Dana 44 identification and numbers help!

I am trying to find out what rear is in my 81 corvette. I know from the bolts it is a dana 44 but I am just trying to identify the year.

When I bought the car it had a 350, th400 trans and whatever rear is in it now.
When driving on the interstate the car would be doing 65mph at 3000-3200 rpm. This leads me to belive that the rear ratio is between
3.70 and 4.11. 81 corvettes only came through with 2 sets of gears from the factory. 2.83 and 2.87 or something close to that.

This means either someone swapped the entire differential or someone swapped the gears. I already know they swapped out the original transmission for the old th400.

Since owning it I have swapped in a big block 427 with 2 4 barrels, nitrous kit, 6 speed t56 transmission, side pipes, stinger hood and a lambo door kit.

Now I am looking to put a set of 4.56 in and want to make sure I am buying the right gears.

Any help would be appreciated! I was under the car today and couldnt find any numbers on the differentiol. But it would help if I knew where to look.

The original ring gear is engraved and has the production date

For instance:
11 12 80 Dana <D> 37792 A3 R375 43 15

11 12 80 is the prod date, dana is obvious <D> = the logo. A3, R375..dunno, 43 = ring gear teeth, 15 = pinion making it a 2.87

more help

I do understand how to tell what ring and pinion I have after the differential is removed. But that is not what I am looking for.

I am trying to identify what differential is in the car now, without removing it.
So I can order gears and have them ready to do the swap. I highly doubt that the rear in this corvette is the original one.

SInce 80-82 dana 44 differentials are different from earlier years, I have to identify which one is in the car now. That is why I am asking where the date and axle codes are stamped and how to decode them.

I hope this helps to clarify what I am trying to find.

That's easy, all 80-82s are the same NON HD Dana44 (ICA). There's no difference apart from the stub axles between those years.

In both of my original posts that I wrote, I stated that there is a good possibility that the rear is not original!

Which means I have to determine what year it came from. That is why I need the numbers.

Thanks for your help but not what I am asking for. thanks again

i'm not following, what else can it be? If it's aluminum it's a Dana44, 80-82. it has a big alu batwing, can't miss.
It's next to impossible that it's a C4 Dana 36 or Dana 44 HD unit. So 80-82, all the same. No differences.

If you crawl under there and the differential has a pinion mount cast into the front of the housing, it's an 80-82 unit. If the camber strut bracket is a large 1 piece unit, it's an 80-82 unit, the other ones have 2 separate ones.

Do the 80-82 units have numbers stamped in them like the iron diffs?



If you think someone has swapped the gears, the only way you can find out the ratio (without opening it up), is the jack up the rear and spin the tire and count the ratio of driveshaft revolutions to tire rev's.

He wants to make sure he buys the right gears, if he has an alu pumpkin with a pinion mount, it's an 80-82 Dana44 ICA and they are all the same. They all take a pinion with 26 splines and a 1.375" shaft and a 10 bolt 8,5" ring gear.

I am asking all this because the car is titled a 1977 but the body and entire interior is no doubt an 1981. SO something somewhere happened. I knew that the car was mixed n matched when I bought it but didnt care, I tear them apart and make them how I like anyway. SO I am trying to figure out exactly what rear is in it. the 1977 or 1981

I can honestly tell you that the rear in my car is not aluminum and no I didnt see the infamous aluminum batwing. So it is not an 80-82 dana rear. Are all the corvette differentials from 69-79 dana 44's???



But I still would like to find the numbers off it....

BBSHARK that picture you have showing the numbers....is that the top of the differential?

the pic is the bottom

All the 66-79 diffs are eatons

ok, getting there

So, we have determined the rear is from 1970-1979 and all the gears should be the same.

From the bolt pattern it is a dana 44

It uses an Eaton differential.

I will see if I can get the numbers off the rear tomorrow, but I think they are gonna be gone. Alot of heavy rust where they should be.

I will keep you posted.

thanks

No, if it's iron it's not a Dana. Only 63 -64? used a cast iron Dana posi unit. The later eatons look exactly the same. If you have a cast iron unit it's an eaton and all the stuff is the same. Read Gary's (GTR1999) papers in the rebuilding section, you'll know pretty much all there is to know about those units.

Here's a bunch of pics to help identify:

63 Dana Cast iron, looks the same as later Eaton unit but weak.



Note the long springs, the eatons on't have that. In my pics the stock metal spring plates and short springs are missing, there are 2 plates and 4 springs between the spider gears)


66-79 Eaton cast iron, see similarity in outer case (easiest difference to spot is that the Dana unit uses a through bolt on the rear pinion mount bracket mounting hole and 2 bolts, one from either side on the front, the eatons have 2 through bolts w/ castle nuts)









These all mount with a big steel crossmember, the diff bolts to it from the cover.



Dana 44, C4 HD unit on the left, C3 80-82 non HD LCA unit on the right (see pinion mount)



C4 Dana 44 HD


C3 80-82 Dana 44 ICA


These all use a batwing (C4 Dana 44 HD on top, C4 Dana 36 below):

Ok, I think I got it.

Since my rear differential is iron, it is an EATON. In the year range
of 70-79 which doesnt really matter, because they all use the same parts.

I checked for the numbers off of it, but with no luck. Way too much rust and poor stamping. I could only make out 2 numbers after cleaning and scraping for 15 minutes. They are long gone lol!

My last question to you, is the following....is there a difference in manual and automatic transmission rears?

thank you for all your help.