What angles for engine/tranny and rear end for street/strip?
05-27-2011, 07:37 AM
#1
What angles for engine/tranny and rear end for street/strip? I'm newb in suspension questions, and after reading numerous threads it's still not clear to me.
What angles should I aim for when setting engine/transmission and rear end? Now while I'm building tranny crossmember I can alter these, but what should I go for? On one hand, you need 2* down for rear end pinion, on the other you need about 3* down for engine/tranny, that makes their relative angle 5* while angle must be 0 for u-joints to work properly.
Please explain what angles do I need?
What angles should I aim for when setting engine/transmission and rear end? Now while I'm building tranny crossmember I can alter these, but what should I go for? On one hand, you need 2* down for rear end pinion, on the other you need about 3* down for engine/tranny, that makes their relative angle 5* while angle must be 0 for u-joints to work properly.
Please explain what angles do I need?
05-27-2011, 09:06 AM
#2
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You get what you get with a lot of fbod combos due to differnt k members, mounts, trans, gm hole locations, etc.
My trans point down toward the diff at 3.5 degrees. My diff pinion points up toward the trans at 1.0 degrees.....when the diff rotates upwards another 2.5degrees under power...it phases the trans output shaft with the pinion shaft at 3.5 to 3.5 for paralled angles....but they are all different...
I'd like my trans at 0 and my diff down 2.0 to get 0 - 0 under load....but it's not happening...
My trans point down toward the diff at 3.5 degrees. My diff pinion points up toward the trans at 1.0 degrees.....when the diff rotates upwards another 2.5degrees under power...it phases the trans output shaft with the pinion shaft at 3.5 to 3.5 for paralled angles....but they are all different...
I'd like my trans at 0 and my diff down 2.0 to get 0 - 0 under load....but it's not happening...
05-27-2011, 01:29 PM
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You can ask 5 different people how to set PA and you will get 5 different answers...lol..I watched a video from a Major Corp on how to do it and it was wrong...tough process to understand.
IMHO pinion angle does not do anything for traction....how can it???? Now if you do not adjust the LCA angle, etc and set a "wrong" pinion angle, you can get positive or negative traction results since it will change other angles also. Example...if your LCA's were slightly positive toward the axle with a zero PA and you are getting wheel hop...then reset the pinion angle to -2 down...wow the hop went away...was it the PA or the LCA angle dropping
But with the better traction you are breaking U joints because they are out of phase...
Positive PA didn't hurt the traction on this pass:
http://www.streetfire.net/video/bris...ph_2061821.htm
The goal is to phase both u joints under load...less parasitic hp loss and better strength for the joints....I have zero vibration. You will need some no load angle built in (2.5 in my case) since the rear will rotate upward under power.
Go to Rossler.com, Bickel, etc and read up on setting PA...don't do it from internet posts like mine! LOL!
IMHO pinion angle does not do anything for traction....how can it???? Now if you do not adjust the LCA angle, etc and set a "wrong" pinion angle, you can get positive or negative traction results since it will change other angles also. Example...if your LCA's were slightly positive toward the axle with a zero PA and you are getting wheel hop...then reset the pinion angle to -2 down...wow the hop went away...was it the PA or the LCA angle dropping
But with the better traction you are breaking U joints because they are out of phase...
Positive PA didn't hurt the traction on this pass:
http://www.streetfire.net/video/bris...ph_2061821.htm
The goal is to phase both u joints under load...less parasitic hp loss and better strength for the joints....I have zero vibration. You will need some no load angle built in (2.5 in my case) since the rear will rotate upward under power.
Go to Rossler.com, Bickel, etc and read up on setting PA...don't do it from internet posts like mine! LOL!
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05-29-2011, 01:45 PM
#12
Yes I already learned that. Now you seem to not understand me.
In all MADMAN's post I read, he says set pinion 2* down. That is for traction. All other irrelevant FOR TRACTION.
Now on the other hand, from what I read tranny should point down about 3*. If we want to satisfy both, then relative angle will be 5* which is huge.
Now highest I can put my tranny is 2* down which still makes 4* relative. So I don't know what to do. I want traction but don't want vibrations.
In all MADMAN's post I read, he says set pinion 2* down. That is for traction. All other irrelevant FOR TRACTION.
Now on the other hand, from what I read tranny should point down about 3*. If we want to satisfy both, then relative angle will be 5* which is huge.
Now highest I can put my tranny is 2* down which still makes 4* relative. So I don't know what to do. I want traction but don't want vibrations.
05-29-2011, 05:37 PM
#13
Put the tranny where it falls. Set the driveline angle and be done with it. I set pinion angle differently BECAUSE it works for me and my customers. You are making this too complicated. As Onfire said pinion angle with a correctly set up suspension doesnt rely only on pinion angle to make the car work.
06-03-2011, 12:57 AM
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your making this to complicated. the whole idea is to have the rear end at 3 degrees down. first the trans and the driveshaft (d/s) need to be angled straight to the axel. that means a straight line between the trans and d/s, set the axel pinion at 0 degrees angle, connect d/s and check trans to d/s angle , you want zero degree between trans and d/s. if it is not at zero degrees then adjust it to zero degrees. once at zero adjust axel pinion to neg. 3 degrees and your set. trans to d/s will not be zero degrees because of axel set at neg 3 degrees, but when you launch the axel pinion will want to rotate up ad hopefully its at zero degrees which will align a straight line from trans to d/s to axel pinion. if you noticed the engine sits angling back, thats because it is set at a straight angle to the axel pinion from factory, if car is lowered or lifted or suspension mods that can throw everything out of wack. hopefully this helps some!
06-29-2014, 09:27 AM
#18
Some update to my old thread. Now tranny is pointing down 2.5* toward the rear end is pointing down 1.5* toward the tranny, so their relative angle is 4* degrees.
Problem is, I have terrible vibrations after 60-65mph. can that be due to centerlines of transmission/rear end being that much not parallel?
I can raise tranny tail about 0.5* maybe but that's all. To raise rear end centerline, I will have to invent something, my UMI torque arm is not adjustable.
Should I try to raise rear TA mount point an inch or 2, or am I doing all this wrong?
Problem is, I have terrible vibrations after 60-65mph. can that be due to centerlines of transmission/rear end being that much not parallel?
I can raise tranny tail about 0.5* maybe but that's all. To raise rear end centerline, I will have to invent something, my UMI torque arm is not adjustable.
Should I try to raise rear TA mount point an inch or 2, or am I doing all this wrong?
