rear differential backlash issues
 

:Wconfused

Problem: excessive slop in the differential.

replaced/ or reset the following:

new pinion shaft bearings and seals
new carrier bearings
all new plates, and cups in the LSD unit
pinion depth set by mazda, (I rechecked, its correct)
backlash between ring and pinion set by mazda (it was at the upper limit when they finished according to the 1984 service guide {FSM} so i reset it to the minimum)

only thing left that I can think of is the actual planetary gears in the LSD, and maybe the interface between the splines on the axles (moser units) and the LSD. any thoughts?

I am at my witts end on this one, it causes no problems when at speed, only at low throttle applications, my cars throttle responce is so quick that it causes the car to start jerking, and that coupled with the slop in the drivetrain cause the car to jerk violently back and forth which then causes my foot to bounce on the throttle making the problem worse.....

thoughts?
opinions?
help?

Kenn

Is there any whining noise coming from the rearend?

Spider gears dont effect pinion/ring interface since they are contained within the carrier itself.But,wear in the spiders and/or axle splines can definately induce more driveline lash.
You didnt mention carrier preload,but I assume if they did all the other stuff,the dealer would have set the carrier bearing preload too.
If the carrier bearing preload was set by the dealer,then there really isnt anything left to cause the play.Carrier preload isnt an exact science since the drag of the pinion doesnt allow a precise setting.Carrier preload is usually just as tight as you can get the adjusters,with a 1' wrench/bar.With shims,its just set snug with as many shims as can be shoved in there.The low RPM of the carrier bearings means they arent likely to be hurt by high preload,and a tight carrier prevents the lash/pattern from changing under power/coast,since the pinion is always trying to deflect the carrier away from itself.

Well, this stuff is a little over my head but I thought I'd ask if the other parts of the driveline are tight. Ujoints, tranny mount, and motor mounts... I'm sure you've got all that stuff covered though. Good luck Kenn. :)

Doc,

No whining, just the slop that causes it to jerk real bad,

after setting pinion, depth (new crush tubes and etc.) and resetting the backlash, i put it on the lift, and with the parking break locked, the front companion flange will turn about 1/8" which is not much, but if you grab the two tires and try to turn them in the opposite directions, they will turn about 1/2" in the opposite directions before the clutch packs(LSD) stop them. it appears to be slop in the spline shafts...

kenn

I don't know Kenn. The jerking problem that you are describing sounds like throttle or mixture problem. I have come across this on other vehicles both carb'd and injected, however I don't remember if it was a lean or rich condition that caused it.
The amount of play that you are describing is very minimal.

Also if you had excessive play in the pinion or gears you would probably be getting some sort of a clunking noise also.

Have you checked the throttle cable to see if it is too tight?

I'm with doc. I dont' see how excessive backlash would cause your car to jerk back and forth. If you had excessive backlash or incorrectly adjusted ring and pinion, you would have some noise issues- whinning or clunking.