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Slim transmissions (pre-turbo hydromatic)


Parm
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In looking for a big convertible from the 1960's, I've had several people tell me to stay away from those with the hydromatic transmissions - commonly known as the slim-jim. They tell me these are nothing but trouble. Can anyone confirm or deny this? If I take their advice, that means I should dismiss every Oldsmobile (a 98 convertible would be my car of choice) made before 1965.

Everyone seems to agree that the turbo hydromatic was a technological marvel and a much better choice compared to the earlier slim-jim variety.

Would appreciate hearing opinions as to whether the slim-jim transmission is a hand grenade in waiting. I know of a neat 1962 Olds 98 convertible for sale, but am apprehensive to pursue it because it has the slim-jim transmission.

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I think they are refering to the Jetaway trans. It all depends on what your going to use it for. It seems like everyone thinks you want a car that turns the low 10s. If you want to drive the car the way it was intended to, any transmission or motor is fine. If you want to get on it more often than not, the 350 or 400 is the way to go. There are allot of fine engine builders out there who can work wonders with a motor. There are allot of fine car builders out there that can make a car look new. I envey them both. They don't allways see eye to eye. A 62 98 convert is not a car you would take to the track. If you want originality and a week end driver, put some $ in what you have. If your like me and like to kick it in the ass more often than not. Plus like to put miles on it go with the 400. You can't go wrong with a 400, and they are easy to come by. If I'm going to spend all that time and money in a car, I am going to drive it. Like a friend of mine said "If you see it on a trailer, it's broke". It sounds like a great car. Have fun.

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Parm, the SlimJim was used 1961-64 and can be troublesome, but if one is set up right it usually works fine. I've got two- one works great, the other does all kinds of hateful stuff but that car has other issues too- as in it won't run.

The big trouble is finding someone who understands them to service them. Modern tranny shops are afraid of them because of their reputation for being difficult to repair and adjust, and they don't want to deal with the warranty work because they didn't know what they were doing.

The TV (throttle valve) rod adjustment is critical to this transmission's operation and is usually the cause of the heartburn. If it's off, the thing is just not going to work right. That said, the TV rod is no harder to adjust than a modern 700R4 or 200-4R TV cable, though it helps to own the special tools for adjusting it.

The fact that many early 60s gassers ran 394 Olds engines mated to B&M Hydro automatics ought to say somethng about what a properly set up one can handle.

Drive the car and see how the SJ functions. Most have a hard RPM drop between 1st and 2nd speeds, but that is a characteristic of these things.

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Rocket Raider, just a note on the B&M hydro comment: those trannies were the dual-range hydramatic, not the Controlled Coupling Hydramatic or the Roto-Hydramatic.

The latter two transmissions are not well suited for hotrod use, but are fine for cruising in a stock restored car. If desired, a TH400 conversion for the pre-65 cars can be had from Tanson's, Dave Smith, and one other source that is in MI (I think).

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Blownolds, have you seen one of those conversion transmissions? and can tell us what is involved in mating it to the Rocket block? I've heard they cut down the case in the torque converter area. If I do anything with the blue Starfire, it's gonna need something like this. I've always said if I could get rid of the 4GC and the SlimJim, I could enjoy that car.

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Here's a picture of a TH350 conversion by Bendtsen's:

0307cr_trans05z.jpg

But I think they discontinued their Olds conversions stating that a competitor had a better solution. You might still be able to see some more pictures on their website at transmissionadapters.com

Here's a Tanson's conversion:

0307cr_trans13z.jpg

Here is a photo of a TH400 conversion that was on a 394 on eBay a while back, but I don't know who did it:

fa9ffc76.jpg

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  • 17 years later...
  • 4 weeks later...
On 11/1/2003 at 7:47 PM, Parm said:

In looking for a big convertible from the 1960's, I've had several people tell me to stay away from those with the hydromatic transmissions - commonly known as the slim-jim. They tell me these are nothing but trouble. Can anyone confirm or deny this? If I take their advice, that means I should dismiss every Oldsmobile (a 98 convertible would be my car of choice) made before 1965.

Everyone seems to agree that the turbo hydromatic was a technological marvel and a much better choice compared to the earlier slim-jim variety.

Would appreciate hearing opinions as to whether the slim-jim transmission is a hand grenade in waiting. I know of a neat 1962 Olds 98 convertible for sale, but am apprehensive to pursue it because it has the slim-jim transmission.

a Olds 98 convertible from 1956 to 1964 should have the better Jetaway Hydra-Matic 4 speed transmission, not the awful slim jim roto hydra-matic 3 speed.

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