cab swap

[seafoam68]

Hey guys, discovered something different about my cabs. I want to put a '81 c-30 cab/clip on a '80 c-30 frame. (The 81 is is much better shape than the '80) What I noticed is the '81 is an automatic truck with a "low" hump floor and the '80 is a 4 speed cab with a very high hump. Question is, why the increadiable difference, and will I be able to use the "auto" cab with the smallblock/4 speed combo on the '80 frame. I had planned to merely cut a hole in the flloorboard for the shifter, but now I don't know if the trans will fit under the low hump floor. Anybody done this ? Thanks.

[Stitch]

you may have to cut the high hump out and put it in the low hump cab

[ToughBowtieTruck]

Cutting a hole just for the shifter will NOT clear the transmission alone. You will have to cut a big hole . . .

73-80 or so cabs for both 4 wheel drive and manual transmissions use a bolt on hump/tunnel cover.

In 1981 for sure however, GM got rid of it. The manual transmissions and 4x4s just got a different stamped cab, with a high hump.

So you either need to modify the hump or get a 73~80 manual trans tunnel and bolt it in place. The 4 speed stick as well as transfer cases were very tall/wide compared to a 2wd automatic transmission resulting in the difference you see.

I have an 86 2wd cab on my '77 stick shift, and no, the trans would not clear the floor by a long shot. I used the bolt in tunnel from the original '77 cab, helping to keep it era correct.

Does the 80 have the bolt in tunnel or not?

[seafoam68]

Thanks for the info, guys. I have not removed the mat yet, so I don't know if the tunnel is a bolt-in. What is confusing me is what is the vast difference ? Is the '80 model 4 speed trans so tall, compared to a auto trans ?

[old Rusty C10]

i always thought the difference was the 2 and 4 wheel drive but maybe its because of the shifter and the height of the gearbox case too

[GM72K10]

Originally Posted by ToughBowtieTruck

Cutting a hole just for the shifter will NOT clear the transmission alone. You will have to cut a big hole . . .

73-80 or so cabs for both 4 wheel drive and manual transmissions use a bolt on hump/tunnel cover.

In 1981 for sure however, GM got rid of it. The manual transmissions and 4x4s just got a different stamped cab, with a high hump.

So you either need to modify the hump or get a 73~80 manual trans tunnel and bolt it in place. The 4 speed stick as well as transfer cases were very tall/wide compared to a 2wd automatic transmission resulting in the difference you see.

I have an 86 2wd cab on my '77 stick shift, and no, the trans would not clear the floor by a long shot. I used the bolt in tunnel from the original '77 cab, helping to keep it era correct.

Does the 80 have the bolt in tunnel or not?

My 83 DOES NOT have a stamped trans tunnel and has a bolt removal type like the earlier ones, could be the fact that it is a K30 dually but maybe not. Definitely needs the high hump for the 4 speed and NP205. The Military CUCV K30s (84-87) have the "stamped" high hump. Why not just cut out a high hump from a C30 junkyard truck and weld or find an early style high hump and bolt it in. Good Luck.

[seafoam68]

Thanks. Both of my cabs are two wheel drive. I will try to remove mat and take a pic tomorrow. Just by looking at your pic it seems like my tunnel is alot higher than that. I will get a pic and maybe a measurement.

[Greenlee]

I have a bolted hump from an 1983 half ton. Yours should be bolted and easy to take out. From what have seen they are weled (or a different cab) after about 1984.