Fear of Slim Jim?

[Guest mortsciguy]

As a new owner of a 1964 Starfire I am a bit alarmed by the references I have seen in this forum to the auto trans in this model. I'm sure there are threads dealing with this subject in detail, but I would appreciate it if someone would give me the broad strokes. What are the key issues, causes, symptoms, etc? Are there any preventative measures to prevent disaster?

Don't let me crawl out on the ledge without cause! Mine seems to work great, so why should I fear the Slim Jim? Let me know.

Kelly Martin:confused:

[rocketraider]

If it's working, you're golden. Just remember they are sensitive to fluid level and throttle valve rod adjustment. Most of them have a rather abrupt 2-3 shift (it's the first shift you feel, the 1-2 shift is almost imperceptible and happens inside the fluid coupling) so if it does that, it's probably close to normal. The 3-4 shift is also very smooth and sometimes can only be felt by watching the tach.

Filters have gotten a little scarce but places like Edwards Transmission or Fatsco should be able to supply one.

The biggest issue with SJ is that there are few people around now who understand how to service it, and even fewer who are willing to learn. They've been told it's a junk unit and they're afraid of it, or I should say more to the point they're afraid of warranty work. It works off the same basic principles as a Chrysler Torqueflite, Chev Powerglide, and even a modern THM 200-4R or 700R4. And a trans guy who can repair an electronically controlled unit but tells me he can't do anything for a Slim Jim is suspect in my book.

[Guest mortsciguy]

Thanks, Glenn. Walk on the ledge averted.

Kelly

[Guest]

The biggest issue with SJ is that there are few people around now who understand how to service it, and even fewer who are willing to learn. They've been told it's a junk unit and they're afraid of it, or I should say more to the point they're afraid of warranty work. It works off the same basic principles as a Chrysler Torqueflite, Chev Powerglide, and even a modern THM 200-4R or 700R4. And a trans guy who can repair an electronically controlled unit but tells me he can't do anything for a Slim Jim is suspect in my book.

All auto transmissions share some basic principals, but if you understand how a Roto Hydro works you will soon discover that the Roto has more in common with the transmission in Olds case and to a lesser degree in Pontiac's case which was one of the best auto transmissions ever made called by Cadillac, P315 and Olds by Jetaway and Pontiac as Strato Flight and later Super Hydramatic. It's common name is Controlled coupling Hydramatic. Without becoming to technical here I will tell you that the roto was made to be a simpler cheaper transmission to produce. The main fluid coupling, the front planetary gearset and the sprag clutch and one oil pump were eliminated. The Roto's only coupling which was the second coupling in the jetaway becomes the only fluid coupling & now handles two duties. When full it becomes a clutch and when empty becomes a complete mechanical connection between engine and driveshaft ( when that trans shifts into second there is a large rpm drop when that coupling empties and goes direct mechanical connection) The jetaway did the same thing only 1st & third the secondary coupling were empty. Many say the Roto had a Torque converter. This is not true because All torque converters have curved vanes in their driving and driven elements and all fluid couplings vanes are straight. The Roto has straight vanes with a third element called a stator ( a fixed stator )( Olds called this a accel-a rotor). This element multiplies torque so as to try to try to make up the difference with the loss of Jetaway's 3.97 first gear. The only problem is the stator blades are fixed and so gets in the way of the oil flow at high speed and matching driver-driven elements in the coupling.

The Rotos downfall was it was less efficient, shifts were slower, gear ratios further apart, poor shift quality, less flexible in passing distances. a potential oil leaker due to high(very high) coupling pressures and coordination of precise linkage adjustment.

That is why Pontiac would not use it in the Bonneville-Starchief series and Cadillac would not touch it either.

But this transmission was based on the dual coupling hydro in hydraulic flow and mechanical application. So from the technical aspect the Controlled Coupling 4 speed Hydra-Matic ( P315, Jetaway, Strato flight-Super Hydra-Matic ) is akin to the Roto Hydra Matic because they both use a controlled fluid coupling.

Don

Edited August 23, 2010 by helfen (see edit history)

[Guest mortsciguy]

What is the proper name for the "Slim Jim" trans? My 57' Cadillac had a 4 speed Hydromatic, and everyone seemed to know what it was. I'm a little confused as to what this beast is by it's proper name. And what other models used it?

Kelly

[Guest]

What is the proper name for the "Slim Jim" trans? My 57' Cadillac had a 4 speed Hydromatic, and everyone seemed to know what it was. I'm a little confused as to what this beast is by it's proper name. And what other models used it?

Kelly

Kelly, did you read my (#4) reply??? Roto Hydra-Matic.

Olds used it from 61-64 in big (model 10) and little versions (F-85 used the little version-model 5 ). Pontiac used it 61-64 in Catalina, Ventura, & Grand Prix in only in the big version-model 10.

Model 5 Roto Hydra-Matic was also used in Opel Kapitan, Vauxhall Velox/Cresta and EK Holden

Don

Edited August 20, 2010 by helfen
more information (see edit history)

[Guest mortsciguy]

Just for future reference, Brian in the trans. dept. at Jasper Engines and Transmissions said they have a builder (and parts) who can remanufacture the Slim Jim, on a custom basis (they remanufacture your unit). He estimated around $1,800 on the high side, dyno tested with a 3 year/100,000 mile parts and labor warranty. No Fear Here.

Kelly

[rocketraider]

Ask the Jasper guys if they are prepared to warranty the unit using the original trans cooler in the radiator. They used to be funny about not warrantying a trans unless it was cooled with an auxiliary cooler and not run thru the radiator cooler AT ALL.

They need to understand that originality is a compelling factor on cars like this.

[Guest mortsciguy]

Glenn,

If I ever have need for a reman, I will certainly double check with them. I worked as a factory rep for them from 93 to 96. If an installer didn't have a trans cooler flusher, we would loan them one for an installation. At that time the only mandatory cooler replacement was on the E4OD trans for Ford applications...and we shipped a new one with each unit.

With most in-radiator cooler applications, the pulsated solvent flush was sufficient to get the coodies out. The original E4OD cooler was too small, as were the lines running to it, so new fittings and lines were supplied as well. Just to be safe, I will ask if their position on this has changed. Thanks for the shout back.

Kelly

[Rusty_OToole]

I knew an old time transmission rebuilder who always installed a new inline hydraulic filter on the return line where it went back into the tranny. He started doing this after a rash of failures in the sixties, caused by metal filings and junk in the cooler.

After he put on the extra filter he had no more trouble. This was in addition to the OEM filter inside the transmission.