Low Hump to High Hump Conversion

[MtBraun]

I found a super clean 86 low hump cab that I'm going to buy. I have an 84 high hump that I was going to cut out and splice into the 86 cab. Other posts suggest the floors may not match up. Anyone done this on the later, non-removable humps? If so, how difficult was it? I still think its going to be easier for me to swap in the hump that do rockers and floor pans in my 84 high hump. Thanks all!

 

[TotalyHucked]

Don't forget about the VIN/registration headaches you may or may not encounter.

That swap should be easy, just remember to give yourself some overlap if you plan to bolt the hump in. I just cut a hump out of an '85 not long ago so we could develop it for guys who need the extra clearance in a later hump. '84-up floors are all the same other than which hump it had, so a high hump will lay right over a low hump.

This is an '87 low hump/2wd

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'85 high hump/4wd

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High hump laid over a low hump floor. You can see the flange I'm talking about. When I swap the 6-speed in my '85, this is exactly my plan, cut the hole an inch or two inside to leave a flange and make the cover removable.

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[MtBraun]

Don't forget about the VIN/registration headaches you may or may not encounter.

That swap should be easy, just remember to give yourself some overlap if you plan to bolt the hump in. I just cut a hump out of an '85 not long ago so we could develop it for guys who need the extra clearance in a later hump. '84-up floors are all the same other than which hump it had, so a high hump will lay right over a low hump.

This is an '87 low hump/2wd

You must be registered for see images attach

'85 high hump/4wd

You must be registered for see images attach

High hump laid over a low hump floor. You can see the flange I'm talking about. When I swap the 6-speed in my '85, this is exactly my plan, cut the hole an inch or two inside to leave a flange and make the cover removable.

You must be registered for see images attach

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Perfect, thank you for the detailed pics. Should be no problem on the VIN tag. I will move the VIN tag from my 84 cab to the new cab.

 

[SquareRoot]

Coincidence? I think not!

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[dhenderz]

I made the exact same swap when restoring the 77 K10 (build thread on this site) using a 77 C10 cab that was more rust free. You will need to weld in the nuts so the larger tunnel will bolt into place. Otherwise pretty simple job.

Leaving the legalities aside, there are places on the web where you can obtain correct VIN rivets for transferring the VIN tag. Not that I would know that...

 

[Bessie]

Don't forget about the VIN/registration headaches you may or may not encounter.

That swap should be easy, just remember to give yourself some overlap if you plan to bolt the hump in. I just cut a hump out of an '85 not long ago so we could develop it for guys who need the extra clearance in a later hump. '84-up floors are all the same other than which hump it had, so a high hump will lay right over a low hump.

This is an '87 low hump/2wd

You must be registered for see images attach

'85 high hump/4wd

You must be registered for see images attach

High hump laid over a low hump floor. You can see the flange I'm talking about. When I swap the 6-speed in my '85, this is exactly my plan, cut the hole an inch or two inside to leave a flange and make the cover removable.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Saw a post last year on this forum with you explaining the "Hump" specifics between years and applications. I was very impressed with your knowledge and method of explanation-short and to the point- I like that. Anywho I bought a couple cabs a number of years ago-1 for my '84 GMC 2500 that I ordered new, and one for my '95 Dodge which I also purchased new. Both are great trucks but I favor GM and "Bessie" named after my grandmother. looked for your post again and joined this forum when I found it because I am finally working on "Bessie" and I have the exact situation that you show here with the High hump laying over the low hump. Pretty much had that figured out but you brought it home. I will attach some pics of where we are and later the hump conversion, just trying now to find a hump better than Bessie's to make the job less intensive and extensive as hers is not great
and would need some restoration of it's own. Thanks for your posts. I will follow this forum and post updates on "Bessie"

an

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[bucket]

Saw a post last year on this forum with you explaining the "Hump" specifics between years and applications. I was very impressed with your knowledge and method of explanation-short and to the point- I like that. Anywho I bought a couple cabs a number of years ago-1 for my '84 GMC 2500 that I ordered new, and one for my '95 Dodge which I also purchased new. Both are great trucks but I favor GM and "Bessie" named after my grandmother. looked for your post again and joined this forum when I found it because I am finally working on "Bessie" and I have the exact situation that you show here with the High hump laying over the low hump. Pretty much had that figured out but you brought it home. I will attach some pics of where we are and later the hump conversion, just trying now to find a hump better than Bessie's to make the job less intensive and extensive as hers is not great
and would need some restoration of it's own. Thanks for your posts. I will follow this forum and post updates on "Bessie"

an

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Yup, @TotalyHucked is kinda the floor hump expert around these parts.

 

[Bessie]

Thanks Bucket I'll be back with more picks and other situations as Iknow there will be harness problems for various upgrade considerations and much more. Glad to be here

 

[SirRobyn0]

If I were doing the conversion to high hump, I'd want to bolt it down as well. I'm also going to throw this out. I'd want to seal the hump. Maybe Butyl Sealing Rope. Wouldn't want it to be glued like you'd get with RTV if you needed to remove it one day, and that stuff is pretty forgiving if there are some minor fitment issues.

 

[Bessie]

If I were doing the conversion to high hump, I'd want to bolt it down as well. I'm also going to throw this out. I'd want to seal the hump. Maybe Butyl Sealing Rope. Wouldn't want it to be glued like you'd get with RTV if you needed to remove it one day, and that stuff is pretty forgiving if there are some minor fitment issues.

Not sure which way we're gonna go yet but thanks SirRobyn

 

[Rickf]

3M strip caulk seals ok and doesn't harden up.

 

[Bessie]

Thanks, really not worried about the sealant, we've got lots of options for that . But we may be making it look like it was factory floor which means it'll be welded.

 

[Bessie]

Well gaining on her. Haven't posted in a while. Found a hump. Was a little more deteriorated than I was looking for but come out well. Got finish paint on the cab today. I'm going to attach some pics of Bessie to this day still hauling wood.

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[Bessie]

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[Br 549er]

Don't forget about the VIN/registration headaches you may or may not encounter.

That swap should be easy, just remember to give yourself some overlap if you plan to bolt the hump in. I just cut a hump out of an '85 not long ago so we could develop it for guys who need the extra clearance in a later hump. '84-up floors are all the same other than which hump it had, so a high hump will lay right over a low hump.

This is an '87 low hump/2wd

You must be registered for see images attach

'85 high hump/4wd

You must be registered for see images attach

High hump laid over a low hump floor. You can see the flange I'm talking about. When I swap the 6-speed in my '85, this is exactly my plan, cut the hole an inch or two inside to leave a flange and make the cover removable.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Howdy Sir,
Great info, I’m in the process of attempting a conversion myself and was wondering if I could pick your brain..?
76 3/4 ton frame manual trans, 1980 2wd body, 89 th400 with 205 tc will be used on the 1980 cab… what donor vehicle “hump” should I look for? What years would work? Thanks in advance!