Differential Identification

The place to discuss problems and routine maintenance questions and tips that are NOT specifically diesel-related.
fasteddie
Regular Member
Posts: 100
Joined: Thu Mar 17, 2011 8:11 pm
Location: Jersey City, NJ

Differential Identification

Postby fasteddie » Mon Sep 23, 2019 8:33 am

I have a '89 Japan built 2.3 2WD. The diff has a third member, no back cover. I'm pretty sure it is a 10 bolt ring gear but some parts house listings mention 10 bolt 7.625" some only say 10 bolt ring gear. Is 7.625" the standard Japan diff that I would have?
1989, 2.3L, 5 speed pickup, original owner

oldestisuzuist
Regular Member
Posts: 1378
Joined: Tue Oct 07, 2008 9:10 pm
Location: N W Arkansas

Re: Differential Identification

Postby oldestisuzuist » Mon Sep 23, 2019 9:42 am

If your truck is Japan-built you have the Isuzu corporate 10-bolt differential. The "10-bolt" designation refers to the number of ring gear attaching bolts, not the number attaching the drop out third member to the axle housing. Ring gear diameter should be 194mm or 7.64", which is nominally 7-5/8" & it may be referred to as such to distinguish it from the larger 12-bolt ring gear.
The 7.625" reference you are seeing usually is to the GM 7.625" 10-bolt found in US-built trucks, it's a Spicer-type with a rear cover attached with 10 bolts, which is the source of the "10-bolt" name, not the number of ring gear bolts. The GM 7.625" 10-bolt had 28-spline axles, the same rear with the same R&P but with 26-spline axles is referred to as a GM 7.5" 10-bolt.
GM & Isuzu 10-bolts are completely different rears, parts do not interchange, use the country in which the vehicle was assembled to determine which parts you need.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.

fasteddie
Regular Member
Posts: 100
Joined: Thu Mar 17, 2011 8:11 pm
Location: Jersey City, NJ

Re: Differential Identification

Postby fasteddie » Mon Sep 23, 2019 12:44 pm

Thanks, oldest. I got a Timken 474133 pinion seal, just want to make sure it's right before I crawl under there. Still a little confusing because Rockauto lists Timken 474133 for 10 bolt cover and National 474133 for 10 bolt 7.625 and an SKF all with roughly the same dimensions. I rarely see Japan or USA built mentioned on any parts listings.
1989, 2.3L, 5 speed pickup, original owner

oldestisuzuist
Regular Member
Posts: 1378
Joined: Tue Oct 07, 2008 9:10 pm
Location: N W Arkansas

Re: Differential Identification

Postby oldestisuzuist » Tue Sep 24, 2019 12:05 am

That's the correct part number for the pinion seal. You do know the caution about overtightening the pinion nut when changing the seal, right?
Isuzu didn't start pickup assembly in the US until about 1991, rear end parts after that date are usually divided by Isuzu/GM or Japan/US-built. No real reason to distinguish any differences for a1989 model, all were Japan-built.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.

fasteddie
Regular Member
Posts: 100
Joined: Thu Mar 17, 2011 8:11 pm
Location: Jersey City, NJ

Re: Differential Identification

Postby fasteddie » Wed Oct 02, 2019 11:50 am

oldestisuzuist wrote:That's the correct part number for the pinion seal. You do know the caution about overtightening the pinion nut when changing the seal, right?
.

I changed the seal with that part number a year ago when I replaced the U joints. It started leaking again. I didn't worry about torque when I replaced the nut. I marked original position on all parts and measured from the end of the shaft to the top of the nut with a depth gauge so the nut is where it was before it was removed. The old seal lasted 30 years, I don't know why the new seal leaked but I don't want to get into opening the diff.
1989, 2.3L, 5 speed pickup, original owner