When did chevy start and end putting that big P on posi cases , from the first one in 57 or later, all the way to the end of the run on some 64-5 chevy II's and chevelles? On my way out to the farm ina bout an hour to cut out about 7 RE's,
with 60s muscle cars all i have ever had had the tag if it was a pois no stamping & my 65 Starcheif is a 12 bolt pois with tag if that helps any ....
I think they had it on all of them, but I'm not sure. My 64 posi case has it. This is on the "drop out third member" type rearend, not the 10 or 12 bolt rear cover type.
yep ,I have all the books and codes, BUT and this is a tip - NEVER carry books to a junk yard ,dead give away your looking for something special, and price will climb dramatically,seen it more it than once ,guy runs up w a big ass grin on his face , pratically jumpin up n down "how much ya gotta have for that RE"? 500 he says , grin dissappears FAST ,(good price actually by todays standards) That Big P on 55-64 RE ends is a dead give away w/o tipping anyone off, older junk yard dogs and 55-64 chevy guys know this and it won't matter, but your average guy does not, too old a trick most of the young guys came along LONG after this was a issue, they want 12 bolts J4YI the codes are stamped right on the middle right side flange face on 55-64 RE's,NEVER go by the tags on these, IF they are there, most often wrong unless its a gennie.
Mike, to my knowledge, ALL 10 bolt posi carriers have the "P" on the case to identify them. Pic shown is a 3:70 unit. Have a good one. Jim
ya that was my thought , but wanted to check , I have a decked out buy comletely shot 57 BA, sitting out there ,that may well have it ,,it HAD but sold off ,pwr brakes,pwr steering , pwr seats, air , elec wipers 283 PPK/ PG and tons of extra trim like a DnN mirror,bumper gaurds,BOTH rear deck antenna's and that funky trunk trim.I want to check that rearend out. also 2 59 sticks and a 60 PG.a 55 + 3 other 57's I have
dont think i have ever saw a pois in one of these cars as that pic of one is not any markings i have saw on a car
Ill tell you this, I had this complete rear axle out of a 63 4-door hardtop 4 speed car laying out in the at the shop. Sat outside for years, everybody had tripped over it or kicked it at one time or another. It was always in the way. It had no P on the case, so it wasnt worth shit to me or anyone else. One day I blew out the one on my 61 and I remembered the that I had a complete axle being used as a foot breaker. So I tore it down and discovered it was a 373 posi with some sort of machined steel caps and twelve point bolts throughout. I never have seen any like that before or since. I think it was a thrown together 3rd member for a racecar from back in the day...point is, just because theres no P doesnt mean it hasnt ever been screwed with ..it just might be what your looking for.
I've scored 2 64 "P" cases out of late 64 fullsize Chevys that were open rears. It appeared they may have been using up cases toward the end of production run and just used the "P" cases since this was the last year for that model rear end. I've had 30 or so over the years and ocassionally still find one. The earliest one I've seen was an April 1957 casting date. They may have been available in the 56 Corvette in late production cars. GM factory racing teams used them in factory racers before 57. They are not as strong as a 9 inch Ford. If you put some heavy torque on them, especially going around a hard corner, they will explode. Most of the time the only thing wrong I've found is sticky clutches in the unit. The easy fix is to change gear lube and put in the special "Posi" addative, then do some very slow tight figure "8's" in a parking lot. This cleans the surfaces of the clutch discs so they don't "snap" or "pop" going around a corner. They usually perform smoothly after that. overspray
the one I was after, I got , but will continue to cut the rest out , I got a 3:08 out of one of my 60's today ,but a rain storm ended the work day, I remember the same about those non posi P cases in lt '64 , I am not going to full time race this thing , but If I do i'll put the 4:11 back in ,I wanted a decent ratio for cruising and turnpikes right now, figuring the 3:08 will fit that bill nicely, tho my motor/cam is rated at 2000 rpm's up X - I'd been wondering about a 4dr hdtp w a 4 spd anyway I looked at it, they did'nt come that way that I know of.Ya just never know what a chevy guy will put together
OK, this is what I was talking about , case code said 3:08 , knew i was in trouble or at least concerned when i undid the case nuts and came up with ORANGE silicone goop around em under the nuts , guess what ? 3:36! nice set but shit! someones been in it they will work fine, but I had 2 chunks w them out already,
As far as I know, 57's did not have a P on their posi cases. The posi in my 57, which is the original rear end from the factory, does not have a P on it's case. However it IS factory stamped as a 3:36 positraction rear end. The car did come from the factory with a posi, and it had never been out of the car, (I know it's history from the original owner). I'm not sure about 58 cases. I read once, that 58 posi cars came with a positraction emblem on the dash, to show it had a posi, but have never seen such an emblem. 59's did have a P on their cases. An easy way to check a 55-64 for a posi, without taking the rear axle apart, is to pull the filler plug, and look in with a flashlight. If you see a CAST differential section, it's an open rear end. If you see a MACHINED differential, it is a posi.
Mike, if you want I will check my CCI tech manual. It has a couple of good articles on rear end id. May shed a light on what you need.
I have the manual , Thanks Reborn , What i was looking for was 3:08 gears , which were not avail in 55-7 , and as long as I was at it ,posi's which were in 57 up ,IDing posi's I have down except for that little plug lookie trick ,forgot that one, I was just wondering about the P cast and when it started , thanks guys , I'll post again after I get the chunks out ,
FYI--3:08 posi came out in 1959--don't think you would like the 3:08 behind the 4speed..been there done that--never again
Mike, 3:08 is a great road gear and best drivability with Wide (2:54) 1st. gear 4-speed. Have this setup in my Impala. Gets a little hairy backing up steep drives but great well, better..gas mileage. Just my .02
I am running a 350 turbo + the 3:36's i think , the 65-9 SS Impala's ran 3:31's as a performance ratio ,so they might work out well.
From what I know about these rear ends, the P cases had larger bearings. Also, the weak link on these rears is one of the main caps (the driver's side, I think), and the axels. The spline count is like 10 or something stupid like that. The cast bearings caps flex and/or break under heavy load. If the cap flexes, the teeth will spread out on the ring and pinion contact area, and bad things happen. If the cap breaks, worse things happen. Moroso and others used to sell a billet steel main cap to fix the problem. Last one I saw on ebay went for over $100. Old racer's trick was to bend a piece of steel strap or machine a piece of bar stock to bolt over the stock cap and reinforce it. According to Reider Racing, the spider gears from a new Dana 44 (I think it's the 44--but it's a modern rear of some type) will interchange with the original spiders, giving you 28 spline axles. A set of Moser axels then, and that problem is solved. New Posi units are again available for them. The Posi units could be fitted into a non-posi case, but there was some grinding or relieving that needed to be done, and I don't remember specifically what it was that needed to get done, but it wasn't a direct bolt in. It possibly had something to do with which gear ratio you ran. Anybody know for sure? Finally, the differential itself was gear-ratio specific: there was a different carrier for 3-series and 4-series gears. Moroso made a shim that went between the ring gear and the carrier (where the gear bolts to the carrier) that allowed a 4-series on a 3-series case (or the other way around--it's late, and I don't remember if a 4-series ring gear is thicker, or if a 3-series is thicker). Even with the improved main bearing caps and upgraded axels, they're no 9-inch. About as strong as an 8-inch. Although, the Super Stock 409s did use them. -Brad
All personal preference--I have 2 3:08 on my shelf forthat very reason. very poor starting out wtih muncie. Agree it is good for mileage but not that great for playing in the lower gears. Just my .02
From the beginning of production for '57 up to April 1st of '57 there was an "X" behind the part # if it was a posi, after April 1 , it has the "P" in the casting.
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