TH350 issue

[FlatBlack77]

sorry for this being a bit long winded

my 79 has a th350/203 setup. the transmission has a Jasper plate on it so its probably not the original transmission. but it could be 20 years on i really have no idea. the previous owner had the truck for almost 5 years and he never had a problem with it. prior to that it sat for a few years.

ive had it for over a year and half and never had a single problem with the transmission. i never beat on the truck or hold it in gear or anything. it hardly ever sees over 2500rpms. i dont tow or pull anything either and no offroading.

so 2 weeks ago i had planned to do the pan gasket because it leaked slightly. odd timing for this issue to arise. i was on a backroad at about 25mph and i hit a bad bump in the road that i usually avoid but my mind was on other things and it was dark. so i hit the bump pretty hard and just kept driving around 25. about 30 seconds later the transmission downshifts into 2nd which is no big deal i was going slow and very light on the gas but it didnt shift back into 3rd when i sped up a bit. then i came to a red light a minute later so i didnt think too much of it.

i didnt have any trouble for the next 3 days then i came to a stop and it didnt downshift into 1st. it stayed in 2nd. this happened once or twice over the next few days.

so i changed the pan gasket as i had planned to do and the fluid was very red and surprisingly clean. very minimal "dust" or "soot" in the bottom of the pan and no chunks. the magnet had a light coating on it but nothing horrible. the filter was very clean aswell.

during this process i noticed that the vacuum line had popped off the module on the transmission. so i replaced the rubber end and used a hose clamp so it wouldnt come off again. i figured this was the not downshifting into 1st issue.

warmed it up and topped off the fluid and took it for a spin and once it didnt downshift into 1st when i stopped. i shifted it manually and it went right into 1st then shifted normally as i got up to speed. then i stopped again and it didnt shift into 1st so i waited about 10 seconds then it did and shifted normally after that.

so i read around online and came across a few people that said a sticking governor could cause this. so this morning i pulled the governor out and it was sticking very slightly. like just barely sticking. i sprayed it with some brake cleaner and it freed it up and it passes the "gravity test".

im taking a break from it right now before i put it back together but id like some advise or any input whatsoever on the topic. ill take anything i can get ive got my fingers crossed that a slightly gummed up governor is the problem. i really dont want to have this thing rebuilt.

cheers guys!

[VileZambonie]

Well you will need to put the governor back in and tell us how it is first.

[FlatBlack77]

no difference. still doesnt want to drop into 1st when coming to a stop or slowing way down. not every time but at least half the time.

[FlatBlack77]

http://forum.73-87chevytrucks.com/smforum/index.php?topic=17358.15

i just read through this thread and realized i didnt actually check if the "valve" is moving. i just checked that the flappers move. so the governor could actually still be the problem

[VileZambonie]

It is very easy to pull apart so pop it back out and check again. If it is sticking you can usually repair it fairly easily.

[FlatBlack77]

its sticking badly. im soaking it in solvent right now

[FlatBlack77]

blew it out and freed it up now it shifts perfectly.

i guess i got ahead of myself making this thread and thinking it wasnt going to be a simple easy fix.

thanks for your help and in the other thread too Vile

[VileZambonie]

Glad you got it worked out!

[rich weyand]

blew it out and freed it up now it shifts perfectly.

i guess i got ahead of myself making this thread and thinking it wasnt going to be a simple easy fix.

thanks for your help and in the other thread too Vile

As with many things, the fix was pretty easy.  The diagnosis is where most people fall short.

Anyway, nice you got it fixed!