Perfect when it is cold but delayed when its hot. Line pressure is low like 60 psi at idle in reverse. When engine rpms come up the pressure still holds pretty low and then suddenly jumps about to 250 and then reverse grabs well. Have a sonnax line booster valve installed when I rebuilt the unit about 2 years ago. Pulled the tranny apart and did find some wear. My fluid was burned from pulling heavy loads. Used cheap WM supertech fluid which I will never use again. I can not find any definate problem now that I have it torn down. Even went through the VB and also checked the reverse abuse valve. I have done about 15-20 of these with never this problem. Not sure but maybe the teflon rings on pump stator could be leaking by. So IDK at this point.

 

Did you check the fluid level? Very common cause of delayed engagement is improper fluid level.

If you're confident the fluid level was fine...then 3 things come to mind as the most common issues with delayed reverse, and all of them can be bandaided by thicker (cold) fluid.
-Bleed hole in the reverse input piston
-Bad seals/teflon rings
-valve body/pump internal leaks

While you have it torn down, replace the belleville plate in the reverse input drum with a waved style. Don't see what year yours is, but some of these units have issues sealing the bleed hole in the reverse input piston sealing with the belleville spring. The idea is the spring steel should flatten out and plug the hole in the reverse piston allowing the clutches to fully apply...the wave does a much better job. I'm not saying this is for sure your issue, but it's one of those "good practice" things I do whenever I rebuild one.

If you already have it torn down, obviously replace every lip seal/o-ring/gaskets and any of the teflon seals as these are all common causes of the slow reverse. Don't skip the teflon seals. It always pains me to no end when someone will take the time to do a rebuild and not touch the teflons.

As with any build, totally disassemble the valve body, clean it all, inspect everything for abnormal wear, sticky valves, loose bores, etc etc and reassemble. If you have access to a vacuum test stand for a valve body, use it, but if you don't that's fine.
Do the same with the pump. With the reverse pressure being delayed like that, I would be looking even closer at the boost valve for bad wear, and the reverse abuse valve and its bore plug. I know you said you checked it...but I'm curious as to how you checked it? Just a visual inspection of the valve won't tell you a whole heck of alot. It might let you know if it's grooved or has been stuck real bad...but a vacuum test is going to show if it has bad internal leaks or not.

 

Go to Walmart and get a 5 dollar bottle of TransX, put it in and your trouble will probably stop. The seals get old and shrunk, TransX will revive them, Good Luck

 

1. He's already torn the trans down...so your comment makes about 0 sense
2. Even if he hadn't torn it down...that's trash advice
3. Lets actually diagnose the problem instead of pouring a bottle of goo in the trans

 

Alright I pulled the trans and AFTER I replaced the seals in the direct drum and air checked it, I could barely get the clutch to apply. I could hear a bad leak. Pulled it back apart and checked the lip seals and reassembled. Still large leak. I finally gave up looking for the leak and rebuilt another drum. This one applys just fine. Installed transmission back into truck and now the converter was locking up in every gear. Only would do it after i reached 1500 rpm. Everything else was fine. Next day I was going to check the brake switch so I had to back it out off the lift. Much to my surprise now has no movement at all. Trans overfull now like converter not picking up. Checked line pressure and has good 70-75 psi. Now I am stumped. I usually replace the converter with every rebuild but this one did not have over 40 k miles on it so why replace it. Do converters fail in this manner?

 

Well I found my problem. zI got into a hurry and did not take note of the proper order of the tcc apply valve and spring. Had the springs on top of the valve instead of the valve on top of the springs. thanks for all the help.....

 

I've seen you say that you've built "100s" of TH350s... and 400s. This post right here tells me that you are lying, any soul that knows anything about transmissions, knows that you don't use that stuff.

 

I want to add something I forgot. i took the time to examine that direct drum that was leaking. Sometimes called reverse input. This is a 2 piece unit with an outer cast and inner shell that is somehow made on this cast piece or somehow welded. I took some brake clean and sprayed it between the case and the shell inside. One side leaks like crazy. I have never seen or hear of this happening. If it`s a wierd problem it will happen to me..

 

He rebuilt them with a bottle of TransX.

 

BINGO
He's sortof popped up in a couple posts in the last couple weeks acting like he's heaven sent and an absolute subject matter expert. His post about TransX made me laugh and then realize I had made the right decision earlier to just ignore what he has been saying lol

 

LOL you guyz know nothing.... its laughable.

 

Can you tell me where to find the best deal on TransX is? I was thinking amazon but maybe you have a better wholesale supplier? Surely you KNOW more about that than me