How much horse-power will a slim jim handle?

[Oldsmobile]

I have the high compression 394 in my Starfire, and I wonder how much horsepower the slim jim transmission can handle? I have a cam for it, a dual quad carb intake, an HEI distributor, and am having the heads ported and polished. My estimation is that this will all land me somewhere in the vicinity of 420-430 horsepower when said and done. Is the slim jim up to the task?

[cobalt]

Im no tranny expert and am old and senile now..but I remember drag racing my dad's 63 with the 394 h/c 2bbl with cam and open exhaust dumps with 3.9 gears...the tranny crashed about every 50 runs so we dumped it for a 61 Cutlass stick shift....something about a cir-clip in the pump assembly (????) that always broke....should be some tranny experts out there than can help...several 389 catalinas with tripower run low 12's so someone knows how to make them slive.

[Guest imported_widomski]

Ask Tom Kasper, he has been doing slim jims forever. He rebuilt the one on my 61 98 bubble top

847-888-4200 or 847-622-9225

A-1 Automatic Transmissions (he used to own it now his son does)

670 N LaFox

South Elgin, Il 60177

[Starfire61]

Yeah, Tom's the guy. He rebuilt the Slim Jim in my '62 Starfire for the previous owner about ten years ago. When I bought the car, I couldn't believe a Slim Jim could shift so well. Like night and day compared to my '61 Ninety Eight. I recently brought him that '61 & he's finishing it up... hope to pick it up in time for Christmas! <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />

[rocketraider]

I just wish he weren't half the country away from here...

'Course if a Slim Jim didn't do the shudder clunk and lurch thing, I'd think something was wrong with it...

[Guest BJM]

Oh my gosh Glenn. Epiphany. I bought a 63 Pontiac Grand Prix about 10 years ago out of Texas. It was my daily driver for about 25,000 miles. The 1st thing I noticed was rev-release-rebound just like you describe. The transmission was supposedly rebuilt. I never took it in for adjustment because it was so old. I even used it to commute to trade school for automotive mechanical and I sold it before transmission class. (I figured it would be good to learn for the adjustment part)

I cringed every time it would wind up, then the bucking, especially in that 20 to 30mph range.

As you describe it, is just the way it was and I feel better knowing that's the way thye are. Certainly they were not that way new but must have turned into that not too long after ownership started.

[Starfire61]

I've been meaning to follow up with a post for awhile. The Slim Jim on my '61 Ninety Eight turned out very, very well. I couldn't be happier with the work that Tom Kasper did on that tranny- all the upgrades thru 1964. Sure, it still has that big 1-2 rev drop, but the shifting all around is remarkably smooth. If I didn't know better, I'd think I had a TH-400! I wish I had it done sooner.

Glen, Tom works on transmissions from all around the country. If you're tired of those Slim Jim headaches & really want to enjoy that car, give him a call- I'm sure he's dealt with a lot of freight companies & would have a good idea of how you could best get your trans to IL.

[junkyardjeff]

Could the 59 or 60 jetaway be subsituted for a slim jim,I almost bought a 63 88 but the trans was bad and I knew no one who would touch the slim jim. Jeff

[Oldsfan]

Yes, I believe mechanically a Jetaway, or Super HydraMatic, could be substituted. The problem on '61 to '64 cars seems to be the low tranmission tunnel. It looks like floor modifications would have to be made.

Paul