How do I know exactly what model I have?

[ChrisG]

Pulled front diff cover off to change fluid and my truck has the limited slip front, did m1008s come with this option or is the truck another model? Thanks

 

[Evil Dr. Porkchop]

It could be an m1028. Check the NSN on the dataplate in the driver's door jamb, that will tell you what it is.

 

[cpf240]

If the data plate on the door is missing, you might be able to decode the VIN number against the table in the CUCV FAQ thread.

 

[FMJ]

Vin on a 1028 will start with 1GCHD, and I think a 1008 will be 1GCGD

 

[ChrisG]

So according to the vin (1GCGD) it is a 1008. Do the 1008s have the limited slip from factory? It doesn't look like the axle has been changed. Not a huge deal just curious.
There is another no. CD30930 on the door plate.

 

[porkysplace]

From the Wiki sticky ;

M1008
The M1008 is a 1984 K30 pickup with a J code 6.2L diesel, TH400 3 speed automatic, and a NP208 transfer case.

The M1008 has a Dana 60 front axle open and Corporate 14 bolt rear axle with 4.56 gears, detroit locker.

 

[ChrisG]

Okay so after looking at the cucv wiki it seems i have a 1028 doesnt really jive with vin but regardless it is what it is. So I guess now my question is with the limited slip front should i be using a different fluid than regular gear oil? I have a service manual but dont see a reference to a gear lube other than standard gear oil
I know admins dont like to see questions about what fluids etc so feel free to delete post if this isnt an appropriate question.

 

[Gunzy]

Should be able to use 80w90 with a bottle of friction modifier. Both available at most parts stores.

 

[cpf240]

Have you looked at the LO? ( Lube Order )

Should be in the TM section of the site.

 

[ChrisG]

Got it...Thanks. So will the number associated with the additive have any relevance at a parts store?

 

[cpf240]

Got it...Thanks. So will the number associated with the additive have any relevance at a parts store?

Probably not. Try a google search and see if an equivalent comes up, otherwise see what others here are using. I have an '09, so have not needed to look into it much.

 

[Recovry4x4]

Odds are, the truck is exactly what the VIN indicates. Either through assy line errors or maintenance in the DOD, you ended up with the trac lock diff. 1028s do not have troop seats, inner bed tie downs but have overload springs in the rear. A previous cab change is not out of the norm either. Does it have rear overloads?

Edited to correct the overload springs.

 

[Bunkerbuilder]

Two of my M1028's have rear overloads 1 had a depot rebuild but the other has no indication of any rebuild.

Odds are, the truck is exactly what the VIN indicates. Either through assy line errors or maintenance in the DOD, you ended up with the trac lock diff. 1028s do not have troop seats, inner bed tie downs or overload springs in the rear. A previous cab change is not out of the norm either. Does it have rear overloads?

 

[Castle Bravo]

Yeah, I thought 1028s DO have rear overload springs. Mine does.

 

[llong66]

This may sound like a silly question but I have ZERO experience with differentials. I plan on changing out my fluids this spring, on the front, once you have the cover off, how can you tell the diff between an open and limited slip front end?

Thanks,
Greg

 

[tim292stro]

Post pictures when you have the cover open.

 

[Bunkerbuilder]

The limited slip diffs have a friction materials samwitched with steel plates.
like a positraction differential.

The side gears also may (I dont remember) have a spring between them as well or at least one of the posi's did that I worked on some years ago... The 12 bolt gm posi unit has a 4 spring unit with 2 plates that transfer the force from the 4 springs to the sidegears.

While a 14 bolt rear with its detroit locker is a mechanical traction device but not at all like the limited slip center section.

when in question theres always google, This goes for just about everything you might see here and everywhere else . That LO lube order Imo is written for your average grunt but some of the things in it are plain wrong also IMO, One of those things is putting ATF into a gear driven transfer case like the NP205 as that is what the LO suggests but as someone who has worked in several transmission shops and a few manufacturers as well ATF is the wrong lube for the np205. that one needs gear oil and I use synthetic gear oil amsoil is what I use.

This may sound like a silly question but I have ZERO experience with differentials. I plan on changing out my fluids this spring, on the front, once you have the cover off, how can you tell the diff between an open and limited slip front end?

Thanks,
Greg

 

[Recovry4x4]

I edited the post above. The shelter carriers do have overloads. I should proof read!

 

[Keith_J]

GM and New Process changed lubricants in the 1980s to Dextron II after testing. Smokey Yunick talked about this in his column in Pop Science magazine, stating Dex II has the extreme pressure package preventing gear wear.

There is also an issue with overheating at higher speed using heavier lubricants, that heat is wasted diesel.

 

[Recovry4x4]

GM and New Process changed lubricants in the 1980s to Dextron II after testing. Smokey Yunick talked about this in his column in Pop Science magazine, stating Dex II has the extreme pressure package preventing gear wear.

There is also an issue with overheating at higher speed using heavier lubricants, that heat is wasted diesel.

This met with some resistance as well. Transfer cases had always had gear oil in them and a number of folks couldn't accept the ATF and switched out lubricants. Usually this resulted in failure.