1956 plymouth savoy 2 Dr hardtop

[jpb56savoy]

Good morning all.  this is my first post and first build. I have 1956 savoy hardtop, I have a mildly built 318 to go in it. I ask what transmission will work with this? And do I need to swap rear end?  I plan on it being a cruiser with great sound and occasionally "abusing" the tires. Any help is much appreciated and needed. thanks

Edited August 13, 2023 by jpb56savoy (see edit history)

[Rusty_OToole]

Is it a 1966 or 1956? It makes a difference. I will assume it is a 56.

 

The 318 should fit without too much trouble as your car was made to take a V8, unlike the 1954 and earlier models. What transmission did the car have to begin with? If it was an automatic it would be a pushbutton Powerflite. It might be possible to fit this trans to the 318 although the crankshaft to torque converter interface is slightly different. A 904 Torqueflite would be a better choice but this will mean fitting a different gearshift. Or , you could use a newer overdrive type automatic. The trans that came with the 318 might be the best choice.

 

If it was a manual trans car it should be possible to fit it to the 318 with a little finageling.

 

If it was a V8 car the original rear axle should stand the gaff. Or, you could change to a newer rear axle. I believe  Jeep Cherokee rear axles from the 1990s and 2000s are a close match in width, and have the same wheel bolt pattern, but may require relocating the spring mounts. A trip to a wrecking yard with a tape measure may turn up some other possibilities. There aren't many rear wheel drive vehicles with solid rear axles, except pickup trucks.

 

If it is a 66 it is that much easier as they already had a column shift lever, and the engine and trans were nearly the same as your 318, and the rear axle will be fine if it was a V8 model.

Edited August 13, 2023 by Rusty_OToole (see edit history)

[jpb56savoy]

yeah, sorry, it's a 56'.  original was flathead six push button automatic.  I did assume that it was going to need a floor shifter installed. I'm just going to hide it so still will hold the push button appearance. only 2 speed trans though. I would like to be able to cruise or run the highway at 65 or 70.  I did read about A904 would be good, but also read 727 would be better!  is it just a matter of opinion?  probably. so 70's 904 or 727 should bolt up to 318?  Looks like a 78 year built. 

[28 Chrysler]

Welcome  jpb

The 904 should be all right and overall I think they are shorter in length than  the 727s.

You may have to have a custom drive shaft made.

Try to make the SBC 318 look like a 1956 with gold valve covers and air cleaner,

 

[jpb56savoy]

thanks for the welcoming comment.  I'll start looking for the 904. Last part of the post, can I leave that rear end or as Mr. Rusty said look for modern?  This helps a lot!  Always wanted to build classic finally able to somewhat afford it. 

[Rusty_OToole]

The 727 is a heavy duty trans usually used with big block cars. The 904 is plenty strong enough for a 318, it is lighter, and saps less power. I would get the 904 or one of the newer overdrive automatics.

 

You may find the six cylinder rear axle is too low geared for hiway use although it might be fun for stop light drag races. If you do want a different gear ratio it is best to replace the whole rear axle as the old one is obsolete and hard to work on. The drive shaft is another issue, it has peculiar universal joints they don't make anymore. It would be best to replace the whole drive train.

[jpb56savoy]

Thanks a lot Rusty. great direction and I appreciate it. 

[3macboys]

You should be able to find a Mopar 8 3/4 rear end that will fit nicely - I suspect that a later 60's to early 70's B body will be about the right width and likely have a decent gear in it.  So long as you don't want a Sure Grip the price will be reasonable as well.  Lots of info online about the widths of the various rear ends.

[Rusty_OToole]

Another thing to bear in mind is that the original hand brake was on the back of the trans, a newer trans will not have this feature. One more reason to change the rear axle.

I did not mention 60s or 70s rear axle because they are no longer easily available. I tried to think of something you could find in your local junk yard, and for which parts will be available for the forseeable future.

[jpb56savoy]

I did read that a 91 explorer rear end would work. may have to move the "shackles"? But supposedly, it marry's up just fine.  this may sound dumb, but I figured the hand brake would be non functioning with a "newer" transmission. sure I'm worng... problem I have now is finding one, I've almost succumbed to the fact I will have to buy one from summit or jegs

Edited August 16, 2023 by jpb56savoy (see edit history)

[TerryB]

Shackles are the end support brackets that attach the leaf springs to the car body.  The allow the spring to flex at the back of the car body.

[Rusty_OToole]

2 hours ago, jpb56savoy said:

I did read that a 91 explorer rear end would work. may have to move the "shackles"? But supposedly, it marry's up just fine.  this may sound dumb, but I figured the hand brake would be non functioning with a "newer" transmission. sure I'm worng... problem I have now is finding one, I've almost succumbed to the fact I will have to buy one from summit or jegs

The spring mounts on the axle will probably have to be moved. This is not a big deal, it means cutting or grinding off the old mounts and welding on new ones, Summit and other suppliers sell new ones, they are not expensive, and in most cases you can reuse the old ones.

 

The hand brake is on the transmission. If you replace the trans, the hand brake goes with it. Newer transmissions do not have a hand brake, it is on the rear axle. The service brakes are connected to the hand brake lever by a cable. This means, you put in a newer rear axle and it has the hand brakes on it already.

 

In short, if you change the trans, you have one more reason to change the rear axle.

 

The Explorer axle may be the best answer, the bolt pattern is the same, if the width matches fairly close.

Edited August 17, 2023 by Rusty_OToole (see edit history)

[jpb56savoy]

Great info Rusty!  definitely appreciate the insight. I want to sell the original engine and trans from the 56' how can I post that on here?  1956 plymouth savoy flathead 6 2 speed push button powerflight transmission. I "assume" the miles are original at 76k+