Pinion angle woes!!

[Annoying Eric]

So what are your opinion on pinion angles. I need to set mine in the next few days and my 4 link is non adjustable so i need to be spot on. Ive always thought a street car. 1/5 -3 degress nose down. Recently someone said 4+ but that seemed excessive.

 

[oldracer22]

General rule of thumb. The angle of the centerline of the pinion shaft should be equal and opposite to the angle of the centerline of the engine/ trans. In other words, if the engine is angled 3* down then the pinion shaft should be angled 3* up. This rule of thumb is for rear suspensions that will not change pinion angle on acceleration (4bar, 3bar, ladder bar etc.) If leaf spring you must account for spring wrapup, angling the pinion shaft down some degree from the above rule of thumb, depending on the amount of wrapup.

 

[Colorodders]

General rule of thumb. The angle of the centerline of the pinion shaft should be equal and opposite to the angle of the centerline of the engine/ trans. In other words, if the engine is angled 3* down then the pinion shaft should be angled 3* up. This rule of thumb is for rear suspensions that will not change pinion angle on acceleration (4bar, 3bar, ladder bar etc.) If leaf spring you must account for spring wrapup, angling the pinion shaft down some degree from the above rule of thumb, depending on the amount of wrapup.

Great info!

 

[jfg455]

Depends on how you set up your 4 link. GM 4 links (triangulated unequal length) like to have about 3-4* down angle. you will get some axle wrap due to having rubber bushings. I would set it at 3* down and then make sure your front u joint matches (3* up)

 

[sgtpontiac]

Yep...what he says..

Depends on how you set up your 4 link. GM 4 links (triangulated unequal length) like to have about 3-4* down angle. you will get some axle wrap due to having rubber bushings. I would set it at 3* down and then make sure your front u joint matches (3* up)

should work well......

 

[donsrods]

Sometimes I feel car builders tend to over think how to set up pinion angle. I have always shot for 3 down on the trans and 3 up on the rear and never have had any driveline issues. Sometimes I have even had to go to 4 degrees down and 4 up and still no issues.

If you look at some of the crazy driveline angles jacked up 4 x 4 trucks and lowriders are running, you can see the extremes these angles can go to. I have even had a mismatch, where the trans was down 3 and the rear up 5 or 6 degrees and it still worked fine.

Don

 

[sneakysnake]

I know 0* is bad because it doesnt let the needle bearing rotate properly but why is 3* the magic number and other than binding or excessive wear why is over 3* bad?

 

[RPM]

General rule of thumb. The angle of the centerline of the pinion shaft should be equal and opposite to the angle of the centerline of the engine/ trans. In other words, if the engine is angled 3* down then the pinion shaft should be angled 3* up. This rule of thumb is for rear suspensions that will not change pinion angle on acceleration (4bar, 3bar, ladder bar etc.) If leaf spring you must account for spring wrapup, angling the pinion shaft down some degree from the above rule of thumb, depending on the amount of wrapup.

This pretty much sums it up. This is how we set up the cars we build in our shop. We only angle the pinion down on an all out drag race car, with slicks.

 

[oldracer22]

I know 0* is bad because it doesnt let the needle bearing rotate properly but why is 3* the magic number and other than binding or excessive wear why is over 3* bad?

3* I think basically comes from the mounting angle of the carb. On a SBC the carb is mounted at
3* degrees from the crank centerline. Engine @ 3* down gets the carb level.
Annoying Eric. In order to suggest a pinion mounting angle, we must know the angle of the engine/trans or at least the angle of the driveshaft, and your method of mounting, (4bar, leaf,etc.) and the type of connectors,(heims, poly bushings, or rubber).

 

[bob w]

I tend to install engines level rather that tilt to the rear. I set the pinion level too. Generally there is an elevation difference between the trans tailshaft and the pinion centerline. That elevation difference creates an angle on the driveshaft. So, in effect the angles are still equal and opposite.

 

[Annoying Eric]

Whole bunch of different opinions. lol. Im running a 4 link with rubber bushings. I guess i'll throw the rearend in the car and set it to maybe 2.5 - 3.5* and try and get a front measurement first just to see what im working with. How does that sound? lol. I wasnt the intial person to set the motor and trans in the car. From what im getting is basically i need to match my front and rear angles.

 

[oldracer22]

Check the angle of the crank with an angle finder on the harmonic balancer or on the tailshaft of the trans. Set the pinion equal and opposite. If you are mounting the 4 bar in rubber, go down probably 2-3* from equal and opposite.

 

[jfg455]

This pretty much sums it up. This is how we set up the cars we build in our shop. We only angle the pinion down on an all out drag race car, with slicks.

Yea I was coming from my days in racing. if you are at 2-3* up on the pinion and then launch hard the deflection in the bushing will turn you 3* up into 6-7* up causing bind, shake etc. There is a whole other world concerning "Bite" of the tires and pinion angles but we don't need to get into it here. [cl

 

[BillM]

I wasn't aware of any issues at launch, my understanding (and experience unfortunately) is that any mismatch rears it's ugly head at high speed - that's when all the harmonic energy of the "not cancelling u-joint orbits" happens. This is also made worse when your axle ratio is high - hence faster spinning drive shaft (and again, high speed). My Swinger had a incorrectly installed offset kit, and suffered from extreme high frequency vibration after about 75 miles an hour. After a lot of checking, I found that the pinion angle was about 4 degrees down.....shimmed the spring pads and it's all better. I'd never noticed anything at low speed or launch.

 

[RPM]

The angles of a drag car are totally different than that of a street car. If you just race on the weekend and drive it on the street during the week, consider it a street car. On a drag car we don't car about having the needle rotate to move the grease around, so the ujoint does not wear as fast. We want the drive line as straight as possible to no use any more power to run it. It takes some power to run the ujoint at even 3 degrees.

So on all out drag car you want the pinion down about 3 degrees. Then when all the power is applied, that rear end will rotate up and the pinion will be in direct line with the trans. So we will have 0 angle on the drive line. Thus taking the least amount of power to run the drive shaft.