I have a 2.56 open 10 bolt out of another '71 skylark in my skylark. The mileage on this unit is unknown. It works well, but the gear backlash seems a bit excessive, I get a little bit of driveline clunk from on-throttle to off, and back again. Can this be adjusted without rebuilding the whole rear? Thanks!
.008-.010" ring and pinion For the spider&side gears in the carrier (more likely the cause of a clunk than the ring and pinion IMO) I would tighten them up to .003-.008 (RAtech sells the shims at summit, or you could get a internals kit with new carrier gears etc) Lots of things make driveline "clunk. Worn/damaged Ujoints for one. Worn/damaged transmission case and or internals for another. Motor/transmission mounts failing. worn rubber bushings. Be sure what the clunk is. Time for a close inspection
Also check your pinion shaft NUT. If that is backing off slightly you will have a wider backlash on your ring and pinion....BUT you will start to hear noise like gear noise if it gets too backed off and a leak from the pinion seal soon after that. SO you have a lot of places to check and all that are listed COULD be the trouble. I highly doubt the ring and pinion are worn to need a reshimming. LOOK else where first. JIm
I'm pretty sure it's in the rear. I recently swapped out a 4.10 rear and put the 2.56 in for economy purposes. I did not notice any extra backlash with the 4.10 rear. The driveshaft was just re-done with new U-joints. I'll have to check the pinion nut. Would there be perceptible axial play of the pinion if that was out of adjustment? How do you measure the clearance on the side gears? Thanks!
IN otu end play of the pinion should be NIL NONE . If you have any in out play you have trouble. DO not confuse this with the twisting of the pinion which will be connected with the backlash of the ring and pinion. Spider gear specs will vary and USUALLY will NOT cause problems unless there is excessive wear or thrust washer or wrong parts were installed from someone monkeying around. SO a once over look at the spider gear teeth should let you know right away whether you have issues there. LOOK for very thin or sharp peak wear on the spiders ...If they look like this you have trouble and will need to replace them quickly. If they are smooth no pitting or break down and have a flat 1/8" peak on all the teeth your probably fine there. Start there and see what you get- The side gears on a open diff will each have one .020-.040 steel thrust washer/shim each pinion/small spider gear will also have a thrust washer...IF these are missing they need to be replaced with new or good used. - Another thing to check would be if the pinion cross shaft (larger steel pin that the small spider gears rotate on) are not pitted over heat broken down etc. THAT pin should slide out very easy or again we have issues and parts need replacement...THIS happens when too much debris/dirt get over heated from excessive high speed spinning from BURN OUTS...lol. SEE this alot on the poor one wheel wonders. Jim
