Originally Posted by cadillac_al (Post 9267113)

Is that modulator getting vacuum?

Originally Posted by kwmech (Post 9266584)

Back of the transmission right hand side is a steel cover plate with 4 bolts 1/2'' socket or wrench. Remove those 4 bolts. There will be a little bit of oil that comes out ---maybe a a cup at most. Pull the governor out --it should remove easily with a small twist--and look at the plastic gear. You can tell if it is in good condition or not. If it looks OK, you can move on to something else. If not...... Sometimes the rear bushing in the case will walk out and catch the nylon gear and strip it out. If the gear is stripped out, you'll need a new gear of course and pull the transmission out and gut it so you can locktite (green) and lightly stake a new bushing in. Then you can reassemble or rebuild at the same time. The governor controls shifting in the transmission and the vacuum modulator will fine tune it.

Originally Posted by kwmech (Post 9266931)

The wire on the side has nothing to do with the transmission up shifting. That wire powers a small solenoid for kick down and only has power when really into the throttle. You don't have to be a mechanic to remove 4 short 5/16'' bolts and look at the governor. At the most you may damage the gasket when removing the cover. The gasket could be either a rubberized cork or a thickish paper.

EDIT: Another thing: when you get the governor out and the plastic gear looks OK, hold the governor by the gear with one hand vertically and flip the weights with the other and watch the small valve on the inside and see if it moves smoothly and does not stick. This can cause erratic shifting also.

Actually post up a pic of the governor when you get it out

Originally Posted by kwmech (Post 9267797)

If it moves, there is no reason to waste money on another one. Cleaning it out was good. If anything buy a weight kit and an extra gear for it if you anticipate issues in the future. There had to have been a gasket on there, if there wasn't there would nave been a huge leak while driving. I'd pickup a couple of gaskets also. As to the shifting?? I don't know, if the valve was sticking somewhat and is now loose. I'd put the governor back in and try driving it and see what happens. If it still won't shift, there may be a sticking valve in the valve body under the vacuum modulator. See if you can pull it out with a magnet. What condition is the oil in....nice and clean?

Originally Posted by dmb (Post 9267910)

the problem may stem from the silicone used to seal the gov cover. An automatic transmission is no place to use silicone. A small chunk of it will get in the governor and case it to stick.

Originally Posted by Dead Parrot (Post 9267882)

One possible thing that might cause a shifting issue is if the o-ring on the filter tube is damaged, worn, or missing.
Amazon link that shows the o-ring as part of a kit: https://www.amazon.com/ACDelco-TF231...2935891&sr=8-3

I noticed that some kits don't show the o-ring. It is needed or you won't get good fluid pickup and will have symptoms similar to low fluid levels. Including bad shifting.

#7 on the diagram shows where it goes. Another thing some folks miss is removing the old one if it sticks in the opening when you pull out the tube #14.

I would finish your check of the modulator and related stuff before pulling the pan. Pulling the pan probably means replacing the pan gasket + 4~7 quarts of ATF. No point in doing that until you know the problem isn't in the modulator you already have off.

Originally Posted by dmb (Post 9267910)

the problem may stem from the silicone used to seal the gov cover. An automatic transmission is no place to use silicone. A small chunk of it will get in the governor and case it to stick.

Originally Posted by kwmech (Post 9268080)

This is a huge issue ^^^^. You may have already dis-lodged the culprit, but A small piece could have lodged itself anywhere in the valve body. Did you try to pull the valve out behind the vac modulator? It's about a 1/2'' in diameter and about 2-3'' long. Magnet will be useful

Originally Posted by dmb (Post 9269225)

He may have to pull the valve body Something is stuck somewhere, 400s just dont give problems as a rule

Originally Posted by kwmech (Post 9269234)

I agree. I think he is going to see if the valve under the vac modulator is free first, that could be sticking in the case

Originally Posted by dmb (Post 9269225)

He may have to pull the valve body Something is stuck somewhere, 400s just dont give problems as a rule

Originally Posted by Captain J (Post 9269285)

I’ll try to pull it out, is it easy to put it back��?

Originally Posted by kwmech (Post 9269464)

It only goes in 1 way. It'll or should pull straight out with a magnet. Just a steel valve. Same as the governor valve it should slide in and out smoothly

Originally Posted by Shifty One (Post 9270569)

FWIW, I've changed my TH400 modulator 4 times in 20k miles. The units you buy nowadays are not so good.

Originally Posted by Captain J (Post 9266420)

I’m not sure if it’s TH400 or R700. When starting the truck it will automatically run as choke is on, then when I press the pedal rpm drops.
Oil level is good, oil clean, I’ll do this test.
However what’s this switch/solenoid that is located at the gas padel with 2 wires (red goes to fuse box 12v, the other goes to side of the trans)?