[jscheublein]

I just finished my 1964 2+2 convertible. I had the original transmission rebuilt. Problem is in drive it shift from 1 to 4 gear and skips the 2 and 3. I can manually go through all 4 gears. Any ideas as to what is wrong. All else is good. It does have tripower and AC but that should not effect the trans. Thanks for the help - Jim 209-601-4408.

[padgett]

Eeeer a Slim Jim (Roto Hydramatic) only has three gears and first to second feels like there should be another gear in the middle. Only the long wheelbase cars got the 4 speed in '64. I am not sure what you have.

[pfilean]

What Padgett says is true. And I hope the old Slim Jim 3 sp or 4 sp argument does not started again. The factory manuals can give the impression both are true depending on what year manuals you have. Probably the best description is that old Jim is a 4 range 3 speed.

But so many Slim Jims have been replaced with something different you have to get under and take a look to determine what you have. The 64 4 sp Hydro can be made to fit in the Catalins body and it had 4 speeds. If I look in a 61 Hydromatic manual as a reference the symptoms you describe don't appear for either the Slim Jim nor the 4sp. I never seem to have good luck on that point and the strange symptom I have with my Slim Jim of course is never mentioned in the manual. If you could sense 4 speeds (three shifts) before it was rebuild maybe someone put in a 200 or 700 OD transmission. Have to get under and look at the oil pan and linkage/vacuum lines to tell.

And if you found someone who would actually still work on a Slim JIm you were lucky. If that is what you have. But in any case you will probably have to go back to the rebuilder and see how nice and knowledgeable he is.

[buds56]

I would check the lnkage from the carb to the transmission, I believe when the pedal is floored the rod on the trans should have no play in it. Good luck

[U47]

OK this is a three speed - 4 range HydraMatic, and when you read the H/M service manual it speaks to you in these terms, and most of the time it's speaking to you as a 4 gear trans. With Super HydraMatic L is 1st & 2nd, With Roto L is 3.50 and 2.93 or 1-2 range and it's all done in the coupling.

So what it says in diagnostic's for Roto is: Drive in First, Second, and Fourth ( skips drive RT or S ) 1. Control valve assy. 2. Coupling

FYI 1952 HydraMatic became Dual Range and Super HydraMatic continued with that along with Roto, and the later call it Drive Left and Drive Rt. by 1964 the column shift cars adopt what Oldsmobile had been doing all along and trade drive right for "S". I believe the console models in 62 use the "S"

[Stuart]

I remember having a conversation with SteveP some years ago about this; the Slim Jim Roto-Hydramatic is described in my 1961 shop manual as a three speed, but by 1964 there some internal changes made and the manual that year did describe it as having four speeds.

In any case, calling it a three speed or four speed is not really the issue here, it's the fact that it's skipping gears in the middle. SteveP is the resident expert on them, he should see this discussion sooner or later and be able to respond with some advice. One thing I do know is they're very sensitive to the adjustment of the TV rod that goes from the carburetor linkage to the transmission; it's possible that needs to be checked and readjusted.

[U47]

Originally Posted by Stuart

I remember having a conversation with SteveP some years ago about this; the Slim Jim Roto-Hydramatic is described in my 1961 shop manual as a three speed, but by 1964 there some internal changes made and the manual that year did describe it as having four speeds.

In any case, calling it a three speed or four speed is not really the issue here, it's the fact that it's skipping gears in the middle. SteveP is the resident expert on them, he should see this discussion sooner or later and be able to respond with some advice. One thing I do know is they're very sensitive to the adjustment of the TV rod that goes from the carburetor linkage to the transmission; it's possible that needs to be checked and readjusted.

My 62 and 63 H/M manual call it a three speed/ four range HydraMatic. But you are right this is not the issue and as said before the H/M manual says look here first;

So what it says in diagnostic's for Roto is: Drive in First, Second, and Fourth ( skips drive RT or S ) 1. Control valve assy. 2. Coupling

[stevep]

Originally Posted by Stuart

I remember having a conversation with SteveP some years ago about this; the Slim Jim Roto-Hydramatic is described in my 1961 shop manual as a three speed, but by 1964 there some internal changes made and the manual that year did describe it as having four speeds.

In any case, calling it a three speed or four speed is not really the issue here, it's the fact that it's skipping gears in the middle. SteveP is the resident expert on them, he should see this discussion sooner or later and be able to respond with some advice. One thing I do know is they're very sensitive to the adjustment of the TV rod that goes from the carburetor linkage to the transmission; it's possible that needs to be checked and readjusted.

U47 knows FAR more than I do about Roto Hydramatics.

[padgett]

and what I remember from driving a 64 GP A Lot is that when it shifts from first to second it FEELS LIKE it skipped a gear. Goes from 5k rpm to 3k suddenly.

If I had a roto I'd seal it in a big baggie and install a 700R4.

[AZ64GP]

I own a '64 GP with the "slim jim" transmission. It was toast when I bought the car and I'm going to replace it with a BOP TH400 transmission. I considered rebuilding it, but I have read that one small part fails in that aluminum trans, and the trans is trash.

I've also considered installing a 200-R4 for 700R4, but those both weak transmissions (stock) and the 700 will need an adapter plate to work behind the Pontiac V8. I don't have the $$$$ to spend $2500 building 700R4 or 200-R4 to survive behind my 389.

Hopefully, you can get your slim jim operating properly, but if you do decide to change, you have options. Good luck!

[Gary C]

I have a '63 Safari w/ 4 spd Super Hydro I had rebuilt, & I needed an engine so I ended up with a slimjim "flex plate" for a '64, if anyone wants it...........

[U47]

Originally Posted by Gary C

I have a '63 Safari w/ 4 spd Super Hydro I had rebuilt, & I needed an engine so I ended up with a slimjim "flex plate" for a '64, if anyone wants it...........

Roto is the only auto I know that has a flywheel instead of a flex plate.

[Gary C]

Ok then, Thank You, I’m just learning this stuff
Now I know who I can offer this to, only a Roto Hydromatic man! G

[Bill Hanlon]

Originally Posted by U47

Roto is the only auto I know that has a flywheel instead of a flex plate.

Original Hydra-Matics (which Pontiac used into 1956) not only had a flywheel, but it doubled as the front of the torus cover.

This picture is from a GMC Master Parts book. GMCs of that era used Pontiac V8s and continued to use the Dual-Range HydraMatic into the early 60s.

Note the 30 bolt holes around the outer diameter of the flywheel and torus cover to hold the parts together.

[U47]

Originally Posted by Bill Hanlon

Original Hydra-Matics (which Pontiac used into 1956) not only had a flywheel, but it doubled as the front of the torus cover.

This picture is from a GMC Master Parts book. GMCs of that era used Pontiac V8s and continued to use the Dual-Range HydraMatic into the early 60s.

Note the 30 bolt holes around the outer diameter of the flywheel and torus cover to hold the parts together.

Yeah, they called it a flywheel , but it's nothing like Roto's thick and heavy one.

[Gary C]

Thanks man, attached (if I did it correctly) are photos of my trans before rebuild showing the 12 bolts, the new flex plate I found in Norwalk showing 6 bolts & 6 spaces, & the slim jim I cannot use

[pfilean]

Just to continue the discussion - or start an argument. The 1961 Hydra-matic manual shows for the Roto a flywheel and for the 315 HM BOTH a flywheel and a flex plate. Although, as pointed out, it looks like the flywheel is also the front torus cover.. And I know the caption for the Roto says 3 speed but lets not start that argument again.

[U47]

In the original Type HydraMatic and 315 the flywheel flexplate / driven torus, drive torus and torus cover are bolted together as one unit. In addition to passing fluid energy from one torus to another they dampen engine vibration. When you pull the trans they are the first things to be seen.

In Roto HydraMatic the driven Torus and drive torus and multiplier are inside the transmission behind the oil pump. The Roto equipped cars have a real flywheel bolted to the crankshaft with a splined spring damper. When you pull a Roto and look into the bellhousing there is no fluid coupling and what you are looking at is the input shaft coming out of the front part of the oil pump and when you look the other way at the engine you will see the FLYWHEEL bolted to the crankshaft. Unlike a flexplate, this flywheel is a heavy unit, not as heavy as a stick shift Pontiac flywheel, but as heavy as a lightened racing flywheel.
The caption for Roto is; A three speed, four range HydraMatic.