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.

 

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

 

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 mph. 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.

 

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

 

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

Norm

 

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

 

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

 

Not maybe.

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

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

 

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





Norm

 

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.

 

Understandable.

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?

Was anyone discussing "gears"?

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

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?

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?

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?

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

 

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.

 

What page?

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

So far, so good

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.

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

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

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

That explains a lot.

Norm

 

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

 

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.

 

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.

 

Looking at all the posts I wonder if anyone really knows how this tranny works. My experience with this tranny is it has a wild shift between 1st and 2nd. The shift to 3rd could not be smoother. Now this argument about first stage and first gear I can't figure out. There is no rpm change according to my tach. I drove another guys car to get a feel on how his worked and found that his was the same. Mine is a 61 and his was a 64. I am by no way an expert on this so I gave up on trying to get to run smoother from first to second because thats how they work.

Pat
1961 Olds Dynamic 88 2 dr sedan
1963 Buick Wildcat 2dr ht (ST400)

 

I have a basic (very basic) idea, but before I can continue, I'll need an answer to the following:

From what I can see, my '61 manual says essentially the same, but the wording is different.

I'm with you.

Switch pitch TH400? 4 speed manual trans? If I didn't know better, I would think someone was trying to start another pizzing contest.

Norm

 

Sorry to interupt. Are these the Hydramatics I read about in Hot Rod a while back that don't have torque converters?

 

No "real" HydraMatic has a torque converter. Strictly fluid couplings, sometimes TWO, and a lot of them had front and rear pumps. They were actually a very good and rugged automatic transmission. Put it this way- GM sold them to Lincoln and Rolls Royce, and if it was good enough for a Rolls... you get the idea.

TurboHydraMatic is a descendant of Buick Triple Turbine Dynaflow, and Dynaflow was always a torque converter transmission.

The biggest reason Olds and Pontiac abandoned HydraMatic was the 1965 Federal motor pool standards that required a standardized automatic transmission shift sequence- P R N D __ - for any carmaker wanting to submit bids to supply government vehicles. Chrysler Corporation dumped their pushbuttons for the same reason.

And after seven years of fiddling with Twin and Triple Turbine Dynaflows, Buick had finally refined them enough by 1964 that GM Corporate deemed them ready for use across the entire model lineup as Turbo Hydramatic 400. Buick had almost as much trouble with those Dynaflows as Olds did with Slim Jims. They sold Chevrolet a version of it as TurboGlide, and after four years and countless warranty changeovers to PowerGlide, Chevy abandoned it. Buick didn't have a backup transmission, so they had to fix their mess.

 

Wow! You learn something new everyday.

I read that GM sold the TH 400 to foreign companys as well.