Planning on changing differential gears to compensate for 37" tires. My truck currently has 30,000 miles on it. Do I need a total overhaul kit or just bearings?

Thanks, DB

 

An overhaul or install kit is mostly just the bearings and seals, with the addition of shims and marking compound. You don't need either if your having a shop install them. If your doing it yourself, then you will most likely need the shims and a way to mark the mesh. I wouldn't expect a truck with 30k miles to need bearings though. If your having a shop do it, leave it to them to determine once they have it apart.

 

Yea Im trying to contemplate whether its worth it to do myself or not.

 

If you have the correct tools and experience setting up differentials, then go for it.

If not, purchasing the tools (quality tools, not Harbor Freight tools) may cost you more than it would to pay someone to change your gears out.

 

If you use the existing shim pack under the large pinion bearing, and the same shims on the differential carrier side bearings (do NOT mix up which side they are in, but if you're not changing the differential itself nor the bearings, you don't need to remove them anyway), you are probably going to get lucky and you will get a good contact pattern.

If you don't know what I mean by "contact pattern", it means a nice oval contact on the driving side of the ring gear. "High spot blue", or just a good black magic marker rubbed onto the ring gear teeth and then spinning the pinion in the "forward" direction should produce a nice oval pattern in the center of the gear teeth.

That, and checking the backlash is within specs with a dial indicator are usually all that need to be checked.

If it's a Sterling rear, you have to set the pinion preload with a crush collar, that can take a lot of patience and if you go too far, need to take everything apart and put in a new crush collar and try again.

The Dana front-end is all shim based, and again, if you just use the stock shims and put them back exactly as they were, you have a good chance of everything lining up correctly. I'd still set the pinion preload on the Dana the "right" way though and not hope it's set correctly.

To get the pinion bearing off the pinion and back on, you'll need a hydraulic press.

(tech note: pinion depth is set with a dummy "standard" pinion, so the shims that are in there match the HOUSING and not the pinion - not changing the housing, the depth should be the same before and after)

Get a dial indicator, a good service manual, study it, and come back and ask questions