Hot Rods Modifications for 57 Chevy rear end ????

60 year old technology is going cost huge to update.
Why not go newer and avoid being left on a dark road in a sleazy neighborhood late at night?


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Something similar was also done. An appropriately located hole was drilled in the third member housing, a nut welded to it, then a brass tipped bolt was inserted and used to "pre-load" the ring gear to prevent deflection. A lot of tricks were used to try and make these rear ends "live". IF I ever have to replace the rear end in the Delivery, it'll be with a 10.5 inch 10 bolt. I hope I don't have too. Maybe I should have kept the early Old's, but I needed the room. I am Butch/56sedandelivery.

 

I often refer back to the 60's HOT ROD magazine for old school info. anyone remember the write in question answer in the old magazines? I remember the late 60's question answer about the '57 rear end. They told the guy The '57 rea end would handle all the HP that the 327 would have.

 

Those are the ones that I used in my Posi. It's a tight fit with the back of the axle housing, but they fit without modifying the axle housing. I'm still using the stock 55 axle housing.


A couple of suggestions....

Don't use a spacer to use 4 series gears in a 3 series Posi unit. Be sure to use shouldered ring gear bolts. The 55 - 64 Chevy ring gear bolts are the same as 10 an 12 bolt Chevys' and 57 - 64 Pontiac / Olds rear ends. I bought some severe duty ones from Fabcraft, but they are ARP bolts for a 10 or 12 bolt Chevy.

http://fabcraftmetalworks.com/product/RA5-0520/Severe-Duty-Ring-Gear-Bolts---Set-of-12/

I was recently told that the open center case is actually stronger than the Posi "P" case. The open case has a reinforcement rib that the "P" case does not. This rib has to be partially ground away to use a Posi unit in it, but part of the rib will remain, so there is still extra strength added. This last info was from a guy who has been assembling rear axels since the mid 1960's.

If the price is in your range check out an aftermarket Posi from Nitro Gear. They look to be a bit beefier than the Auburn or Eaton units, and are definitely higher quality and stronger than an original Chevy Posi unit.

http://www.justdifferentials.com/PLGM55P-3-17-p/plgm55p-3-17.htm

 

To this day, I chuckle about this.
What would a person do?
Scenario
A guy has his third member tore apart, spread all over the bench, has a question.
So he writes out the question, sends it in, and waits till the magazine chooses (his) question, waits for his next magazine to show up (which isn't the one because of typical lag time in magazine production), waits again for "that" issue again, not there, comes to the conclusion that they don't plan on answering his question and just figures it out for himself, that or he takes it to the neighborhood hot rod guru and asks him.
Still makes me chuckle.

 

Also, avoid the 55 and 56 third member castings, they are cast slightly thinner. Same deal with the 62 and 63 Chevy II/Nova's third member castings; those are EXTREMELY thinner, and use smaller/narrower bearings, but they will swap in and work in any housing. The 57 Positraction casting does't have the large "P" the 58 and later castings had. There were also two versions of the large "P", a thin P and a thick P.There's also an "early" and a "late" Positraction unit, best to use the later version, as the spider gear trunnions are larger (and I forget the year that change occurred-I know, that does't help!). The Nitro brand Positraction for the 55-64 Chevrolets is a virtual copy of the stock units with 4 spiders; the Auburn and Eaton units use only 2 spiders. And the final thought, on the stock Positractions, the clutch plates are stacked for "standard" use from the factory, but it is recomended the plates be re-stacked for "performance applications"; that info is in the factory manuals and in Motors Manuals and Chiltons. My head is starting to hurt. I am Butch/56sedandelivery.

 

WOW!!! All this information has been great. Thanks to everyone. Here is a pic of the 4.56 I will be using. I have no idea what year it is from but I'm sure you can identify it.

Thanks,
Rex [/ATTACH]

 

If you plan on running it at the track with slicks you may want to put a diaper on it so the track clean up wont be so bad.

 

Because we're stubborn and we like the way old stuff looks and feels. . Sorry, I couldn't resist answering that one.

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H 22 6 casting date on that posi case indicates Aug 22 1956

Pat

 

For years my cousin wouldn't give up on stock rear in his 57 after 30 years and probably 50 pumpkins his last one had side gears out of a Dana 44 (I think ?) 31 spline axles , billet caps some kind of post and it lived for a few years of abuse , real healthy small block and 4,500 stall th 400 2 years ago he blew the pinion out the bottom of the case and finally threw in the towel ...

Probably could of built 2-3 good rears on all the money wasted on that rear

 

My thoughts exactly.

 

Or, 1966 (Jr. Stock era) , over the counter. Would't be a late 56 manufacture for a 57 car, because the 57 Positraction cases did not have the "P" on them. It also has the thicker "P" (later); the narrow "P" (earlier) is basically just a line. Can't see the size of the spider trunions, but it would figure, based on the other things, they are the thicker ones. JMO. I am Butch/56sedandelivery.
I know there's about half pro/half con on continuing to use these rear-ends, but for those that really don't want to change the overall look of their car, we don't really have any other choice. It's also why I have the 4.88 Positraction in the Delivery, had another 4.88 Positraction in the 51 Business Coupe, have another spare 4.88 Positraction, AND a spare 5.13 Positraction. I'm embarrassed to say how much I have wrapped up in them! For cars that don't really get much road time, the steep gears are't really a problem, just no extended freeway driving. Those gears also help dealing with some of the other issues, like wide/sticky tires, but you also have to address the wheel-hop issue with traction bars, cap supports, using new/better fasteners, better axles, but most of all, just not doing anything really STUPID, like using 10 inch wide slicks, on a prepped drag strip, with a high RPM launch. Something not a lot of people know is, on the Tri-Five Chevrolet's, and the 56-62 Corvette's, the spring pads are only SPOT WELDED in three spots on each side of the spring pad (we won't include the 62-63 Chevy II/Nova). You HAVE to run a full weld bead. Break the spot welds, and the whole axle housing will try to spin. If you have a Tri-Five Wagon (not 9 passenger with a different style gas tank) or a Delivery, if the spot welds break, and the axle housing spins, you take out the fuel tank. Then all it takes is a spark...............................................................................................................................................................

 

Mickey Thompson made magnesium housings for them so they can't be all bad. add me to the list of people who broke stock-old-worn rear ends. I don't think that is what he has in mind.

funny thing here with some of the replies. guy wants to use old timey outdated parts on his car and people tell him to step up and put a 9" in it. I can safely say when someone comes here wishing to use a Ford banjo rear, 3 speed and a Flathead not one person here has ever said those parts are all crap and you need to upgrade or you will grenade them all.

funny how that works

 

I SURE would like to find one of those MT magnesium units.

 

Well, All you have to do is go to the classifieds here, look up "Mickey Thompson aluminum center with posi for 57-64 Chevrolet", and get in line. It says sale pending, but nothing more. Last time I looked it was still available, but that's been a few weeks. They do come up on E-Bay every once in a while. They were really made for the Junior Fuelers to help keep them light weight. I am Butch/56sedandelivery.

 

Thanks Butch. Your replies have been very helpful.

 

Found that out the hard way at last years Meltdown Drags. The year before, it was the spacer and ring gear bolts. Yeah.......3200 lb. 55 Chevy.....283, (bored to 301), Muncie 4 speed, 4:88 Posi and 5000 RPM starts. Add in 8 1/2 " cheater slicks and Byron Dragway's super sticky track prep.....Ouch....Will see how things go, this year, first at USPEC, and then at The Meltdown.


The new housing has fully welded spring pads, plus they are reinforced. The housing was trued up, at the same time.

By the way, the 59 GMC has the 57 Pontiac rear axel.

 

56SD is on the right track. There were no production cars equipped with positraction in 1956. It was not available until after Dec 56. The factory did make replacement parts for their cars for 10 years, generally, beyond the model date. Since that differential case was produced through the 1964 model year, it was likely available over the counter through 1974. Even though there was no positraction option available on production cars in 1955 or 1956, that differential case wud still fit those earlier axle housings. So, someone either bought it over the counter or took it from another vehicle and put it on the 1956 housing. It appears the whole differential is a conglomeration of several different year's parts. The ring gear is a 4.56 (9 41) and the casting date on it is Jan '69 (1 69). From what I can see of the actual posi unit, it appears to be of the later style and not of the earlier style. It wud be interesting to see what numbers are on it. In regard to the "P" on the case, those with the "thin P" were produced in Detroit and had a single-digit for the year code. They were used on all positraction equipped Vettes from 1957-1962, in addition to positraction equipped passenger cars from 1958-1964. The "thick P" was produced in Buffalo, NY and had a two-digit year code. It was used only on positraction equipped passenger cars from 1958-1964.

 

I like that 58/59 GMC tow rig. Had an ex-NAVY 58 3/4 ton once, right down to the battleship gray paint. Someone before me had installed a 55, 4 barrel, 265 in the truck. I snapped the input shaft on the 3-speed leaving a stop sign in a normal fashion; had a replacement out of the 63 Chevy II Wagon my younger sister had wrecked. I bought it in the Norwegian/Swedish part of Seattle, Ballard, for $400.00, after his niece told me about the truck. I worked with her in the E.R., and she said he went on a weeks long bender with the money. Was there a change of underclothing involved with Byron I am Butch/56sedandelivery.?

 

Didn't need to change any clothing, but a few words were uttered that my Mom would not have approved of. LOL

It was basically a REALLY LOUD BANG, right at the starting line. While changing out the housing, I kept finding other bits of damage. There's a good sized dent in the trans tunnel, under the rear seat. Not sure if this is from the drive shaft, or from the pinion rotating up and hitting the floor. Also bent one lower shock mount, and one of the U-bolts for the drive shaft.

 

There is a guy on U Tube Jonathan W . He is putting a 427 and turbo 400 in a little 59 british car. Using a 3/4 ton rear. check out how he narrowes the rear and turns down brake rotors. Ive got a 456 no spin out of a 3/4 ton. Ive been studying about narrowing that rear and changine the outer hubs from the full floaters to a pressed in bearing axle.

 

Cool info...........I will be looking for adding a Deeper Gear Set for the wagon. 4:88 / 5:13

 

Lots of info here...still no talk about how they lived behind 409 4spd cars and the Z11s . Just curious cause the stock class guys hammered em hard. The 56 Bel Air I had as a kid would bust spiders pretty regular with a pretty mild 350 turbo 400 , but it was one legged with 10" tires.

 

They didn't live long behind the 409 cars. Face it they are a weak rear end. better and cheaper in the long run to swap in a better stronger unit.

 

Years back I had a buddy with a '57, 454, dual quad tunnel ram, 4-speed and a bunch of 4.56 blown up posi units. He ran through 3 before he saw the light and found a made-up Olds or Pontiac rear ready to bolt in.

I snuck a 9" Ford, actually a Lincoln with discs... under my Nova stock car, told the tech guy it was out of a '63 Chevy..

 

This was something that was done with many different dropout style third member rear ends (Chevrolet 8.2", Ford 9", MOPAR 8-3/4", and the big Olds/Pont 9.3"). Another similar modification involved setting up an anti deflection stud for the ring gear where the ring and pinion mesh together. Weld a nut to the case, use a bolt that had a brass tip brazed/pocketed to ride against the ring gear/carrier; helps to keep the ring gear riding against the pinion, and not getting deflected. You don't see these sorts of things any more. If anyone's interested in the Bruneau style cap supports, I still have a pair my nephew machined up, and instructions from the Bruneau set I bought (Just send a PM). I can beat Bruneau's price substancially!!! I just have the supports, never bought longer bolts, or drilled/tapped the spanner adjuster lock bolt holes. I probably should have kept my Olds/Pont rear end, already set up for the Tri-Five Chevrolet's, but I needed the room. Besides, I have several Chevrolet, Positraction third members to keep me supplied for a while.
I am Butch/56sedandelivery.

 

Butch I know a guy looking for a set of caps.

 

Great info, altho I like the Olds/Pont. as about bullit proof as they get!! Just saying!!

 

A rear end out of a v6 with overdrive Ford Explorer 4wd 1990 up is the same width as a 55-57 Chevy and most have a locker with 373s and disc brakes in later years and will handle 500+ hp. About $400 around here. 7 inch sticky tires on a Chevy rear end 55-64 will twist an axle.