Vacume Regulater Valve

[Flathead]

I have a 1984 6.2L in a 26 ft motor home 400tranny. Wont shift from first to second and second to third unless you really wind it up. Replaced all lines and hoses have 22in of vacume at pump,modulater has been OKd. Where is the best place to get a vacume regulator valve and what brand or manufacturer. Thanks

[DmaxMaverick]

It's a Napa item. So is the TPS (vacuum switch on side of injection pump), which is just as suspect. Confirm you are getting vacuum to the modulator, and it varies with throttle position. High vacuum at idle, low vacuum at higher throttle position.