What tranny in a 1979 GMC K2500 auto?

[Jesse Jaymes]

Sorry for the many questions, but I am shopping for trucks a long way from home and more often than not, I either get a woman, who just knows how to start it on, or a dude, who barely knows how to start it.

Found a 1979 K2500. It's an auto, which I did NOT want, but it's very clean. Lady has no idea about what it has or does not have. But she told me it's an auto.

I did see a pic to confirm that it does have the 14FF rear axle. So that's a bonus.

I am guessing it's a TH400 with a NP205. It's all original. So could there be any other possible options?

Please don't tell me it could be a NP203 and TH350....

 

[pseudomike]

I had a '78. It was a TH400 NP203. I doubt you will have a 205 in a '79 3/4T but I could be wrong. Tell tale without climbing under it will be the full time 4wd either no locking front hubs or the t-case shifter. It is definitely a 14FF and likely a 10B front (perhaps a 44...can't remember the cutoff).

 

[Jesse Jaymes]

Has manual locking hubs from the pics. And I think I asked the lady before what the shifting pattern is on the t-case. I don't recall what she said.

 

[75GmcJimmy4x4]

Sorry for the many questions, but I am shopping for trucks a long way from home and more often than not, I either get a woman, who just knows how to start it on, or a dude, who barely knows how to start it.

Found a 1979 K2500. It's an auto, which I did NOT want, but it's very clean. Lady has no idea about what it has or does not have. But she told me it's an auto.

I did see a pic to confirm that it does have the 14FF rear axle. So that's a bonus.

I am guessing it's a TH400 with a NP205. It's all original. So could there be any other possible options?

Please don't tell me it could be a NP203 and TH350....

could be thats my combo................................

 

[75GmcJimmy4x4]

Has manual locking hubs from the pics. And I think I asked the lady before what the shifting pattern is on the t-case. I don't recall what she said.

tell her to just take a pic under the truck of the tranny and the t-case shifter knob

 

[toomany]

could be thats my combo................................

That's what mine had too. Mine is a 77 though.

I read somewhere that autos got the 203 and sticks could be had either way. With the part time being more common.

 

[pseudomike]

The hubs really aren't an end all be all. A lot of them were converted, mine was, so it really only holds true if it's an all original truck. The t-case pattern or shift knob should tell you for sure. I can't remember that well know other than 4x4 was 4loc on mine.

 

[jonathon]

I thought by 79 GM had phased out the 203?

 

[b454rat]

79 was the last year for the 203. My 79 dually had a 400/400/203, and all original.

 

[jonathon]

Interesting...

My neighbor's 77 K20 has a 400/203 in it.. and I know it's stock. Still the original motor though he swapped the heads early on.

 

[Burbdood 74]

My dad had a 79 3/4 ton with a 400/400/205 all stock.

 

[onetonbb74]

I had that same truck, mine was a gmc high sierra k25 350/400/203.

 

[pseudomike]

Ok, I was doing some more research on this. 1979 was the last year of the 203. 1980 was the only year of the TH400 205 in non-1TON trucks. In 1981 GM went to the NP208. We all know that car makers do funny thing on model year splits and such. This said, a '79 should have a NP203 but there is a slight chance (if a late '79) that it could be a 205 truck. This would possibly explain the claim of a 400/205 '79 above.

Mike