DIY: a quick outline on why & how to set pinion angle.

[assassin10000]

Setting pinion angle is about eliminating driveline vibration & ensuring u-joint longevity.

In a perfect world the 'best' place is to have the pinion angle parallel to the engine/transmission angle. For example, if the engine/transmission are 4 deg nose up, the pinion should be 4 deg nose up. But since its not a perfect world, pinion angles are typically anywhere from .5-4 degres under the engine/transmission angle. This is due to play/slop/load/compression of the suspension bushings/joints.


A few a general rule of thumb's when it comes to setting pinion angle:
1. You do NOT want the u-joints operating at 0 degrees! You want a 'working' u-joint angle of 1-3 degrees so the u-joints stay lubricated. (See links below.)

2. The pinion angle should be anywhere from parallel to the transmission/engine angle OR anywhere up to 4-6 degrees below it. The amount of angle below depends on your suspension, both type/design and soft/stiffness. Typically it will be something along these lines:

Link suspension:
Solid bushings/Heim joints = 0-1 degrees below
Semi-solid/mixed setup = Up to 2 degrees below
Stock/softer bushings = Up to 4 degrees below

Leaf suspension:
Depending on power/suspension/setup = 2-6 degrees below


Don't believe the hype. Pinion angle has little to no effect on power or feel. In the old days it was considered important on drag cars with squat characteristics built into the rear suspension (and usually with leaf springs), as they try and line up the driveline under accel to get the 'most power' to the ground... and possibly to prevent from exploding their u-joints with extreme axle wrap.


Want to know more? There's a lot info in these links so I don't have to regurgitate everything else:
http://www2.dana.com/pdf/J3311-1-DSSP.pdf
Slightly older and some out of date info from me here:
http://forums.club4ag.com/zerothread?id=31679
http://www.hachiroku.net/forum...23559


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The car does not have to be on level ground to do this. BUT the car does need the rear suspension loaded (weight of the car on the differential) to get the proper angle at ride height. I would recommend having the diff housing on jackstands and a jack at the 3rd member/pumkin to raise and lower the diff to 'settle' it after adjusting.


I've found when it comes to taking measurements don't use the usual angle gauges available at hardware stores, the scale/resolution is not even close to good enough. I also prefer NOT to use the angle gauges that measure at the u-joint caps, or a socket in the cap to place an angle gauge against to measure. Doing it this way is not accurate enough, as can be seen here:






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I like removing the driveshaft for taking the actual measurements, as I prefer to get it directly from the output shaft/pinion flange like so:



Note: if you have a 2-piece it's a little more complicated, as you also measure the angle at the flange between the front & rear halves.


Engine/Transmission angle measured:




Pinion angle before measurement:



Then you adjust your pinion angle, start it parallel and adjust downwards as necessary to eliminate noise/vibration when cruising. On the AE86 that usually requires adjustable length 4-link. So bust out your wrenches and lengthen/shorten the upper/lower arms as necessary to get your desired angle.


Pinion angle after measurement:



For reference, the driveline angle:




Remember where I mentioned above the recommended u-joint operating angle is 1-3 degrees? If you look at the numbers on mine it works out to .40-.45 degree's. Despite that fact, it's not a problem on the AE86 which has a compound angle driveline.

I took a quick measurement and found that the pinion itself is offset approximately 1 inch from the centerline of the car in the horizontal plane (assuming you've centered your differential if lowered). That offset works out to about 2.4 degree's in the horizontal plane, or 1.2 degree's each u-joint. That works out to about 1.3-1.4 degrees operating/working angle for the u-joint's and is pretty much right where you want it, as between 1-3 degree's is what you want.


Andrew

[ditn]

old post revive but i have a question on this.
due to another gearbox i want to check this.
i was wondering which reference surface you use for the gauge.
or am i missing something hre on how gauge works?

[Ivan141]

The gauge probably works with an accelerometer, which references ainst gravity. You could also use a smartphone with an app to do this.
Since your measuring a vertical surface, you'll probably need to zero the measurement against something perpendicular to the floor the car is sat on.
That measuring cube has the advantage over a phone in that regard, you can just zero it on the floor.

[ditn]

I have a measuring cube,but the floor isnt always even and 1-3 degrees is not much.
Since its rallycar the floor is also flattened, so i was wondering which zero point of the car i take

[Bean]

As far as I'm aware you are looking at the difference between the measuring points, so just 'zero' on the first point and take it from there

Sent from my SM-T800 using Tapatalk

[ditn]

still very confused

you have to measure if gearbox shaft lines up or is parallel to the diff pinion right?
and then also the working(u-joint angle?) angles for both diff pinion and gearbox shaft and middle part.

good pic


all measurements like this?
engine gearbox and front shaft in 1 line
measure diff pinion and it should be parallel
afterwards measure the working angles


at rear i have rose joints for axle and poly rubber on chassis
gearbox mount has a bit stiffer rubbers almost like oem.

Ill try to measure all i can and come back with results next week.

[ditn]

no one ?

[Bean]

Waiting for you to come back with results from what you measured, we'll take it from there

[ditn]

ok ill do it this holidays.
stumbled on some delay with the project

[ditn]

Measured the first part
placed tool on valve cover and set it to zero
measured on the front axle and it said 1 degree up
So ill start with getting this even