68 GMC 4X4 rear axle
 

Having a difficult time in determining what type of axle I have .....the rear cover is 10 bolt and about 12" in diameter, floating axle with a 10" ring gear (maybe 10.125")....the differential come out as one piece from the front with same 10 bolt pattern.....has a 4:57 ratio....GM corporate as stamped on the gear and parts....has an "M" stamped on the diff housing and appears to have clutches (limited slip)....someone said that it may be military...and someone said it may be a NAPCO rear end....some say it is actually a 1.5 ton rear axle.....I can supply pics if needed

Re: 68 GMC 4X4 rear axle
 

From your description it sounds like you have the "stock" Eaton H052 rear end. manufactured from 1938-1972, it came factory in 3/4 tons and 1 tons
Although I have never seen one with a clutch type positraction, most were detroit lockers called a "No Spin"

Re: 68 GMC 4X4 rear axle
 

Looks like you have some experience in these trucks...I think you are most probably right that it is a locker versus a clutch type....I have no drawing or info on this style.....would a pic of the cone areas give you the information....we have a extra unit that shows us the spider gear style...the unit sorta stuck...when I removed it it appeared ti be back ti normal.....is it worth taking it apart and inspecting it...and is so what would I find

Re: 68 GMC 4X4 rear axle
 

A picture would help to identify yours, as far as taking apart your extra one.. If it is stuck you probably can not hurt it anymore.. I couldn't say what you may find out what wrong.. those rear ends are tough, but have a very limited gear selection, and are difficult to get parts for.

Re: 68 GMC 4X4 rear axle
 

Thanks for all the info....you were right in identifying it as a NO-SLIP.a Detriot locker and an Eaton HO 52. I was able to find a website that had info on this type of locker. According to the manufacturer, there is a lot of "backlash", up to 1/4 turn on the driveline. Mine has similar and did the test as they said to do and seems OK...I guess that is the"nature of the beast". Hopefully once I did the brakes to act properly, plan to get it road certified and painted. I was going to send a picture, but the picture size was too big to send and need to reformat them. Anyways thanks

Re: 68 GMC 4X4 rear axle
 

Sounds like you got to the bottom of it.These are great rears.Most GMCs would have a Dana60 and these Corporates or HO52s were much tougher.Every bit as strong as the well loved 14-bolt which replaced it...with far less bulk.The "No-Spin" is a Detroit Locker.I love the "drop-out" center assembly.The ratios started at 4.10 for the tallest and just got more grunty.I`ve had good luck with parts from Napa.

Re: 68 GMC 4X4 rear axle
 

Some pics for reference of a No-Spin I had saved....