I have the car up on jack stands such that the body appears to be level on the stands (when measured on the top of the rocker panel... just to give me a zero reference). When I check the tailshaft on the tranny, it is -8 degrees. Everything I read says you want zero to -3 deg of pinion angle so I would need to set the rear pinion at an upward angle of 5 to 8 degrees. That don't sound right to me.... Will the car hook-up right on acceleration with that kind of upward set-up on the rear (it's not a race car - just a cruiser - but I don't want to break a driveline....). I have also read that leaf spring suspensions can be set up w/ -5 to -7 deg pinion angle, which would only require about 1 to 3 deg of upward angle, right?? I have no room to change the tailshaft angle by moving the tranny up due to the design of the Walton xmember. I could cut the motor mounts and reconfigure to lower the front of the motor, but I would only gain about 1/2". I haven't crunched the numbers to see how that would impact the tailshaft angle, but I suspect it ain't much.. Can somebody give me some guidance here?? I will be calling a driveshaft shop as well..
The main thing to remember is that the pinion and the trans tailshaft are to run in parallel planes. I set the car on jack stands, with the stands under the rearend housing (you want the rearend to be positioned at "ride heigth"). The number of degrees of angle relative to "true level". If your garage floor was poured with "slope", then your car will not be truly level. I use my angle protractor and take a reading of the transmission tailshaft and set the pinion at (or near) the same reading. If you are running a 4 link rear suspension, you should set the pinion angle at exactly the same as the transmission. If you're running ladder bars, you may want to add 1 or 2 degrees to the pinion angle. If you're running parallel leaf springs, you may want to set the pinion angle at 1 or 2 degrees less than the transmission. The reason for varying the pinion angle for ladder bar or parallel leaf springs is because the pinion angle will change during acceleration. I'm no expert, nor to I claim to be... But, this is the method that I've used many times and have never experienced any problems with this method. Good luck.
This is such a pisser. I need to gain about 5 deg somewhere.. Thanks guys - I also found another thread from back in 1996 that helped as well. Back to the drawing board.
So you want it at ride height (jacked up under front control arms and rear axle tubes, but also want the car level, right ?? I don't have a flat spot on the frame - is best place to check for level on the lower door seal (top of rocker panel)???
dont get caught up on "level" the axle and the tranny dont care if it's up hill, down hill, front on a ramp or pulling a wheelie... just make the tranny output the same angle as the axle input when the car is under power (knowing that the rear will probably rotate upwards about 3 degrees under power). the trannyoutput-driveshaft-pinion should look like like a really mellow zigzag. with the two ends being parallel, yet offset.
69Fury is right.... Don't worry about "level". The angle protractor's reading of the number of degrees of the transmission angle is just a "number" to use to set the pinion angle by. The garage floor could have two feet of slope, making a 20 degree reading of the trans... You'd set the pinion angle relative to the 20 degrees of the trans. The number of degrees is relative to the surface you're working on, not a number to use regardless of the "flatness" of the work surface.
right you shouldn't worry about the car being level.. just set the car up to ride height then take your readings.. how are you measuring the angle of the tail shaft? are you sure your true with the shaft, just making sure your not taking a measurement of the tailshaft housing or something crazy.. i would also say that, even though your trans is at 8 degrees, i would still only put the diff at around the three mark..because, the more off angle there is, the more chance for viberation..and of coarse you dont want it straight inline either, you got to keep those needle bearings rollin. in a perfect world they would both be set to 3 degrees. you'll be all right
69fury and 4ever18 are right...plus there is a ton of info on this subject if you search... Most importantly, this is a discussion about the angular relationship between the engine/transmission and the rear axle, REGARDLESS of the angle of the "body". That being said, "pinion angle" is better thought of as "drive line phasing" because it's not JUST about the pinion, right? The whole thing is really simple. You have to imagine a center line extending rearward from your transmission...and a corresponding center line extending forward from your rear axle. These imaginary center lines must be parallel. Yes, the rear center line can be rotated down a degree to compensate for axle rotation during acceleration, but let's stay with parallel. In a perfect world, these center lines are between 1/2 degree and 3 degrees offset. Hot rods don't always offer that perfect scenario, but what you don't want to do is compromise and "just make the parts fit". If you have to reduce the elevation of your motor mounts to bring the center lines into the offset parameters, then bite the bullet and do it. The center line offset is necessary to "work" the needle bearings in the u joints. This is an over-simplification, but accurate. The other thing to keep in mind is that, so far...this discussion is talking about these angles when looking at the drive line from the "side", right? Well, you also must consider the offset when looking from the "top", because these angles are compound. Which means that you can have the drive shaft in line with the rear axle in one plane, but NOT both.
I was taught to phase the trans and dif at the same degree. But it makes sense to compensate for different suspensions.
Gents, thanks a bunch for all the feedback. I agree whole heartedly with everything mentioned. I have done a lot of research, but NONE of it (except one diagram I found) addresses the extremes of the angles (i.e. - an 8 degree tailshaft angle). I agree that the car doesn't necessarily have to be level, but here's my argument in favor of having the car at ride height AND level.... Say your car is sitting on a downhill slope of 10 degrees and you don't bother to even check to see that it is or is not level - you just simply jack it up on stands and check your angles... You get a reading of zero degrees at the back of the tailshaft - so by what I read with you guys, I simply rotate the pumpkin -3 degrees and call it good, right?? - this would give me a pinion angle of -3 degrees..... Not so fast - in reality since I was on a slope of 10 degrees, the TRUE tailshaft angle was not zero but -10 degrees. I now have set up my rear end w/ a +7 degree angle instead of -3 degrees. I have excessive angles w/ a tailshaft angle of -10 degrees and corresponding excessive angle at the differential - EVEN THOUGH the pinion angle is -3 deg.... From what I have read, if I have these kinds of excessive angles on set-up, I will destroy something.... So am I just totally insane here - I am starting to confuse myself.......
Rustbucket, I think you are misunderstanding the angle of concern. It is my understanding that once you have the imaginary line through the pinion parallel with the imaginary line through the tailshaft, the other angle that you need to be concerned about is the angle between those imaginary lines and the driveshaft itself, not the angle that either of those makes with the ground (which is what I believe you were referring to). I'm sure someone else can explain it better - while I've been around cars my entire life, most of that time was spent handing someone tools
To re-iterate what's been said: The pinion angle is REALTIVE to the tranny shaft angle. It is NOT RELATIVE to the ground or anything else. So if you jacked up the car so that the tranny shaft is perfectly level (meaning the rear of your car is probably higher than the front), you'll want to put your pinion angle level as well. Point it down a couple degrees of compensation of torque applied to the leaf springs.
But then I wonder how critical all this is when I look under some of these radically-raised 4x4's where the pinion is pointing upwards pretty sharp. I think the biggest issue is that there is some angle at both U-joints so the needle bearings will keep walking (instead of wearing little low spots in the joints).. and that the angles not be too extreme to put undue stress on them.
In my years of building shafts and correcting driveline angle troubles, I have always had the vehicle at normal ride height. But, the angles relate to each other whether the car is upside down or standing on it's bumper. I always use the same terms for each end of the vehicle. As stated before, if the centerline through the engine/trans is higher at the front, lower at the rear, I use nose up to describe attitude. Most vehicles have the engine placed at 2.5 to 5 degrees nose up. In a vehicle with a single driveshaft, the pinion angle needs to be equal or within one degree. If the vehicle will be using a two piece driveshaft, the pinion angle needs to be 1.5 degrees flatter than the engine/trans attitude. Angle through the u-joint and RPMs will also determine u-joint life. Most of what we would build would have less than 5 degrees through the u-joint, so I feel like that shouldn't ever be a problem. In Jeep Wranglers, K5 Blazers, and bigger 4wd trucks, then you start having problems.
I just set the carb mounting on the intake level (front to back). This will put the transmission at the proper angle. Measure the angle of the tail shaft and use that for the pinion angle.
It's hard to reset driveline angles on a diesel school bus if you're using the carb as a reference. One thing I didn't touch on previously is NOT having enough angle to make the u-joint work properly. You must have at least 1/2 degree operating angle through the u-joint to make the needles rotate around the cross. Everyone has added valid point here, depending on what stage of assembly or troubleshooting.
Thanks guys.... SLIDE, your last comment is the one that worries me. The angle of the tailshaft to driveshaft and corresponding angle of the driveshaft to pinion will be 8 degrees if I leave it the way it is... THAT's what concerns me..... All the stuff about parallel lines I agree with - but fact STILL remains that these angles are kinda steep IMO..... - regardless of what I reference against. I think it would put undue stress on the u-joints. Unfortunately due to clearance issues with the stock front crossmember and the configuration of the Walton tranny crossmember, I can't move the components too much (say enough to get the intake completely level)...... Check out this picture - I found it on another thread. The last illustration and comments in the second paragraph above it are what I'm talking about....
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