Ive been having a dispute with some of my friends on which trans is in my truck.
Its a 3 speed auto which makes me think TH350, however others tell me it came with a 700R4. The trans is the one that was in the truck stock. ive tried checking to see if the trans was a vin K or R but theres no letter thats visable. When i tried finding a pan that looked the same as mine the TH350 looks the same. The reason i ask is that my trans needs to be replaced and i dont want or need overdrive. The big question is can i bolt up either one without having to change the bell houseing? TH350 is much cheaper then 700R4 and of course id love to save the dough.

thanks.
89 Blazer K-5.4x4 chevy 350ci. bone stock.

 

Your trans should be a 700R4.

Chevrolet K5 Blazer - wikipedia

With that said, about the only thing you'll want to watch out for is that I believe the 700R4 case is longer than a TH350, meaning your driveshafts may not be the proper length...


You'll want to pay attention to the case length because overall length doesn't mean much for a 4wd application. So you could measure your transmission to see what you have. From that chart above, the 700R4 is 1.75" longer than the TH350.

 

Still unsure because my trans is a 3 speed. D 2 1 is all it has as far as gears go.
It figures id have to redo driveline stuff. i guess i expected that. so realy i wouldnt save much at all until it came time to rebuild. That sucks. the estamates i got for a rebuild were all between $1200 and $1500. thats almost the full cost of the truck.
Thanks for the info.

 

Your truck came from the factory with a 700R4 transmission. If you only have a 3 speed, someone changed it. Look for yourself, factory brochure.
http://www.coloradok5.com/brochures/1989/blazer3.jpg

Link to the rest of the brochure.
http://www.coloradok5.com/brochures/1989/

 

If oyu go back, the last year a 3 pseed was in the K5 from the factory was in '82 and that was a manual tranny. Either you have the wrong year, or someone swapped trannies and columns.

To find out exactly what your truck came from the factory with, take your vin code to a dealer and have them run a report. It will list all the options.

 

Ok. ill try a few differant things suggested.

Thanks.