[56GMC]

I have a stock ‘62 Catalina with a 2bbl 389, rotohydramatic & 2.69 gears in the back. Car is a great cruiser and not looking to make it into a race car. Need to do something with the transmission due to the usual issues related to the slim-jim; leaks & large gear ratio change between 1st & 2nd . My choices are either rebuild the slim jim with parts from Fastco or replace it with a 3 or 4 speed auto; TM350/400, 700R4. Have been researching some of the magazine articles & forum entries on this conversion but would like to hear back from someone who actually went through it. The trans works fine but who knows what I may find on disassembly? Conversion to a newer unit could involve an adapter plate from Wilcap or Bendsten, new starter, driveshaft mods, rear mounts, linkage, tunnel massage, etc. Fortunately I have a 2 post lift & trans jack in the garage as I plan to do all the work myself. Just looking for feedback from people that have gone through this or know of other write-ups on the ‘net. Money is always a concern as a rebuild kit will cost at least $300 - $500 while the conversion will run at least $1500 minus the trans. Not too concerned about keeping the drivetrain original however. Thanks!

[Keith Seymore]

I threw a TH400 into my Grand Prix, mostly because I already had it.

It was from a '67 Riveria; since the bell housing was the same as the block an "adapter plate" per se was not needed but I needed someplace to hang the starter. Bendsten makes a "starter plate*, which I used and which allowed re-use of the production starter.

New one piece drive shaft and fabricated the console shift linkage using a coupling nut, threaded rod and a tie rod end from a John Deere garden tractor.

K




*blueprint for the starter plate can also be found in one of Pete McCarty's books, if you have the means to make one yourself.

[Ragtop Man]

Not familiar with the Rivvi TH... long or short tail?

How did you handle the kick down switch?

Did it keep the switch pitch convertor?

[Stuart]

If you do go with an overdrive transmission, I'd suggest changing the differential ratio as well.

[694.1]

I'd be inclined to do a 3.08 rear & see what you think of that first.

[tom s]

Screw the auto!Change it to a 4 speed.Leave your rear gear alone and put a 3.42 first gear ST-10 in it!Same combo I have in my 62 421 GP,you will like it a lot.I have a belhousing if you do,Fabcraft has everything else you need.Tom

[mgarblik]

Originally Posted by tom s

Screw the auto!Change it to a 4 speed.Leave your rear gear alone and put a 3.42 first gear ST-10 in it!Same combo I have in my 62 421 GP,you will like it a lot.I have a belhousing if you do,Fabcraft has everything else you need.Tom

First off, I really like the look of your car from the pic. Black and red is hard to beat. Having a converted 62 Cat from Slim Jim to Muncie 4-speed in my case, can't be beat IMO. But it was done when I bought it, so I can't say what it cost. It seems like it would be much more involved and expensive than keeping it an auto, which you may prefer anyway. I have owned a few Slim Jim cars, and personally felt they really sucked the life out of those great cars. Possibly the ones I had were shot, but the one/two shift was always terrible in the ones I owned and every one I have been in as a passenger. All that being said, if you don't mind the general way they perform and have the skill to rebuild it, fixing the leaky Slim may cost the least. I wouldn't go that way myself. I would be inclined to go turbo 400 if staying with an auto. I just like the feel of a 400 shifts, the strength and durability without having to buy lots of aftermarket parts. A 350 turbo is plenty strong enough and lighter, with the good parts available would hold up fine. But with budget constraints, a 400 may actually cost less because a stock one with a shift kit is all you need. I think the OD autos would be a budget buster by the time you get all the necessary parts to install and beef it up for reliable use. Also, if you have a 2.69 gear, you really don't need an overdrive. Changing the rear axle ratio on the 9.3" can also become an expensive adventure if it needs additional parts in there. You have some decisions to make.

Based on your original post, I would be inclined to install a nearly stock 400 turbo and enjoy your beautiful car. Good luck.

[U47]

Most people are afraid of Roto. The shift quality can be adjusted, but I must admit that the 1-2 or 3-4 range shift in them is harder than a T350or 400 and if you know the mechanic's of it you know the reason why. This transmission which is the only automatic with a fluid coupling and a small fixed stator not only uses the coupling for connection to the engine, but when draining it for 2nd gear uses it to control the front planetary gear set. The harsh I-2 shift is because 2nd gear is FULL mechanical connection. Also when this transmission is in 3rd gear it is in the split torque mode ( same as the 4 speed Super- HydraMatic when it's in 4th gear ). Split torque feature divides the engine torque in the transmission between the coupling and mechanical connection so 40% is through the coupling and 60% mechanical. A T350 or 400 all the engine torque goes through the converter =more slippage. Roto and Super HydraMatic in high gear are the most efficient automatic's until the introduction of lock - up torque converters.


If you ever get the chance to watch the 1963 Indy Nationals pay close attention to the A/SA finals. The final is between a 62 421 Catalina and a 63 426 max wedge wagon. A Roto VS Torqueflight. They start out even, but when that Catalina shifts into 2nd gear it's quite evident it's now in Full mechanical connection and he pulls a fender, and holds that lead the rest of the way.


The only problem you had with Roto and Super HydraMatic is they are governed to upshift around 4,400- 4,600.
To make both shift even quicker and harder you can modify the exhaust valves to drain the fluid coupling from the normal four tenths of a second to about two tenths of a second.

Royal Pontiac had a pressure modifier kit ( springs and washers) to hold the shifts up to 6,500. As long as you have the specifications you can make one on your own. It's easy to do on a Roto because the coupling is inside the trans case and there are two inspection holes in the bell housing where you can easily get to the pump which is on the outside of the case.

[Keith Seymore]

Originally Posted by Ragtop Man

Not familiar with the Rivvi TH... long or short tail?

How did you handle the kick down switch?

Did it keep the switch pitch convertor?

Long tail (I accommodated the length with the new fabricated drive shaft)

No kick down. I just pull the floor shifter down into L2 when necessary

I had my transmission guy fab up the biggest tightest convertor that he could make (no switch pitch).

K

[mgarblik]

Originally Posted by U47

Most people are afraid of Roto. The shift quality can be adjusted, but I must admit that the 1-2 or 3-4 range shift in them is harder than a T350or 400 and if you know the mechanic's of it you know the reason why. This transmission which is the only automatic with a fluid coupling and a small fixed stator not only uses the coupling for connection to the engine, but when draining it for 2nd gear uses it to control the front planetary gear set. The harsh I-2 shift is because 2nd gear is FULL mechanical connection. Also when this transmission is in 3rd gear it is in the split torque mode ( same as the 4 speed Super- HydraMatic when it's in 4th gear ). Split torque feature divides the engine torque in the transmission between the coupling and mechanical connection so 40% is through the coupling and 60% mechanical. A T350 or 400 all the engine torque goes through the converter =more slippage. Roto and Super HydraMatic in high gear are the most efficient automatic's until the introduction of lock - up torque converters.


If you ever get the chance to watch the 1963 Indy Nationals pay close attention to the A/SA finals. The final is between a 62 421 Catalina and a 63 426 max wedge wagon. A Roto VS Torqueflight. They start out even, but when that Catalina shifts into 2nd gear it's quite evident it's now in Full mechanical connection and he pulls a fender, and holds that lead the rest of the way.


The only problem you had with Roto and Super HydraMatic is they are governed to upshift around 4,400- 4,600.
To make both shift even quicker and harder you can modify the exhaust valves to drain the fluid coupling from the normal four tenths of a second to about two tenths of a second.

Royal Pontiac had a pressure modifier kit ( springs and washers) to hold the shifts up to 6,500. As long as you have the specifications you can make one on your own. It's easy to do on a Roto because the coupling is inside the trans case and there are two inspection holes in the bell housing where you can easily get to the pump which is on the outside of the case.

If you are really interested in the Roto or Super Hydramatic transmissions, there is about 3 hours of video on Youtube which does an excellent job of showing and explaining how they work. I used to blow them off as just another old terrible transmission. After watching the video and understanding how they work, I have much more respect for what they were trying to do. The end result, though, especially the 3-speed Roto Hydro, was a very unpleasant driving transmission.

[Ragtop Man]

Stick and 3.42s / 3.55s with all that torque is a blast to drive, if you want a manual.

[U47]

Originally Posted by mgarblik

If you are really interested in the Roto or Super Hydramatic transmissions, there is about 3 hours of video on Youtube which does an excellent job of showing and explaining how they work. I used to blow them off as just another old terrible transmission. After watching the video and understanding how they work, I have much more respect for what they were trying to do. The end result, though, especially the 3-speed Roto Hydro, was a very unpleasant driving transmission.

I found stuff on super, but not Roto. include a link.

[mgarblik]

Originally Posted by U47

I found stuff on super, but not Roto. include a link.

I think you found the same stuff I referenced. It was really about the super hydro, but he did talk about the Roto a little. All the hardware in the video was super hydro. My primary interest was general knowledge and learning how the taurus member worked. Lots of similarity between the Roto and the Super on the 1/2 shift, I think? The video was where I learned the thinking behind NOT using a torque converter. The idea of a mechanical hook-up looked good on paper, but at least in the ROTO, the rpm drop and the harshness in second without the slippage and cushion of the converter, was just miserable IMO. I sold a 63 GP I had just because the Roto was so awful.

[U47]

Originally Posted by mgarblik

I think you found the same stuff I referenced. It was really about the super hydro, but he did talk about the Roto a little. All the hardware in the video was super hydro. My primary interest was general knowledge and learning how the taurus member worked. Lots of similarity between the Roto and the Super on the 1/2 shift, I think? The video was where I learned the thinking behind NOT using a torque converter. The idea of a mechanical hook-up looked good on paper, but at least in the ROTO, the rpm drop and the harshness in second without the slippage and cushion of the converter, was just miserable IMO. I sold a 63 GP I had just because the Roto was so awful.

Super HydraMatic & Roto controls the front planetary by way of a sprag clutch being applied and released by filling and draining the small fluid coupling. Roto eliminates a gear, adds a fixed stator to get reduction by multiplying hydraulic pressure twice to get the gear it eliminated and as the coupling spools up the fluid passes straight through the coupling going from 3.50 to one to 2.93 to one so what you have is the 1-2 gear of the old hydro only you can't feel it happening. This is why HydraMatic division called Roto a FOUR range HydraMatic.
Roto also replaces the large fluid coupling in Super and makes the small fluid coupling that was in Super Hydramatic do two jobs 1. to connect the engine to the transmission, and 2. drain and fill to control the planetary gear set. That by the way is a ingenious idea!

Once Roto is in 2nd gear ( 3rd range) and Super is in 3rd gear the two transmissions shift into high gear with the same feel. The coupling fills in 3rd gear or fourth range and the secondary coupling in Super also fills from 3rd to 4th gear.

Roto's 1-2 change is 2.93 to 1.56 and with this happening being mechanical it's a lot more harsh between the engine and transmission. If there were a hydraulic connection like the Super always had between 3rd and 4th ( 2.55 to 1.55 ) with the large fluid coupling it softens up the shock.


My feeling is that Pontiac division was made to take Roto. The Roto was Oldsmobiles thing, however Olds didn't sell enough cars to make Roto's production cost cover it. Cadillac didn't sell enough cars to make Controled Coupling profitable either. Catalina, Ventura, Grand Prix help out Olds and Bonneville and StarChief help out Cadillac.
What they should have done is have all divisions stay with Controlled Coupling until T400. FYI Controlled Coupling is known as 315 to Cadillac, Jetaway to Olds, Super HydraMatic to Pontiac. I just call it Controlled Coupling Hydramatic, after all they designed and built it.

[stevep]

The Controlled Coupling has a ton of names.
In the transmission business, we just called them Jetaways.

[U47]

Originally Posted by stevep

The Controlled Coupling has a ton of names.
In the transmission business, we just called them Jetaways.

That's a Oldsmobile term. In the transmission business "the G.M division that made it" call it "Controlled Coupling HydraMatic".


If someone called you and said; how much to build my Jetaway? You would have to say which one? Controlled Coupling or ST300 as they are both nicknamed the Jetaway. Best not to be confusing by using the Oldsmobile term.

[Poncho60]

IMO if neither the car owner nor the trans shop never get beyond just the "assumed" name of the transmission, then neither should probably be in the business or the car hobby.

[tom s]

If a shop does not know what a "Slim Jim"is they will not know how to work on it.JMO,Tom

[stevep]

Originally Posted by U47

That's a Oldsmobile term. In the transmission business "the G.M division that made it" call it "Controlled Coupling HydraMatic".


If someone called you and said; how much to build my Jetaway? You would have to say which one? Controlled Coupling or ST300 as they are both nicknamed the Jetaway. Best not to be confusing by using the Oldsmobile term.

Transmission shops never called the 300 a Jetaway.

If they asked how much for a Jetaway, I'd ask them what car it was in.

I don't know of any trans shop that referred to a Dual Coupling as anything other than a Jetaway.

I also know that you know your stuff about them.

I'm a Pontiac guy so misusing an Oldsmobile term doesn't really upset me.

They also called the Dual Coupling many names.

[U47]

Originally Posted by stevep

Transmission shops never called the 300 a Jetaway.

If they asked how much for a Jetaway, I'd ask them what car it was in.

I don't know of any trans shop that referred to a Dual Coupling as anything other than a Jetaway.

I also know that you know your stuff about them.

I'm a Pontiac guy so misusing an Oldsmobile term doesn't really upset me.

They also called the Dual Coupling many names.

Fair enough OK?