Setting up your own gears on an 8" diff


Dec 17, 2008
I've been setting up my own gears for a long time now (infrequently) and just ran into a few industry changes that caught me off guard (specifically Yukon Gear, but others are likely the same). Hopefully I can save "the next guy" some trouble by putting this out for anyone that doesn't already know. At least it'll give people the knowledge to ask more questions beforehand to be sure of what they're getting and how to install it. (Unless I've been doing it wrong all this time? Geez, I hope not!)

1) MOST gear sets for Toyota 8" diffs have been 27-spline pinions until recently. Toyota apparently began changing over to 29-spline pinions at some point with the V6 Tacomas, so now the gear manufacturers are phasing out 27spl stuff for the 29spl stuff.

The 29spl pinions are stronger.
New [Yukon] gear sets come with the needed [3-pattern] flange. (for now)

You cannot reuse your old flanges.
You cannot use pinion seals you may have on hand already.

2) It appears the way to set up the inner pinion bearing has changed... At least on the V6 diff. I have not checked if the same is true for the 4cyl diffs with smaller bearings, but my guess is that the following info probably pertains to any of the 29spl pinions.
Instead of pressing the inner (larger) pinion bearing on and off to change shims, you now shim the race within the housing instead. I figured this out the hard way after realizing the bearing was substantially harder to press off than any I have done before.

Significantly easier to R&R the race in the housing than it is to R&R the main pinion bearing.

New shims will have to be acquired since the OD of the race is much larger than the OD of any current shims used for a Toyota 8".

Amplifying info:
I have only ever set up Toyota 8" diffs including 4cyl and V6 low-pinion rears and high-pinion fronts.
When setting up new gears, I have only worked with Yukon and USA Standard Gears.
I always set up gears with solid pinion spacers, no crush sleeves used.
I almost always reuse my bearings since they're on a crawler.
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