Truckarm Pinion Angle

[Hellsing]

This is my first post and my first thread so please bear with me.

Suspension type, Truckarm. Problem; trying to set my pinion angle which is another first for me, for vibration free driving at high speed and still get the best 'bite' possible, which is a term I've head thrown around although the physics behind it remain mysterious. Apparently a negative pinion angle (pointing towards the ground) is required. I have also heard that a positive pinion angle (where the pinion is pointing up) is undesirable and will result in unpredictable behavior.

Unfortunately, my dilemma is that with my transmission output shaft angle running at 5 degrees down, and my driveshaft running 4.5 degrees down, sloping towards the rear end, will require my pinion to be pointed up at an angle of at least 4 degrees. Which not only seems like a lot but it looks like a lot too!! :eek:

I don't know how much axle wrap up should be taken into account with a truckarm suspension. Although the arms themselves seem vary ridged in this respect some deformation will undoubtedly occur, at least in the bushing, but I would imagine not more than a degree or two.

I could shim my transmission up but I am concerned about the resulting angle of the carburetor. Would I then need to have my intake manifold machined back to level? :hmm:

Am I over analyzing and over complicating this as I've been told many times I have a tendency to do?! Is the thing to do just to set my pinion angle facing up and call it a day or are there some tenths of a second to be gained here?



_Jon

[discipletwo]

Yes you are over thinking how do I know because I have been trying to solve the same problem. Its easy. The internet leads one to believe that the pinion should point towards the ground. Most think that means that when you look at it it should look like it is pointing down. Not the case although that is how some drag cars are set up because of weight transfer. Most cars going down the road have the engine and tranny sloped down in the rear and pinion pointing up at the same degree. When you se negitive pinion angle or the words noise down that means in relation to the tranny tail shaf angle. So if you measure the engine at 5 down you need to shim your rear pointing 4 up that will give you a rear pinion angle of 1 degree down even though it is
4 up compared to the level ground. Don't even worry about the drive shaft angle what you want is your. Tranny and rear to run about 1/2 degree from being parallel with the pinion being down or less by that amount while under load. If you were working on a leaf spring car you would go dow more on the pinion and run it at say 2 or 3 degrees up to compensat for rap up not so much the cas withtruck arm setup

[discipletwo]

On your carb question intake manifolds have a 3 degree wedge machiened into them because factorys use to set the engine at 3 degree rear tilt so it may be better for you to shim the tranny up to 3 degrees( point down that was compared to the 5 you have now) and then set your rear at 2 degreese up. Remember all mesueements are on level groun at ride height wit full weight on vehicle. If you ar worried about carb just make sure the mounting surface on the intake is level when you set your angle. I would recomend that you set these angles with the option that will run the thinnest shim under the rear its not good to have. Thick blocks between rear and arms