how do set correct pinion angle
how do set correct pinion angle
(OP)
I installed a 9" FORD IN MY STUDEBAKER. HOW DO I SET PINION ANGLE?
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
how do set correct pinion angle
|
RE: how do set correct pinion angle
I'm assuming you've got a live rear axle
1) measure the rotational stiffness of the rear axle system, in terms of degrees per ft lb of wheel torque. call this k
2) measure the installed angle of the pinion nose in the original installation, with the wheels on the ground. call this alpha.
3) Call the old axle ratio R
4) call the new axle ratio N
5) call the maximum output torque from the gearbox T
Then the new installed angle = alpha-NTk/R
where - means anticlockwise viewed from the left
In more general terms it is hugely complicated, and as usual it's a compromise. In an 'ideal' system using the centreline of the output shaft of the gearbox as the datum, then you set the diff centre on that datum, then point the pinion nose down a bit to allow for windup under torque.
If you can't put the diff on the datum then it is a good idea to point the diff at the gearbox output shaft, and then drop the pinion nose a bit.
Rule of thumb: UJ angles less than 2 degrees for good refinement (actually need to be within 0.3 degrees for some apps). UJ angles not to exceed 4 degrees at maximum torque. UJ angle at no load could be -2 degrees (ie pinion points below gearbox), so giving you 6 degrees of windup, if you need that much. Half of all the above figures is a better bet.
Make sure you understand the phasing of UJs.
Cheers
Greg Locock
RE: how do set correct pinion angle
Good luck!
RE: how do set correct pinion angle
Rod
PS---Do you have a formula for setting up a crownwheel and pinion?
RE: how do set correct pinion angle
Hey, that was the crudest approach that I thought might work straight off the drawing board. I can make it as complicated as you like (well actually I'd hand you over to someone who can work out the geometry of the UJs)! In production this stuff is pretty crucial - if you can keep UJs instead of CVs you've save 20 or 30 bucks a car, and got a more durable system. if you can keep a single piece driveshaft instead of a two piece that's about fifty buck a car, minimum, and a lot less trouble. That means we can throw 80 bucks into a car if we get these angles wrong- which would pay for a lot of bells and whistles.
My mechanic tells me that the recommended way to set the diff preload after dissassembly is to torque up the pinion nut until you get the same torque to turn as you originally had (our diff is set up using a collapsible spacer).
Demonstrably in our experience over the past year this is a bloody good way of introducing axle whine into a previously quiet diff, so the answer is no!
Cheers
Greg Locock