I noticed that my pinion seems rather flat if not pointed down a bit. I have 4" lowering blocks in the back would there be any issue putting some shims under the blocks to angle the axle up a bit?
Have you measured it ? are you having driveline problems ? vibration, u-joint failure , etc . Sounds about right to me.
I haven't measured it yet. I don't even have the car running yet just thought it looked a little off.
Measure it up first to see where it’s at, being a degree or two downward might not end up being that bad while driving, it’s gonna rotate up some and the blocks are going to make that aspect of it a bit worse.
Lowering blocks will change the driveshaft angle with respect to the ground, but also with respect to the engine/trans. shaft C/L: this changes the operating angle of the universal joints , which is the important thing. Plug your info into the calculations shown here: https://spicerparts.com/calculators/driveline-operating-angle-calculator.
I use a Tremech app on my phone and so far it seems to work well and is easy to use and it takes some of the guesswork out of setting up the driveshaft angles. https://www.tremec.com/menu/tremec-toolbox-app/
U-joints can operate in a 22 degree range. If your not having any problems and service them when you grease the rest of you zerk fittings you should not see any extra wear. We use angle shims on our dirt oval track car.
How you set the pinion depends a lot on what type of suspension you are using. With a leaf spring set up, the pinion is best being level or slightly down. As you apply power the torque will rotate the pinion snout upward some and then you have the correct relationship. If you point it slightly upward it will posibly rotate too far and cause the u-joints to fail. If someone has a 4 link set-up it doesn't allow the pinion to rotate, so the relationship set-up is different.
Your car is so far away from a point where you should be worrying about pinion angle just don't worry about it.
Boy howdy I thought that nonsense and bullshit got tossed out in the 90's. From back in the 60's and 70's when the spit and whittle club hanging around the Shell station told you that you had to have your pinion pointing down because the torque would cause it to rise and if you had the prescribed pinon angle you would tear things up. That foolishness has been dispelled times over over the years. I remember some know it all telling me that in 1973 when he heard I was changing my 48 to open drive. Sounds great at Ricky Racer bullshit sessions but in actual function it only does anything except eat U joints when the car is under hard acceleration and spring wrap for a very minute time allows the pinion to rise. Driving down the road with the pinion down eats U joints as bad as it does on lifted 4x4 rigs with excess angles on the U Joints. For Topher 5150 and anyone else, you have to have the full weight on the suspension to be able to measure pinion angles. You want the pinion to be on the same plane as the output shaft of the transmission. That is what gives you the best all around life expectancy for U joints and cuts down on possible vibration caused by one or the other joints having the wrong angle. Meaning that the angles have to match. Shims work but make sure that your pin that holds everything in place is long enough. I've seen some thick caster shims on front axles that didn't leave much of the end of the spring bolt to go into the hole in the axle.[/QUOTE]
I have also found this app to be of value. It takes the guess work and incorrect information out of the equation. It just plain works.
trans 3 degrees down, pinion 3 degrees up. they do make shims to adjust this if needed. I had a car where the guy took a rear end and use the spring pads that were on the rear end when he got it, right width wrong angle. the rear was 4 degrees down and the trans was level. changed the angle when I made some lowering blocks. I honestly could not tell any difference while driving, but I bet my U-Joints appreciated my efforts.
[/QUOTE] As with many things, people interpret them incorrectly. Your diagram above is somewhat correct, but what it does NOT point out is that these parallel angles only happen when the pinion starts out pointing somewhat downward from the angle of the engine/transmissions angle. The eng/trans angle may not (and often isn't) parallel to the ground. Cars are raked backwards and forwards in their stance and the ensuing engine/trans location may be anything but parallel to the ground. In many cases, the OEM car manufacturers install their engines with an angular posture. The important difference is that "down" means down in relation to the transmission, not down in relation to the earth. It can therefore be "down" in relation to the transmission, but parallel or even up in relation to the earth. The relationship has to be between the eng/trans angle and the rear end pinions angle. (and that is essentially what you are saying......BUT) The generality here is that they should operate in a parallel plane, and to a certain extent that is correct. That generality is for understanding a basic concept. The U joint NEEDS to have movement so that it doesn't wear out prematurely, and the variation in torque loads provides it with much of that. To reach the generally accepted concept that the pinion will be in a parallel plane to the eng/trans, it MUST (with leaf springs) start slightly below the angle of the engine/trans. Below are some videos which show rear ends moving up and back down as torque is applied. Notice that they always move UPWARD when torque is applied, so to get to some semblence of "parallel", they must start out below that point. Add to that the fact that the springs not only wrap under torque, but they rise when a load is placed on them. So take a spring in the rear of a truck (or car) and when gasoline is put in the tank....people enter the vehicle.......weight is placed in the trunk/bed.....or the road itself is not flat, and you have essentially raised the rear end in relation to the transmission. Again thats not helping a u joint. You mention having the "FULL WEIGHT" on the suspension when setting the rear pinion angle. Yes, thats a good starting point.........but its not a constant. Its just another "generality" because everything still moves upward from there. Basically you are setting up the "bottom point" of the movement (unless you go over a whoup de do and unload the weight on the rear. (Mr48Chev) told you that you had to have your pinion pointing down because the torque would cause it to rise and if you had the prescribed pinon angle you would tear things up. So I still believe that the pinion should start out pointing down (in relation to the trans, not the earth) and that it will rise when torque is applied. Those that want to think I'm incorrect are welcome to do so.......... One other thing that should be considered is the actual angle of the driveshaft running from the trans to the rearend. Generally the preferred angle that its on should be no more than 3 1/2 degrees different from the trans/rear end planes (not the earth). So if you take a donor engine and trans from a long wheelbase vehicle and put it in a short wheelbase vehicle like a coupe, shortening the driveshaft will also increase the angle its installed at. Yes, we have all seen the huge monster trucks with exaggerated driveshaft angles.......but for our needs keeping the driveshaft at a 3.5 degree angle or less and allowing for axle wrap when mounting a rear end is (in my optomistic opinion) the correct way to do it.
][/QUOTE] Great video showing what’s possible with a u-joint. 1-2 degrees really is going to matter . There are You Tube videos of oval track modifies and late model’s that show rear joint movement.
Here is another video which I think makes things clearer. In the later part of the video he shows you how everything becomes a constant speed when he tilts the OUTPUT end of the shaft to have the same angle as the Driven end of the shaft. These are exaggerated angles for sure, but they demonstrate that under power the trans and the rear end need to operate on the same angle. Since a vehicle with leaf springs WILL have a torque reaction which lifts the nose of the pinion, it must start out on a different angle when at rest and then let the torque reaction cause it to rise to the point of being in the same plane during normal (or even aggressive) operation. Its only a two minute video.
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