727 transmission locking up
 

I have an 86 Dodge Ram 150 with the slant six and a 727 automatic trans. When it is running and put in reverse or forward it locks down so hard it kills the engine and the truck almost jumps off the ground. It acts fine in Park or neutral or if the engine is not running. I am changing the truck to a 360 w/727 trans but would like an idea of what may be wrong with the old trans and would it be worth fixing to sell. I think it must be pretty rare as I have been searching junkyards for nearly two years to replace it and so far have only found 904s behind slant sixes. Thanks for any information you may have.

Just a guess ?? A bad converter lockup clutch

Better guess than me.

that's what it sounds like to me.

Convertor clutch
 

Thanks guys. That was my first thought but I forgot to mention that after some consideration I think it is also locking the rear wheels. I guess the intelligent thing to do is, with the help of the Internet, tear it down and see if it is broken or not. Thanks for the guesses though, they make me think I was maybe guessing right. I really can't tell what the back wheels are doing when it locks I just know it jerks so hard it is like throwing a rod through the block.

Where is your idle set at?
The /6 727 is kinda rare, Trucks mostly, I would guess. Probably not much of a market for 'em. The 727 is esy to rebuild so have at it. If nothing else, you might learn why it is doing this. Then you can tell us. There is a really good book by Monroe for these transmissions.

Thanks for the info on the book.