Isuzu Differentials FAQ
Author: Randy Burleson

Pre-release -- work in progress, but good info, I think.

OK, here's the straight information on the differentials, from two sources: the Hollander Salvage Yard Interchange Reference and my own junkyard testing. If you find any exceptions, I'd love to hear of them, so please email me at [email protected].

Three types of Isuzu corporate differentials exist: 8-bolt, 10-bolt, and 12-bolt. The number of bolts refers to the number of bolts holding the ring gear to the differential carrier and not to the number of bolts holding the third member to the axle housing. Note that on this page, unless otherwise specified, Corporate X-bolt means ISUZU Corporate X-bolt, and not a GM Corporate X-bolt -- these terms are NOT interchangeable.

The Dana 44 is not an Isuzu-manufactured axle, and we don't have a lot of information on it. Similarly, the GM 10-bolt differential is not an Isuzu-manufacturedaxle, so we don't cover it in depth here. Most products made for other these axles for use under trucks of other brands should work for the corresponding Isuzu axle, as well, though some may require creativity and modification.

General Applications Across Models and Years

The following options in this section represent my best guess at simplifying the differentials assembled in Isuzu light trucks that were sold in America: Trooper, Amigo, Rodeo, and P'up. This extends to other makes that were essentially rebadged Isuzus: the Chevy Luv was a P'up, the Honda Passport was a Rodeo, and the Acura SLX was a Trooper. I don't have data for the foreign trucks (Vauxhall, Holden, etc.) but I imagine much of the info is the same, especially if the truck in question was assembled in Japan.

8-bolt corporate differential (??-spline axles)
Front differential on pre-2/88 Troopers and Luvs
10-bolt corporate differential (17- spline axles)
Front differential on all late model trucks (American AND Japanese-assembled trucks)
Rear differential on pre-2/88 Troopers and Luvs
Rear differential on certain late model trucks with rear drum brakes.
12-bolt corporate differential (26-spline axles)
Rear differential on any Japanese-assembled truck with disk brakes
Dana 44
Rear differential on any America-assembled truck

Hollander Crossreferences

Here's what Hollander says will crossreference - note that Hollander does not specifically call out that 10-bolt front differentials will fit in the rear, and vice-versa. That doesn't mean it won't necessarily fit -- Hollander doesn't know much about this kind of sleight-of-hand swap, even for mainstream vehicles like Jeeps.

Below, the lines are grouped according to what Hollander says will interchange. According to Hollander, the 89 Amigo front differential would interchange with a 94 Passport but not a 93 Rodeo.

FRONT
Trooper 84-1/88 Front

Amigo 89-92 Front
P'up 88-92 Front
Rodeo 91-92 Front
Trooper 2/88-10/92 Front

Acura SLX 96-97 Front
Amigo 93-94 Front
P'up 93-94 Front
Passport 94-97
Rodeo 93-97 Front
Trooper 11/92-98 Front

REAR
Trooper 84-85 Rear
Trooper 86-87 Rear Locking

P'up 88 rear axle through 1/88 with drum brakes
Trooper 86-87 Rear non-locking

Notes:
What's this locking/non-locking business? Dunno for sure. Odds are that it is Hollander's nomenclature for the Isuzu Limited Slip Differentials (LSD) that certain rare trucks came with. No one that I've talked to has ever seen a factory-locking differential for these trucks. I'm not honestly sure that is what Hollander is talking about when the say "rear locking," but that's my best guess.

My guess is that when you factor out the antilock brake differences (tone ring, sensor, etc), this list of interchanges will match the one above in General Applications. Thus, in the example I cited above, with the 89 Amigo front differential that Hollander said would interchange with a 94 Passport but not a 93 Rodeo, my guess is that the 89 differential WOULD interchange with one from a 93 Rodeo - and vice versa. You just might not retain the anti-lock braking functionality.

If you find any exceptions, I'd love to hear of them, so please email me at [email protected].

SWAPPING -- What Will Work?

Ok - here's the real question - what can you swap?

Well, first keep in mind that if you have anti-lock brakes and want to keep them, you need to find a donor truck with antilock, as well. Also remember that you need the front and rear gears to be within 2% of each other if you ever want to engage 4x4 and not destroy expensive drivetrain parts.

You should be able to swap any differential for another if it has the same number of ring gear bolts, regardless of whether it originally came in the front or the rear. Since 8-bolts were only available in the font, and 12-bolts were only in the rear, they are pretty simple. But 10-bolts seem to be universal - they all use the same 17-spline sidegears. I say this after test-fitting an actual 17-splined axle into 20-25 front AND rear 10-bolt differentials at the junkyard.

Lockers

PowerTrax LockRite
What all this means is that the pre-2/88 Trooper LockRite will almost assuredly work in all 10-bolt differentials. If you verify fit of a LockRite into a differential, I'd love to hear about it. So far, I can only verify that a 10-bolt rear locker from a pre-2/88 Trooper fits into an 88 front differential and works. But I bet it will fit the rest of the front differentials in all late model Isuzu 4x4 light trucks.

ARB Air Locker
ARB currently only makes air lockers for the Dana 44 and Isuzu Corporate 12-bolt, more on this soon

TrueTrack Detroit Locker
Works only on the Dana 44, more on this soon

TrueTrack Easy-Locker and Gearless Locker
Currently only applications for the Dana 44, but there may be some exciting developments on this soon - wouldn't it be cool to have Gearless Lockers for 10-bolt and 12-bolt Isuzu corporate differentials?

Limited-Slip Differentials

There's only one maker of limited slips for Isuzus - Tojico Fuji (sp?) in Japan. They market their locker to a whole bunch of aftermarket manufactures, some of whom sell it under a different name, but it seems to be the same locker regardless. Limited slips are available for the 10-bolt and 12-bolt, but I've not seen any for the 8-bolt, and doubt that one exists. If you KNOW FOR SURE, please email me at [email protected].

Let's get to the bottom of this...

I've no information yet for the 98-99 trucks - they aren't in the interchanges yet and I haven't popped one apart myself. I have confidence that the front differential is the same as all the other 10-bolts. If you KNOW FOR SURE, please email me at [email protected].

As for crossfitting lockers, there's been scads of "I heard that...." and "I wonder if..." floating around -- I'm looking to get to the bottom of this. If you have hard anecdotal evidence (i.e "I did it and it worked for me."_ please email me at [email protected] and I'll add you experiences. If you know somebody who has done it -- cool, send me their email, or there name and phone number. I'll post more here as I know more.

Proven crossfits include:

  1. So far, I can only verify that a 10-bolt rear locker from a pre-2/88 Trooper fits into an 88 front differential and works.

Please mail the 4x4Wire Isuzu Staff if you have questions or comments about this page.


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