Rear Diff 489 Bearing Preload Help Needed

[magoo426]

Hello everyone.

I'm trying to rebuild my 489 rear diff.  I'm having some trouble with the pinion bearing preload.  I've bought Dr Diff's crush sleeve eliminator kit and along with new 3.73 gears from them as well and their rebuild kit.  Before I start applying torque to the pinion nut the pinion rotates freely, no problems.  When I start torquing the nut on the pinion to the spec of 170 ft-lbs.  The bearing preload is too high and is difficult to turn.  This is my first time rebuilding a rear diff so I'm learning as I go.

Has anyone experienced this before or have some ideas of what I'm doing wrong?  My pinion depth is right where it needs to be I believe. 

I'm sure I'm leaving out some important info to help with the diagnoses of this item, so if more information is needed then please let me know.

Thanks!

[dakota]

  This is one of my upcoming tasks, so I'm curious to see the replies.

[magoo426]

I may figured something out.  I haven't used the shims that were in the kit as shown in the picture.  So I'm assuming this will push against the bearing that is at the top of the pinion as it tightens while preventing the bearing from bottoming out on the cup. 

Does this sound right? 

Thanks.

[jhaag]

Yes you have to use the shims to adjust the preload. How do you know your pinion depth is correct? Depth is adjusted by shims behind the rear pinion bearing. Sounds like you are unsure. To do it correctly you really need a pinion depth gauge.

[magoo426]

Hi jhaag.

I measured the pinion depth as illustrated in the photo I found.  The pinion gear was etched with 2.766 and when I measured that distance it was about 2.762~2.768.  So I think I'm pretty close.

I'll take the pinion back out and put a shim or two on top of the sleeve to see if this will reduce the bearing preload so it spins better.

[Chryco Psycho]

  If it is tightening up with torque you need to add shims to increase the length of the spacer so it will turn correctly

[soundcontrol]

This is one of my upcoming tasks, so I'm curious to see the replies.

Same here.
(just posting so I get notifications of replies).

[jhaag]

Magoo, you can get by using that method and then double check your depth and contact pattern when you install the ring gear. However a pinion depth gauge would be the preferred method. I understand most people don't have access to an expensive tool you rarely use. Looks like you are on the right track. 

[magoo426]

Well the shims did the job.  Had to use 3  0.010" thick shims to get the bearing preload in spec.  Also, the pinion depth was in spec as well, so that was nice to see.  Now onto getting the backlash set and all that fun next.

Thanks for your help guys.