TH400 question. Something is wrong here!

[380tom]

My transmission seems to shift solid but when I manually drop it into second gear (auto trans) it seems to free wheel. If I press on the gas it engages to second gear but when I let off the gas it coasts. Like it's in neutral. i.e. no engine braking
First/third gear holds solid on or off the gas pedal but second doesn't
But as soon as I touch the gas pedal it drops down and engages???
What's going on here??? Any ideas??
Come on cheap fix!!!!

 

[blazinzuk]

There are aftermarket valve bodies that don't allow engine braking, sounds like you have one

 

[4X4HIGH]

Could be the one way sprag going south.

 

[Snowy Rivers]

Manual second is accomplished using the overun band.

If the band is bad or the servo that controls it is not working then you will have what you describe.

Second gear while in drive is accomplished using the intermediate clutch pack, which has a sprag in it. The sprag allows for a very smooth shift from second to third gear as the high clutch pack applies the sprag just overuns and then the itermediate clutches disengage.

To fix the issue you are having will most likely require a teardown.

The bands do break.

You can probably run the rig the way it is for quite a while without too much issue.

How many miles on the tranny ???

You may want to pull the pan and see if there is any crap in the bottom that would indicate things chewed up.

Snowy

 

[380tom]

Not sure of the miles? Previous owner said it was rebuilt a couple years ago.
Also I just noticed it while manually in second but I think it does the same thing while in Drive. I think thats how I originally noticed it.
I am going to drop the pan next week to see if there is any chew remains?
I was hoping not to have to tear it down but it sounds like I,m gonna have to.

 

[380tom]

Had a transmission guy tell me he thinks it's the Governor thats causing the issue but I would think if it's the governor it would affect all gears?
What do you all think?

 

[Greg Ducato]

I would be more inclined to think the intermediate band is not holding the drum. Have you tried this at speeds below 25mph? Unless the trans has been modified for downshift control, then the governor will not allow a manual downshift to a lower gear after a certain speed is reached, you may be in between at the speed you are trying this at.