Thread: GM rear end?

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Ok I need to try and find out what read end I have under my frame here... The guy I got it from doesn't know and noone else I know or talked to knows either. A few people said maybe a 55 chevy but I don't think 55's had drain plugs under the differential. Anyways here are the numbers I got off of it just now...
on top there was three numbers:023 and then under that the numbers, 3725899GM33
Does anyone know what this may be or where I can go to find out and put those numbers in and see what it is? I looked at pictures and none looked like mine. All I know is that it has 10 bolts and the back of the differential is welded up not bolted up.

Any info is greatly appreciated. I need to try and find out in the next day or two before I head to the local junk yards to buy a new one. At first when everyone told me it was a 55 I was going to just go get a 9" but now that I hear it's not I am holding.
Oh one more thing... it has 3 73 gears in it.

Thanks again!


SMF-

Hey FMX,

If it has a third member with a 10 bolt ring in it I would say you had an 8.2" GM 10 Bolt available on GM cars from 1955 thru 1965 or so.

Some one posted a good website before...I think its Drive Train Superstores, you might want to check their site out or give them a call.

Thanks man. I have been there before but will read it some more. It isn't a 55 I know for sure but I had someone on chevytalk look it up and he said the numbers match up for a 57 but 57's didn't have 3.73 so the guy must have put the 3.73 in it. Do you think this rear would hold up to a 454 BB?

Oh also what is a third member? Sorry for the dumb question but I don't know a damn thing about rear ends and especially transmissions.

That's a 1957 (or thereabouts) Chevy 10-bolt. Not the strongest around, but a lot of them were used for hotrods.

Is there a series of letters or numbers before the casting number?

B281 decodes to February 28, 1961.

G187 decodes to July 18, 1957.

L66 decodes to December 6, 1956

The letter is the month, the last digit is the year, the middle 1 0r 2 digits are the day of the month.

Alright thanks... I guess I will just try and find a 9" or something... Any idea's on a rear end that will be able to take a big block 454 and have disk brakes? I am going to narrow the rear anyways so I don't care about width or nothing. Also how much is it to narrow a rear end down, isn't almost like a grand to do that? I am going to narrow the frame and all myself though. Any idea?

I agree...not the strongest rear end around as they still use the old ball-bearings, but on the bright side...they dont use c-clips either.

As far as being strong enough for the 454, it all depends. They were being used in hot rods with Olds Rocket 88s back in the day and up to 1962 in the Corvette. If your using it in a unibody car like a Camaro you will probably bend a trailing arm on the chassis before you break the rear end. BTW...Pontiac used them in GTOs with the big blocks.

Oh and third members are differentials that can be taken off the axle in one piece instead of the dif (ring, pinion, carrier, bearings) being bolted directly to the axle like the late model model mustangs.

If your going to narrow the rearend your better off going to someone like Currie (I think you can get one from them all new for as little as $1200? ) that will build it for you to your specs...here's why:

Aside from the initial cost for the axle:

The axle tubes need to be cut and the flanges welded back on which means to get them straight you are going to fab up some sort of jig..

Secondly...you need to find someone to cut down the axles themselves and then have them recut the splines on them...not easy to find someone with that equipment, factor in shipping costs and theres more money out of pocket for you.

As far as accepting disk brakes...not a big deal...you can piece together something yourself or find a kit...Master Power Brakes has a complete kit or you can hunt down some brackets to weld on to the axle tubes and use brakes of a Ford Explorer or Cadillac Deville with built-in parking brakes. Speedway Motors has brackets and kits including some from Wilwood. Either way you can fit discs on any rear.

Ok thanks. I will call Currie and ask them about it. I looked on their site and for everything for the rear it looks like it's way more than 1200 bucks. They have the housing on there and then other things... What do I ask them for, a complete rear end then? I wish I knew more about this kind of stuff but once I do it and get it ordered and put on my car I will know what is what and all.

If I went with a Currie rear end then where do I find the brakes for the rear at and what do I ask for a Ford 9"? Also what year? I know Wilwood has em because on HorsePower TV they did a currie rear end and wilwood brakes but the brake kit they used was way over a grand and I won't spend that kind of money on a brand that is expensive mostly because of their name brand and how much they advertise...

It is amazing how many different options you have in disc brakes...name brand or not.

Even for the 9" rear there are two axle tube diameters made with different size flanges...for the 8.8" theres even more. If you go with a kit all that is taken care of for you...if you piece something together, all you need to do is get the right bracket and then figure out the offset for the flange. I know it sounds difficult or confusing, but it always seems that way until you get your hands in it.

Currie offers their rear ends with a choice of brake options...including discs. Interestingly enough an 11" x 2" rear drum will give you the same stopping power as a stock Ford rear disc setup as the front brakes do most of the braking anyways. Just something to think about.

Something else to think about...you can buy an assembly from the boneyard and cut the tubes down your self...if you have the confidence to do it Id say do it. The only thing is getting the axles cut down and Currie (or any other rear end specialist) can just do that part of the project for you. If you go that route at least you know what year and car it came from and buy your discs accordingly. But remember that you still have to go through that boneyard rear end and check the seals, bearings etc...to make sure they are in working order, and then replace those if needed and possibly change the ring and pinion to suite your needs.

Many ways to skin a cat here, and some more expensive than others.

BTW...what is this going in?

Here's what Currie charges on rear end work.

Currie Price Menu

To cut and respline a pair of axles is only $99. On stuff they sell only which bites.

But Moser will do it on any axle for $95

Thanks a ton man, your a big help. Looks like the best way is to just go the Currie route since they take care of everything and all I will need is the coil overs in the rear and bolt it up and a 4-bar. This will go in my 48 Chevy coupe. I may get this 1953 Chevy truck and keep the inline 6 that is in the truck and I could use the rear end I have now in that since I won't have a huge engine in it and it's newer. I will need to find out what kind of rear it is still then because where the driveshaft goes into the rear end (I think that's the yoke it's called) it's leaking oil pretty badly so I will need to know what seal to put back in and all.

Your welcome, its all part of doing my part to further the hobby. Good luck with your build...sounds like a cool ride.

These # was on the gears 552746 '5-4' GMK also G6 Can someone tell me what size these are was told a 273?