Just rebuilt my trans, replaced all the wear parts, converter and electrics. Did a few test drives up the road, everything worked fine, shifted good. Went on a short drive (2 miles) lost all foward gears but still have reverse. Sounds like it could be the rear clutch but could something be wrong with the electrical servos in the valve body. I pulled the pan, fluids clean, nothing in the pan. About six quarts drained out. I'll check the front-rear clutch with air tonite to see if they still work (did this before installing VB, ok then).
What do the experts think and what would they check before pulling trans back out.

Check line pressure before pulling it apart. At least you have a reference point to use.
There are no electrical servos in this trans. If no movement in manual low, no scrapping noises, then likely you lost the rear clutch or something in that circuit is defective.

Thanks, I thought one of those switches-whatever they're called, controls line pressure? One thing I noticed when pre-oiling the clutch discs, after they seemed fuzzy, almost nappy headed. This was a factory overhaul set without the bushings, thrust washers. Was using ATF-4 when these parts where designed for ATF-3 present a problem. 2001 trans.
Getting an updated education.

Using ATF-4 has no negative effect on the trans as a whole - in fact it has many benefits.

This trans has a governor pressure control solenoid - run by the PCM - if it had no electrical control it would default to third gear and you could still manually pull it down to low and launch the vehicle.

The other two solenoid are overdrive and lockup - simple on/off solenoid where the governor pressure control solenoid is a duty cycle (modulated) solenoid.

Since you have the valve body down just reduce your air source to 30 psi and apply the rear clutch and front clutch. Applying both of these one at a time should give you a good feel for proper application. You can hold the rear clutch retainer while applying it and you should feel it move while hearing it apply. The front clutch generally doesn't move much since it's riding on the pump support and the piston inside is just clamping the clutch pack.

Two seals on the input shaft - the rear small one and a large one on the piston support plus two lip seals in the rear clutch to apply that clutch assembly. Check the accumulator piston to make sure those seals are good too.

Well, applied air to rear clutch, no bump just hissing, spraying fluid out, front sounded ok. Sooo out she comes. I'll also get new fiber discs. What a pita, getting to old for this. I just so wanted it to be something else.
Thanks for your help
Mike

The "hairy" clutches are not an issue. If you didn't wound them on your road trip you are good.

When you build it this time take the front and rear clutch assembly and place it on the pump and apply the same 30 psi to each port on the pump housing. That will test your front and rear clutches.

Update, did the air check and got hissing noise in the rear clutch. Got trans out and apart. Rear disc-steels burnt and warped bad. Setting on the front pump housing after replacing with new steels-disc, applied air pressure, piston moved but small bubbles around inner seal so I replaced. Seems to be working ok now.. I'll go thru the VB tomorrow, might have got something wrong in it.?
Anything else I need to check?

If it shifted on the road trip sounds like the valve body is ok.

I'd leave well enough alone unless you've had those 4 speed valve bodies apart before or have a good service manual. There is a very small check ball that many people lose when they split the valve body from the plate.

After building the trans and before installing the valve body I would apply pressure to the rear clutch port in the case. That will verify you didn't damage any seals during frt & rr clutch installation.

Watched a video on another post about valve body. Saw where there was a small plug that I didn't put back. The pic shows where it's at, on first tear down the clip had broken and found plunger in the filter, thought that was the only piece. Visio showed differently so I tore the filter apart and found the other plug. Would this piece cause my problems? What other damage could have been done?

Other

Images are not opening for me for very long - best I can see before the image disappears - it looks like you are referring to the boost valve. That increase pressure to the converter lockup piston. The metal plate on top should have a hole drilled in it if this is the area you are photographing. Has nothing to do with the gear changes or clutch failure.

The metal horseshoe that holds the boost valve in the valve body is prone to breakage.

Correction - the boost valve sees line pressure so depending on what is missing it may affect your line psi to the clutch stack.

How about the pcm modual, does it control line pressure?
Trying to hit everything. Reason being the previous owner changed all the 32 pin connectors to the modual by splicing (half assly) in new ends and could have messed up with those wire crimps. I have one code I still can't get rid of after replacing everything in that circuit.

This trans has the same pump regulation as an old 727. Just the reg. valve.

What code are you getting, first you have mentioned of a code.

The only pressure electronically modulated on this trans is the governor pressure.

No code for trans, just emissions. Rear clutch has a lot of up and down on the hub, 1/8" ok?
You've been a lot of help so far thanks.

PM sent to you just now.

Here