Transmission woes

[PotvinGuy]

My TH400 is acting strange. I've put the car's rear up on jacks, and I move the shifter arm at the trans to see what happens. I can run thru all the gears...and nothing moves. But if I leave it in R or D for a while the tires start to spin. The fluid level is good. But the trans is 25+ years old and has lost fluid several times (busted pan, etc). Most recently it threw a fit, blew out the dipstick and several quarts of fluid. Like Old Faithful it was. Is it toast?

 

[old round fart]

I’m not a trans man but that doesn’t sound good! I think it’s trans time. Look for a 700 r4!

 

[Spanky]

I would stay with the TH400 myself. They're pretty tough and not that hard to work on. Here's some info I copied off the H.A.M.B.

Before you pull that tranny, I would check 2 things. First, make sure your governor valve is free. Here's how to check it: hold it by the plastic gear, and snap the weights in and out while watching the inner valve. It should be sliding up and down. If it's stuck, drive the 1/8" roll pin out, pull the plastic gear out, and then pull the valve out. Clean it out, lube it with WD40 and make sure it's free when you put it back together. Also check your modulator valve, it's in the case, behind the vacuum modulator. While it is possible for one of the shift valves in the valve body to stick, it's not likely. Also the kickdown solenoid could cause it not to shift. It doesn't have to be plugged in to cause a problem. Take one off another trans & check it out.

 

[Indycars]

would stay with the TH400 myself. They're pretty tough and not that hard to work on.

Remember he doesn't get over 60 mph and rarely ever stands on it enough to get
into boost! hehehe!

I like getting 21 mpg on the highway at 70 mph with an overdrive trans (200-4R), the
motor is just loafing along at 1900 rpm.

 

[Indycars]

My TH400 is acting strange. I've put the car's rear up on jacks, and I move the shifter arm at the trans to see what happens. I can run thru all the gears...and nothing moves. But if I leave it in R or D for a while the tires start to spin.

How does the fluid look? Does it have metal in it? Does it smell like it's burnt?

The clutch packs are doing their job for some reason. Could be the clutches or there is no
pressure to apply them. Since you don't have any gears, then it points to the pump being
the common denominator.

https://www.crankshaftcoalition.com/wiki/TH400_rebuild_tech

 

[PotvinGuy]

Spanky, thanks for the good info.
Indy, you know too much...now you must be silenced...permanently.

There's a new symptom. The trans has 5 gears, right? P,R,N,D,L. Well, I just found a new one below L! It seems to be another Neutral; nothing moves.

Looking at left side of trans. Now it may be my fault. I did some small mods inside the trans years ago to make the electric shifter faster. Of course as long as it doesn't hurt anything I can just ignore it. But I'll still drop the pan sometime and see what is going on.
And there is new behavior. Now the gears seem to work, at least with the tires off the ground. It's like the trans is possessed. I'll drop it and see if the ?#*@% car moves.

 

[PotvinGuy]

Fluid is a nice clear red. Indy, that good link gets you a reprieve.

 

[Indycars]

What you have labeled as L should be 2nd gear and ? is low or 1st gear.

 

[Indycars]

Indy, you know too much...now you must be silenced...permanently.

I always thought the wife would be the one do that, but if you must be first......

 

[PotvinGuy]

What you have labeled as L should be 2nd gear and ? is low or 1st gear.

Good grief, do I feel silly. I never use 2 or 1, just D. I forgot all about 1st. Jeez, my dementia is showing

 

[PotvinGuy]

The vote is in and I am certifiable. Now the tranny seems to be working, but the electric shifter isn't selecting gears correctly. And I am going to take a shower and a nap. Then maybe I can figure it out.

 

[Indycars]

The vote is in and I am certifiable.

 

[PotvinGuy]

Madness takes it's toll. Let's do the time warp again! My trans has gone back to not having a 1st gear..or maybe a reverse..in any case there are only 5 stops on the shift lever. I have been able to put it in neutral, but the trans makes "ratcheting" sounds, like it's not quite sure. I guess I'll drop the pan tomorrow and see what is inside. Maybe the detent wheel has jumped a notch. Stay tuned.

 

[Gerry]

Normally when you hear ratcheting sounds its the paul bouncing off the park plate (it means the outut shaft from the trans is turning so you have some kind of drive through it.. Park is designed so that it will not engage at speed, just bounce the paul away. Could just be that your selector lever/system is out of adjustment.

Both rear wheel off the ground put it in Park. Grab both wheels at the same time (if normal open diff) and try to turn them. If they will not turn you are in park. If they turn or ratchet you are not fully in park.

The other reason for the ratcheting is that you have drive through the trans but the drive line is broken or ripped out further down. Prop shaft, drive shafts or diff.

TH400 is a 3 speed. You will have P R N D 2 1. Some had lock up converters if fitted with the aftermarket kit.

 

[T-Test]

Sounds as though the one way clutch is broken or the converter/front pump broken.

Take it out and carry it to Rick---he'll fix it!! It's broken but it can be fixed.

 

[fletcherson]

Sounds like deeper investigation is imminent. Hope you installed a drain plug on the pan. Me, I have learned to loath working on auto trans... too many experiences laying under them with fluid dripping everywhere. I now let them sit and drip overnight or at least an hour or so to minimize this but the valve body is full too. I would pay close attention to the selector on the valve body before dismantling it just to rule out something simple, especially since it has been modified and you installed a electronic solenoid gizmo, from memory... my thought relating to that is you may not have noticed a change in its operation as one being shifted with a traditional linkage type shifter where you would feel the detents, etc...

 

[PotvinGuy]

I had to go to Dallas to sort out family, but back at it now. Dropped the Derale pan:

Pretty clean inside, typical thin grey muck on bottom (clutch material?). No shavings or other bad news. Now I've going to do what Spanky suggested. Also, I had made a small mod to ease shifting, a washer under the detent spring, and I've removed it since it seems to not hold P at well as it could. And I'll compare what I see to the pics in the TH400 manual.

 

[Gerry]

Pretty clean inside, typical thin grey muck on bottom (clutch material?).

Almost certainly T Converter muck. We see it all the time. Converters always spread this muck, even 3 months after a rebuild.

 

[PotvinGuy]

Learn something new every day. What in the TC could make this muck? Maybe something from a mod or rebuild?

 

[PotvinGuy]

Have removed the governor. Reminded me of my days in EOD, slowly twisting and pulling and sweating bullets, but that's a story for another time.

When I push both primary weights in, the inner spool goes down about 1/8". Then pushing both spring-loaded secondary weights moves the spool down some more. There is minor scoring on the shaft lands. This all seems normal per the book. I shall continue to explore.