Differential compatability
 

I have an 89 4runner V6 5speed and I want to regear it to 4.56 or 4.88. To save myself the hastle of regearing my own, I am looking for a used set from a similar model. My questions are:

1. Are trucks and 4runner diffs the same?
2. Salvage yards keep asking me if its a 4 or 6 cyl, reg cab or extended. Does this matter?
3. What year trucks and/or 4runners are direct bolt in applications?
4. Are there any other considerations that I should know about before I drop 500 bucks on a set (ADD, auto hubs, etc.)?

Thanks from the eternal noob,

Andy

(For the rear diff)
1. For an 89 they should be, some models of pickups will have a rear anti-lock brake sensor hole and some don't.
2. There are different diffs for the 4 and 6 cyl models, the V6 3rd is a little stronger but you can use a 4 cyl 3rd in a V6 axle housing (I did for about 45,000 miles)

(I don't know about the front)

The only real difference if between the V6 and 4 cyl rearend. The V6 3rd's have larger bearings and stronger carriers. They are pretty much all interchangeable.

86-95? Sweet. That makes the search so much easier. So if a front has an ADD and I put it in my older 4runner, I can run it without it making a difference?

The rear you can go up to at least 2000 in a 4Runner. The elocker can be made to work too (but they only came with 4.10 and 4.30).

As for the front, I'm not sure about using an ADD diff on a non-ADD truck. I know you can do the other way around - it's a pretty common mod for people who have issues with the vacuum actuation system. Search on ADD removal or conversion.

If you want 4.88 diffs, some of the 90-95 4runners came with this from the factory. Look for a 90-95 4runner with the 3.0, auto tranny and 31" tires from the factory, these will have 4.88s. Check the drivers door sticker.

Note that the factory 4.88's are not regearable. If you DO go this route and change your mind, you're back hunting for diffs again.

Pickups too (with the 3.0, auto tranny and 31" tires from the factory) had 4.88s. But yeah make sure you really want 4.88s.

What makes them not interchangeable?

The pinion is offset in the housing so the ring gear is a totally different thickness. I wouldn't say it's a RARE option, but there surely aren't enough out there to interest the aftermarket in tooling up for replacement gears with the special thickness.