[Super Duty D]

I have a 73-74 TH 400 PQ trans that has just started to have a problem after less than a 7000 mile rebuild. I would like any opinions.

After the car is fully warmed up and you jump on it or cause it to downshift to first,
sometimes as it reaches yellow line to go in to second gear it just slips, like you put it into neutral. Let off the gas fast and let the rev's drop to about 3500 and punch it again and it shifts to second gear with authority. No problems shifting to 3rd under full throttle.

Any ideas?

SDD

[Half-Inch Stud]

Yea, Time to change the SUSPECT filter.

And get the fuild level correct:
1. Drive car around till warm, then idle it. Then shut down. Pull Vac Mod to see if fluid comes out. Add Fluid till it comes out.

Or if you got the terrain:
2. Drive car around till warm, then park it on a severe downhill (my driveway) & idle it. Over-fill the TH400 till it pukes out the vent pipe while car is pointed on severe downhill.

3. Go by reading the TH400 dipstick. Good luck with that.

[kyle_blake]

Mine did this if I understand your post.
intermittent SPRAG

My tranny... I'd WOT from a get go or doing 30 mph and WOT. it would kick down.
go to redline shift, make the shift......then feel like it flies into NEUTRAL, so of course YOU LET OFF

and then it goes back into gear
I have a picture of the SPRAG and mine was even Heavy duty that broke.
To many patches!

Yup
Yup
Screaming chief told me that and he was right!

[stevep]

I was thinking intermediate sprag also.

[Super Duty D]

Thanks for the replies.
Maybe I need add some more information.....Trans oil seems to be perfectly clean, no burnt smell of any kind, it's not dirty at all, still light cherry red.
When I check the level, hot, in park and running, it's about a 1/4"to 3/8" over the full mark on the dip stick, a little over full but I would not think that to be the cause.

Again 7000 miles on this rebuild. It has a "tight ten" torque converter in it IIRC.

HIS,

How could a trans filter cause this? I would think only if it is severely restricted / dirty which I don't think is the case here.

1) Why would you do this? Do you not trust the dip stick or the guy that is checking it

2) Please send over your drive way and I will be happy to spill trans fluid all over it
Again why would you do this?

3) I'm not getting the sarcasm please enlighten me????

Kyle,

Your condition when shifting is just slightly different than what I have.......
When WOT, in 1st(not all the time, only when fully warmed up) it just "forgets"
to shift to 2ond. goes past yellow right up to red line and will go past it if you are not quick to get out of the go pedal.

I would like to here more about your SPRAG theory. Can you post a picture of the result of this break down?

Thanks all, keep the input flowing!

SDD

[kyle_blake]

WOT responsabilities are the govenor's. Unreal only 7000 k on rebuild and this is happening. Your situation is a bit different, I could always depend on my shift coming but after completing it would then fly into neutral. It sounds as if yours just scares the crap out of you as it would keep climbing to what 7000 rpm ? I take it your not going to risk that.

I've heard of this condition before, Half inch probably has better questions relating then my experience has with the sprag.

Sorry couldn't be much more help. I will try and take a picture of the HD sprag that went in my tranny.

Darn that sucks. Any chance the shop will take a look at it that rebuilt it?

[steve25]

Yup, sprag failure from coming out of a tire spinning session/burn out and just dropping off the gas pedal.

[kyle_blake]

Ya I've always wondered how is the right way to burn out then given that info.
Hold shifter in 1st , foot on brake, floor it and just keep it around 4000 rpm? Then let off brake? You don't get a lot of speed out of that.

What about holding it drive, foot on brake, then floor it, get it up in 3rd gear spinning away.. Then let off brake... Then the thing down shifts and gets traction once it gets going but thats gotta be real hard on it and crank...

Always wondered that. Guess thats why I had to get mine rebuilt!

[TTS]

I don't agree with the sprag theory. A failing sprag will not cause a neutral condition, the transmission will just remain in low. A neutral indicates a leak in the circuit, or an otherwise low line/ low oil problem- Or H.I.'s idea of a filter.

[TTS]

Originally Posted by Super Duty D

Thanks for the replies.
Maybe I need add some more information.....Trans oil seems to be perfectly clean, no burnt smell of any kind, it's not dirty at all, still light cherry red.
When I check the level, hot, in park and running, it's about a 1/4"to 3/8" over the full mark on the dip stick, a little over full but I would not think that to be the cause.

400's don't like overfilling. They actually work better slightly a ~quart low. The fluid could be aerated, or the filter collapsing/ sucking air.

Originally Posted by Super Duty D

Again 7000 miles on this rebuild. It has a "tight ten" torque converter in it IIRC.

HIS,

How could a trans filter cause this? I would think only if it is severely restricted / dirty which I don't think is the case here.

1) Why would you do this? Do you not trust the dip stick or the guy that is checking it

2) Please send over your drive way and I will be happy to spill trans fluid all over it
Again why would you do this?

3) I'm not getting the sarcasm please enlighten me????

As a rule, transmission fluid should reach only the top of the pan max. Sticks cannot be trusted.

Originally Posted by Super Duty D

Kyle,

Your condition when shifting is just slightly different than what I have.......
When WOT, in 1st(not all the time, only when fully warmed up) it just "forgets"
to shift to 2ond. goes past yellow right up to red line and will go past it if you are not quick to get out of the go pedal.

I would like to here more about your SPRAG theory. Can you post a picture of the result of this break down?

Thanks all, keep the input flowing!

SDD

"forgets to shift to 2nd" is usually a bad sprag. In your case of having to warm up, could be a sticky shift valve.

In your original post you described a neutral.