what transmission is this?

[mark]

I'm considering the purchase of a 1986 3/4 ton 4wd.  It has an automatic transmission, and I've heard that the 400 transmission is the best.  How do I tell if it is a 400? The VIN is 1GCGK24M8GS122671, and the specs in the glove compartment say option "MX1 3-speed automatic transmission".  Any insight would be appreciated.

[Snuke87chevy]

You can tell what kind of transmission you have by looking at the transmission pan on.  A TH350 will look like a square with one corner cut off and the TH400 is kind of irregularly shaped anddoesn't really resemble any shape.  From the factory, all trucks with straight-six and small block v8 engines had either the TH350 three-speed automatic or the TH700R4 four-speed autoamtic.  The TH400 was only used in big block applications.  Hope this helps.      

[mark]

Thanks, it must be a TH350, because it has a 350 engine.  What is the scoop on a TH350 - good transmission? I need a truck that will pull.  

[73K20]

The TH400 also came behind SBC's as well.  The TH350 is a good tranny, but not as strong as a TH400.  If your looking to do alot of pulling you would be much better off with a standard tranny.

[Snuke87chevy]

I didn't know that, i was always told differently.  Was it an option, like a towing package or something?  Couldn't a shift kit help for pulling trailers?