Never Change a Differential...

Just swap the entire rear end. It’s easier.

So I learned a valuable lesson over the last few weeks. I now understand why so many people laughed at me when I said I was going to do a diff swap from an open carrier to a posi-trac Auburn with fresh 3.08 gears.

You don’t do that unless you’re insane apparently.

I’m a pretty good amateur mechanic, good enough I could probably do it full time. But I don’t think I’ve ever tackled anything quite so repetitive and frustrating as changing out a set of gears.

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Shim the pinion; press on the bearing; put the pinion in; line up the carrier; shim the carrier and then discover the teeth don’t line up quite right. Take it apart. Press off the bearing; shim the pinion; press on the bearing; put the pinion in; line up the carrier; shim the carrier and then discover the teeth don’t line up quite right. Ad nauseam.

We must have shimmed and re-shimmed a dozen times the first try and when we figured we had it right and got all excited, we buttoned everything up and took it for a drive!

WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOoooooooo..... the diff howls. Accelerating and coasting.... pinion too far in. F**k.

Another week goes by and another weekend arrives, back up to the shop, take it apart, go through the shimming process again with fresh crush sleeves. We shimmed about a dozen more times before we finally got the teeth just right, and this time it didn’t howl on the test drive. Finally done. Only took us three weekends worth of work, 8 liters of diff fluid and two of posi-trac additive, two crush sleeves and almost dropping the diff and pinion on two separate occasions. Oh and our first weekend where we ended after realizing that all the carrier shims we had were the wrong diameter, that was absolutely the highlight.

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But it’s done! After sitting on my Auburn posi differential carrier and Yukon 3.08 gear set for over eight years it’s finally done and in. Both wheels spin, no howls or growls.

And then my 2004-R transmission decided to give up the ghost.

I bought a TH400 last week and that’s going in next weekend. If my Pontiac 400 manages to kill the Turbo 400 then I give up.

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