Swapping Gears

[comet_666]

Got a sweet deal on new Youkon 3.23 gears for my 489 case 8 3/4
What other parts should I change out when making the gear swap?

http://www.manciniracing.com/man834489cas.html


http://www.doctordiff.com/8-3-4-bearing-rebuild-kit.html

[Voss]

Would say it depends... I decided to replace my pinion and diff bearings when I changed my gears. Might not be needed if yours are good. A set of pinion shims is a must. Since you have a 489 case you also need a new crush sleeve. Gear marking compound is handy when you check the contact pattern.

A bearing puller is needed to swap the old pinion bearing, be careful not to damage your old bearing if you are going to reuse it. It won't come off easy! You also need a couple of torque wrenches to set the pinion bearing preload (in lbs) and for tightening the yoke nut and the ring gear bolts (ft lbs). To set the diff carrier bearing preload and backlash (0.007") I just used a 12" spanner wrench which I bought from Dr. Diff. The backlash is measured using a dial indicator. Measure at least at 4 places.

It's a trial and error work to dial in the correct pinion depth, so the critical part is to not damage your pinion bearing when changing shims. I actually bought two bearings and enlarged the inner diameter on one which I used as a test bearing. A good starting point is to use the same amount of shims as you currently have and take it from there.

Be aware the ring bolts are left hand thread! I gently sanded the surface on my new ring gear and the area on the diff, you do not want any burrs or residues on those areas. When installing the ring gear I gently heated it, makes it easier to slip it on. A tad of Loctite on the new ring gear bolts and you are done on that part. I used new ring gear bolts, probably not needed if yours are good and not over-tightened.

When checking the pinion bearing preload make sure the bearings are oiled, also make sure you oil the pinion nut and washer. When you have tightened the pinion nut, turn the pinion a few times to allow the bearings to fully settle, then check the preload. Should be 20-25 in lbs for new bearings.

If you use green bearings the thrust spacer inside the diff can be removed. If not, make sure it sits in place and does not fall out when you reinstall the rearend in the housing.

I also bought this tool to hold the rearend while I worked on it. It does not fit our rearends out of the box but you can easily modify it.

http://www.speedwaymotors.com/Assembly-Stand-for-9-Inch-Ford-Differential,2612.html

Take your time and good luck!

[myk]

^^^^^^yeah I'll be taking mine to the shop...

[comet_666]

^^^^^^yeah I'll be taking mine to the shop...

lol
Not something I would attempt, however my engine builder has done this many times.