[mrrat1]

Originally Posted by alleyCat

Scarebird is hitting on the downside. My 61 Safari was converted to a T400 . It has a 2:87 factory rear gear ratio. Probably excellent with an original hydro but with the 400 its hard for it to get out of its own way from a stoplight. I am going to have to address this with a 3 series gear set sooner or later.

My old man had a 66 cat 389 2bbl auto trans with 2.41 gears.......he beat many late 70's performance cars off the line. He always had it in top running condition though!

[hurryinhoosier62]

Originally Posted by b-man

Turbo 400 plus 2.75 low gear set, win-win.

X 2, Bart.

[AZ64GP]

Originally Posted by hurryinhoosier62

X 2, Bart.

I was just reading about the 2.75 low gear set. I had never heard of such a thing! That seems like a pretty neat idea...you get better off-the-line performance like I would with a higher (numerically) rear end gear, but without increasing the RPM on the highway at speed. They sure cost a pretty penny! Cheaper than a rear end gear swap or going to an OD transmission, but $750 is quite a bit when the trans rebuild may only cost $1,200.

[Tim Younker]

I did the Slim Jim swap to 400 Turbo over 10 years ago on my 62 Catalina. DO IT MAN, JUST DO IT! You'll be glad you did. The only thing I would have done differently on my project was to also swap my original 389 for a later year or 400 or 455. The adaptor kit is expensive. I just didn't want to take out the original motor since it only had 71,000 miles. Hindsight is 20/20. I also put in 3:08 gears. I had a hard time locating 3:23 gears for the right price. 3:08s work just fine with the 400T. Good Luck!

[hurryinhoosier62]

Originally Posted by AZ64GP

I was just reading about the 2.75 low gear set. I had never heard of such a thing! That seems like a pretty neat idea...you get better off-the-line performance like I would with a higher (numerically) rear end gear, but without increasing the RPM on the highway at speed. They sure cost a pretty penny! Cheaper than a rear end gear swap or going to an OD transmission, but $750 is quite a bit when the trans rebuild may only cost $1,200.

You run a 2.75 low gear set (they make sets that are even lower!) with a 3.08 rear gear. In low gear, the actual ratio is 5.83:1, yet at highway speed it's still 3.08. You get the best of both world....One of the guys that used to post here had a '64 Bonnie with the 4 speed Hydramatic (3.27 low gear) with a 2.92 rear gear....

[tom s]

a 64 block should not need the adapter.Tom

[Poncho60]

Your 2.75 first w a 3.08 rear gives you 8.47 effective off the line. The hydro in the 64 Bonneville has trans low gear of 3.97. W a 3.08 rear you get an effective 12.23 off the line. My 60 has that same setup.

[hurryinhoosier62]

Originally Posted by Poncho60

Your 2.75 first w a 3.08 rear gives you 8.47 effective off the line. The hydro in the 64 Bonneville has trans low gear of 3.97. W a 3.08 rear you get an effective 12.23 off the line. My 60 has that same setup.

8.47? what figure did I leave out of the calculation? As for the Hydramatic, I remembered it as 3.27 low gear, but it's been ten years since the guy has posted here: I accept your info as correct.

[pfilean]

Multiply. Don't add.

[codyyy]

I'm going through the exact same thing. I have the 4-speed automatic version with 2.87 rear gear I believe. I've been trying to research as much as I can for the pros and cons of each transmission. I originally wanted a TH-350 however the first gear is not so good and getting the planetary conversion to get it closer to usable for this car is about $500-600 by itself. A 4L60-E would be awesome however the controller to run it is about $600 and as with any overdrive, the 2.87 rear gear I assume would render OD useless on the highway. I am leaning towards using a 700-R4 and just regearing the rear end.

[Goatracer1]

Two points. I have a T350 in my 1964 GP with a 421 4bbl. Its been in there for over 10 years with no problems. I changed the rear gear from 3.23's to a 2.69 and have not had a problem with lack of pick up. Second if the Turbo 200-4R is built correctly you will have no problem with that either. How do I know? I have been running one in my 1967 supercharged 428 GTO for the last 16 years. It was built by Bow Tie Overdrives.

[MUSLCAH]

Iam in the same boat with my 64 Grand Prix....got that gawd awful slim Jim.....but does work...if you call it that. Trying to gather up all the parts for a 4 speed conversion....without the holy grail console...LoL

[hurryinhoosier62]

Originally Posted by pfilean

Multiply. Don't add.

Thank you.

[codyyy]

BTW- a great site for finding out information on transmissions is here:
http://novak-adapt.com/

I know it mainly pertains to Jeep conversions but they do have a good bit of information regarding engines and transmissions.

[U47]

Originally Posted by stevep

I just rebuilt a Slim Jim for a 64 Olds and the guy is going to spend well over 3 grand installed. Do yourself and you car a favor and put a 400 in it.
We rebuild a lot of classic transmissions, but in my opinion converting to a 400 is a selling point.

Not many shops have the required tools to rebuild a Roto. When you say you rebuilt a Roto for a 64 Olds does that mean you replaced the EIGHT thrust bearings and thrust washers, Check all specifications on all the FORTY springs, check, replace the sprag and roller clutches, Plus the usual neutral clutch plates, front clutch plates. gaskets/"O" rings?

BTW , Just look at the planetary gears in D type HydraMatic, Super HydraMatic, Roto HydraMatic compared to 2004R or 700R4 side by side & only then you will know the latter transmissions are not designed for the HP and weight of a 4,000+ lb. car.

Why does Roto feel like there is a big ratio between 2nd range and 3rd range? It feels this way because in 3rd range the coupling is empty and the trans is in full mechanical connection so... there is no fluid cushion from 2nd and 3rd ranges. If you are careful you can adjust this inconvenience out. Why is there a lazy 3rd to 4th range shift? The fluid coupling drains 3rd range and fills 4th range in 4 tenths of a second. There are ways to speed this up by playing with the valves, playing with the pressure regulator valve and a few other tricks.

BTW, look at the A/SA 1963 Nationals at Indy winner. A 63 426 wedge Plymouth wagon with a 727 Torqueflight against a 62 Catalina. You will notice both cars come out of the whole about even, but when the Catalina gets into 3rd range ( 2nd gear) and is in full mechanical connection it jumps and pulls away from the Plymouth and so on for the win.
https://www.youtube.com/watch?v=9jQsd1fZV8k

FYI, HydraMatic, Dual Coupling HydraMatic(, Cadillac calls 315 HydraMatic , Pontiac calls Super HydraMatic, Olds calls Jetaway) and Roto HydraMatic all these transmissions have split torque and in Roto HydraMatic's case it means when the trans is in 4th range ( 3rd Gear) only the coupling only handles 40% of the engine torque and the rest 60% is in mechanical connection. This means all three hydros in high gear are more efficient than T400 or any trans without a lock up torque converter.

[alleyCat]

Originally Posted by Poncho60

So based on your 61 Safari the huge majority of full size Pontiacs were dogs off the line (w turbo 400s)...??? Interesting.

Forgot to mention my wagon has a 350 Pontiac in it....not exactly brisk with a T400 and a 2:87

[Jeffs64Cat]

My 64 Cat has a beautiful shifting slim Jim it her. But because I was planning on mildly building the 389 I decided to do the 4 speed conversion. I've found a non cracked bell housing and original flywheel. Went through Fabcraft for everything needed and picked up a 64 Gto Muncie 4 speed. With all these parts I'm at just under 4 grand spent. And still needing more to complete the conversion. So I Guess what I'm saying is it depends what you want to spend your money on too do it right.

[63 Pontiac]

Back around 2001 I had the slim-jim in the 2 dr sedan rebuilt by a 78 yr old transmission guy who worked on those cars back in the 60's. That car was my daily driver for several yrs and I had no problems out of the rebuild. Sold the car in 2008 and it was then changed over to a Muncie.

Now have a th400 behind the 389 in my '63 with a 2.87 rear end. I haven't done any highway cruising yet but I don't regret having a th400.

[MUSLCAH]

Originally Posted by Jeffs64Cat

My 64 Cat has a beautiful shifting slim Jim it her. But because I was planning on mildly building the 389 I decided to do the 4 speed conversion. I've found a non cracked bell housing and original flywheel. Went through Fabcraft for everything needed and picked up a 64 Gto Muncie 4 speed. With all these parts I'm at just under 4 grand spent. And still needing more to complete the conversion. So I Guess what I'm saying is it depends what you want to spend your money on too do it right.

Bet that don't even include a console.....Yup...how bad do you want it....that's why I haven't pulled the trigger on a 4Speed yet....Yous ain't getting that money back....cuz these cars ain't worth crap.

[Stuart]

Originally Posted by U47

Not many shops have the required tools to rebuild a Roto. When you say you rebuilt a Roto for a 64 Olds does that mean you replaced the EIGHT thrust bearings and thrust washers, Check all specifications on all the FORTY springs, check, replace the sprag and roller clutches, Plus the usual neutral clutch plates, front clutch plates. gaskets/"O" rings?

I'd guess that out of anyone who has responded to this thread, Steve is the one person who would really know how to rebuild one of these things.