Technical Help Identifying Rear End?

@57chevymadman I guess I’ll be pulling both axles

@gotta56forme I think it has the 4 3/4 bolt circle. I will have to check to make sure because at this point nothing surprises me with this car anymore . Not sure if I’ll be doing Smokey burnouts in this thing. I would like to but, if it doesn’t have posi already, then no haha. If it does, then yes I will light them up once in a while. Thank you for bringing that to my attention.

 

Did the diff have a disc brake setup in its previous life?? That bracket looks a lot like a sliding mount for a disc brake caliper... Buuuuttt, I could be wrong, the material looks a bit on the thin side, and it's been welded to the axle housing tube (no signs of any bolt holes)..

 

@inthweedz that is a great question that I cannot answer haha. Recently, I asked the previous owner about the rear end and he said he has no idea as it was in the car already when he got it. I did notice something today on the p***enger side. The plate on the axle tube that the bearing cap bolts to, was cut/trimmed all crazy. So, I know it was larger before. Currently it has large single piston calipers (non ebrake) with 11.75” rotors with a relay deep hat. Maybe they trimmed the plate for the deep rotor hats, so the caliper can clear the wheels? I have no clue at the moment until I figure out what year and model the housing is. In the next few days I will be pulling the axles to measure them. So far I know it’s a 56 GM 3rd member with 11.75” rotors on it.

I just found the caliper brackets online at the speedway site as a GM 78-88 and I think the rotor hats are 3” back spacing because they are really deep. I’ll measure tomorrow. I wonder if the damn 4 link is just some off the shelf universal kit too. Time will tell I guess.

 

The wonky wheel studs are probably related to the disc brake conversion....

 

Replacing axle studs with bigger/longer is common a**** racers of all sorts. The fact that they are drilled is no surprise. Studs can be had with different sizes of the knurl, and different lengths. Look at Speedway, Summit, any good race shop. I always used Moroso, they seemed to be a better quality, I'd stay away from Dorman.
Start with the biggest hole and drill the others to match, remembering you are going to want a press fit.
I'd be more concerned about finding the correct bearings and seals.
Good Luck

 

That caliper bracket looks like the cheapo brackets that Speedway and a million other vendors sell to stock car racers.

I didn't see a large P cast onto your center chunk, so I doubt it's a posi.

I would guess the rough cut "spacer" between the housing and the axle retainer is the leftovers of the original backing plate. Probably trimmed away but still there to provide proper spacing so the bearing is clamped correctly.

 

@squirrel I’m starting to believe so. The more I’m educated on these type of rear ends, I’m starting to spot the little clues that it was a drum brake housing prior to the disk conversion.

@Rex_A_Lott you’re correct, the Moroso studs are of nicer quality. I just might end up getting bigger knurled studs for now. I have a big box of different sized studs that I can go thru if I take that route.

@alchemy they definitely are some cheapo brackets. I did find some thicker 1/4 thick brackets. A little piece of me was hoping it was a posi hahaaa. Now that you mentioned the rough cut plates, that’s exactly what it’s for. I was scratching my head of why they were cut so sloppy. Now it all makes sense in my head

 

I just found somebody that has a 9” for sale near me. 61” drum to drum 54 3/4 backing plate to backing plate for $400. He said he doesn’t know what it came out of. I’m going to see it the axles have a 4.75” bolt pattern. I just might get it

 

No Ford 9” came from the factory with a 4.75” pattern. Measure carefully and make sure the axles aren’t worse than your current ones.

 

@alchemy ah that’s something I didn’t know and now I know. I’m hoping he measured the stud spacing incorrectly. Maybe he did center to center, when it should be back of one stud and center of the other. I measured mine center to center, not knowing LoL. I told the guy I’ll let him know in a couple days because I’m fighting a brake fade issue with my brakes. Idk if the booster is too small for 4 large single piston calipers? Or the master bore needs to be larger? I’m new to all of this but, I’m definitely learning quickly as I go. A little headache from not knowing but, I’m working through it as patiently as I can.

 

You current rearend has disc brakes, correct? It appears so in the pics.

Swapping in a different rearend is going to bring about an entirely new set of issues, especially if you use something with drum brakes, so if the current rear suspension is working properly and was safely installed, you could keep it and "only" replace the axles and bearing on both sides. New axles aren't terribly expensive new, and as mentioned, you can probably find used ones, too, with the correct/factory 5x4.75" bolt pattern. There are plenty of people stepping up to aftermarket axles for additional strength and/or a bolt pattern change who would be happy to get something for their old ones.

You definitely should take stock of everything currently on the car (rearend housing, differential, brakes, brake lines, etc.) before making any purchases. No sense in spending money on something you don't need at this point.

 

Or a piece of chain and the spare tire!

.bjb

 

An old wives tale I have had two 60 Chevy rears without drain plugs, I converted one to parallel leafs and it is now under my 53 Chevy.

My father started working at a local service station after school/summers in the mid 60s and as Chevrolet line mechanic (Dealership) from the late 1960s until the mid 1990s.

In that time, he worked on alot of 55-65 Chevys and saw many 57-64 Chevrolet rears without drain plugs. In fact, he hadn't heard of this "all 57 and up rears had drain plugs" until about five years ago.

You have to remember Chevrolet was in the business of building cars for sale, they were not going to shut down the ***embly line down because they didn't have rears with drain plugs. They were going to use what they had or could get and keep the line moving.


The only way to tell a 55/56 from a 57 in axle bearing size, 55/56 are smaller than 57 and up.

 

@In_The_Pink Yes, it currently has rear disk brakes. Large single piston brakes with no e-brake on all 4 corners. It has terrible stopping power at the moment. Trying to figure out the issue. You are correct about opening up new issues. I was getting ahead of myself. I need to figure out all the issues with the car first and attack the small and important ones first before I go tackling the big stuff. I also need to separate my wants and needs. Hard to do when I recently got the car and starting to find all the things I didn’t see prior to purchasing. As they say, I bought somebody else’s problem haha

@Jokester Unfortunately the car did not come with a spare tire LoL

@Moriarity i am not too fond about those welded caliper brackets on the tube either. When I seen it, all I could do is shake my head hahahaha. Then I go to measure each side and the driver side is welded about a 1/4” further from the plate, than the p***enger side.

@Robert J. Palmer that was some cool and useful info to share. I’m going to research the bearing sizes from 55/56 and a 57 housing.

 

Once I get up and around (off from work the next two weeks) I will check my notes in the garage.

 

Rock Auto is a great source for finding specs. This is 1956 bearing which is also the replacement for 55 which was a little different at the start.

Here’s non Rock Auto pic for referance.

 

@Robert J. Palmer No worries. It’s your day off for the next 2 weeks. That’s awesome!

@Johnny Gee I never thought to look on rock auto for specs. Going to keep that in mind. That photo is a great reference photo! Thank you for that. I’m going to save those 2 for future reference.

After some really good thinking, I’m going to stick with this rear setup for now. Whether I swap to a 9” in the future? Who knows at this moment. I can say I dislike how this rear end was done. Not my style of poor measuring and craftsmanship. I’m thinking I should wait for the swap when I notch the frame this coming summer. I need to carefully plan for all of that and not compulsively start doing things hahaha.

Soon we will find out what the housing is. I’m going to buy a pinion seal, third member seal and maybe new axles if the cost is too steep for a machine shop to drill out the holes and press new studs.

I’m singing to a choir with this car so bare with me ya’ll . I keep telling myself, one thing at a time!

 

Better read up on replacing that pinion seal so you don't mess up the bearing pre-load .

 

@2OLD2FAST uh oh, is it difficult? I haven’t done one so I have no idea. Worst case I can take it to a rear end shop and have them to the seals, bearings and axles. If it’s doabl at home, I’ll tackle it. As long as it doesn’t require some crazy science or special tools haha.

 

Hey Rough 54, I'll probably get flamed for saying this..
Note... Replacing new gear sets require the correct specs/torques..
But on used diffs, lots of people freak out about replacing the pinion seal, regarding the bearing preload.. I've done many without the tensions required, and never had any problems at all.
Observe approximately how tight the pinion nut is on removal, this will give you an idea how tight to do it at the end..
Get the drive yoke off, remove /replace the seal (don't forget sealer around the edge) fit the yoke back on to the splines (lock***e on the threads) and take it up to the point where it just touches the bearing (no play in the bearing), then tighten a bit more (as mentioned above)
The collapsable spacer takes a lot of effort to crush, just don't be a gorilla and overtighten., ..
I've never used a torque wrench, and had no problems at all..

 

You can mark the pinion shaft and nut with a dot (punch) or line before removal. Pay attention to how many threads are showing. Dis***emble and replace seal. Then put nut back on and put to same position based on exposed threads and lining up the marks you made. That keeps the preload same as it was prior to removal. No need for special tools.

That 55-64 Chevy rearend is strong enough for a small block without any concerns, ***uming regular street tires. Your brakes setup needs to be figured out, but general rearend strength of the 55-64 Chevy rear is OK. Not the strongest rearend of course, but also can work just fine on the street behind reasonable power and traction.

 

Here's what you left out , it takes serious torque & a means to hold the pinion flange to remove the pinion nut without a HD impact wrench , you have to count the turns ( don't know how you'd accurately count threads) , " guessing " how tight it was means zilch , you may need a puller to get the pinion flange off , check the surface of the flange where the seal rides to determine whether or not it will hold a seal. ( grooves , pits ,etc) , retightening generally tightens the nut farther than it was . There's a matter of " touch" involved doing things like this that inexperienced folks don't have & its fairly easy to mess up . I've watched others fail for years ,both in & out of shops !