TH400 Problem

[fullbore]

Hello all!!

Hope someone has had this same problem. I have a th400 that as you put it into drive ans start to move when it starts to upshift to 2nd bounces right back into 1st. Then if I hold the peddle there it will go back and fourth untill i stomp on it or let off. The rpm climbs hi then shifts into 2nd. i believe with the governor. Then has a real big problem shifting into 3rd. Sometimes it does and sometimes not. When it does get into all the gears 1-3rd there isnt any slipping .
I have changed out the modulator and cleaned the " Hard " line from the intake. Also removed the governor and checked for proper valve movement and inspected the gear.
Anyone have any other ideas?
Thank you in advance

 

[HotRodPC]

if you've checked all the easy most likely to be items, like the fluid level, governor and vac modulator and still the same. Then I'd go for a pan drop with intent of a filter change and hoping the filter may be clogging or restricting fluid pick up. While the pan is dropped, you may see the obvious as in broken brass pieces or tons of metal shavings and know it's time for a rebuild. If it were a Th350 I'd say it sounds like an ailing intermediate roller clutch but I'm not positive if a Th400 is dependent upon the intermediate clutch to make 2nd gear or not without getting out the TH400 bible and a bit of research.

 

[fullbore]

Thanks HotRodPC.....figured that what was going to be needed next.

 

[K201979]

Made any headway on this problem? My 79 with the th400 is doing the same. Only when its cold and if i go back n forth thu the gears while warming it up it doesnt do it. I havnt addressed it yet but im about to change fluid and filter to see if that helps. I let you kno. Btw mine only does it first to second

 

[Matt69olds]

Time to drop the pan. Hopefully you won’t find little chunks of aluminum (about 1/8 thick, about a 1/2 inch long) laying on top of the filter or in the bottom of the pan. Sometimes the pressure regulator valve will stick, causing line pressure to go high enough to break the tabs that retain the intermediate (2nd gear) clutch snap ring in the case. When that happens, the 2nd clutch backing plate will push up on the direct drum, causing it to **** on the shaft it spins on. That tears up the sealing rings and the drum, and destroys the center support.

If you dodged the broken case bullet, make sure the detent solenoid is tight.

Lastly, it’s possible the low/reverse servo piston is cracked. The servo apply in reverse, and inside that servo is the piston for the 1-2 accumulator. If the piston is cracked, oil that should be applying 2nd gear could partially apply the reverse bamd, causing a bind up condition. Unfortunately, to check the servo will require valve body removal.

 

[K201979]

Good info. Mine only does it when its cold out and trucks cold. Would that b the case in any of those scenarios?

 

[Matt69olds]

If the govenor and modulator check out, you have eliminated all the easily accessible stuff. Drop the pan, that’s about the only sure way to judge internal condition without trans removal and tear down. All the worn clutch and thrust washer wear will end up in the pan, stuck to the magnet ( which is hopefully installed) or in the filter. Good luck!!

 

[K201979]

Dropped the pan today and it had some metal on the magnet but not too bad. Mostly just small stuff but i did find two chunks of metal that are bigger and concern me. Fluid was thin and a little dark but theres no tellin how long itd been in there and it didnt smell burt or really look too bad. Video of pan before cleaning and some pictures of the small chunks of metal:
Had to screenshot the video. Couldnt figure out how to post it.

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[K201979]

I did replace the modulator too a week or two ago. We will see if the problem persists on the next cold morning.

 

[Irishman999]

Those look like broken off case lugs. The center support is held in by a snap ring but the groves dont go all the way around, the big ass snap ring is only holding about 70% of the radius. They make a bolt in center support for TH350's that works awesome, not sure why they dont make one for a TH400.

I would suggest getting the Transgo 1&2 kit, it comes with a really heavy duty snap ring. I have used the snap ring on a case with broken lugs in a pinch. Your fluid looks red enough I would just pop out the pump, pull out the drums and pop in that snap ring. The rest of the kit is cake to install, you can fine tune how it shifts.

 

[K201979]

I will look into that but its my (only)daily so it probly wont happen soon. Id like to eventually go to a sm465/205 so i may have to start sourcing parts more rapidly than i had planned. Probly means i gotta devote some more time and $ to getting my wifes daily(84 cj7) back on the road too. Trans shifts great now after fluid and filter and shows no signs of the previous problems yet but it hasn't been real cold past couple days so im not sure yet. Even before the service it shifted good once it warmed up and went thru the gears once. Maybe its something from before a past rebuild and the cold noise/1-2 shift problems were thin fluid and filter not sealing?
Edit: the noise is kind of a whining just when its cold. Should kno in the am if its gone or not.

 

[K201979]

I was told the transmission was from colman taylor when i bought the truck so i dont kno if that would b new or rebuilt. It has a big "28" cast into the top of the bell housing and under the pan. Not sure what that means.

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[K201979]

Update: new filter and fluid, below freezing, no whine, no 1-2 shift problems. Im thinkin thin fluid+hardened seal on filter=the problems mendtioned above. Y in the cold i cant speculate tho. As for the chunks of metal, im gonna cross my fingers and follow the plan above. Anybody in southern missouri got a parts truck with a 265/205 cheap? Or a good engine for a cj?

 

[Matt69olds]

Those look like broken off case lugs. The center support is held in by a snap ring but the groves dont go all the way around, the big ass snap ring is only holding about 70% of the radius. They make a bolt in center support for TH350's that works awesome, not sure why they dont make one for a TH400.

I would suggest getting the Transgo 1&2 kit, it comes with a really heavy duty snap ring. I have used the snap ring on a case with broken lugs in a pinch. Your fluid looks red enough I would just pop out the pump, pull out the drums and pop in that snap ring. The rest of the kit is cake to install, you can fine tune how it shifts.

The “heavy duty” snap ring TransGo includes in their shift kit is a rear clutch snap ring from a Chrysler 727 trans. The included snap ring measures .098 (I think) you can fit up to .108 in the case. I think the thinnest ring is .068, the thickest is .118 but won’t fit in the 400 case groove. You can use the Chrysler rings to set the clutch clearance.

 

[K201979]

Its confirmed. 23 degrees this mornin. No noise no 1-2 shift problem. Whatever it was, was cured by fluid and filter