72GoldOlds350

Hello,

I'm swapping out my stock TH350 transmission for a TH400, for my 1972 Cutlass. Do I need any new brackets/linkage/cables/ etc.? So far besides the build I have a new tranny mount for it, but that's it.

Thank you

svnt442

If you want the parking brake to work, you're going to need the correct cables for a TH400 car.

matt69olds

oldcutlass

In addition you'll need a new drive shaft yoke, and mod the driveshaft length.

70cutty

Don't waste money on cutting the existing driveshaft, have them make you a new solid tube driveshaft with new parts.

"2 piece" driveshaft came on (small block, low power) AT cars and it will separate at the isolation joint, especially with added power of the new engine.

72GoldOlds350

Yes, I'm going to have a new driveshaft made for the car, too.

Any links to companies that supply all the cables / parts needed for the swap?

droldsmorland

Food for thought... I don't know if it matters to you or if you are aware that a TH400 has a greater paracidic driveline loss vs a TH350. This means less HP/torque to the wheels. It is enough that you may not like the results? I did this swap on my first car 72 Biscayne with a 350/350 and noticed the loss right away. Couldn't kill that TH400 no matter how hard I beat on it.

matt69olds

70cutty

FYI you can easily build the TH 350 to handle the power your engine puts out. Mine was build with Jake's performance stage 2 kit and it's been putting up with the abuse from BBO for last 5 years.

72GoldOlds350

What about an Olds 350 block w/ almost 600ft/lbs of torque?


Well, the 350 is a 434ci stroker and just put down 530hp/580tq. I think the TH400 will suffice.

72GoldOlds350

Does any vendor sell them?

svnt442

This is a complete set of cables.

https://www.opgi.com/cutlass/1970/br...rakes/C990261/

72GoldOlds350

Awesome - thank you!

All other cables can be reused from my TH350? kick down cables, etc?

svnt442

TH400 uses an electronic kickdown. There normally is a switch and bracket attached to the gas pedal, but you don't have that. Seeing as you're not going for originality you can use the same type of switch used for nitrous systems and just make sure it activates at WOT. All you'll need other than that is power to the switch when the ignition is on and then run the control wire to the solenoid on the drivers side of the trans. You can't miss it...it will be a spade terminal just hanging out doing nothing waiting to be plugged in.
EDIT: IF by chance you have a trans that was designed with the TCS system, there will be two terminals on the trans.
Looks like this: Connect the wire to the detent terminal of you have two terminals.

70cutty

With ease, if built properly with right parts th 350 will put up with much more than that. When my new engine arrived from Mark I was debating on going with th400, after talking to my transmission guy and realizing that it might be more cost effective and less work for me, I decided to keep and build up my th350. The only thing I added was a big transmission cooler.

72GoldOlds350

That's good to know - I'll run this by my transmission builder and see what he thinks, too.

matt69olds

droldsmorland

Ahh ya you left out that tiny detail.

72GoldOlds350

Correct, I did. My apologies. I'm 99 percent sure I'll be sticking with a TH400.

oldcutlass

T400 hands down, built it usually will last through the most severe beatings.

rustyroger

GM designed and built the TH400 at considerable expense to handle their big block torque monster engines. Modifying a 350 might be fine for someone who knows what they are doing and has a specific goal in mind, but for a motor putting out nearly 600 lb-ft I thing the extra losses incurred with a 400 don't really matter, nor do I thing fuel economy is a factor either. Starting with a transmission stronger from the factory seems the way to go to me.

Roger.

oldcutlass

Rockauto or your local autoparts store carry parking brake cables
https://www.rockauto.com/en/catalog/...ake+cable,1696

72GoldOlds350

I love rockauto! Thank you.

svnt442

This is why I suggested this kit:
COMPLETE SET INCLUDES:
(1) Front cable
(1) Intermediate cable
(2) Rear cables
(1) Large S-hook
(2) Small S-hooks
(2) Connectors
(3) Clips
(1) Equalizer.

72GoldOlds350

That's the one I got.

coppercutlass

I Have built a few Th350's and currently running one that was behind a friends 455 running low 11's . The TH350 can handle the power and wont eat as much up as the TH400 and the Th400 has much bigger and heavier internals. To put some perspective to it guys in stock eliminator are running metric 200's because they are light . The th400 in stock form isn't as strong as many think. They still have their weak areas and need work to handle anything over a mild built 455. In stock form its stronger but has much more rotating mass but there is a fine point where it will need some work to live .

To all those saying the th400 can take a beating. I killed a th400 behind a mild 350 running low 13's 6 years ago and it wasn't the builder some hard parts failed.

svnt442

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