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Author Topic:   PINION ANGLE?
start79
Dirt Full Roller

Total posts: 56
posted March 03, 2001 11:54 AM
I have read on this forum that pinion angle doesn't effect forward bite. I have always been led to beleive that it did. If pinion angle doesn't effect forward bite, what does it effect? Thanks.

jammin
Dirt Administrator

Total posts: 3279
posted March 03, 2001 01:39 PM UIN: 16262997
Pinion angle affects two things.....1) U-Joint Life....because the more angle, the more it redirects the torque to the movement of the joint instead of hitting squarely on the side of the caps. 2) it is to keep your driveshaft from falling out under axle wrap....

The reason that people think that this enhances forward bite is because, when you give yourself more pinion angle in a car, and you dont change the mounting points of your trailing arms(or brackets), it increases the angle of the trailing arms when the pinion is pivoted down. The angle of the arms is what is giving the car the bite, not the pinion. It is something that people argue all the time, but this is exactly what happens. I hope this clears some confusion up for some people.

The only other scenario is when a car is on bird cages, and then the angle is strictly for driveshaft and u-joint purposes because the bird cages stay exactly the same since they float.

awkwardjeff
Dirt Freak

Total posts: 218
posted March 03, 2001 08:16 PM
Start79,
Go to the street stock page, go down to a thread titled FORWARD BITE the date is January 25 There is a lot of input on this subject, you can get jammin's opinion, my opinion, and another 15-20 people......
there maybe tooo much information for you to get through........never mind, don't look, it will only confuse you......LOL

I remeber that thread too well Jammin, That was a FUN winter time project, getting other people to see the world from our rose colored glasses.

Jeff

bbracer17
Dirt Maniac

Total posts: 168
posted March 03, 2001 11:46 PM
I've got a question about pinion angle that would go with a question I asked before. Everyone says 5-7 degrees of pinion angle and I'm sure everyone is checking this at the yoke with an angle finder. Now if pinion angle was just for u-joint life then wouldn't it be checked in reference to the angle of the drive shaft? My drive shaft is not level and I'm sure alot of others are not either.

start79
Dirt Full Roller

Total posts: 56
posted March 04, 2001 12:31 AM
Jeff,

Thanks I read the post you referred to, it helped explain a lot. I certainly do not want to open up that can of worms again. Although I will admit that some of it did make for humorous reading...

jammin
Dirt Administrator

Total posts: 3279
posted March 04, 2001 08:45 AM UIN: 16262997
Now, BB, I didnt say it was JUST for U-joint life did I? The downward angle on the Rearend keeps the yolk of the driveshaft in the tranny as it rotates upward under acceleration...If the pinion was straight to the driveshaft, both were flat, there is a possiblility of loosing a driveshaft when the rotation of the pinion occurs when your on the gas. This is because the rear end rotates around an axis.....this means the closest point to the rear end(which would be 0 degrees of pinion angle in relation to the driveshaft....not the ground) would be the closest point. If your static setup is at that point, then all the driveshaft has to do is go away from the tranny upon pinion rotation. If you set it up where the pinion rotation will push it in further, then the rearend movement(trailing arm geometry affects it too) will actually counter anything you do to the suspension. If you do not do this, and you run it flat, then with the combination of the pinion rotation and the rear trailing arms, it is very possible to loose a driveshaft. That is probably the MAIN reason for ensuring that angle is in the driveline. But the U-Joint life is important too.

jammin

bbracer17
Dirt Maniac

Total posts: 168
posted March 04, 2001 10:13 AM
I do understand all that, but what I was curious about is if your pinion angle was at 7 degrees and your driveshaft went upward toward the trans at 5 degrees now you have 12 degrees of pinion angle in relationship to the driveshaft. But if your driveshaft was level then you would have just 7 degrees of pinion angle compared to the driveshaft. does it matter? As far as I can figure if you don't pull the driveshaft out of the trans it will be ok either way but I just want to make sure. Thanks for your response.

awkwardjeff
Dirt Freak

Total posts: 218
posted March 04, 2001 12:56 PM
bb17, I explained what measuring the angles do for you and what angles to measure in the post I referred start79. Go back and read ALL of that thread then post any other questions you don't understand.....
.
PINION ANGLE......is the relationship of the pinion to level, or parallel to the ground.

DRIVE LINE ANGULARITY..... is the relationship of PINION ANGLE.....DRIVE SHAFT ANGLE.....AND TRANS TAIL SHAFT ANGLE.....

All these angles are from level...a positive angle is referred to when the front is higher than the rear.......
the pinion needs NEGATIVE we all understand that, the driveshaft will be positive, and the tail shaft will be level or positive depending on who constructed the car......MINE IS POSITIVE.....

People talk about pinion angle and drive line angualarity like they are the same thing. they are NOT.......some people measure pinion angle the way you describe, what they get is call THE WORKING ANGLE OF THE REAR U-JOINT........That's all they got.

Jeff

[This message has been edited by awkwardjeff (edited March 04, 2001).]

bbracer17
Dirt Maniac

Total posts: 168
posted March 04, 2001 02:04 PM
Thanks Jeff, I'll go read that thread.

bbracer17
Dirt Maniac

Total posts: 168
posted March 04, 2001 07:47 PM
Hey Jeff can you give me some numbers on driveline angularity or tell me what book would be good to learn more about it?

GnarlyCar
Dirt Forum Racer

Total posts: 96
posted March 05, 2001 11:04 PM
The easiest way to explain this is to say that the final goal is to have the pinion shaft parallel with the tranny output shaft under load. If your output shaft is level and your rear end wraps 6 degrees inder load, then set it at 6 degrees negative. If your output shaft is angled, say 2 degrees positive, and you get 6 degrees of wrap, then set it at 4 degrees negative. Output shaft at 2 degrees negative, 6 degrees of wrap, set it at 8 degrees negative. The final outcome should always have the output shaft and pinion shaft parallel under load. This will promote u-joint life, and ensure that your driveshaft won't fall out of your tranny, as it will be into the output shaft nearly as far as it will go at this point.

Matt

[This message has been edited by GnarlyCar (edited March 05, 2001).]

start79
Dirt Full Roller

Total posts: 56
posted March 06, 2001 10:32 AM
Matt, How do you determine how much wrap your rearend has under acceleration?

Thanks,

Ronny Taylor

GnarlyCar
Dirt Forum Racer

Total posts: 96
posted March 06, 2001 01:34 PM
the best way is to put some sort of travel indicator on your lift bar or pull bar. If you'r running any sort of braking shock on either one, you can use that. If you haven't got anything like that, you can make one pretty easy out of some coat hanger and a few o-rings.

Piece of cake,
Matt

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