Pinion angle is part of driveline alignment.
The goal of having your pinion angle set is to have your driveline in line. Correct?


John

 

No. Pinion angle is exactly what it says. Getting your driveline in line is something different.

 

So what's better, higher or lower? Cuz I have a little area to play with where I mount my torque arm on my th-400 crossmember, right now I kind of have it in the middle of it, so I could go either up or down.

 

Up hits the tire hard and then tends to unload the tire farther out. Lower tends to plant the tire and keep it planted down track.

 

Cool, thanks a lot man, i'll try and move it down a little and see what happens when I get back together! Hey, are you at ur shop by any chance, just wonderin if I could call to order the oh **** bars while it's on my mind?

 

I just got home. I will be there in the morning at 5.00am if you are up. I have 10 sets ready to ship.

 

so if im unloading almost instantly and my front is at the top of the adjustment on the bmr relocation k-member and my pinion is at say -2, you are saying i should bring it down a lil in the front which would give me say -4 or so then readjust the bottom rear adjustment together more to move the rear back up to get my -2 back without moving the torque arm. hence i still have the same pinion angle but now the front of the torque arm is much lower? am i starting to get this?

 

Sweet, i'm off work tomorrow and will probably be pullin my motor after I get up at the *** crack of dawn to go do my turn-in at the office, so i'll give ya a call on the way, probably around 7ish am florida time, hehe!!!

 

That's what i'm thinkin, I have basically the same setup as you, except I have the crossmember for the th-400 from yank instead of bmr, but they're basically the same piece, i'm gonna try and move it so the bottom bolts to the lowest hole.

 

Hey, this is the number I got off ur website (281.290.8899), is that still the right number, cuz on the front page it says it's changed, just wanna make sure I call the right one.

 

Okay. So pinion angle is set in relation to what? There are only a few choices…the ground or the driveshaft.

I understand why it would be in relation of the drive shaft but I do not know why it would be in relation to the ground unless you are assuming that the engine/transmission and drive shaft are at 0 degrees in relation to the ground.

John

 

Correct. PINION ANGLE is just what it says - a meaningless phrase. It has no meaning without a frame of reference. ie, pinion is at 2* down from the moon, or pinion is at 2* down from horizontal, or pinion is at 2* down from imaginary line from rear contact patch through instant center, or whatever. So saying pinion angle is 2* down has no meaning what so ever.
Um, no, if your crank is at 0* WRT horizontal, and the pinion is down 2* from horizontal, you have done it right. Like I said, the drive shaft angle from horizontal doesn't mean squat. What you have done is set the pinion angle 2* down WRT the crank.

 

Lower in the pack, ie pointing up a bit. That should move the instant center up.

 

With a standard torque arm or aftermarket arm with a link in the front, the vertical location of the front mount has no effect on the dynamics of the chassis or load distribution under acceleration. Because of the design of the F-Body rear suspension, the torque arm plays only a minor role in instant center location. Now, a Madman TA that bolts solid in front without a link will act differently. If you remove the LCAs, you would have an instant center at the front TA mount. If you don't remove the LCAs, the rear end will bind because of the different attempted instant centers. Which would dominate? Not a clue.
Torque arm length will make a difference in chassis dynamics in two ways. First, the TA puts a vertical load into the chassis. This is distributed front to back according to the ratio of the TA length to wheel base. That is, if WB is 110" and TA is 55", the lift would split 50/50. Shorter lengths will tend to lift the rear more than the front with more of the vertical force going to the rear. Thus a shorter TA will reduce squat at lanch and can even cause rear end lift at launch if short enough. Again the TA acts sort of like lift bars (or ladder bars) except the link at the front prevents the IC from being located there. Second, a shorter TA will move the instant center to the rear, which will improve weight transfer.

 

Only with your TA, not with a BMR or the stock one.

 

It won't matter unless you have a Madman TA.

 

Wow, I leave for a few days and...Look what happened to this thread!
Just goes to show that people are learning the importance of a well tuned suspension!


LOL...MADMAN looks I got back a little to late, seems that you covered the subject pretty well in this thread!..."move er up 'n' pitch er back"... Umm, played with some wish-bone "T"s and some old school "shortys" have we?..lol Our vernacular may differ but we think alot alike.


later,
maggie

 

[QUOTE=critter]This isn't rocket science, guys.

UH...Well, actually it is. The exact same laws of motion apply...Velosity, acceleration, weight, mass, distance and time. Without Newton's Laws we could not begin to understand the dynamics of the forces influencing the actions of the vehicle of our sport.

Happy tunning,
Maggie

 

[QUOTE=Maggie] I'll give you that. What I should have said was it isn't black magic - it is simple physics (or rocket science if you prefer)

I think I menioned a lot of misinformation on this subject. On a lark, I googled for "pinion angle". Here are the first 10 hits. I didn't look for quality sources or filter this in anyway - just the first 10 hits.

http://www.carcraft.com/howto/91758/
http://www.2quicknovas.com/happypinions.html
http://buickperformance.com/Pinion.htm
http://www.4x4wire.com/tech/pinionangle/
http://www.iedls.com/ptsetup.html
http://www.drivetrain.com/driveline_angle_problem.html
http://www.wolferacecraft.com/pinionangle.aspx
http://www.quickperformance.com/PinionAngle.html
http://www.maliburacing.com/ssm_instructions.html
http://www.baselinesuspensions.com/info/pinionangle.htm

More than half of them get it wrong. People who should know, like Jerry Bickel, Inland, and Driveline Performance mostly get it right, but, surprisingly, Wolfe doesn't.

 

So since I have a Yank TA mount off the tranny and the TA is in the center holes..am I leaving some 60' on the table? I also have my LCA's set on the lowest hole and the adj. TA set at -2. It seems to hit really hard and sometimes spins just after it hooks. Is it unloading the rear because the way I have it setup? Here is a pic of it launching. It seems to do just the opposite of most people I see launching. Ya'll have any suggestions?