[Starfire61]

Taken verbatim from the 1961 Service Manual:

"Two planetary units are used to obtain neutral, three forward speeds, and reverse."

"A fluid coupling is used to provide additional torque multiplication for first and reverse gears and to lock members of the two planetary gear sets together to provide third speed (direct drive). A multiple disc clutch is used to lock the drive torus and front unit internal gear together to provide reduction in the front unit for second speed. This clutch is also used with the fluid coupling to lock the front and rear units together to provide third speed (direct drive)."

"A sprag clutch is used to lock one member of the front or rear unit to the case to provide reduction for first and second speeds."

It's quite clear in the '61 manual that this is a 3-speed transmission. From '62 on, things get fuzzy, which coincides with the advertising people calling it the 4-S Hydramatic. Indeed, if you look at a '62 service manual, they recycle most of the same diagrams that were used in '61- it's obviously the same trans, yet they start referring to four forward speeds.

If you read between the lines in a '62 or '63 manual, it's apparent that Olds viewed the torque multiplication in the "Accel-A-Rotor" (limited torque convertor) as two distinct forward gears, while they made no such claim in '61. This makes things very confusing when discussing the functions of this trans with people familiar with different sets of semantics. In '61, when the fluid coupling empties & the mechanical clutch locks the drive torus to the front unit internal gear, this is considered the 1-2 upshift. The very same function from '62-'64 is called the 2-3 upshift.

If you look at the manuals from year to year, the ratios change very slightly. I don't know if this is due to them calculating different degrees of torque multiplication or if they used different gearsets in different model years (or both).

I've had several needlessly heated discussions over the years about just how many speeds were built into this 46-year-old obsolete transmission. Once I had to hand a guy the service manual & say "show me where it says there are four speeds." He stood there reading it for a good 10-15 minutes before he gave up- his buddies laughing at him the whole time. I'll be honest & admit that I don't know a whole lot about the workings of automatic transmissions. Nonetheless, I've talked shop with a lot of folks smarter than me about these things & the general consensus is that the Slim Jim just has some weird & unique features that put in in a class all by itself as far as auto trannys go.

I have three 61's & two 62's- all with Slim-Jims. There is no difference in the performance of the trannys in the two different model years. All of them have two distinct shift points, with the first shift being most pronounced. This is the point at which the fluid coupling empties & the mechanical clutch grabs hold. In some cars this can be quite rough depending on the condition of the clutch itself & the damping plate between the trans & the engine. Furthermore, the significant ratio change causes the RPM drop so characteristic of a Slim Jim.

So, I guess it has as many speeds as whichever manual you want to believe!

Hope this helps....