The 904 has been doing well aside from a lil flare or hesitation from first to second gear recently. So I drove it less than 150 ft to my neighbors house to check and set the timing. I cranked it after 5 minutes to see if the timing was good. And then tried to go in reverse nothing. Drive nothing. Or 1st or 2nd

To add to that. After having the truck running for 10+ minutes the transmission is still stone cold

Sounds broken to me.

_________________
Joshua

Have you adjusted the bands?

I have found this diagram extremely useful in diagnosing what part of a 904 transmission has failed:



This is something you find in a factory service manual, which you should get for your truck. Sounds like you should inspect the low/reverse band, but if it doesn't do anything in "D" the rear clutches might be gone.

Have you verified the accuracy of the gear selector?

No I don't know how and it probably requires a torque ratchet and I don't have one. Has the symptoms of low or no fluid but it's topped off and I've triple checked the shifter to the transmission and kick down linkage. A backyard mechanic that I've had experience with said it might be the front pump have stopped working

Also the valve body in it is lock up when I'm thinking the vb it originally had was non lockup

Here's how:
https://www.youtube.com/watch?v=hoIH8ebXNZY

Don't need a torque wrench, but you do need to know the year of your trans. The number of turns the adjuster bolt gets backed off varies depending on the year. You need to drop the trans pan and have a set of box end wrenches.

Did you get in the trans and swap out the valve body?

Thanks and yes the 904 manual shifter arm kept jumping out and I think I messed up the calibration on it so I used the 727 valve body

Year is 76

With the truck off I dropped it in to reverse then drive and it moved forward and backward. I had the hood popped and hear the band or clutch attempt to move. It was a short clicking noise. The torque converter didn't move.

What?

If the torque converter didn't move, then the engine is off or the engine is disconnected from the flex plate. If the engine is off then the transmission pump isn't pumping and the bands won't attempt to engage.

However, if the truck did move forward and backward under its own power, then the engine is running, the torque converter is spinning, and the trans pump is pumping. But if the truck was off it wouldn't move under its own power.

What are you saying you did and what are you saying happened?

Or are you talking about moving the shifter linkage with the engine off? If you are talking about the shift linkage, then if the engine is off the torque converter won't move. The clicking noise you hear is not the bands attempting to engage, it is the stop going through the detents in the "rooster comb" on the gear selector mechanism on the valve body inside the transmission. The bands and clutches don't engage unless there is sufficient pressure in the transmission oiling system from the front pump.

Well in that case it's your second statement. And how can I see if the front pump is working?

The only way to check if the front pump is working is to have the engine running and either follow the factory procedure to check the pressure outputs on the transmission (you need pressure gauges that read hundreds of pounds of PSI).

The messy cheap and not terribly accurate way is to get a 5 gallon bucket, disconnect the trans cooler lines from the radiator, point them into the bucket, have a friend put the transmission in neutral and start the truck (with the brakes engaged). If the transmission pump is working, transmission fluid should squirt steadily and forcefully out of one of the cooling lines. Only run the truck for 5 seconds or so. It will be very easy to tell if the pump is pumping fluid.

The problem with this method (aside from the mess) is the pump can be pumping, but at too low of pressure for the bands and clutches to engage.

I think if I was in your situation I would start by cleaning the 904 valve body and installing it. I recall there was a difference between the 727 and 904 valve bodies that made them not directly interchangeable. I found this online:

I cleaned the valve body disassembled and reassembled it. Cleaned with carburetor cleaner. The issue is the vb has a b&m shift kit installed by previous owner and I don't know the specs

Does the 727 or the 904 VB have the shift kit? A shift kit won't make the transmission not go into gear. I still suggest reinstalling the stock valve body and seeing if that changes the behavior of the transmission.