1971 C10 250 I6 Transmission Question

[Mike-P]

Hi Everyone,

Hope you are all well. I recently picked up my first C10, I've always wanted one and finally stumbled across a 71 with a frame off resto for a good deal. It currently has a 250 I6 with 4 Speed Manual Transmission(Muncie?). I recently discovered a leak in the tranny and it had me thinking about converting the truck to automatic at this point.

My question is, it appears that newer transmissions with OD are the recommended upgrade here. Could you suggest what automatic transmissions would be compatible for a 71 C10 with a 250 I6?

Thanks for your time.

-Mike

[68bowtie]

hi there. don't know the answer to your question, but welcome and nice looking truck you've got there.

[wbc409]

Most would recommend the 5 spd from a 1 ton or 3/4 ton. The 5 spd out of the 1/2 ton trucks is pretty weak. I believe the recommended 5 spd is the NV4500.

[Overdriven]

The 250 I6 has the same Bellbousing bolt pattern as a small block Chevy, so any 200r4 or 700r4 with that bolt pattern will bolt right up. Personally I'd go with the 200r4 for its more even ratios and smaller size. I don't know how either compares to the dimensions of the SM465 that's probably in your truck but you'll likely need to move the transmission crossmember and modify the driveshaft length either way.

You'll need a neutral/internally balanced flexplate from a I6 or small block, just count the teeth on your flywheel or look it up because I don't know it. Can't really help with the torque converter either but I'd assume a stock I6, V6 or small V8 would be fine.

[Grumpy old man]

Automatics are for girls

[Mike C]

As mentioned above, either the TH700R4 or the TH200 4R (my preference!) are good. And for a manual, a T5 from a 4.3 equipped S10 or Astro van would be the way to go.

[Mike-P]

Thanks for all the help. I think I am going to spend the next 6 months gathering the parts and hopefully grab an automatic steering column.

Much appreciated.

-Mike