Hot Rod Forum banner

1 - 2 of 2 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
Hello All, I am working on installing an TH400 into an 89 Chevy Silverado that previously had the 4 speed transmission (TH700) with the TV cable.

Where is the best place to install the vaccuum line for the modulator and is the wiring there for the down shift relay?

Any help on this would be great as I am having a hard time finding a wiring diagram for the transmission.

Thank you All
 

·
Registered
Joined
·
135 Posts
T400 Swap

The T400 swap in a truck is a very good choice. I don't know what you are using the truck for but the turbo 400 is tough and reliable, much more than a 700R4. So you don't have a overdrive, I would rather have the reliability of the T400. The modulator hook up should go to full manifold vacuum, either to the intake manifold or just under the carb or TBI. Also use a metal tube with just about 2 inches of vacuum hose hooked up at the manifold and modulator. The metal line won't suck closed. A rubber hose can be sucked closed, collapse, causing erratic shift issues and is prone to fail around hot exhaust.


The Trans kickdown solenoid is on the left side of the trans, this is wired +positive to a activation switch on an adjustable throttle bracket. You can also just leave it unhooked and shift manually, This is just a down shift activation solenoid, not line pressure control, it won't hurt anything, just watch what RPM you are at when you manually downshift. There is a shift kit (transgo) which will allow a downshift manually at any speed. Just use common sense and don't down shift into 1st at 70 mph.

Good luck with your swap!
 
1 - 2 of 2 Posts
Top