Author Topic: 700R4 into a 1955 Coupe  (Read 505 times)

700R4 into a 1955 Coupe
« on: April 02, 2018, 04:32:17 PM »
Hi All,

I'm looking for information as to drive shaft and X-frame issues & modifications with respect to installing a 700R4 into a 1955 coupe...

...Is there anyone on this site who's done this to their 1954 or 1955 Cadillac series 62 or coupe chassis?
(I assume the '56 would be similar as well).

I put a 1962 390 ci in my '55 a couple years ago and the original Hydra-Matic is no more. I've got the adapter kit and will have a fresh 700R4 by the weekend. Most of the install and fabrication work looks straight forward enough, but I'm not sure as to any clearance issues with running a single extended drive shaft through the X-member. I'm keeping stock ride height, NOT lowering the car so I think the X frame should be able to remain mostly intact???

Or will I need a lot of cutting and stiffening?
Or should I be looking for a two-piece drive shaft & carrier bearing?
Or am I over thinking this?

I appreciate any information from anyone who is familiar with what it takes to complete the swap or can refer me to anyone who has done this in the recent past!

Thanks!
Nate

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Re: 700R4 into a 1955 Coupe
« Reply #1 on: April 03, 2018, 09:06:59 AM »
I have a SBC 350 with a 350 Turbo Hydromatic transmission in my '56 coupe (I know, I know...no torque, but it still gets me down the road!). My tranny has the long output shaft, so its the same length as the 700R4. I was able to use the same rear transmission mount bracket and even the original driveshaft (thanks to an odd universal joint) So unless its physically bigger around the middle, it should slide in no trouble. If I was ever going to do ths again, I might opt for the 200r4, and I still might. On the Interstate at 75 mph, she's spinning over 2800 rpm....I bit much for my liking.
At a gas station the other day, a guy asks me "what kinda gas mileage do you get with a big old car like that?". "Who cares?" I replied, "it's a Cadillac!!"

Re: 700R4 into a 1955 Coupe
« Reply #2 on: April 04, 2018, 08:05:25 PM »
Hi ICAD,

Thanks for the reply!
Would you happen to have any pictures of the driveshaft passing through the X-member on your 1956?

That '56-'64 Hydra-Matic must be a lot shorter than the '41-'55 unit. I just picked up my 700R4 yesterday and started to do some quick comparisons...
The 700R4 has a total case length of 30.75",  with front-to-motormount length of 22.5"
The '55 H-M has a total case length of 38.5" with front-to-motormount length of 27.13" (these are fast & dirty numbers from a measuring tape)

So even with the Wilcap adapter plate thickness of .75" added to the 700R4 I'm still estimating an extension to the driveshaft of approx. 7" and a 5.38" trans mount modification.
So where the factory driveshaft was completely past the X-frame it will now enter that area to reach back to the 700R4.

When it gets warm enough to crawl under the car again I'll re-install the factory transmission mounting bracket to try to guess where my yoke is going to end up...

...one way or another I'll get this to work!


Nate

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Re: 700R4 into a 1955 Coupe
« Reply #3 on: April 05, 2018, 03:25:18 PM »
Hi Nate. I just flashed it up for the first time this season yesterday, but its too crappy here to take it for a drive. I'll probably be under it this weekend anyways doing an oil change so I'll take a few snapshots. The original H-M packed up a few years ago so I junked it and the smokin' 365 and did the SBC swapout so now I have nothing to compare it to. I'll bring a tape with me while on the creeper.  KenO
At a gas station the other day, a guy asks me "what kinda gas mileage do you get with a big old car like that?". "Who cares?" I replied, "it's a Cadillac!!"

Offline Chris_Oz

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Re: 700R4 into a 1955 Coupe
« Reply #4 on: April 06, 2018, 05:16:39 PM »
I have a 62 model deVille with a r700 in it.
It was 1" longer than the original transmission when mounted.
I used the original 2 piece shaft, just had the rear section replaced and shortened as it was twisted.
It is the perfect trans for them, mine will smoke the tyres from a stop sign if you want to.
On 235-75-15 tyres and the 3.21:1 rear end its doing 1650 rpm at 65mph.
Lock up only in 4th as I don't have a 3rd gear pressure switch.
I have the lock up running through a relay, with switch on the brakes, so if you brake, the lock up is off so the engine won't stall in a locked rear tyre situation.
Works perfectly.
I used a hi torque gear reduction starter for a big block Chrysler, powermaster unit, its is fine, noisy, but fine.
They are much larger in the body, I had to massage the tunnel to get clearance for the cooler lines.

I would do it again I  a heart beat. Makes the car so much better to drive.
Current Cadillac's
1962 Park Avenue Sedan deVille
1962 6 Window Sedan deVille
1962 Coupe deVille