63 tranny slimjim?

[exmoparluver]

In addition to my other post.Is there an easy way to identify the tranny as being a slim jim?..It is a 3 speed.

[Swed Olds]

Another question about slim jim, how do you know if it is an 3 or 4 speed, some guy told me that theese trannys hade both.
Olds Dynamic88 1964

[rocketraider]

For all practical purposes they're a 3-speed. There's a very deep 1st gear but it's done in the Accel-a-Rotor section in the fluid coupling. The 1-2 shift is imperceptible and occurs before the car hits 5 miles per hour. It's the 2-3 that unnerves everybody. I heard it described once as "shudder-clunk-lurch".

Easiest way I know to ID one is to look at the pan. It covers both the case and the tailpiece.

[88 coupe]

Originally Posted by Swed Olds

........ some guy told me that these trannys had both ........

OK. First up, normally I don't do trannys. But, in this case, I'll make an exception.

From the beginning in 1939, Hydramatic, Dual range Hydramatic, Jetaway Hydramatic, and Roto Hydramatic were 4 speeds.

The confusion comes from the number of positions, shown on the quadrant/dash.

'39-'51 Hydramatic was N D Lo R (Lo = 1-2 and D = 1-4) = 4 speeds.

'52-'56 Dual Range Hydramatic was N D S L R (L = 1-2, S for Super performance =1-3, and D =1-4) = 4 speeds.

'56-'64 Jetaway and Roto Hydramatics, were P N D S L R (same as the Dual Range, except park was moved from R to P)

Bottom line? 4 speeds and 3 positions = confusion.

Norm

[88 coupe]

Originally Posted by rocketraider

........ I heard it described once as "shudder-clunk-lurch" ........

Good description of the 2-3 in a Hydro with the TV linkage out of adjustment.

Norm

[Olds64]

The Slim Jim Roto Hydramatic is split in two pieces you will see where the front and rear parts of the transmission case meet.

[Oldsfan]

Originally Posted by 88 coupe

'39-'51 Hydramatic was N D Lo R (Lo = 1-2 and D = 1-4) = 4 speeds.

'52-'56 Dual Range Hydramatic was N D S L R (L = 1-2, S for Super performance =1-3, and D =1-4) = 4 speeds.

OK, so, you put any HydraMatic built between 1939 and 1956 in low, and it'll shift from first to second.

What happens if you put a Roto-HydraMatic in low?

Paul

[Swed Olds]

OK, so if I understand you right, it has 4 speed but from 1st to 2nd you maybe not feel it?
My slim only make 2 shift if i dont make a kick down then it is a speed between, and you can be sure that you feel it! Like someone bump in your rear bumper!
//Fruck

[88 coupe]

Originally Posted by Swed Olds

........ 1st to 2nd you maybe not feel it? ........

Not maybe.

You should not feel (another cause of the confusion) the 1-2 shift.

Originally Posted by Swed Olds

........ My slim only make 2 shift ........

Those shifts are: 2-3 and 3-4. The goal was to make the 1-2 and 3-4 shift as smooth as possible, as one shift was acceptable to most "luxury car" buyers of the day.

Originally Posted by Swed Olds

........ if i don't make a kick down then it is a speed between ........

The WOT 3-2, at 30-35 miles per hour is a great boot in the azz.

The 4-3 shift was called "passing gear" in the day. Many people thought it was a separate gear.

Norm

[88 coupe]

Originally Posted by Oldsfan

........ What happens if you put a Roto-HydraMatic in low?

From my '63 Service Manual, page 3-26:





Norm

[Olds64]

There is a throttle valve adjustment for the Slim Jim that is CRITICAL! If it isn't set correctly the transmission won't shift properly. If you don't already have Oldsmobile service manuals for your car I suggest you buy them.

[Oldsfan]

Originally Posted by 88 coupe

From my '63 Service Manual, page 3-26:

I was hoping for a reply in your own words...

Notice what is printed in your service manual refers to 2nd STAGE, not 2nd GEAR, or 2nd SPEED.

A Roto-HydraMatic is a three speed, with a variable vane torque multiplier (Accel-A-Rotor) in the fluid coupling, much like a Switch-Pitch Turbo-HydraMatic three speed with variable vanes in the torque converter.

A Roto-HydraMatic shifts from 1st to 2nd, and from 2nd to 3rd. The first "shift" that is not felt is not a shift at all, it is a change of pitch in the multiplier vanes - not a gear change.

Paul

[88 coupe]

Originally Posted by Oldsfan

I was hoping for a reply in your own words ........

Understandable.

Originally Posted by Oldsfan

........ Notice what is printed in your service manual refers to 2nd STAGE ........

Here it is, again:



OK. I read it again. This time, I did "notice" that it has not changed since the first time I read it.

Do you think I posted it, without knowing its contents?

Originally Posted by Oldsfan

........ not 2nd GEAR ........

Was anyone discussing "gears"?

This is a technical discussion. I avoided using the word, specifically, to keep semantics out of it.

Originally Posted by Oldsfan

........ or 2nd SPEED ........

In the context of this discussion, and in the context of its use in the Manual, how are the words "stage" and "speed" not interchangeable?

Originally Posted by Oldsfan

........ much like a Switch-Pitch Turbo-HydraMatic three speed with variable vanes in the torque converter ........

Much like?

How is it the same, and how is it different?

What "ratio" defines each change in pitch?

Does the "torque multiplication" provided by my 2200 converter give me a lower "ratio" than its 1600 counterpart? 2.6:1 vs 2.5:1, for instance?

Originally Posted by Oldsfan

........ The first "shift" that is not felt is not a shift at all, it is a change of pitch in the multiplier vanes ........

Which, according to pages 3-8 and 3-10 (in the same Manual) results in a ratio change from 3.32:1 (first stage) to 2.933:1 (second stage).

How is a "ratio change" not a shift?

Originally Posted by Oldsfan

........ not a gear change ........

Was anyone discussing "gear changes"?

Do we need to discuss the remaining ratio changes (as shown on pages 3-12 and 3-14) from 2.933:1 (second stage) to 1.56:1 (third stage) and the one from 1.56:1 (third stage) to 1:1 (fourth stage)?

Norm

[Starfire61]

The Roto-Hydramatic debuted in 1961. 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."

In 1961, when the fluid coupling empties, this is called the 1-2 shift. In 1962 this is called the 2-3 shift. I have long been under the impression that the change in '62 was a marketing ploy by GM.

Between spares & units installed in cars I own seven 1961-2 Slim Jims. They look & perform exactly the same. Was the Slim-Jim redesigned so extensively between '61 & '62 that the torque multiplication of the rotor became a separate stage or speed? What changed, engineering or marketing? Please shine some light on my misinterpretations.

[Oldsfan]

Originally Posted by 88 coupe

Do you think I posted it, without knowing its contents?

Absolutely not! I am mortified that you would even suggest that I was inferring that you didn't know what you were talking about...

Originally Posted by 88 coupe

Was anyone discussing "gears"?

Why, yes. Yes they were. I believe Rocketraider made some mention of a "very deep 1st gear."

Originally Posted by 88 coupe

This is a technical discussion.

Oh. Well, now. If you're going go and get all technical on me...

Let's see what the technical engineers at Detroit Transmission had to say. I submit the following, excerpted from their "Roto Hydra-Matic Principles of Operation" manual, printed January 1962.

This is the very first paragraph in the manual:

slimjim.jpg

Originally Posted by 88 coupe

In the context of this discussion, and in the context of its use in the Manual, how are the words "stage" and "speed" not interchangeable?

Let's look at a 4-speed manual transmission. It has 4 "gears" (there's that word again...), or 4-speeds (duh...). You shift it three times. I guess you could call them stages if you wanted to. The RHM has 3 "gears", or three speeds (shifts twice - says it right there in the manual). But, it has 4 stages - first gear (or speed) has 2 stages - the first stage with the torgue multiplier effective, the second stage with the torque multiplier ineffective. Hence, I do not feel that "stage" and "speed" interchange. The manual says it right there: "three gear speeds plus a torque multiplying (that would be a stage, even though it doesn't say it) fluid coupling.

Originally Posted by 88 coupe

Much like?

How is it the same, and how is it different?

The same in that they are both three speed automatic transmissions, and that they use a torque multiplying fluid coupling or a torque converter.

Different? I couldn't begin to tell you all the ways that they are different. For starters, the THM has the converter outside of the transmission, in front of the pump. The RHM has the fluid coupling inside the case, behind the pump.

Originally Posted by 88 coupe

What "ratio" defines each change in pitch?

I'm sorry, you lost me. Could you rephrase the question?

Originally Posted by 88 coupe

Does the "torque multiplication" provided by my 2200 converter give me a lower "ratio" than its 1600 counterpart? 2.6:1 vs 2.5:1, for instance?

What? My head hurts...

Originally Posted by 88 coupe

How is a "ratio change" not a shift?

I don't know. I guess we'll have to let the Switch-Pitch THM-400 guys answer that one. I wonder how many of them think they have a 4-speed transmission...

Originally Posted by 88 coupe

Was anyone discussing "gear changes"?

Yes. I was. I'm allowed. It's a free country.

Originally Posted by 88 coupe

Do we need to discuss the remaining ratio changes (as shown on pages 3-12 and 3-14) from 2.933:1 (second stage) to 1.56:1 (third stage) and the one from 1.56:1 (third stage) to 1:1 (fourth stage)?

No. I don't think these forums could take it.

Paul

[rocketraider]

Was the Slim-Jim redesigned so extensively between '61 & '62 that the torque multiplication of the rotor became a separate stage or speed? What changed, engineering or marketing? Please shine some light on my misinterpretations.

Chuck- there are NINE different valve body revisions for 1961-64 Rotos, five in 1961-2 alone. They were constantly fiddling with them trying to make them shift better. That wildass 2-3 shift didn't set well with owners used to earlier transmissions. 2.9>1.5 is a pretty big drop- nearly akin to a 700R4, which often reminds me of a Slim Jim in some of the things it does.

Why the hell they didn't just go back to the Jetaway like Pontiac long wheelbase cars and Cadillac, I'll never know.

[88 coupe]

Originally Posted by Starfire61

........ From the 1961 service manual: ........

What page?

Originally Posted by Starfire61

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

1st = 3.6394:1
2nd = 1.577:1
3rd = 1:1

So far, so good

Originally Posted by Starfire61

........ "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." ........

There was an optional valve body modification on '49-'50 Eighty Eights that disabled first gear, so “Granny” could have a smoother ride. The above description fits it very well.

Only three gears were used, but it was still the same four speed.

Originally Posted by Starfire61

........ In 1961, when the fluid coupling empties, this is called the 1-2 shift ........

1st = 3.6394:1
2nd = 1.577:1
3rd = 1:1

Originally Posted by Starfire61

........ In 1962 this is called the 2-3 shift ........

1st = 3.51:12
2nd = 2.933:1
3rd = 1.56:1
4th = 1:1

Originally Posted by Starfire61

........ What changed, engineering or marketing? ........

Not much chance marketing would be directly involved with trans redesign/modifications.

Originally Posted by rocketraider

Chuck- there are NINE different valve body revisions for
1961-64 Rotos ........

That explains a lot.

Norm

[Olds64]

NINE different valve body revisions for 1961-64 Rotos

I wonder if a shift kit was ever available for the Slim Jim?

[rocketraider]

B&M made some stuff for them, but the transmission wasn't really rugged enough for serious dragstrip duty like the Hydro was. Plus it had that rotten gear ratio spacing which caused a lot of RPM loss right when you needed consistency.

Interesting to note that Hurst's original Dual/Gate shifter was designed expressly for the SlimJim and marketed to Starfire and Grand Prix/Catalina owners in 1963. The MoPar version was released later that year.

[Olds64]

That is interesting to know. I thought there might have been aftermarket parts made for the Slim Jim back in the day. I agree, the Slim Jim isn't a very strong transmission.