Replaces the collapsible crush sleeve in a Chrysler 8.75 489 case pinion with a solid spacer and shim pack so bearing preload holds.
If you are regearing or rebuilding a Mopar 8-3/4 rear from a Charger, Coronet, Challenger, Road Runner, Fury or Dart and want pinion bearing preload that does not move after the first hard launch, this kit takes the collapsible crush sleeve out of the picture. Yukon part number SK CSC8.75 is a solid pinion spacer with an assortment of preload shims, built for the 489 case dropout. You set preload by shim thickness, measure it, and it stays where you put it.
The pinion in a 489 case rides on two tapered bearings, and the space between their inner races decides how tightly they are loaded. From the factory that space is held by a soft steel sleeve that collapses as you tighten the pinion nut; you stop when the rotating torque hits spec. The trouble is that a sleeve only crushes one way. Go past the number and the only cure is a new sleeve and another try, and a sleeve that relaxes after hard use lets the bearings go loose. The solid spacer here does not collapse. The pinion nut gets torqued to full spec every time, and the shims under the spacer set the preload. If it reads tight you add shim, if it reads loose you remove some, and nothing is used up on the way.
With the driveshaft off, grab the yoke and check for end play, then turn it by hand to feel for roughness. Learning whether the noise is axle or transmission saves a lot of guessing; our guide on telling transmission noise from differential noise walks through it, and pinion bearing noise symptoms covers what a loose pinion sounds like. The full rundown of this axle is in our Chrysler 8.75 problems and rebuild cost guide.
This kit is for the 489 case only. The 8-3/4 was made in three center sections. Mopar references identify them by the large mark cast on the side of the housing: an X for the 741, a 2 for the 742 and a 9 for the 489. The 741 and 742 set preload with shims and their own spacer and do not use this part. The 489, with its larger tapered pinion stem, is the one that came with a crush sleeve. Check the casting before you order. If you are not sure what you have, send us the casting number and vehicle year and we will check it. Bearings for the 489 are in the Allstar ALL68531 489 installation kit, and more axle parts are under hard parts.
For more on the trade-off, see crush sleeve vs solid spacer.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is for the 489 case only. The 741 and 742 cases use a different pinion bearing and spacer setup. Look for the large 9 cast on the side of the housing to confirm a 489.
No. It contains the solid spacer and an assortment of preload shims. Bearings, the pinion seal and pinion nut come separately, for example in a 489 installation kit.
Torque the pinion nut to full spec, measure rotating torque with an inch-pound torque wrench, then add shim if it is too tight or remove shim if it is too loose until you hit the service manual figure.
It is most useful on cars that launch hard, tow or get a ratio change, because the preload cannot relax the way a crushed sleeve can. It also lets you reassemble as many times as needed without buying new sleeves.
If they are smooth and unpitted you can, but set preload to the used-bearing figure in the service manual. On a regear most builders replace them while everything is apart.
