Roto Hydramatic "Slim Jim" transmissions

[electra225]

I watch this guy's videos and find them well-done and interesting. I'm not sure I agree with him on this one, though. The video is about the worst transmissions GM built. While grateful that Dynaflow didn't make his list, I'm not so sure that the Slim Jim was all that horrible. It wasn't very smooth, but no non-Turbo Hydramatic was. The Slim Jim handled the power from the awesome Olds Starfire 394 V-8. I know the old "Hydro" guys didn't like it and the Turbo Hydramatic 400 was a definite improvement, maybe one of the best automatics ever built. You Oldsmobile guys might be able to shed more light on this. It is also mentioned in this video that some of the Pontiacs used the Slim Jim and some used the old Dual Range Hydramatic. Did some of the Oldsmobiles use the Dual Range? I thought Cadillac used the Dual Range Hydro until the '64's when they stole the TH 400 from Buick. In their defense the 429 and TH 400 was an AWESOME power train.

https://www.youtube.com/watch?v=IUq8PDoopzs

[TC Chris]

OK, I'll confess to being an oddball, but as a kid, I just loved the sound the RotoHydramatic made. It wound out a bit in first then dropped into 2nd at a much higher ratio and burbled along. When I was driving the '65 Starfire I'd manually shift the THM to make it sound like the older transmission. My buddy's grandfather had this magnificent '61 Starfire convertible, a grand automobile, and it just sounded great. My Dad's Chevy with its two-speed Powerglide just was in another category. Of course, the Powerglide kept going forever.... same with the '65 THM.

I was surprised that the video didn't start off with the Chevy Turboglide, a transmission with a lifespan measured in gas tank fill-ups. Most people have never heard of it because it disappeared pretty quickly.

Chris Campbell

[walyfd]

Cadillac used the dual-range from '56 through '65 on the 75 series only. The '64 entry-level 62 series still used it and the rest of the line got the TH400. The different shift pattern had to have been tough moving same year cars with different trannies around the dealership. Took me awhile to remember R is full down...

The '56 was the worst. '57 slightly better but I never got rid of the 2-3 lag. Sprags would break, plates would burn... ugh... by '58, they worked out most of the bugs and they were pretty bulletproof.

[electra225]

Buick had the Flight Pitch Dynaflow, the equivalent to the Chevy Turboglide. Remember both Dynaflow and it's little cousin Powerglide were torque converter-type transmissions. HydraMatic used a fluid coupling, which is why they shifted so roughly. Neither Flight Pitch nor Turboglide were bad transmissions, necessarily. They were used wrong. People tended to use the Grade Retard position as a low gear. That's not what you were supposed to do. Why they needed a grade retard position is anybody's guess. My Uncle Vic raced Oldsmobiles thru the early 1960's and he always used a "Hydro". He raced the Slim Jim and was not easy on it. He could wring more power out of a 303 or 324 than anybody around.

[TC Chris]

Neither Flight Pitch nor Turboglide were bad transmissions, necessarily.

Turboglide seems to have lacked durability. It just didn't survive normal use. They disappeared in a hurry. They were notorious for crapping out. Powerglide? Just two speeds, low gear was too high and high gear was too low, but "deleted", they last forever.

Chris Campbell

[electra225]

Both Turboglide and Flight Pitch Dynaflow were solutions for problems that didn't exist. Dynaflow and Powerglide were both fairly utilitarian as far as performance was concerned, but, as you pointed out, they ran forever. Dynaflow leaked forever, but that was part of their personality. When a Dynaflow quit leaking, it was time to check the fluid.

[Ken Doyle]

The "Slim Jim" Roto-Hydramatic is OK if you don't rub it the wrong way when it's shifting to 2nd, and you know an older rebuilder that knows how to rebuild it properly.

The Dynaflow was very inefficient, but at least it was durable.

[Firedome]

OK as "the" Olds guy here, if I may say so... I founded OCA's Blue & Gray Chapter ion 1984 and have owned 15 Olds between 1936 and 1977... the Slim Jin RHM has a bad reputation with Olds folks. When right it was OK, and it did make those good sounds as it wound up higher than other GM auto trans, but it was fragile when beat on hard. Although '61 is a favorite year of mine I've never owned one and I'm not familiar with the specific failure modes, and is one of the reasons I haven't owed a '61 or '62, but to the best of my knowledge even a TOL 98 with the great 394 was stuck with that semi-crummy trans, not available with Dual-Path THM, fortunately only for a fairly short time.

[electra225]

What years, then would Olds have had the Slim Jim? Did it start in '56? Even Unk's '63 98 Holiday had the Slim JIm? That thing ran like a scalded dog.....

I found this article on Dynaflow. It is pretty good, with only a couple mistakes. Dynaflow was still called Dynaflow up until the end. In 1961, it was marketed as Turbine Drive in preparation for the introduction of Buick's new automatic, the Super Turbine. My '63 transmission still has "Dynaflow" cast into the main case, just like they did in 1948.

https://en.wikipedia.org/wiki/Dynaflow# ... %20reverse.

[Firedome]

In '56 Olds had the newly introduced Jetaway HydraMatic which was an improved 4 spd HM with a 2nd hydraulic coupling and clutches added to smooth out the jerky upshifts a common complaint on the old HM. I had this trans In my '56 Super 88 convert, '56 98 hardtop sedan, '57 S 88 convert and '58 S 88 sedan, it was used thru '60. It was a tough well-proven transmission, shifts were smooth, and acceleration excellent with both 324 and 371 engines. My '47 Olds and '50 Olds 98 had that characteristic upshift jerkiness in spades, quite rough on upshifts with both the 257 straight-8 and the 303 V8. It's easily confused with the later Jetaway 2 spd which was actually a Buick Super Turbine 300, and not related to Chev's PowerGlide.

Slim-Jim was quite different than the 4-spd HM and earned a reputation for not being as tough. With the right treatment and servicing they were satisfactory, and performed well, but few knew/know how to rebuild them. Used by Olds '61 to '64 until the new THM400 came along in '65, those being a huge improvement to both the SJ and even to Cad's traditional 4 spd HM. I actually prefer a tough 2 spd Jetaway II/ST-300 to the RHM SlimJim, but some think they are OK. Some Pontiacs in that era used them also. They came about as a cost-saving tool but were a rare mistake by Olds in the powertrain department, the diesel being the other big one. Cadillac wouldn't touch it the Slim (Slime?) Jim, and Buick remained oddly wedded to their obsolete inefficient DynaFlow + torque tube drive for a while I (not sure last year for the TT?). All was well by '65 however.

[electra225]

The Dynaflow is revered by most Buick collectors. Like the nailhead and the OHV straight 8, they were pure Buick, nobody else had anything like them, good, bad or indifferent. 1960 was the last year for torque tube drive and for the starter on the accelerator pedal. Buick was slated to get the Super Turbine (TH 400) trans in 1961. Due to poor sales and several engineering faux pas starting in the 1957 continuing thru the awful 1958 and 1959 model Buicks, the bean counters delayed the Super Turbine transmission "indefinitely" along with a planned all-aluminum, turbocharged 425 slated to power the Wildcat series. The 1960 Buicks were not so wildly styled as the '59's and some of the bugs were worked out of the 401. The 1959 401's had 10.5 to 1 compression and high-dome pistons that proved problematic. For 1960, the dome was modified and compression lowered to 10.25 to 1. The 1961's sold fairly well, but the hot-selling 1962 and 1963 models put Buick back on the map, sufficiently for the bean counters to release the Super Turbine not only to Buick, but to other GM divisions as the Turbo-Hydramatic 400. The Buick Division hastily put the old 1953 open driveshaft parts in production to convert Dynaflow to an open driveshaft continuing thru the 1963 models. My '63 Dynaflow drives like any other conventional transmission of that era with the exception of it's little whine you can hear when you have it working. Smooth as a straight 8......

There really wasn't an automatic transmission built by anybody in 1963 that could be considered effecient by today's standards. Effeciency wasn't what they were after. Smooth power and reliability, at least enough to prevent damage to their reputation was all they wanted. I've heard of people selecting Low in a Dynaflow to get better acceleration. I never did that, and still don't. The variable-pitch torque converter will do all the work. Just drop it in "Drive" and nail the throttle. That old 401 and Dynaflow were well-matched. I've seen pictures of the aluminum 425 with its guts hanging out the bottom of the oil pan. Dynaflow couldn't handle the power. If that aluminum 425 had gone into production, it would have made the list of the worst GM engines ever built. Buick had enough trouble with the little all aluminum 215. Nobody knew how to work on an all-aluminum engine. I shudder to think what would have become of that big, rowdy turbocharged 425. I always figured the '61 Invicta Custom was intended to be the first year for Wildcat. Wildcat came out in 1962 as a trim option for Invicta, and carried the same model number, 4747. Wildcat became its own series in 1963, riding on the Electra wheelbase chassis. A cast iron version of the 425 was available in the '63 Wildcat along with a four-speed gearbox and Positraction. And Dynaflow......

[Firedome]

In '63. TorqueFlite was pretty efficient as well as tough. Never had a problem with it in either the cast iron version or later aluminum one starting in '62.

Wow an aluminum Turbo 425 "IF" done right would have been amazing!

The Olds improved version of the 215 used in the JetFire Turbo, world's first production turbo, was fine if treated properly which meant using the Jetfire alcohol fluid and correct maintenance. The basic design of the Buick developed 215 was very strong, after being licensed to Rover it was still in production well into the '90s. The biggest problem was poor casting methods resulting in porous blocks, making for a rejection rate of something like over 30% hence grossly excessive production cost, so the resulting Buick iron V6 based on the same architecture was the result. The Olds 215 built by racers can put out some prodigious horsepower numbers, the Olds 6 stud head version was used as a basis by Repco for winning 1966 Formula 1 when Coventry Climax ceased production of their world-beater engines the year before. Too bad GM, as usual, released the 215 too early then didn't stick with it.

[Ken Doyle]

There really wasn't an automatic transmission built by anybody in 1963 that could be considered effecient by today's standards.

There actually was a reasonably efficient transmission that came out in 1962, but it was designed for cars with smaller engines and less than 140 horsepower. The aluminum Borg Warner 35 3-speed automatic used by Rambler, Studebaker, and many foreign makes.

https://en.wikipedia.org/wiki/Borg-Warn ... ansmission

[TC Chris]

My '60 Rambler American had that B-W transmission. I think AMC called it the Flash-O-Matic in those years. It had the start-in-second option. When I got the little car, at Bill's (and my) favorite price, free, the speedo/odometer was disconnected. It just needed some lube in the cable housing. But in any event the actual mileage o the car was a mystery. It turned over 100K while I owned it, but undoubtedly had more miles. That was a lot for a 1960 vehicle. Never had a problem with the transmission. It was a happy car--it made people smile, a little inverted bathtub on wheels.

Just before I sold it, to make the move to Traverse City, I put 4 Michelin radials on it. That made a huge difference in handling. Before that it was recaps. Remember recaps?

Chris Campbell

[William]

Didn't Ford have a tranny that you could start out in 2nd? That was actually a cool feature. If you wanted less torque, like being stuck, just put it in second and walk away. Well, hopefully!

Bill

[TC Chris]

My Ranger has one of those. It's called "manual transmission." Even starts in 3rd or 4th if you don't mind burning up the clutch. Or stalling. Sometimes I try it accidentally.... But 2nd, it will actually start in second and it's the solution for ice and such.

I just love the manual. It lets me feel like I'm actually participating in making the vehicle go. Never have figured out the allure of the autonomous vehicles. Maybe they're great if you're a drinker.

My daily drivers have been manuals for 42 years now plus one year in 1970 when I had the Corvair, And I still sometimes stall from a start. Always made me feel bad. Then I read a column (or heard a radio show) be the Magliozzi Brothers, Click and Clack. They held that if you're not stalling 1 out of 10 starts, you're wasting your clutch. Now when I stall, after looking around to see if anybody was looking, I mentally pat myself on the back for being careful with my clutch.

Chris Campbell

[electra225]

Bill, I believe the Cruise-O-matic had that feature. I have never owned a car with a standard shift. The wife had a '63 Falcon with a 144 six and two-speed Fordomatic trans. Quite possibly the slowest car ever put on four wheels. The only vehicle I'd ever want to drive with a stick is a truck. I liked the Roadranger 13-speeds. Now you can get an 18-speed Roadranger. Same shift pattern only you have one more compound split. Considering all the cars I have driven in my life, I have never driven a Model A nor a Model T Ford. Hudson had a oil bath cork clutch. Nasty job to replace the facings, but that thing was almost like having an automatic transmission. You couldn't slip it and you couldn't "pop" the clutch.

[TC Chris]

The only vehicle I'd ever want to drive with a stick is a truck. I liked the Roadranger 13-speeds. Now you can get an 18-speed Roadranger. Same shift pattern only you have one more compound split.

I'm just the opposite. The only tractor-trailer I've driven was for the recycling organization, and (thank goodness) it was an automatic. But cars, I've had 4 with automatics (Powerglide, TH400 x2, Flash-O-Matic) and 5 with manuals. Well, if we count the '57 Buick, I've had 5 with automatics. When I'm on my deathbed I'll still regret letting that '57 go to the junkyard, rusty as it was.

Chris Campbell

[electra225]

Automatic transmissions are becoming common on semi diesel rigs. Less driver fatigue and they can control fuel mileage better.

[Firedome]

My knees are too creaky for manual shift anymore, thanks to some high-speed skiing accidents and resulting surgery, but I've held onto our '87 SAAB 900, and still do take it our for a short spin in VT once in a great while, it's so fun and driving it reminds me of being in a little airplane. Otherwise I'm more than glad to have modern, efficient, little-to-no maintenance automatics. If needed the front-mounted clutch on the 900 iis super easy to replace, but has been done only once in 250,000 miles.