Center hump

1984dually · Nov 17, 2022

1984 c30 dually. Swapping to a nv4500 from a auto. Got a removable hump from a earlier truck and it is not even close to matching the floor pan. Correct me if I’m wrong but even the high hump floors from that year(84) was not removable? Is there that much difference in the floor pans? Local yard has a bunch of square body trucks. Be better to cut out the center hump from one of those And weld it in? Don’t really care if it bolts in. Thanks

Keith Seymore · Nov 17, 2022

Column shifted 2wd vehicles got the low hump. So that would be automatics or three on the tree.

Floor shifted manuals (MY6 and M20 SM465) whether 2wd or 4wd and all 4wd got the high hump.

K

1984dually · Nov 17, 2022

I realize that. Got a high hump removable pan and it doesn’t fit the floor contour on my 84. Question is are the later floor pans different With the non removable hump?

TotalyHucked · Nov 17, 2022

Yep, '73-80 has a column shift low hump 2wd, a high hump manual floor shift 2wd and a high hump (bolt in) 4x4 whether it's column or floor shift. The high humps are all bolt in.

Then '81-83 has a column shift low floor and a high hump 4x4 bolt in hump.

Then '84-up has a column shift low hump floor and a non-bolt in high hump 4x4 floor.

TotalyHucked · Nov 17, 2022

'73-80 column shift low hump 2wd

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'73-80 4x4 high hump bolt in

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'73-80 bolt in high hump floor shift manual 2wd

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TotalyHucked · Nov 17, 2022

'81-83 2wd column shift

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'81-83 bolt in high hump 4x4

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'84-87 2wd column shift low hump

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'84-87 4wd high hump

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TotalyHucked · Nov 17, 2022

So we all know the 2 generations are the '73-80 and '81-87. BUT, the '81-83 floor and '84-87 floor ARE NOT the same. An '81-83 bolt in high hump WILL NOT match the contours of the '84-up 2wd low hump floor. We're working on a bolt in hump for the '84-up trucks, which I basically just cut the hump out of a 4wd and we're gonna make it with a lip to give different options for installation.

SquareRoot · Nov 17, 2022

Recently swapped a 4500 in my 85 K20. Mine had the high hump so the trans fit in the tunnel without issue. The 4500 I have in it now is a placeholder until I finish rebuilding my second 4500. Their both early versions (92-94) but the one installed has the non-removable tower. It is a major PITA to install with the engine installed. It requires MAJOR tilting of the engine to get the shift tower to clear the cutout in the floor. Fortunately, the other trans has the removable shift tower making life much easier. And make sure your reverse (backup) light switch is installed before the trans goes in because you cant get to it after installation.

SquareRoot · Nov 17, 2022

TotalyHucked said:
So we all know the 2 generations are the '73-80 and '81-87. BUT, the '81-83 floor and '84-87 floor ARE NOT the same. An '81-83 bolt in high hump WILL NOT match the contours of the '84-up 2wd low hump floor. We're working on a bolt in hump for the '84-up trucks, which I basically just cut the hump out of a 4wd and we're gonna make it with a lip to give different options for installation.

A wealth of good info you just dumped on us! Thanks

TotalyHucked · Nov 17, 2022

SquareRoot said:
A wealth of good info you just dumped on us! Thanks

Working in the repro sheetmetal biz has its perks lol

Ontheboulder · Nov 17, 2022

all I know is that laying out a new floor mat on the high hump is a PITA!!

1984dually · Nov 17, 2022

Thanks for the replies and the pictures. Clears up a lot of questions. Only question I have is there any difference between the 84-87 high hump with a manual 2wd and auto 4wd except the obvious hole placement for the shifters?

TotalyHucked · Nov 17, 2022

1984dually said:
Thanks for the replies and the pictures. Clears up a lot of questions. Only question I have is there any difference between the 84-87 high hump with a manual 2wd and auto 4wd except the obvious hole placement for the shifters?

To our knowledge there isn't, but I also can't 100% verify that cuz we haven't torn down a manual 2wd later truck

CalSgt · Nov 17, 2022

I'm pretty sure this '81-'83 high hump is the one my Dad retrofitted in my 1980 4wd, it didn't ever fit perfect but we were able to make it work. The factory one for my truck had already been cut up too many times, 4 speed + 205, then 5 Speed + 208 with a custom linkage to work with a GMT400 shift lever, then 700R4 + 208 with '83 shift lever...

The bolt holes near the firewall & down the sides lined up perfect but the rear was longer so a few inches got trimmed from the back and 2 new bolt holes drilled to line up with the older floor pan.

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bucket · Nov 17, 2022

@TotalyHucked that is probably the best floor hump info and pictorial that I've ever seen!

Center hump

1984dually

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