Moondog22

Hi All,

Would like some info from anyone who has expereince changing the vacuum modulator on a TH400. The current unit in my '68 has developed a leak in the crimp area and is making a mess on the exhaust (not to mention a trail of smoke behind the car), so I have bought a replacement unit. I have instructions on how to replace the unit itself (looks pretty simple), but I have a question about the ATF already in the transmission. I only plan to replace the vacuum canister itself, not the valve behind it. I don't have any prior experience with this, so my question is....do I need to drain the ATF level down below the trans modulator hole to avoid a big mess with fluid flowing out the hole, or will the the valve prevent the ATF from leaking out while I switch out the module can?

Thanks!

C3 Stroker

No, you don't have to drain the fluid.....there may be some slight leakage, but you will be able to replace the module without getting messy. I changed mine some years ago and had no mess issues.

Moondog22

Cool...thanks for the help C3 Stroker. Plan to change it this next weekend.

JimT

I just pulled the modulator on my '72, TH400 and fluid went everywhere, at least a quart! Do I have an overfill issue?

marz

Be sure not to over-crimp.

markdtn

Maybe, maybe not. I always just jack the car up from the rear for this job or back onto ramps. That way the fluid is forward.

Easy Mike

Count on it.

Provided you are not lying under it when you take it out.

C3 Stroker

I jacked my car with the fluid heading the other way, too.
Just happened to be an easy way to reach it.....must have lucked out.

jimvette999

The position of the valve has a lot to do with how much fluid will escape as does which end of the car is elevated. For T400, I'd jack the front up.