another pinion angle question!!

Ths is primarily a 4X4 site but big tires crawling over rocks puts a lot of torque on a drive line. See the "Tech" section for drawings and note the CV joints.
http://4xshaft.com/index.html

 

confused again!!

 

Anytime power is diverted in another direction you are going to lose something.

Anytime a U-joint is spinning on one end it should have the same angle on the other, zero to three degrees.

Most people are trying to guess what the pinion angle is going to be under acceleration. No one can say how much your suspension is going to compress and change that angle. No one can say how much differential wrap you are going to experience on launch.

I believe Mack trucks set their drive-lines up at zero degrees and they can be pulling 80,000 pounds up a steep hill.

I have a Jeep TJ that has a very short drive-line with a steep angle due to a lift kit. I have the shaft directly in-line with the pinion shaft BUT I have a CV joint on the tranny side.

As I remember it your concern was not that you were blowing the drive-line appart but that the car was squirrly. In that case I'm no expert but maybe this will help:
http://home.earthlink.net/~whshope/

 

the car drives fine it just pops the wheels then bang back down and bang back up.a guy looked at it for me and said that i had it setup wrong and he couldnt believe i havent ripped the tailshaft off the trany yet.i deff.dont have the money to fix the trans and dont want to blow 9 quarts of tranny fluid on the track.changing the pinion angle isnt that hard and i just want it to be right{or as right as possable}.i am going to put the upper bar for a true ladderbar setup and before i weld it in place i want the angle right.

 

proper driveline angles require that the diff be up the same amount that the trans is down, So yes your rear should be 0-1.5 up. The issue with the trans being lower is a different issue, this only adds to UJoint working angles, yours is only 3/4" lower so I dont think thats too much but to be sure you have to take some measurements. On a Drag race only vehicle you set the angle of the diff with the suspension loaded [ like it will be going down the track under full torque ] different suspensions act differently, on a leaf spring suspension the springs wrap up,so setting the pinion down some when its not loaded brings it up the the required amount when its loaded under torque. hope this helps.

 

ok so if i set it at zero at ride height and not under load is this going to cause the ujoint to bind?im sure when i leave the line it will go up some{1-2 deg}which will be enough to work the joint and lube them.also i heard that setting the pinion angle will change how hard the car will hit off the line.right?

 

Still just trying to help here, With your 2 deg down, that means your expecting your spring wrap to lift the nose on the diff 3.5 degrees,to equal the trans that is 1.5, Right? the trans being lower than the rear only affects the joint working angle, can you write down the angle of your driveline, then we can do the math to see if your going to over work the u joints and fatigue them and test your drive line loop.

 

the trans is at 0 deg.and the rear is at about 7 down.i can lower the trans down alittle if i had to but cant pick it up{unless i cut the floor}

 

what are the angles of your trans output shaft, the driveline and the diff input shaft?

 

trans output shaft is o deg.and pinion {diff input shaft?}is 7 down.

 

If you're expecting 1-2 degrees of spring wrap on launch, then set your pinion angle down, 1-2 degrees from horizontal. It really doesn't matter if your trans is lower, as long as the angle relationship between the trans and pinion is correct. If the trans output is at zero degrees, then ideally the pinion should be at zero degrees. the 1-2 degrees down the pinion is to compensate for spring wrap in a race only application. If it was primarily street driven then I would set the pinion angle at 0 degrees. Hope this helps. If not, it's "seed" for more discussion.

 

thats what im thinking.im sure that the pinion angle will change some under hard launches,even with the ladderbars.from what im told o angle is optimum during a pass down the track.but you need some angle in the joint so that they spin and greese themselves.