Roto ("Slim Jim") Hydramatic - kit/aftermarket source?

[ChrisBcritter]

I want to put an automatic transmission in my AMT '62 Catalina; it would have used the smaller GM Roto Hydramatic (aka "Slim Jim"). I think my only option for this would be the '63 Olds Starfire; but are there any aftermarket Rotos available? I'd think some builders would like them for the Moebius kit as well (along with the correct brake pedal, which is in the old Revell Stone-Woods-Cook Willys IIRC). Over to the experts... 

Edited September 11, 2017 by ChrisBcritter

[Ace-Garageguy]

Hmmmmm....I just pulled down a '63 Starfire and looked. The transmission is a blobular thing that looks kinda-sorta like a "Slim Jim", but is not a correct representation of the 375 "Slim Jim" at all. The oil pan shape is wrong, and the case is wrong. Olds engines of the period had a cast-in integral partial bellhousing, to which the trans case is bolted...and this is entirely wrong on the old Johan model too.

Pontiac engines of the period had a more conventional separate bellhousing, and the attachment was therefore different as well. 

Far as I know, you're SOL as far as accurate Roto Hydramatic 10, model 375 (big car)  "Slim Jim" availability goes.

PS. I have a real Slim Jim in my '63 Dynamic 88 convertible (the car I learned to drive in quite a few years ago), and it's not a gearbox you really want if you have a choice.

Edited September 11, 2017 by Ace-Garageguy

[waynehulsey]

 

PS. I have a real Slim Jim in my '63 Dynamic 88 convertible (the car I learned to drive in quite a few years ago), and it's not a gearbox you really want if you have a choice.

That was my first through when I saw thread posting.

[ChrisBcritter]

Oh, I know - I had a '64 Catalina 2+2 convertible once whose Roto was just beginning to slip when I sold it; my boss's '64 Starfire's trans cost over a grand to rebuild. I guess I'll just go with "kinda-sorta" since another board member just gave me a clean resin copy of one. I checked the '64 AMT Grand Prix, which should have the Roto, but it's the same trans as the Bonneville.

[1972coronet]

Is the transmission included in the AMT Chevy 283 & Pontiac 421 parts pack a Hydra-Matic or a Roto-Hydramatic ?

[Ace-Garageguy]

Is the transmission included in the AMT Chevy 283 & Pontiac 421 parts pack a Hydra-Matic or a Roto-Hydramatic ?

The gearbox with the AMT Pontiac described as "B&M Hydro transmission" is a Hydramatic (NOT Roto), converted to the B&M "Hydro-Stick" configuration.

The Revell parts-pack Chevy 283 and Caddy engines have two different versions of the Hydramatic as well...neither one is a Roto.

[Casey]

Chris, I think I recall you finding the trans you were seeking, but I found this (what I think is a) Roto Hyrdamatic auto trans from a JO-HAN ________ (not from the '63 Olds Starfire kit), so I'm curious (A) which kit it is from, and (B), which 1:1 trans the part is supposed to represent....let's throw in (C), is it accurate, too, while we're at it.

First four images are of the red JO-HAN part:

 

Below, a real 1962 Pontiac Hyrdamatic "Slim Jim" (I think):

 

Next, the Oldsmobile Hydramatic "Slim Jim" (I think):

 

Edited July 16, 2021 by Casey

[Mark]

The red engine block/transmission is from a Jo-Han Olds F-85 ('62, later added to the '61 wagon kit).  That would be a smaller, lighter duty automatic used with the small aluminum V8.

For the Roto, the only option besides the Starfire is apparently scratchbuilding...

[Ace-Garageguy]

Glad youse guys started this thread. As a result, a while back I did all the required research on the Roto (that's in my '63 Dynamic 88 convert), bought the factory manuals, some hard parts that are very difficult to find, found sources for the soft parts (clutches, bands, seals, gaskets) and flagged a buncha internet links to discussions of the beast.

And once again, this is one of the things I've liked the most about this hobby...the opportunity to LEARN about the workings of real things in the real world.

[Mark]

With a few strategic photos, and some basic measurements of the 1:1 article, it should be possible to scratch a convincing replica.

The basic shapes you'd want to get right would be the bellhousing, pan, and tailshaft (shape and length).  None on the detail on top, from the bellhousing back, will be seen on the assembled model.  Concentrate on what is visible from underneath, and the bellhousing, and you're golden.

Edited July 16, 2021 by Mark
Info

[Foghorn Leghorn]

The GM 375 Roto was in several of the Jo-Han 1960's Cadillacs even after the GM 400 Turbo hit the market for the 1965 model year.

[Mark]

The Cad units are roughly the same as the Olds piece, as far as accuracy is concerned.

[StevenGuthmiller]

A modified Johan 1962 Olds F-85 tranny. (like the red one above)

I did some stuff with the bell housing area, and lengthened the tail shaft.

Not perfect, but about as close as I was going to get for my ‘64 Pontiac Grand Prix.

 

 

Steve

Edited July 17, 2021 by StevenGuthmiller

[OldNYJim]

On 7/16/2021 at 10:21 PM, StevenGuthmiller said:

A modified Johan 1962 Olds F-85 tranny. (like the red one above)

I did some stuff with the bell housing area, and lengthened the tail shaft.

Not perfect, but about as close as I was going to get for my ‘64 Pontiac Grand Prix.

 

Steve

This is a super-old thread, but I was researching something...nice engine Steve!  Love that realistic weathering!

[Calb56]

Casey has one but description says "50s style".

 

https://www.ebay.com/itm/Resin-1-25-GM-Hyrdamatic-Automatic-Transmission-with-Separate-Pan-/265986350957?mkcid=16&mkevt=1&_trksid=p4429486.m46890.l6249&mkrid=711-127632-2357-0

 

[StevenGuthmiller]

26 minutes ago, Calb56 said:

Casey has one but description says "50s style".

 

https://www.ebay.com/itm/Resin-1-25-GM-Hyrdamatic-Automatic-Transmission-with-Separate-Pan-/265986350957?mkcid=16&mkevt=1&_trksid=p4429486.m46890.l6249&mkrid=711-127632-2357-0

 

That looks like pretty much a direct copy of the transmission in the Monogram '59 Cadillac kit.

 

 

 

Not quite the same as the Pontiac "Roto-Hydromatic".

 

 

 

 

Steve