Been doing my first real drives in the '60 and I'm not convinced the transmission ever gets out of 3rd. I've read a TON of posts here and other places but none that describe what a properly functioning Hydramatic feels like.
I've ordered a tach so I can see if the RPMs fall at all. I feel a distinct 1-2 upshift, much later an almost imperceptible 2-3 upshift. I've only had her up to about 65mph. I understand it's not an overdrive but if 4th is 1:1 the engine should be turning 2300 rpm at 60mph with a 28.9" tire and 3.21 gears. My ear says it's higher than that but the tach will tell the tale.
Any input is appreciated.
G'day Richard,
What you are describing is at odds with what I found with my '60 CDV.
The 1 to 2 shift is very hard to feel, and occurs at around 5 mph at normal throttle, whereas the 2 to 3, and 3 to 4 are felt as normal shifting.
That 1st gear is there to get the car moving from a stop, and I thought I had the same problem as yourself until I realised what was happening. I couldn't feel it, but eventually did.
Bruce. >:D
Bruce, maybe that's what's happening. When I shift it manually, it shifts two distinct times. That said, I've noticed what could be a 1-2 upshift under 10 mph, but it happens so quickly and smoothly I ignored it. Im so used to modern overdrives. The problem could be the "loose nut behind the wheel ".
As mentioned, the shift 1-2 is imperceptible as well as 3-4 because both are pure hydraulic: a small fluid coupling is getting oil during the shifting, rendering it very smooth. 2-3 is usually more perceptible because the small fluid coupling is getting empty and some mechanical actions are performed. By 1960, the transmission was refined enough to have this 2-3 shifing acceptable.
If unsure, drive at 65 mph and put the lever into D3. If the transmission was in 4th speed, you will notice immediatly the difference. If the transmission is not upshifting into the 4th speed, you will not feel a difference when the lever is in D3 or D.
The 4th speed is not an overdrive; then the transmission is just in direct drive, 1:1.
Which one is D3? Aren't all these transmissions P N . . R ? And the 2nd . is maybe 2nd gear for ice according to the manual? Or am I thinking of a different year that said that?
I have a 55 so its the older one, but still the Hydromatic.
I often find myself wondering the same thing and then counting the shifts the next time I leave a stoplight.
Please remember as stated above that the 1-2 shift is no faster than when you walked your dog this morning.
Another thing is that your kickdown rod may be out of adjustment. You may need more throttle to keep it at 60 than the current adjustment allows, but you aren't going fast enough for the governor to overide the kickdown rod-- Again I have the older version but mine was out of whack and shifted all over the place. Just something to think about.
Kickdown kinda implies a wide open throttle on off sort of thing. On these I believe the rod is doing stuff through its whole operating range so its a pretty critical adjustment. Seems like where many people go wrong is changing the carb. If the new carb doesn't have the proper geometry on the arm or different characteristics you may not be able to get it adjusted for factory like performance.
Check your linkage. If not adjusted properly you may only be in the lower setting of Drive. Shifting should be almost unnoticeable.
When moving at speed (35-50 MPH), move the selector over to the right hand drive position. It should have a distinct downshift sensation with speed abruptly reduced.
Quote from: Eric DeVirgilis CLC# 8621 on August 29, 2025, 01:17:32 PMWhen moving at speed (35-50 MPH), move the selector over to the right hand drive position. It should have a distinct downshift sensation with speed abruptly reduced.
It does. I assumed (perhaps erroneously) that was 3-->2, maybe it was actually 4-->3?
Quote from: bigoilman on August 29, 2025, 06:05:14 PMmaybe it was actually 4-->3?
Correct. D-D-L is 4-3-2/1.
The adjustment of the TV rod is extremely critical, as the TV is a graduated valve, applying internal pressure as it is required.
The change to a Kick-down switch came with the TH400 which is an electric switch.
Bruce. >:D
my 60 was rebuilt a year ago, and 1st to 2nd is very smooth. But 2 to 3 has a jerk which pisses me off. The only thing I can do maybe do is find a different trans, Maybe the TH400, but I dont no much about it fitting.
From what I understand, the shift from 2nd to 3rd is the most pronounced in the Hydramatic because there's more mechanical involvement while the 1-2 and 3-4 shifts are mostly done by fluid.
Quote from: 60eldo on August 30, 2025, 09:43:45 AMmy 60 was rebuilt a year ago, and 1st to 2nd is very smooth. But 2 to 3 has a jerk which pisses me off. The only thing I can do maybe do is find a different trans, Maybe the TH400, but I dont no much about it fitting.
If I ever change transmissions in this car, it'll get a modern overdrive transmission. When I swapped the 454/TH400 combo from my '77 C30 crew cab dually for a turbocharged LS and 4l80e it made it a much more enjoyable, driveable truck.
Take it the way you like: I have a '56 Biarritz and a '72 de Ville. I prefer by a large margin how the '56 transmission is working compared to the THM400. As a bonus: the older transmission is more efficient and use less fuel. Not really relavant with less than 1000 miles each year...
I'm pretty sure this is the transmission that is basically 2 2 speeds stuck together so that 2-3 shift is the shift when both sections have to shift so timing gets involved since its not a single element. Its like 1st is LO LO, 2nd is HI LO, 3rd is LO HI (so both sections had to shift) then 4th is HI HI.
You can tell how old many of us here are when we consider a THM400 modern. Last built in 1991? So almost 35 years ago? Its been out of production loner than its run of 27 yeaers. 64-91 was a pretty good run tho. Most of the cars were done by 79 so it was just trucks and I think the Allisons started taking part of that market in the middle 80's then GM came out with the 4L80e. Modern I think you are talking about the 10L80? which is one of many things making the current trucks junk.
There is a lot involved in a swap. You can buy a kit for $1250 to bolt a 'classic' Chev trans to a 54-63 Cad engine but then you are on your own for mounts and mount related stuff, driveshaft, shift linkage indicator parnk/neutral, and the electric kickdown. Not as big a deal with a rat rod where you can cut and weld and slap a B&M floor shift in but on a car you presumibly want to keep stock? Also the OD could cause issues, these cars were designed to spin where they are spinning at various speeds. Knocking down the R's at those same speeds could mess up the economy and overall tune as well as performance of cooling and AC systems.
https://transmissionadapters.com/collections/cadillac/products/1954-and-up-cadillac-365-to-chevy-automatic
https://transmissionadapters.com/collections/cadillac/products/1954-and-up-cadillac-365-to-chevy-automatic
The THM is a more efficient design than the H-M according to the following article:
The original Hydramatic was a bulky, less efficient 4-speed transmission that used a fluid coupler, while the Turbo-Hydramatic introduced a more compact and mechanically efficient 3-speed design with a torque converter and a simpler Simpson gearset, leading to less internal friction and better fuel economy.
The article forgot to say that a fluid coupler is more efficient when the RPMs between pump and turbine are near identical and that the H-M is transmitting the power part mechanical and part via hydraulic.
On the other side, the H-M was a complex construction and expensive to manufacture.
Quote from: TJ Hopland on August 30, 2025, 01:28:13 PMI'm pretty sure this is the transmission that is basically 2 2 speeds stuck together so that 2-3 shift is the shift when both sections have to shift so timing gets involved since its not a single element. Its like 1st is LO LO, 2nd is HI LO, 3rd is LO HI (so both sections had to shift) then 4th is HI HI.
It's exactly that way.
Quote from: TJ Hopland on August 30, 2025, 01:28:13 PMI'm pretty sure this is the transmission that is basically 2 2 speeds stuck together so that 2-3 shift is the shift when both sections have to shift so timing gets involved since its not a single element. Its like 1st is LO LO, 2nd is HI LO, 3rd is LO HI (so both sections had to shift) then 4th is HI HI.
You can tell how old many of us here are when we consider a THM400 modern. Last built in 1991? So almost 35 years ago? Its been out of production loner than its run of 27 yeaers. 64-91 was a pretty good run tho. Most of the cars were done by 79 so it was just trucks and I think the Allisons started taking part of that market in the middle 80's then GM came out with the 4L80e. Modern I think you are talking about the 10L80? which is one of many things making the current trucks junk.
There is a lot involved in a swap. You can buy a kit for $1250 to bolt a 'classic' Chev trans to a 54-63 Cad engine but then you are on your own for mounts and mount related stuff, driveshaft, shift linkage indicator parnk/neutral, and the electric kickdown. Not as big a deal with a rat rod where you can cut and weld and slap a B&M floor shift in but on a car you presumibly want to keep stock? Also the OD could cause issues, these cars were designed to spin where they are spinning at various speeds. Knocking down the R's at those same speeds could mess up the economy and overall tune as well as performance of cooling and AC systems.
https://transmissionadapters.com/collections/cadillac/products/1954-and-up-cadillac-365-to-chevy-automatic
https://transmissionadapters.com/collections/cadillac/products/1954-and-up-cadillac-365-to-chevy-automatic
I probably wouldn't go to the 10spd but the 6l80e and 8L90 are great (in my experience). All that is just conjecture at this point, anyway. This car runs great and it appears that it may be shifting as designed (the purpose of this thread was to help me determine that).
Quote from: bigoilman on September 01, 2025, 09:35:03 AMI probably wouldn't go to the 10spd but the 6l80e and 8L90 are great (in my experience). All that is just conjecture at this point, anyway. This car runs great and it appears that it may be shifting as designed (the purpose of this thread was to help me determine that).
Good choice.
The trouble with too many gears is that these transmissions are designed for engines with a very narrow torque band, and require so many gears to get any sort of performance and meet strict anti-pollution requirements. The top couple of gears are simply added overdrive gears.
Bruce. >:D
Quote from: The Tassie Devil(le) on September 01, 2025, 07:16:20 PMGood choice.
The trouble with too many gears is that these transmissions are designed for engines with a very narrow torque band, and require so many gears to get any sort of performance and meet strict anti-pollution requirements. The top couple of gears are simply added overdrive gears.
Bruce. >:D
I fully understand the modern transmissions (I've done a few LS swaps in addition to the factory stuff I own/owned). I'll bet a 390 Cadillac would perform very well in front of a modern overdrive transmission. As much as I love the LS platform, unless you plan to build for high 3 digit HP (or even 4 digit HP), there's not much an LS (or LT) can do that a traditional SBC or BBC (or Cadillac engine, won't. Parts are easier to get and cheaper but the real advantage is in the transmissions. I'd love to see a 390 with EFI and a modern transmission put together but it's probably more trouble than it's worth just for the sake of being different.
Not quite the same, but after over 44,000 highway miles a 700R4 works very well behind the 472 in my '35 Cadillac and I am most happy with it. Building another car (not a Cadillac) with the 472/700R4 combination and expect the same.