The Stovebolt Site Forums The Shop Area Engine Shop how to Identify 66 3/4 ton rearend?

I'm trying to find out which rear end is in my truck.I believe it is an eaton,but am not sure.It has a round differential housing.It is a positive traction unit.I'm pretty sure it has a detroit locker.Is there a tag on the rear end somewhere that will help settle the question? What rear ends were offered on this year model?The truck is a 66 C/20,by the way.

If the rear end has bolts on both sides of the round center section it is a Eaton. I have a Detroit Locker in mine also.
Larry

Chances are it's the big, beefy Eaton full floating rear. Does it look like this:
C20 rear
The only other rears I've seen otherwise have been Dana 60's and aesthetically they're quite different. Don't see the Dana's too often on the 60's trucks but, have seen some on Camper Specials and such.
-David

I found stamped numbers on my Eaton locker under the rear pan gasket surface. I never did see if I could look up their meaning though. Mine's from a 63 K20,
Scott

The DL units are hard to find these days. I bought a whole differential from eBay just to get the DL, and it's the only one I've ever seen advertised on there.

As best as I can remember,yes it does.I WAS going to crawl under it this evening to check when I got home from work,but on the way home this evening some punk chunked a piece of concrete from an overpass and nearly creamed me.After circling the area where the perp could've been ,looking desperately for a cop(or his worthless butt) I came home and plum forgot about it after the third beer. I'll check again tomorrow.I was hoping to get a model# or series # so I could check for parts and upgrades such as disc brakes.There doesn't seem to be a whole lot of aftermarket concentration on the c/20's.I understand that C/10's were more common,but when I finally build my truck,I want to take advantage of such upgrades if possible....

By the way thank all of you who replied to my post(s).I am just starting this journey to get the truck I have always wanted,and appreciate every consideration...

The aftermarket stuff is 95% C10. The C20 disc brake aftermarket stuff is so expensive it's not really worth it. My '65 has power drums and stops just fine. If you've got non-power, find yourself a booster and make sure everything's in good working order. That drum brake system is plenty good. The only way I'd bother with front discs is if I decided to use drop spindles and therefore required to convert.
If you really want disc brakes, you can do the front fairly cheaply by using later model truck parts like 73-87. That's a whole 'nother thread. Try doing some different keyword searches here and you'll probably find some info.
-David

Where can I even see the aftermarket stuff for C/20's ?. I guess I haven't been lookin in the right places. I would like to at least look at the offerings,if only to dream. Seriously,I have all power factory options already(I think...), and would really like to see what IS available.Which aftermarket have the best springs,brakes,etc..?

These are the main two that I know of for C20: Classic Performance
Early Classic

What are the advantages/disadvantages of Eaton vs Dana?
Eaton=good?
Dana=better?
What's an Eaton Locker?
What's a Detroit Locker?
What's a DL?

I've got a '65 C20. The rear axle looks like the one in David's (mugsy's) picture, above.

Been wondering what F/D ratio my truck is running and what mods are available for running lower RPM at highway speeds.

LGriffin
Wrench Fetcher
Stovebolter # 2913

posted 11-04-2005 08:14 PM
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If the rear end has bolts on both sides of the round center section it is a Eaton. I have a Detroit Locker in mine also.
Larry
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Posts: 86 | From: Oakdale, CA | Registered: Nov 2002 | IP: Logged | I am now positive it is an Eaton.Thanks guys. Is there a distinguishing model number for these rearends? Was it used in other trucks? By other manufacturers? Does anyone know how long this rear was produced? Does it share parts with later/earlier models? Sorry to bombard you guys with so many questions,but I figure I can get some good leads on answers here since it'll be a while before I can get to the library.And I'm not sure that I'd find the answers there. john

Nothing wrong with the old Eaton axle...since it was used until '72, parts aren't hard to find. Danas are probably a bit easier to get parts for. Danas most likely have a better selection of gear ratios available, the lowest commonly offered in the Eaton was a 4.10. There are some factory 3.90 Eatons out there, but good luck finding one...

Eaton Locker and Detroit Locker are the same thing (and DL is just me being lazy and not wanting to type out Detroit Locker). DL made the same Eaton axle locking differential unit to be both sold aftermarket and by GM as a factory install. The company is still going strong, but that unit ceased production around the same time as the axle in 72.

Your rear is probably a 4.57. You could do a pumpkin swap with a late 60's up to '72 C20 and get a 4.10. However, with a 1:1 final ratio tranny, it's not super beneficial. You're going thru things I went thru a couple years ago trying to figure out what to do about driving faster than 60 mph. I opted for an overdrive transmission and kept my 4.57 rear. An OD tranny is going to get you the best gain. If it's just an every now and then driver, find a 4.10 rear and put 215/85/16 tires on. You'll be able to drive 65mph.
If memory serves, the model of the rear is H-072 or H-071.
-David

I don't want to take over this thread from 66... but
Just wondering about care and feeding of these rear ends. Haven't had my truck very long. I just changed the Diff oil yesterday, using Valvoline 80/90.
Is it enough to just change the oil every 10,000mi like the book says? Any advice on getting the most miles out of one of these rear ends?
Also: Do the labels "Positraction", "Limited Slip", and "Locking" mean the same thing?

Positraction and Locking differentials are different beasts. Posi (and limited slip - generic name) use clutches to reduce slippage. Locking differentials mechanically lock both sides together. Searching Google for locker and positraction should come up with some good explanations of the differences.

These axles have survived a long time, often being abused. If you follow the manual directions, you should be fine for a long time to come.