The Stovebolt Site Forums The Shop Area Driveline ID for rear-end in 56 3100

I am looking to identify what i have in my 1956 Chevy 3100. The numbers i was able to get off the rear-end look to be the following. Driverside number shows 339 (2 screw heads on each side, to right of that is a symbol, 12 raised dots in circle, with a screw head in middle, raised) Passengerside shows 3707340, and below that it has a symbol that looks like a sliced pie looking down on it, and next to the symbol is D2 The pie symbol as i call it, is the same size basically as the numbers. Any help appreciated. I am pretty sure this is the original rear-end to the truck. I am looking to switch the gear ratio to something like a 3.38 so i can go over 50mph.
A rear-axle id chart i have shows that i should find the letters AF for 3.90 gear ration or AG for the 4.11 ratio. But i don't see those letters anywhere? I just want to make sure i know what i have, and am ordering the right gears and components to switch it out. Thanks for any help.
Gene

Hy niobrarafun, one picture is worth a thousand words. Does the rear axle in your truck have a removable rear cover, if it does, is it round or an odd shape, how many bolts retain the cover?

I am looking to purchase from Classic Parts the "(1955-62) Rear-End Gears-3.38 Ratio" for $350 and "(1955-62) Rear End Gear Installation Kit-Complete" for $300 to do all this. Am just wanting to make sure this will work in my Rear-End before purchasing it. Again, any help appreciated. It just dawned on me to just call them and see if their tech support could really come through for me on this. I will do that and update this to let you know how i turn out, for those interested. But feel free to give me any advice, thoughts, or let me know what your experience was in doing this if you have already been there done that. Thanks.

Sorry about not loading up a pic or two. If it was easier to do i sure would! LOL But to answer your question it is a ten bolt and yes has the removable cover. And is round. In lower center of cover is the fill hole, oil plug. Thanks again for any help.

Here are a couple of screen shots from pertinent resource books that tell you exactly where to find your '56 3100 rear axle code/serial number along with the info to decode to know what you have.

The code/serial number is "stamped" into the face on the front axle pumpkin surface (left edge if you are facing towards the rear of the truck). The other "raised" numbers and symbols are part number and casting date code info that help define when it was manufactured.

Probably going to need to hit that surface with a stiff wire brush to clean off any road grime/oily residue to expose the stamping.

Hope you are able to use this info to confirm your info before ordering.

Dan

Unless you have something with more torque that the original 235 six, you will be extremely disappointed with the performance of a 3.38 rear end. Even if you never intend to haul something heavier than an iced down Yeti cooler to the local car show, you'll end up with an anemic ride that can't get out of its own way.

I put thousands of miles on a 1958 Chevy Del Ray coupe with a 235, a 3 speed, a 3.70 rear end and low profile 14 inch tires. It had no problem whatsoever running 70 MPH or more and not only kept up with, but outran the majority of the traffic I encountered on the highways of Tennessee. There's no reason your truck can't run 65-70 MPH with no modifications whatsoever.
Jerry

Hotrod
Think a 261 has enough juice to run 3.38? Are there other rear end gear ratios readily available?
At 55 I am running right at about 3000 rpm and it'd be nice to drop it down a few hundred.
It doesn't bog down at all right now, can power right up hills.
I'd like to squeeze a few more mph out of it, I'm sure it's a trade off though.

I drive that speed in a 216 with a 4.11 rear end and the rpm is about 2500.

Sorry I should have mentioned that my 56 3100 has a 283. Just a two barrel. Thanks again for the help.
Gene - Niobrarafun

Niobrarafun--
Yours is likely a 3.90 ratio. All the 1/2 ton's I've been around have the 3.90. I've had my 57 since 1968. Put a 63 1/2 ton C-10 rear with limited slip in it about 1977--It had 3.73 ratio & that made it a bit more hiway friendly.. Just my 2 cents! delkydave in wyo

Pictures are very easy to load, there are even instructions somewhere here:
1. Click on ‘Use full editor’
2. click on Attachment manager’ in yellow
3. Click on ‘select a file to attach’
4. Select file.
5. Finish the job. Practice a few times on your diff!
Ed

I took a look and it appears to be an original to the truck with the letters and numbers AF205 stamped on it's right side, just as the document shows. Thanks Gdads51, appreciate those documents you posted.
I am still wondering if anyone has updated theirs with these components from Classic and how it went and if they have any tips or tricks. I plan on having someone who knows what they're doing install this for me.
But still curious how it went for others. Thanks again.
Gene - Niobrarafun

Thanks Ed i'll do some practicing, i was under the impression you had to get a link from some photo app web application. Maybe that was the old way. And things have changed. But thanks.
Gene

Gene,

This conversation has been broached and discussed in many variations here. Not saying it can be discussed further, but there is a lot of existing info you can read to help make your decision.

HERE is just one of many previous conversations about the gear change you are considering.

If you want to see and read more, use the Search the Site tool (link found in the left main page margin) to search for more previous conversations.

Dan

OK thanks Dan, i will take a look at this. Appreciate you pointing this out.
Gene