Auto Transmission will not go into any gear

[stanzuray]

Last night needed to get towed home. One minute I parked all well and when tried to move again the transmission will not go into any gear. Revving engine does not help as with burnt bands. Fluid looks new and linkage is moving fine. Some things that may mean something are it goes into park and holds fine. Also I keep fluid right at correct level (checked when running) but dipstick reads slightly high when not running. However when started now and checked, reading stays at slightly high and is exact level as when not running which it never did I think. Planning to pull pan when I get a new filter in (old one is new really) but thought I'd check with anyone whose a tranny expert or had this problem. Thank you. Stan

 

[cucvrus]

Dumb question but is the torque converter still bolted fast to the flex plate?

 

[stanzuray]

Dumb question but is the torque converter still bolted fast to the flex plate?

Got trans pan off and nothing obvious there. Not a dumb question - I will pull cover and check flexplate and converter. No bad sounds from there but I'll let you know thanks. Stan

 

[diesel583]

Is the transfer case in gear? Years ago my daughter kicked the lever getting out of the truck. It took a bit to figure it out.

 

[Coffey1]

My thoughts are you said level high not running level lower when running now it's same level running or not.
That sounds like the pump went bad.

 

[stanzuray]

Is the transfer case in gear? Years ago my daughter kicked the lever getting out of the truck. It took a bit to figure it out.

CUCVRUS - flex plate bolted solid to converter and all looked good there.
Diesel583 - transfer case tried in all positions however maybe linkage is broken and it's in neutral - will check. Also if something is broken in transfer case could it stop movement of front and rear shafts out of case. Yet still allow transmission park to lock vehicle from movement. As I mentioned park still works fine and locks vehicle down. Thanks, Stan.

 

[stanzuray]

My thoughts are you said level high not running level lower when running now it's same level running or not.
That sounds like the pump went bad.

Is the pump accessible without taking trans out. Never rebuilt an automatic or did any more than adjust bands. Level does not change at all after engine running?? Stan

 

[rustystud]

OK, first off Stan the shifter linkage is a metal rod that when put in park physically contacts the side of the case and pushes a "pawl" into the park gear which is solidly mounted to the output shaft. So there is no fluid pressure involved at all in "Park" in a TH400 or any other automatic transmission for that matter. Since the fluid level does not appear to change I would suspect a faulty pump. Either the "Tangs" on the pump broke off or the regulator valve is jammed. There is a plug on the drivers side of the transmission just above the linkage. This is the "main pressure galley" for the TH400. I would install a gauge there and see what kind of pressure you have. If none is present then the transmission must come out.
Just a note, you cannot adjust the bands of a TH400. The intermediate (2nd gear) band is anchored to the case and applied with a servo piston from the valve body. The rear band (manual 1st/rev) is also anchored at the case and also applied with a servo piston. The apply pin can be changed for the proper depth but you need the correct tool to make sure the correct pin is selected. I have never had to replace a factory pin due to improper length. In fact you cannot even get these pins anymore. Most all pins have the "two bands" on them, meaning they are "medium length" .

 

[stanzuray]

Thanks Rustystud, I have read a lot of your transmission posts in the past and said to myself "there is a man who knows transmissions". I will check pressure when I get the new filter and fluid in. From what you said about the park pawl am I correct to rule out a busted gear etc in the transfer case as the problem as park does lock the drive train and wheels though the transfer case? Thanks again, Stan

 

[rustystud]

Thanks Rustystud, I have read a lot of your transmission posts in the past and said to myself "there is a man who knows transmissions". I will check pressure when I get the new filter and fluid in. From what you said about the park pawl am I correct to rule out a busted gear etc in the transfer case as the problem as park does lock the drive train and wheels though the transfer case? Thanks again, Stan

If when the transmission is placed in Park it holds the truck then yes your correct. There would be no gear damage.
Have you had a chance to check the main pressure ?

 

[rustystud]

Picture one shows the rear planetary assembly which has the lugs on the outside that the parking "pawl" locks into when park is engaged. Picture three shows the pawl. Picture five shows the output shaft and picture six shows how it fits into the rear planetary assembly. Picture seven shows the rear servo piston for the rear band and picture eight shows the two "rings" on the stem (pin) which means this is a "medium" length pin.
I worked for over ten years as a transmission specialist. Automatics and manuals. Then later on I specialized in differentials. My last 25 years has been working as a "General" diesel bus mechanic at the county transit agency. Since I had been specializing in "gear" work for years they gave me a lot of drivetrain work. That's why my body is so shot now. You cannot keep working on heavy crap for years and not have to pay the price.

 

[stanzuray]

If when the transmission is placed in Park it holds the truck then yes your correct. There would be no gear damage.
Have you had a chance to check the main pressure ?

Ordered the filter and pan gasket today. Takes about 5 days or so to get it mailed to the village here. I'll check pressure then and let you know. Checking some other vehicles lately and so far they all have slightly higher levels on the dip stick when parked overnight and when started the level goes down. The truck in question does not so I expect to find no pressure and it be a bad pump as you thought. Just want to rule out an easy fix that I may be missing but doesn't seem that way. Thanks again, Stan

 

[stanzuray]

Sure could use some of that knowledge out here in our town of 225 people. Often there is just no one to ask. This forum has been an incredible help on many issues. Thanks for info on band adjusting - was wondering a number of times if I should do that and now I know to not worry about it. Take care and guess we all get old and worn out. Stan

 

[royalflush55]

I have a 1980 K20 camper special that was purchased in 1992 with 31,??? miles. It was just used for hunting and fishing vacations by a man that had 3 of these pickups. This truck drove nice and straight and everything was tight for a 12 year old pickup. I pulled a trailer one night and the 400 transmission got weak all of a sudden and quit going after I had reached a small town. Changed the filter and oil. Made no difference.

I didn't have time to work on it so took it to a nearby town transmission shop. They checked it out and put in a new reman torque converter. They said this pickup had set so much it had affected the original converter. I used this pickup on the farm putting over 300,000 working miles on it with that transmission after that. All I did was change oil and filter about every 50,000 miles. That shop treated me right on that job!! I can see how this might be possible with a military vehicle too.

 

[Tinstar]

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Picture one shows the rear planetary assembly which has the lugs on the outside that the parking "pawl" locks into when park is engaged. Picture three shows the pawl. Picture five shows the output shaft and picture six shows how it fits into the rear planetary assembly. Picture seven shows the rear servo piston for the rear band and picture eight shows the two "rings" on the stem (pin) which means this is a "medium" length pin.
I worked for over ten years as a transmission specialist. Automatics and manuals. Then later on I specialized in differentials. My last 25 years has been working as a "General" diesel bus mechanic at the county transit agency. Since I had been specializing in "gear" work for years they gave me a lot of drivetrain work. That's why my body is so shot now. You cannot keep working on heavy crap for years and not have to pay the price.

I think a new "Rustys Corner" help section is needed.
Troubleshooting, pictures of internals
What and what not to do for maintenance etc.

Thats the one thing I have never attempted to work on other than oil and filter.
Confusing as heck.
I can draw out and explain in detail helicopter gear reduction and transmissions from the Chinook down to the little birds (MH-6).
But the light truck and car transmissions stop me cold.
I know the theory and basics of operation of course, but I know my limits.
I will leave transmission work to the professionals.

 

[rustystud]

I think a new "Rustys Corner" help section is needed.
Troubleshooting, pictures of internals
What and what not to do for maintenance etc.

Thats the one thing I have never attempted to work on other than oil and filter.
Confusing as heck.
I can draw out and explain in detail helicopter gear reduction and transmissions from the Chinook down to the little birds (MH-6).
But the light truck and car transmissions stop me cold.
I know the theory and basics of operation of course, but I know my limits.
I will leave transmission work to the professionals.

I always thought the same about Aviation Mechanics as being the most difficult and demanding job, and would never dream of working on a helicopter engine or transmission ! I guess it just comes down to what you where trained for.

 

[Tinstar]

I always thought the same about Aviation Mechanics as being the most difficult and demanding job, and would never dream of working on a helicopter engine or transmission ! I guess it just comes down to what you where trained for.

I fly them
I don't fix them.

But being an Army Aviator (CW4) means you have to know your aircraft inside and out.
Have a detailed working knowledge about electrical systems, hydraulic systems, powertrain etc.
If you know how the systems work in detail and with each other it will help troubleshoot a problem.

I've been doing it for 28 years now.
Retirement is just around the corner.

 

[rustystud]

I fly them
I don't fix them.

But being an Army Aviator (CW4) means you have to know your aircraft inside and out.
Have a detailed working knowledge about electrical systems, hydraulic systems, powertrain etc.
If you know how the systems work in detail and with each other it will help troubleshoot a problem.

I've been doing it for 28 years now.
Retirement is just around the corner.

I always wanted my own helicopter ! Maybe someday the engineers can finally come up with the flying car they promised us in the 1960's !

 

[stanzuray]

Want to give an update on the transmission. Fluid and filter change didn't fix it (as expected) but had a friend visiting for a few days that does rebuilds so he looked at it for me and said it had no pressure and he'll be back and help me fix it so we can do it in town here. Eventually need to get another trans as this one has a crack at the rear top just before the transfer case but at least be able to get my fall work done if he can fix it, which he seemed confident about. Thank you all for the help, Stan

 

[Haoleb]

Want to give an update on the transmission. Fluid and filter change didn't fix it (as expected) but had a friend visiting for a few days that does rebuilds so he looked at it for me and said it had no pressure and he'll be back and help me fix it so we can do it in town here. Eventually need to get another trans as this one has a crack at the rear top just before the transfer case but at least be able to get my fall work done if he can fix it, which he seemed confident about. Thank you all for the help, Stan

Great! I look forward to seeing it in action on the next episode!