to cause the rearend to pivot up or down. This is one of those things where different cars react to different measurements. You will be able to adjust to within 1/2 degree fairly easily. Good luck. Here's a pic of the protractor to get:
compair parallel lines My understanding is that you should begin setting the pinion from the transmition and rear pinion at the same (parallel) angle, then drop the nose of the pinion 2 or whatever degrees. My trans sloped down 3.5 and pinion sloped down 4.5 (factory stock!)for a total of 8 degrees below parallel. When this happens, your DRIVESHAFT is hanging below the trans and rear end because both are pointing toward the ground. NOW, if the u-joint caps point up they are being crushed into the drive shaft and when pointing down, they are being pulled apart. If you draw a line rearward from the tailshaft, it usually runs just over the top of the rear yolk at a slight downward slope. with the rear set at the same exact angle (sloping slightly upward toward the trans) a similar line would run just under the front u-joint yolk. NOW THEY ARE PARELLEL.You should get the SAME reading on the angle gauge at both ends. Now your drive shaft and u-joints are equal on both ends and absolutely no bind. This prevents broken joints, shafts, trans tailshafts, etc. AT THIS POINT, ADJUST YOUR PINION DOWN THE DEGREES YOU WANT so when you put power to it they will be parallel again when under full throttle with no bind or power loss. NEVER ALLOW THE TRANSMITION AND REAR END TO SLOPE TOWARD THE GROUND, AS SET BY THE FACTORY, UNLESS YOU NEVER RACE!!
That's a great article. It is my understanding that without any driveline angle, there's nothing to keep the needle bearings in the u-joints turning? That would cause longevity problems, especially for those of us who drive our race cars a lot. The stiffer your control arm setup, the less pinion angle you can run (less deflection under load), but I'm not sure that I would want mine at 0* under load: I'd like a little something in there keeping my u-joints alive. Perhaps someone with a bit more experience has a better idea? Thanks
Correct on all counts...at least that is the party line in the Engineering community (I was a driveline development engineer at the GM Desert Proving Grounds for four years). I will say this, however: I think engineers in general tend to be more anal (and analytical) than what may be required in the real world. Even if you had the driveline set at zero it seems there would be enough relative motion dynamically to cause the u joint working angle to change during use (to some non zero value) and allow rotation of the bearings, which would keep them from brinnelling in the cups. Said another way, it wouldn't stay at zero throughout its usage. Having said that, my vote: set it to 1 deg - 1.5 deg and let 'er rip. :TU: K
The fact is, on our a-bodies, if you set both trans and rear pinion set at zero or any other equal parallel setting, the drive shaft will have some angle and the u-joint bearings will be turning all the time. The reason is because the centerline of the rear will be UNDER the centerline off the trany because they are off set at the factory and never share the same centerline. The driveshaft always makes up the difference with some amount of angle at each end, which guarantees movement of the u-joint bearings at all times. Some websites, books, magazines, etc, say to use the DRIVESHAFT for pinion settings. Never take advice from those who say to set pinion angle off the DRIVESHAFT for a single driveshaft (2 u-joints) GM a-body like ours. We must use the trany vs pinion method to avoid disaster. Other methods are used for those with 2 drive shafts, constant velocity joints, "Bigfoot" trucks and some other designs.
