hydromatic 4 speeds

how long ago did people use the 48 to late 50"s 4 speed olds hydro trans in race cars. did people use them behind small blk chevys. I have heard they used to make differant bell housings to fit other engines. also whats up with the strange converter? thanks for any Info oldsman71

 

do a search,use my user-name(yorgatron),or DON_WOW or backyardbeliever or d2willys we've written about these a lot already.

 

As I recall, they were actually used in the Chevy Sedan Delivery, in the mid '50s....and popular for drag racing up to the mid '60s.

 

There's a large cast-in warning on most Hydro bellhousings that indicate they MUST stay with the trans. You could get a 4spd hydro behind a Chev Pickup in the early days of the V8....they weigh a jillion pounds, but after B&M (and others) got through with massaging them...you just couldn't shift any better or faster with a stick.

"whoever said the pen is mightier than the sword obviously never hefted a BAR..."

 

that strange converter is one torque multiplying bitch. i run a hydamatic behind a cadillac 331 in my model A roadster. b&m made them for different applications. in the 60's a lot were used in gassers. its one tuff trany. first shift is at 7 miles per hour. it was used to make a 6000 lb. car move off the line. cadillac dave

 

all you need is a dial indicator to remedy that problem.
it helps if you have access to a lathe to make offset dowel pins.

 

I believe that a Cameo was the source for the small block hydros but sedan delivery sounds reasonable too. For you youngsters, This is where B&M got started and earned their reputation. Cad, Olds, Pontiac, came with them but people like B&M put them behind anything including blown hemis.

 

The extremely low first gear helped, too. I think it was 3.86:1! Also...as I recall...the biggest jump between gears was the 2-3 shift, and underpowered cars did not do well when the trans pulled them down this much.

 

thats not a torque converter, it is a fluid coupling and has no torque multiplication, its the reason for the really deep first gear. warning on bell housing was to keep it with same block, 4th gear i believe bypasses the fluid coupling and is direct drive through the transmission, years ahead of modern lockup converters

 

The transmission was way ahead of it's time. Developed in the '30s it had features that surpassed alot of automatics. One unique feature was the hidden parking gear. When you put the trans in R with the engine off it functioned as a parking gear. Ratios were 1st 3.82, 2nd 2.63, 3rd 1.45, 4th 1:1 and R 4.3
Very durable transmission, but heavy.

 

A fluid coupling has two basic parts; the driving torus that vaguely looks like a doughnut with half it's insides containing blades radiating out from the center and inside the other half is another half a doughnut (driven torus) with another set of blades. The faster you spin it, the harder the oil gets thrown from the driving torus to the driven torus and the more efficient it gets at transmitting the power from one to the other.

I think I read once a fluid coupling is upwards of 97% to 98% efficient at high RPMs, but because a fluid coupling doesn't "increase" the engine's torque, the fluid coupling Hydramatics used four forward gears with a very steep first gear (3.97 to 1 in the case of the 50s Pontiacs I've owned) to get the car moving. As fuel was relatively cheap at the time these transmissions were built, the addition of an overdrive gear was considered unnecessary or not considered at all, so high gear was simply one to one.

The modern three element torque converter is a fluid coupling containing the driving torus and driven torus of a fluid coupling, but also containing an additional wheel (stator) with an extra set of blades to redirect the oil to the driving torus, actually increasing the available torque at breakaway (the convertors stall speed), reducing the need for a super low first gear. However as you spin a torque convertor faster, the addition of that third set of blades causes the torque convertor to lose efficiency (sometime shortly after the initial breakaway or takeoff), because that third element never really allows the two main parts (the fluid coupling) to hydraulically lock together. For modern cars, with their emphasis efficiency and economy, this requires the addition of a lockup clutch to bypass the torque convertor and allow all the engine's power to pass straight through into the transmission.

I hope all you old heads and engineers that understand all this crap will forgive me my simplistic explanation and any errors, but it seems like there is a great deal of misconception amongst those not around when these transmissions were the norm and not the exception, thus my explanation.

 

i stand corrected....on the torque converter comment...because i was around when all this happened...i can't remember it all correctly...now thats really being there man...thanks for setting me straight...i remember now...cadillac dave

 

The Hydramatic was used in Chev trucks from '54-'59, but was not a sedan delivery option. They were legal in the NHRA stock classes for sedan delivery bodied cars because that body style was still designated as a truck by Chevrolet.

 

thank you all for the great info, its good to learn from the past to make better use of things we have today. I like to hear from other gearheads that like to buildstuff, run the hell out of it ,then build more cool stuff!!! thanks again oldsman71

 

Not all were 4 speeds in function . Some Olds and Pontiacs sold in the plains states came with a blocked passage in the valve body . For a nominal fee , your local GM dealer could give you an extra gear by removing said plug and giving you that grunt 1st gear .