Technical 57 Pontiac Transmission Interchange

I had asked about using an Olds transmission as a replacement, and I got some excellent response. However, I couldn't come up with the needed parts to make the swap. I've now found a 1956 Pontiac trans, and I'm wondering if it would be the same, and just a bolt-in affair? I realize they used the earlier Hydramatic in some Chieftains, but this has a 15 bolt pan so it would be the later model.

 

Here is a similar thread from yesterday that may add info for you

https://www.jalopyjournal.com/forum...ydramatic-transmission.1170074/#post-13294956

 

Wasn't a specific answer here. Thanks.

 

I have a '57 9 passenger wagon. Came w/o a motor or trans. I used a '55 287 bolted to a slantpan so I could drive it. Found a 347 last May bolted to a '57 dual coupled stock unit. Installed that pair and I love it. I just bought a good used '57 trans for $200 to keep as a spare. The early 1956 Pontiac with the 316, first 4 or 5 months had the slantpan hydramatic.. After that the 1956 unit with Park (Jetaway) was used. Then the 1957 unit with Park was used with minor mods. I believe it was changed in the 1958 models. I think it is a great trans, and when gone through, with some newer parts they are very dependable. They have the lines that cool the fluid through the radiator. Pull your old one apart. There is a utube video of a guy rebuilding one. Fun stuff. If it has the cooling lines on the right side, it is a 1956/1957 and it should mate right up to the carrier. The slantpan Torus assembly is different and has 30 bolts. The 1956-57 has more of a torque converter. I can send a couple pics of the trans if you like.

 

Thanks for the info. I can't decide what to do. Most people say the best thing would be to buy a kit and install a later TH350 or 400. A lot of work, not cheap, but fairly safe due to the popularity of the transmissions. A shop near me has a rebuilt 56 trans for $1000. I have no idea how good of a job the rebuild is, and if I have a problem this guy is the only one I could find that even knows what a Stroflight Hydramatic is. Not exactly comforting. The rebuild kit for the Hydramatic is really expensive, and even though I'm pretty capable with car stuff, if I screw it up, then what? Just not sure what to do, with no easy answer.

 

If it has been professionally rebuilt, with a guarantee, then it is not a crazy price. My '52 has a flatpan, and the '55 Chieftan has a slant pan. My '57 has the Jetaway with Park. I like it. So smooth you don't feel the shift, just an rpm difference. If you are going to be driving it hard, the later model might be good. Although the early hydramatics have a good rep with stomp on it guys.

 

Castro Transmission shop.

https://www.yelp.com/biz/castos-automatic-transmission-service-belleville

They have a 56 rebuild kit they will sell you for likely cheap money. Tried to get me to buy it and I should have but mine was working well. Very old repair shop. Only place I would have allowed touch my transmission. Has had this kit and said they doubt anyone would ever ask them to rebuild one again.

 

I had good luck with Fatsco in New Jersey for my '51 Hydra-Matic, they have spares and were really very helpful.

https://www.fatsco.net/products.html

$0.02

Phil

 

Fatsco really is great to deal with. They'll bend over backwards to help you out

 

Unfortunately, the local guy makes me nervous. He's been missing from his shop sometimes because he was in jail drunk. A guarantee is great if you have someone to back it up. If I had any problems I would have to pull the trans back out myself and take it back to the same guy. I certainly have no problem with the price.

I called Fatsco. It would be an expensive proposition with shipping. As good as they are, they're human and could also make a mistake. That, of course, would mean pulling it back out and shipping it back and forth.

Doing it myself could also be a waste of time and money. I know it sounds like I'm looking for something ideal here, but I do have to live with the decision I make. I'm just trying to consider the merits of each scenario, then try to make my best choice. A later transmission that I could get locally, one that everyone, including myself, could work on, is starting to look like the best option. Not that it seems to mean as much today, but I have a Super Chief 2 door hardtop with factory air, PS, PB, and a numbers matching motor. A later trans would ruin this a little, although I could always include it with the car if I sold it.

 

Get an adapter.

http://www.wilcap.com/

Weld side mounts to the transmission and most people would pay you more money for the car than if it was all factory. As you have found out, fewer and fewer can or will fix these transmissions.

 

I've spoken to Pat at Wilcap. A friendly, knowledgeable guy. I would have no problem dealing with them. All of my local buddies agree with you, ditch the StratoFlight and move on.

 

It's impossible to give you any guidance because you haven't made it clear what your intentions or desires are.

It sounds like local guy has no idea what he's doing and I going to give-it-a-go at an early hydro. A proposition I wouldn't want to deal with given what a pain in the ass it is to remove the transmission, assuming he'd even make good on a mistake. You'd also probably be out the tow for breaking down somewhere, and the parts that got ruined in this guy's experiment.

I wasn't aware that Fatsco does rebuilds, I thought they just sold parts. Assuming they will do a rebuild, or even refer you to a local shop they trust to rebuild a Hydro with their parts, you've raised the concern about shipping. But I just Google Mapped your location to Fatsco and it's barely 3.5 hours. If the shipping is that much of a concern, take a sick day and drive up and back. I drove to DC for a good 57 Ford bumper core. You do what you have to do, and the trans would probably fit in the trunk of a mid-sized sedan and not cost you more than $75 in gas and tolls.

wvenfield, IMHO, raised the proper answer, which is to simply run an adapter from Wilcap. For $750 you solve all of your transmission problems by going to a later model Chevy transmission, and you can even add Overdrive if you so desire with a 700R4 or 200R4. You mentioned that you didn't want to do this either because the car is numbers matching and it would "ruin" that. I couldn't disagree with you more in that regard. First, this is a hot rodding and customizing board, so we don't care about "numbers matching", you can take that sentiment to the AACA forum. Second, if the Hydro was so wonderful, GM would have kept making them and us as hot rodder would be pining for them. The reality is they are an obsolete, inferior transmission to any of the later TH350 and TH400 in both performance and cost to service, and you'd see a significant improvement in drivability with the improved gearing of the 700R4 or 200R4, which is something we're all looking for here. Third, any minimally-competent shop would be able to service these common transmissions, and you could deal in better-than-factory components available through the aftermarket. In fact, you wouldn't even need to source one locally to do the job. Call up Wilcap and Jeg's place your order, and everything you'll need will show up in your driveway.

I wish this option was available reasonably priced for my Olds 394, I'd pitch that shitty Roto-Hydramatic "Slim Jim" in a lake in exchange for a 700R4.

 

I am capable of rebuilding automatic transmissions. However I don't like them. I would convert to a stick shift. I did have all the necessary parts. However I sold wvenfield the clutch pedals and linkage.

 

I recently rebuilt my Hydra-Matic. Compared to modern autoboxes it is quite different to drive- it's pleasant enough and really echoes the state of the art back in the early fifties- if not a little bit lumpy when it has its' moments between changes.

However, in planning on pulling it apart I will say this: I had no idea what I was getting into when I first started work on it. The reason for disassembly was that it leaked very badly and did not change gears correctly. It would hold first gear for a long time then dump hard into third, sometimes fourth.

It does need some special tools to take it apart but nothing that cannot be created with some pliers, a saw, a drill and some metal bar from the hardware store.

My main thing was that the bearing surfaces were utterly ruined. Externally, there was no sign of this, before dropping the pan there wasn't, either. It still went forwards and backwards (badly) and wasn't making any really horrible noises other than a bit more of a whine than I cared for.

So, what went from a clean and a re-seal with new gaskets ended up being a full bearing replacement, two new drum ends, fluid delivery sleeve, spacer bushings and a new oil pump due to the fact I managed to make a stupid mistake and break the old one.
So, all in all of my time, about 40-50 hours of work I think and close to $900 of parts.
Do I regret rebuilding it? No. Have I learned a lot about the gearbox and how it works? Yes. Am I sure it would have been rebuilt right if I sent it somewhere? Really I'm not sure but I know that the unexpected extra labor time and parts would have been crippling in terms of cost for me.

So, as it has been said, make absolutely sure what you have in your mind what you want to do first- yes, these transmissions are old and antiquated. Yes, GM made leaps and bounds in the years following in terms of design and reliability, driveability and smoothness of operation. Yes, the newer gearboxes are better. Yes, you are much more likely to be able to find someone who knows what a TH350 is than an original Hydra-Matic. Do you want to keep it original or are you willing to sacrifice that a little for the personal peace of mind that you can get towed to a shop anywhere in Nowheresville, USA and get it fixed or get a junkyard replacement late model transmission if the one you fitted throws its' toys out of the stroller?

There's a very large amount of knowledge here but we aren't here to make your mind up for you. We can offer up opinions (you know how much those are worth), which may sway your choice but really you need to know, for sure, what you want to do- then I know for sure there'll be someone here who knows someone or something that'll help you get it done and make it work in a way that'll make driving the car a real pleasure.

That there is my two cents. Your mileage may vary.

(and, a clickable for how it behaves post-rebuild: the 2-3 change is never much better than that)

--Phil

 

Great, really worthwhile responses. Everybody, including me, loves this car. It's just a little different than a 57 Chevy, but has the same attraction. I just want to drive and enjoy it. As for the originality, I just feel a little guilty changing a somewhat rare car. Some people are still really into that. I have to point out that the car came with the original air cleaner, wheels and hubcaps. I sold them all. So if I decide to install a later trans, It's not going to bother me since, as I mentioned, if I ever sell it I could give the original trans to the new owner.

Fatsco does not rebuild transmissions, but they have a guy that does, $1750 for mine. Correct, the drive to NJ isn't bad - unless I have to make it more than once.

The bottom line is that I asked for, and received, some good opinions from people whose replies made sense. I need to digest all of that and decide what to do. It's what I wanted. I do want to thank everyone since a number of the responses were pretty long and took time to write.

 

Does that $1750 include parts? Because if it does that's a great deal. Even if it doesn't, you're going to be further into a conversion than that monetarily. Even the Jeg's or Summit branded transmissions will set you back $1500, then you still need a converter, a $750 adapter, slip yoke, either shorten the driveshaft or get a new one made, starter... it will be pricey quickly. Whereas a rebuild of the factory unit will be an out-and-back-in swap. The question you have to answer is how much do you want to spend, and is the improvement in drivability and parts availability worth the extra money up front over the stock rebuild. Ultimately your decision. Good luck.

Edit: Whichever way you go, please keep us posted on this thread or make a new one about either replacing the hydro with the adapter or having yours rebuilt. The HAMB has gotten piss poor as of late with technical threads.

 

It seems there are several people here suddenly with '55, '56, '57 Pontiac engine or transmission swap questions. Seeing as how I am one of them, I believe I will follow this thread.

 

I'd be happy to update, but it won't be quick. The weather has gotten cold, and I don't have a lot of heat in the garage.
In addition, my kingpins and front brake hoses were bad. I decided to tear the entire front suspension off and replace everything. I'm in the middle of that now.

 

As a Pontiac guy, I ask only one thing. Please don't put in a crate Chevy 350 with matching trans. That will ruin the whole thing. Good luck

 

Don't worry, that's not going to happen. Too many problems with that swap, besides I have 347ci already, 10 to1 compression ratio, 270 horsepower, and everything fits. It's just a driver, and I could easily upgrade to 315hp, plenty for my needs, and more than some of the crate motors have.

 

Not necessarily a Pontiac guy, but yes, thanks for not bastardizing it Pontiac in Pontiac, Ford in Ford, etc.

 

"It's just a driver"
Imagine...A '57 Pontiac is just a driver.
Come on now!

 

There's a member here from Florida, with a very nice 57 Pontiac; built motor, and backed with the cast iron, single coupling, dual range, 4 speed Hydra-Matic (like the old B & M Hydro-Sticks were based on). I forget his handle, but you may find it by searching for 57 Pontiac. I would think the old Hydro would be a far better trans than the dual coupling model you have. I am Butch/56sedandelivery.

 

What's wrong with a 1957 Pontiac being just a driver? What should it be?

 

Amen!

 

There's a '57 Pontiac 2dr sedan on Craigslist locally under auto parts. It's very rusty, but looks to be intact. If anyone needs a donor car

 

There is a local welding shop that has a talented cobbler. He built a adapter plate to mount a 6V92 Detroit engine in a W26 case loader. I bet you could get a 3/8 steel plate and make a adapter to mount any bellhousing pattern trans to your engine. make template out of cardboard. then transfer that to thin plywood. and take your template and steel to a machine ship to be cut and drilled.

 

You could find the oldest trans shop in the area and try them. There is one here that has be doing business since 70’s, they know old transmissions.

 

I think what he was getting at is "that's a very cool and special car, much more than just a driver to a lot of us who love old Pontiacs" A helluva nice driver! Post some more pics of it - go ahead, show off a little.....