I have trouble identifying my rear axle. the car is a 74 newport.

I doesn't look like a 8 3/4. But a bit like a 7 1/4 which (for me) looks like a 9 1/4. But I just googled some pictures. So maybe I found the wrong pictures.

Here you go.

Dennis

My bet 9 1/4, could be a 8 1/4 also but definitely not a 7 1/4 if it is OE. Is it a big block? Count the bolts on the axle cover.

wow. thank you very much for the picture.
It's not a 8 3/4 (knew that before).

It has 10 screws like the 8 1/4. But the cover looks more round on my axle.
But the big left-sided bumb looks also like the 8 1/4.

Is that a good axle I can work with?

Some of those description could also fit the dana axle. But I don't think so. Do you?

Can I measure something from the outside?

You are confused. I've never seen a 7 1/4 under a C-body. Also, 8 3/4s were gone by 1973.

I'd be surprised if it wasn't a 9 1/4, but if it wasn't, it'd be an 8 1/4.

Easy way to tell 9 1/4 without crawling under the car, it has two bolts exactly level with each other on the bottom of the differential cover.

The diff cover, upon closer looking, will be an octagon.

Hope this relieves some of your angst.

R.

look at the location of the bolts in the picture provided and compare what are you going to be doing with it?

I wanted to change the gears to 3.55, rebuild the rest of the suspension (rear sway bar and such) and make the engine more powerful (new pistons, moderate heads and cam). nothing hardcore. The car will never go near 500 hp.

EDIT: No racing or dragging. Just fur the fun of it.

A 9 1/4 should be up to the task. 3.55s were a standard ratio in Ramchargers so stock-type gears should be available new for cheap.
An Eaton Detroit Truetrac is available for this rear end and would help put power to the pavement.

www.doctordiff.com would be who I'd contact for a complete kit, everything you could possibly need. You'll have to email or talk to him because the 9 1/4 things are not in his online catalog but he's a board member and has the best reputation.

R.

he is saying 10 bolts so I think that rules out the 9 1/4

Dana 53?

I made a picture:

http://abload.de/img/dscf2062jxshx.jpg

I hope it helps.
The cover is almost round and 30 cm (about 12 inch) in size (like a vinyl LP record).
There is a big bump on the left (the flash took that away). The bump takes about 3/4 of the whole cover area.

I don't know if it's an aftermarket cover without oil plug or if it's original.

I know it is probably a 8.25 but it looks like a Ford 8.8 or GM 10 bolt when you look on the cover only.

8 1/4 should be ok with what you are doing but obviously a 9 1/4 would have been better. I have used a 8 1/4 before in some performance applications without any issues.

Looks original to me. Should be a fill plug in the housing. Otherwise how would you fill it?

I mean the "plug" which can be seen on the picture cudaboy posted. I have a bit of a hard time to explain things in english.

So it is a 8 1/4?

Should I swap it for another?

I think the later years 8 1/4 had the fill plug in the cover. The earlier ones were in the housing IIRC.
Is it a 8 1/4? You kinda ran out of options( 10 bolt, round cover) so from the picture I would say yes. Swap it out? that`s up to you. I would personally be fine with it but you never said what size engine.

It's a 400 cui engine. In the future I want to change pistons, heads and cam.
I don't want to race it. But sometimes I will step on the gas.

All the 9 1/4 rear ends have taperd, stepped axle tubes, all the rest of the rear ends in Mopars don't There straight from the center section to the brake backing plates IHTHs,

Looks like none of the rears in the reference pictures,the cover is completely round with 10 bolts ?

yes. it is about 12 inch wide and high.
maybe the housing is flat at the bottom and the cover is not. but I think then the bottom screw should be higher.
I really don't know.
It has 10 bolts for sure.

are there differences in some diameters that I could measure?