1960s 1960 Hydramatic...What's it SUPPOSED to feel like?

[bigoilman]

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       

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).

[The Tassie Devil(le)]

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).

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.

[bigoilman]

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.

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.

[35-709]

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.