Rear end play
 

When I jack up the rearend and turn the tires one way then the other, how much play should I have before the driveshaft starts turning?

Ford 9".

Any help is appreciated.

Do you have a posi in the diff, or is it open? jimig@standardtransmission.com

I have the traction-loc with 3.20 gears

Worry about the backlash betwween the pinion and ring gear
 

danc30 Worry about the backlash between the pinion and the ring gear. If you are running a posi the backlash is looser than an open rear. Different posi's lockup in different ways. I have a locker in my Jag rear that drags the tires maken sharp turns but works fine for dragracing. Some lockers work with clutches and springs, some are gear to gear like(Gleason-Torsen) some are air controlled. You will have alot more rotation at the tire than the drive shaft. If you are running the car hard and is a clutch plate rear, you need to change the fluid with adders for offen to keep the posi work good. After awhile you may have to replace the clutch packs with new springs, clutch plates to get the same good posi effect. You want to put the car in netural and spin the drive shaft back and forward and feel the play. After 20+ years in mechanicing I have a good feel for backlash. You need to really pull the rear cover if it has one or the pumpkin assembly and check with a dial gauge. Checking the fluid for metal shavings also may give you a per warning about possible problem in the rear. Bearing going bad, clutch material, pinion spiders having wear problem. Lock the parking brakes and turn the shaft, movement should be no more than1/4". THIS IS A GUESTAMENT. If you are not sure take the car to a GOOD KNOW race shop in your area and have the rear checked. Fluid change only with FORD products. Rick L.

Thanks Rick