C6 - Delayed or No engagement, any gear when HOT.

[DuckRyder]

Working on a C6/ FE completely overhauled using a TCI kit, has ATI Fuel Master HISTALL and a Trans GO valve body kit.

~1000 miles (But several years) since overhaul.

When cold it works fine, shifts fine with no problems.

When hot it also shifts fine and works with no problems except that if the truck is turned off when it is restarted it will either delay engagement or fail to engage. Selector position is independent R, D, 2, 1 seems to make no difference. Sometimes when it does not want to engage flaring the throttle with it in gear will cause it to slide in. (Do I need to say this is not exactly a recommended or safe procedure and should be avoided)

To the best of my recollection this began to occur at the time the ATI converter was put in. (it previously had a TCI breakaway)

The truck does not have an external cooler and I know it needs one, but I am reluctant to add it until the transmission is working correctly, because I have just about had it with automatics much more money and this thing might have a TKO in it.

When I say hot, I mean idling it for 10-15 minutes to verify fluid level will usually make it do it. At no time has it ever failed to work perfectly after cooling for several hours.

I have had the vale body out several times and can find no sticky valves and everything corresponds to the diagram in the TransGO instructions and ATSG manual. A torque wrench was used throughout.

Other things that might make a difference, it has parts house type F in it and the filter is from trans parts and is a metal filter with a single large hole in it.

So here are the questions:

1) Could the Torque converter cause this?
2) Is it possible that it is heating the fluid up enough idling that it is turning too thin to work?
3) Any other ideas about what would make it act this way only when HOT?

[BobbyFord]

Try turning the modulator in a little to increase the line pressure.

[rjewkes]

mine would do this before i replaed the trans cooler lines it would leak enough fluid that when it got warm it would start slipping. just from stop not while travelling.

[averagef250]

A good friend had a CJ5 with a 289/C4 in it that would do exactly that. Turned out to be the pump was shot.

[Thunderfoot]

So here are the questions:

1) Could the Torque converter cause this?
2) Is it possible that it is heating the fluid up enough idling that it is turning too thin to work?
3) Any other ideas about what would make it act this way only when HOT?

1. The converter could be a possibility but I would think you would have some other issues when it was warm all the time...
2. You would have to almost cook the fluid before it wouldn't work... The power glide in my racecar has no cooler what so ever and runs a hard 1/4 mile at a time with no problems. So your 15min of idling wont get it very warm...
3. Like Dustin suggested it could be the pump or it could be the sealing rings on the back of the pump. You could also have a sticky valve in the valve body that when it gets warm and you shut it off the fluid is draining out of the drive clutch, so when you start it up it takes a bit a pressure to get the valve to move so that it can apply the clutches again...

Hope you get it figured out.

[DuckRyder]

Thanks for the suggestions:

I changed the filter and it passes the driveway test. I will need to run it around town for a few days to see it that was truly the problem.
I do recall now that I was not crazy about the filter or the gasket when it I put them in. The filter was deeper than standard, and the filter gasket was a metal embossed deal. I could find no indication that the filter was actually contacting the pan; it could not have had much room.

This is the problem with it being months between having time to mess with this thing, I forget about the little details like this.

If that does not do it, I will have to get the pressure gauges out and get more involved.

[DuckRyder]

Anybody want to buy a truck?

Pressure is bottom of acceptable idling @1000 in all gears. Its much lower than Trans Go says it should be though.

When it is acting up (IE not going into gear) pressure is zero. When it slides in gear pressure goes to bottom of acceptable.

It is like the pump is "losing prime". seems to be worse after a short hot soak, like filling with gass and restarting.

I am thinking the pump is bad?

[rjewkes]

yeah you may have shelled the pump. i got a c4 rebuilt with new pump, steel cooling lines, new torque converter. and e few other new goodies. for 955.96 at cottmans.

[Jake11]

Might just be valve body. There aluminum and and when hot the
valves hang if it's not good. I would pull it and make sure all the
valves are free to move and it's flat on the gasket side. They do
warp. KeithP

[DuckRyder]

GRRRRR...

I pulled the valve body again and disassembled the main pressure regulator valve again. Boost valve and sleeve look kind of rough, the pressure regulator valve was sticky at the very bottom of the bore. I polished it lightly to free it.

This seems to have helped. (Definitely didn't fix it, but less frequent)

Now here is another thing I don't really understand.

Each time the valve body comes off It takes at least 10 and usually 12 quarts of fluid to refill it. At 12 quarts there is only 2 quarts left in it which means the converter is draining? How is that possible?

[fordman]

the top half will drain out from gravity. if the bottom half is draining maybe it is from suction? thats all i can think of.