What vac at idle do you have?

[corelokt]

I know mine isn't what the TM (had my wife read it for me) says. Mine is 8 inches at idle, the TM says 10 at wide open throttle, to start at 20 at idle. Truck seems to shift ok, just a tad late into third.

 

[Westech]

well your right the tm says 20. Now I just installed a brand new vacuum pump the other day ($$$) and at the pump it will suck your finger right out of the socket. But at the trans it is a tad weaker. I would say your in the ball park with your readings. What speed does it shift in to 3rd... should be in the 30-35 mph range

 

[corelokt]

45-55mph. Sounds like it needs adjusting.

 

[Westech]

there should be a screw in the vacuum modulator on the passenger side of the trans. turn that out a couple turns and see what happens. It should drop the shift points a little. other wise your having the same problem I have and I am waiting on a new governor to get the shift speeds back in order. seams the TH400 is a picky SOB when it comes to Governor shaft ware. Even in 30k miles it can become a problem. I will know later today if a new/used governor changes anything.

 

[corelokt]

No screw in the old or new one. Just put a new one in when I replaced the vac lines, filter etc.

 

[Westech]

hmm.. all the after market ones I have ever seen have a adjustment. the screw is in the vacuum nipple. Its a little one you need a "pen" type screw driver to adjust.

 

[corelokt]

I found that screw, turned it out and set my vacuum. Wow, what a change. I don't even feel it shift and can only just barely tell it when it does. Very smooth. I might need to turn that screw back in for towing as it has lost a lot of torque that it had before, loads and hills will be seeming different.
Thanks West.