Differential Gears In 1986 M1028A2/A3

[hg adams]

I just purchased a 1986 M1028A2/A3 dually. I have read that some of these had 4.88 gears instead of the usual 4.56 gears. Just wondering if anyone could help me with this question.

 

[11Echo]

I just purchased a 1986 M1028A2/A3 dually. I have read that some of these had 4.88 gears instead of the usual 4.56 gears. Just wondering if anyone could help me with this question.

So, where you been reading that stuff?


GM didn't offer 4.88's in the civilian squarebody K30 dually pickups, ever,(3.73, 4.10, and 4.56). Never heard of one in a CUCV either from factory. The 4.88 gears could be bought aftermarket for those that wanted them.

 

[AJMBLAZER]

I read that in a wiki faq or something somewhere. It's wrong but I know it's out there on the interwebnets.

4.56's only in the CUCV pickups.

 

[pigfoot63]

Pull your rear diff. cover and check the tooth count on the ring gear and pinion. Pinion should have nine teeth and ring gear 41. If you lokok on the ring gear more than likely it is stamped 9/41. This is a 4.56

 

[overkill375]

Mine had 3.73's swapped in JUST the rear straigtht from the GSA sale. It sure made the 4wd not work worth a crap. never heard of 488 though.

 

[hndrsonj]

Don't believe everything you read on the internet.

 

[Westech]

Don't believe everything you read on the internet.

that's how WWI started ya know

 

[POOR WHITE BOY]

never seen a corporate manufactured 4.88 ring and pinion for 14 bolt rear

 

[11Echo]

never seen a corporate manufactured 4.88 ring and pinion for 14 bolt rear

GM used Dana 70HD in the dually pickups. The CUCV dually conversion kit included the Dana axle.

 

[POOR WHITE BOY]

GM used Dana 70HD in the dually pickups. The CUCV dually conversion kit included the Dana axle.

true if it was a dually with dually fenders and bed. but if it was a cab and chassis then it more than likely had a 14 bolt. i HAVE A 1982 GMC 3500 4X4 AIR FORCE AMBULANCE. IT HAS THE NARROW 14 BOLT REAR

 

[BKubu]

POOR WHITE BOY is correct. Someone, including the military, could have converted the truck to a dually using non-military parts. CUCVFAN bought a dually M1028A3 without a bed that had a civilian axle in it (translation...no rear locker). PM Neil if you have questions about his truck as I don't know much about it.

 

[noel.isaac]

if anyone has questions about the military rear diffs in ALL CUCV applications, here are the relevent TM's. Please note: M1028 and M1028A1's have GM 14 bolt 4.56, and the A2 and A3 have a Dana 70 (I believe). The part numbers and NSNs are different, as well as the entire axle axle assemblies. As for Gearing in the Dana 70's, I do not know for sure. However, I was told by a Warrant Officer in my unit who has been in for 25 years that the A2 came with 4.56's and the A3's had 4.88's. As for any first hand knowledge, I have none other that my 1028 has 4.56's and the locker chirp's everytime a turn a corner in town. Here are the axle excerpts from the 34P. if anyone would like any of the TM's emailed in PDF file, send me an email. goatmountaineer@gmail.com

 

[Crash_AF]

I'm fairly certain that the A2/A3 kit was exactly the same. The only things affected were the fenders, hubs and rear suspension. The only difference is the designation based on which truck was used for the conversion, a 1028 or 1028A1.

All of the CUCVs came with 4.56 gears except for the 1009 which has the 3.08s.

Later,
Joe

 

[POOR WHITE BOY]

Lets see a photo of a cucv - 1028 a2 or a3 with a gm installed dana 70 rear ?????????

 

[AJMBLAZER]

Picture a dually C30 or K30 pickup 1973-91 body style and it'll have a Dana 70. Chassis cab trucks actually had a narrow 14 bolt FF.

 

[POOR WHITE BOY]

Already know what the cilivian trucks have. cucv m1028 a2 or a3 with a gm installed dana 70 - photos ???????????????????????? THE NARROW 14 BOLT YOU MENTIONED IS WHAT US TRUCK PULLERS USE TO OFF SET ARE TRACKING .

 

[AJMBLAZER]

The dually CUCV's got the standard GM Dana 70 with a Detroit and 4.56's. GM didn't put a special axle in them. If you want photo's do a search, a few members on here have them or have had them and I can remember one guy even bought the government issue conversion kit that included a Dana 70 in a crate.

 

[POOR WHITE BOY]

Did they have a rear stabilizer / sway bar ? I want to see how it was mounted on a cucv . Thanks

 

[AJMBLAZER]

Yeah. I remember him saying he had it and wasn't sure if it was going on or not. The consensus was the purpose built CUCV duallies got them but not all the converted ones got them.

 

[Recovry4x4]

Here you go PWB. The second one has the pics with the sway bar visible.

http://www.steelsoldiers.com/cucv/25229-m1028-m1028a3-gov-conversion.html
http://www.steelsoldiers.com/cucv/29482-m1028a3s-euc-sent.html

I'm sure PWB knows this but for those of you that don't......! GM dual wheel pickups of the 73-87 CK models and 88-91 RV models all came with a factory DANA 70 rear axle. This was a wide rear axle. 2 wheel drive versions had a rear sway bar but the 4x4 versions did not. Cab/chassis versions of the truck came with the narrower 14 bolt axle unless you ordered the ambulance chassis which then gave you the wider DANA 70 axle. There were a few cab/axle measurements options but most were 60". The CUCV duallys, more specifically M1028A2 and M1028A3 were converted from the M1028 or M1028A1 trucks. Kits had everything from the 70 rear to the fenders to the hubs for the front to the data plate. A rear sway bar was also included in this kit. More info can be seen in the 2 links above.