The Stovebolt Site Forums The Shop Area Driveline 1958 apache, rear differential identification

Hello..would like some help identifying the following rear end, it is a 10 bolt and pretty sure a DANA.

Looking from back of truck:
Has two us patent numbers (2018188 and 1968818);
Has an 'A' within a circle and a '45' below it;
On other side has a '2 A' with the A in a circle and 'C30147'.

On back side (looking from front of truck):
has a '45'

On bottom left bolt there is a tag that says '47-12' and '3.92';
On another bolt has tag that says 'T'

If I jack up rear end and spin wheel other wheel rotates in opposite direction. However, blocked one tire and other one locks up...so indiction is that it is positraction. But, wonder why the old tried and true method did not work?? Any ideas.

So...I would like some help verifying this rear end.

rom my research I think it is a DANA 45 (upgraded DANA 44 with large 20 spline axle shaft( with posi and a 3.92 gear ratio. Anyways..if anyone has apaches or real familiar with old 1950s tranny's and the markings then please let me know.

If the other wheel turns in the oposite direction it is not a positrac. If it has a drop out third member with a near round rear cover it is the standard GM corporate rear end
, which practically all of them are on that model. If the houseing is all one piece with rectagular cover it is a Dana/Spicer.

Also, if the transmission is in gear (or park for automatic) when you block one wheel, you shouldn't be able to turn the other.

So..there is a tag in the cab below the radio that says poitraction, second owner (who I bought it from) bought the truck when had 6k miles on it. Said plackard was original. Also, has what I understand to be the positraction lubrication tag identifier tag 'T' on the bottom bolt passenger side which is where its suppose to be. This truck was very special order (fleetside, shortbox, big window deluxe cab, v8, 3-0n-tree with Positraction and any chrome option available (both bumpers with arrow caps) and has the 50th annivesary paint job( Anniversary gold/honey biege). It is likely this was a dealer demo showroom model and had the very special option of Posi which they were getting ready to put on the 1959 Apache. Engine was manufactured in April 58 (engined code F404M) and so likely put together near end of the 1958 years run (vin V3A58O112237). It is definitely a DANA (have compared to DANA pictures on internet - 10 bolt w? bottom drain plug) and has a big casting '45' on both sides of differential. Though not very common there is a DANA 45 which is a heavyier duty DANA 44 and is the one with Positraction. My rig was in nuetral when I blocked one wheel and it locked up. So....with all that said I still do not understand how when both wheels are off ground they rotate in opposite directions. So, I know it is rare to find posi on the 1958s so if anyone else knows of one I would be interested. Anyways, because dont find posi on 58s I am still looking for some for validation (from markings) and the opposite rotation thing has me scratching my head. Thanks for responses, appreciate anymore sage advice. Any advice who to contact, etc) on getting details ontruck from the production number in VIN would also be good

you won't find any details from the vin/sequence number short of running across some 80 year old with a good memory who worked at the Oakland plant in '58

if those were patent numbers you could search them, the db is on the net - more likely they're casting numbers

with both wheels off the ground they rotate opposite because that's the way differentials work to go around corners, by it locking with one wheel down and able to get traction, it shows it's a posi

1958 was the year GM started a number of rear end options beyond the usual 3.90 and 4.11 [with OD], particularly the 3.38 'mileage minder' ratio, so it's not too surprising you've come up with a rare one, especially on a heavily optioned truck .... OTOH, the 3.92 ratio sounds like what might have been used in the NAPCO conversions, which could have been posi

Bill

Supreme1, sure would like to see some pics of that truck!

Its posible its a posi & the clutches are worn out. The best way would be to pull the cover & take a look.

Thanks for input.

I will definitely pull cover and take a look at rear. Will also test for Posi again to be 100% sure in neutral (only 99% sure last test in N), so will verify.

Would like to know what 'OTOH' and 'NAPCO' mean, sorry I am an old guy and have been immersed in my 1940 VC1 pickup restoration the last couple of years and not as familiar with the 1950's vintage chevy's or computer lingo. Do however know what OMG means since my daughter says it daily.

Will provide pictures of Truck tonight. Bought within the last month so in process of degreasing, changing fluids, fixing some electrical issues (done), brakes, gathering info and ordering knick knacks (hoses, belts, chanin protectors, etc). In process of letting Marvel Mystery oil work on the cylinders, so have not tried to turn it over yet..so cannot at this time assess things such as does it run, does clutch work, does tranny work, etc.

Story is that was parked 4 years ago when brakes went out, and that ran/operated great till then (?). Has 160k miles on it. Have resisted urge to replace differential fluid till I do some more digging, may need 4 oz additive. Will take off back plate with buddy of mine who has some experience assessing these older trucks before do anything.

Is it hard to find a 3.92 DANA on one of these trucks, anybody heard of a truck like mine out there? I have not run across one yet.

OTOH= on the other hand

Thanks...lol.

NAPCO is the original 4 wheel drive conversion that GM moved in-house in the mid 50's, they used corporate axles and the front and rear were the same ratios or very close, no doubt like anything else back then, a buyer could specify what they wanted even if it wasn't a normal RPO [numbered regular production option]

Bill

Ha Ha I AM looking for that 80year old guy. Was pretty sure nothing could be gleaned from VIN but hey worth a try.

Also, looked up NAPCO and looks like only 4x4 retro... mine is 2wd.

Also the us patent numbers cast into the rear end actually say...'US Patent' then the number.

40casey...see that you have 58 fleetside also.. so brother... I will make sure to get pictures up.

a "NAPCO" was the 4x4 conversion, made up of modified corporate pieces, originally by a 3rd party, then taken in house - a NAPCO rear axle is just a GM rear axle, could have been used in anything, and as I said, wouldn't be a suprise if the rear axle used for the 4x4s was a posi and a slightly odd ratio .... if you can track those patent numbers [which may no longer be valid] you might find they were issued to the National Auto Parts Company

Bill [another 58 fleetside driver]

From the 58 shop manual and the 59 suppliment, the posi was offered in 59. But since I recently got a supposed stock 59 old style rear end and it has a posi unit in it. Have not counted teeth yet. Also the axle in my 59 is the new style unit that was offered as the posi option. So I'm thinking they did an old style bolt in differential 3rd member with posi for a short period, then switched to the new style. Since I have one. Anyone else know about this?

The Eaton HO33 axle wasn't offered with the Posi option until '60, but that 3rd member will swap right into the older axles. A '59 Posi will be the Spicer 45, same axle found under the GMC. 3.92 was a common GM ratio in the Spicer 45, as well as the Spicer 44 used as a front axle in the '60 and later 4x4. I don't beleive positrac was an option on 4x4 GM trucks until the mid-'70s.
A '58 with a Posi, especially if it can be confirmed as a factory install rather than a later dealer or aftermarket swap, would definetly be an odd one, as the option was not officially offered until '59 in trucks (passenger got it in '57).

talked to a friend today who's an encyclopedia of GM info - said the same as Bill, "posi" not available until '59, [but maybe the '58 was very late production and special order] ..... he also had a dash tag from one, which doesn't say positraction, but limited slip .... and he said the 3.92 Spicer 45 axle started on the GMC's about 56, so if anyone has GMC master parts books it might be found there

Bill

Here's the manual section on the Positraction equiped axle for '59.
Something that should be noted, the terms "posi" or "positrac/positraction" tend to get used far too often as a generic term for limited slip, even when referring to a non Chevrolet axle. Positraction and Positrac are Chevrolets sales terms for a limited slip differential.

I have a 1958 gmc longbed stepside. I jacked up one side, tried to turn the wheel and it was locked. So I'm guessing its posi. This truck was all original down to the glass fuel pump when I got it. Also there were a few broken lugs I tried to replace and had to order the ones for a posi rear end cause the other ones I ordered did not fit.

If is a posi it is most likely a 44 series Spicer. It would also have the offset drums on the rear brakes.