TH400 drive off and shift problems/weird acting

[Dave15]

Hi guys and girls,

my TH400 is showing a strange behavior, since 2 days when i come to a stop at a for eg. traffic light and i want to go i hit the gas like always and there is a 50:50 chance that it wont instantly go forward, takes a few seconds and little more RPM than it will move, its not always

secondly since yesterday this problem also occurs in reverse gear and additionaly (thank god it just happend two times until now) the trans can´t decide between 2. and 3. gear and jumps 4 or 5 times through the gears until it stays in gear.

i asked Doc. Google but there was no similar thing to find.

 

[NickTransmissions]

How many miles on the trans? Any recent work done to it?

Delayed engagements, "hunting" usually indicates burnt clutch packs...Sounds like it needs an overhaul.

First check fluid level if you haven't already and smell it. If it smells burnt, drop the pan to see what's at the bottom. Lots of burnt clutch material and dark/black fluid will confirm what you may already be suspecting.

 

[squaredeal91]

Had similar symptoms on a th400. It was in an 84 1 ton. Truck sat a few years till I got it. Right away knew something was up with the transmission. I Kept doing burnouts and fried it. When changing transmission and flushing lines for replacement transmission I realized the cooler lines were clogged. Right then I realized that the transmission was probably okay when i got it and it was simply a clogged line.

 

[NickTransmissions]

Had similar symptoms on a th400. It was in an 84 1 ton. Truck sat a few years till I got it. Right away knew something was up with the transmission. I Kept doing burnouts and fried it. When changing transmission and flushing lines for replacement transmission I realized the cooler lines were clogged. Right then I realized that the transmission was probably okay when i got it and it was simply a clogged line.

Good callout on the line and cooler flushing - both must be flushed before reinstalling the trans after overhaul.

I always advise doing burnouts in manual low to ensure you have as many applied elements involved to spread the stress out so no one clutch pack or band suffers.

 

[squaredeal91]

I was younger and having fun but was pretty mean to it. Next trans was out of an 81 diesel with that Warm 454 it would pull good 1st to 2nd gear burnouts often. And would
tow anything but Got 14mpg no matter what period. ?? Lol. Loved that 3+3 and miss it.