When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
There should be an o-ring on the insert end of the modulator - bet yours is needing replacement. Simple to unscrew the bolt and bracket, pull the modulator out and replace the o-ring. (When you pull the VM out, make sure the old o-ring isn't stuck in the transmission hole.) Looks like your trans cooler nuts may be leaking too.
If you are satisfied the way your Vette shifts, then simply purchase a stock unit.
If you prefer an earlier or later shift, bringing the RPMs up before gear change, then purchase an adjustable unit. Adjustables have an allen screw inside to tweak your shift points. The modulator aides the transmission in determining which gear it should be in according to engine load. All done, by the amount of vacuum from the engine. Or lack of vacuum. (full throttle)
Thanks everyone! I decided since the original is 50 years old and I’ll be losing some fluid I’ll just replace the unit vs just the o-ring, picked the B&M adjustable from summit since it had good reviews
There is a bolt and bracket that holds the old modulator. After removal, make sure old "O" ring is not still inside the port. You may have to shorten the new hose also.
Apply some lube on the new unit before installing. It should "click" into position.
I hope your new unit comes with instructions. Basically, turning either an allen or a reg screw inside the unit clockwise increases where the shift will occur.
Instructions should note how many turns equals what. Basically, the adjustments are for 2 - 4 MPH increases.
Here is where a pair of ramps will be a Godsend. Obviously, you don't want to jack this car up after every test run. You may have 5 -6 tests runs to satisfy your mods.
The B&M modulator is the infamous "red stripe" unit.......these are made by a couple of different manufacturers......B&M doesn't make their own.....you can find that same exact piece in the NAPA Balkamp Catalog......but if you bought it, stick it in.......the red stripe is a performance orientated modulator and its overall window of adjustment is different than the "green stripe" which is like for dad's old station wagon.......
Help identifying TH400 part
