Transmission Issue

[2bo.c10]

Hi All,

I have a th400 in my 65 c20. Ive had a few issues that Im hoping some of you may be able to help me figure out before I have to spend money. It is a column shift.

Some background:

I changed the pan gasket and filter in hopes that it would stop dripping tranny fluid. It was dripping A LOT. Like...almost all of what I put in was eventually ending up the ground. I have yet to put any tranny fluid back in it since I've been working on other things (wiring & lighting) so I didnt want to have to deal with more leaking tranny fluid.

When it does have tranny fluid in it, I can shift into the low gear and the truck will being to move forward and I can accelerate. When I click up a gear to my 2nd low gear, it again will move and I can accelerate forward. The problem comes when I put it in DRIVE. It will not accelerate forward and will not move forward like most cars do when put into drive.

Any thoughts on what could be wrong? Linkage? Gears? Thoughts? Help! What are some things that I can check or do prior to bringing it to the tranny shop?
Im not familiar with transmissions or exactly what they entail. To get it to a tranny shop, I'd have to tow it. It is currently in my garage which, since it is not drivable at the moment, makes it very difficult to get out- let alone get onto a trailer.

Thank you everyone for your continued help and support!

-2bo

[chevylookin]

Where is the fluid coming out of? Pan? Front or rear seal? There could be a number of issues wrong. Something as simple as a linkage out of adjustment to toasted pump bodies and diaphrams. Who knows, it just might need TO BE RESEALED. But I can tell you this: if it is dumping that much fluid, you probably have no other choice than to drop the whole tranny. Your best bet is to get in touch with a tranny guy (shop), see what he says and work out a deal for him to disassemble and inspect. He will probably give you a certain diagnosis for around a$100. It sounds like you want to keep this on a tight budget. So you're gonna have to do the dirty work. Th400s are plentiful and finding a good used one or a reasonable rebuilt one is easy and economic. I found a good used 700r4 and swapped my buddys old granny 4 speed with TV cable and shortened driveshaft and everything to get it running for less than $700 a couple years ago. No big deal. There are tons of articles and info here to get you confident-ally started. Drop the darn thing and find out whats going on.

[2bo.c10]

Originally Posted by chevylookin

Where is the fluid coming out of? Pan? Front or rear seal? There could be a number of issues wrong. Something as simple as a linkage out of adjustment to toasted pump bodies and diaphrams. Who knows, it just might need TO BE RESEALED. But I can tell you this: if it is dumping that much fluid, you probably have no other choice than to drop the whole tranny. Your best bet is to get in touch with a tranny guy (shop), see what he says and work out a deal for him to disassemble and inspect. He will probably give you a certain diagnosis for around a$100. It sounds like you want to keep this on a tight budget. So you're gonna have to do the dirty work. Th400s are plentiful and finding a good used one or a reasonable rebuilt one is easy and economic. I found a good used 700r4 and swapped my buddys old granny 4 speed with TV cable and shortened driveshaft and everything to get it running for less than $700 a couple years ago. No big deal. There are tons of articles and info here to get you confident-ally started. Drop the darn thing and find out whats going on.

I believe it is (or was) leaking from around the modulator. I replaced the modulator too. I do want to bring it to a tranny guy and try to salvage this one if possible. I know it is possible to get another for relatively cheap. Maybe thats a better way to go? Are all TH400's the same or do I need to find a specific one for chevy / my engine?

Thanks for the reply!

[Captainfab]

No, not all TH400's are the same. Aside from the Chevy or BOP bellhousing bolt pattern there are different tailshaft lengths as well as a bolt on yoke or a slip yoke.

[rvrfoot]

I think is to try to fix what you have.