Technical TH400 question

OK, just to be clear. On the TH400 the vacuum modulator controls the shifts at normal street speeds. The governor controls the shifts at wide open throttle (WOT). I have a 454 with a .600 lift roller cam and 4.88 gears. The vacuum modulator isn't hooked up. We use this thing just for fun, bracket racing. Bracket racing isn't real drag racing because its about doing the same time not going faster. So, we put it in drive and mash the throttle and let the trans do the shifting.
My question is, are we doing any damage by leaving the vacuum modulator unhooked to any vacuum source?
Thanks

 

Nope

 

I don't think its going to hurt, but why not hook up the modulator? does it a manual valve body?

 

Nope was my guess but its nice to have it affirmed.

 

just lazy and no manual valve body

 

The modulator and governor work together to control shift points. The governor tells the valve body how fast the car is moving. The modulator tells it how much load is on the engine.

The way you have it now, the transmission thinks the throttle is wide open all the time, and will shift hard and late. Which is fine for a bracket racer, but not so nice on a street driven car.

You won't hurt anything.

 

Thanks for the info squirrel. Its never driven on the street, well, OK … just before we load her into the trailer a quick pass down the street is always called for simply to ensure it takes throttle (grin)

 

With the modulator unhooked you will have very high pressure in reverse wish could cause problems.

 

The modulator controls pump pressure so you do stand a chance of premature pump failure.

 

Hook up the modulator won't hurt to have an easy up shift back to the pits. And you might check into a different set of governor springs to change the rpm of governor shift point. Most stock 400's put in manual 1st. and mashed shift @ 4500 some thing like a vett shifts @ 6500. The governor allows upshift and the springs are a snap to switch around.MW

 

It just might be a good idea to hook the modulator up to avoid the possibility of excess pressure in reverse and/or premature pump failure. Besides it would make the drive back to the pits a little more comfortable. My only concern is that with my luck I'll end up with a vacuum leak (grin). Oh, and I have decided to get a set of TCI governor weights and springs.

 

As mentioned, the high per Vettes had nice high shift points. I had a 74 with the high perf 350 that shifted at 5500 every time. Kickdown switch was connected on it, which does make a difference.