Has anyone here actually converted a cab from low to high hump ?

[Tx Firefighter]

This topic is an FAQ- "73-87 Converting a cab from low to high hump"

I have an 85 model low hump cab and have a line on a 78 model SM465 4 speed transmission and the bolt in high hump floor from the same truck. Thing is, I don't have a way to put hands on it right now and see for sure.

My question is, will the high hump cover drop into place if I cut the hole and make arrangements for the hold down bolts ?

This may seem a stupid question, but I know from first hand experience that 60-66 trucks have a different firewall and require a good bit of modding to make it work when swapping low to high. I further know that 67-72 trucks, it's just cut the hole and bolt the hump in place. But, I've never done this on a 73-87 and my current cab is finished to near show quality. If it requires more than cutting a hole and some weld nuts I won't mess with it.

Thank you,
Kevin

[joe b]

I put a 4 speed in my 87c/10 . the floor is not like the 67-72 there is no outline like 67-72 has

[Tx Firefighter]

Did you bolt in a high hump to your previously low hump cab when you did the swap ?

[78cheyenne292]

wow this post couldnt have came at a better time i was just looking for a 4 speed manual and i was wondering what it would take to switch my hump. if someones got pics please post!!

[eke82]

yes it should but is it also 4wd or not you might have to cut part of the old cab out where it is under the seat to clear the transfer case it sets up about 2 inches higher the the 2wd cab

[f.monroe]

This may be what you are looking for . I remembered this thread and looked it up .
Frank

http://67-72chevytrucks.com/vboard/s...=383629&page=2

[Tx Firefighter]

Well the answers were kind of varied so I decided to just dive off into the project.

This is an 85 model cab and a 78 model high hump. Both trucks were 2wd. Best I can tell by looking at the junkyards, most newer model cabs like mine (85 model) had a built in high hump or a built in low hump. I could not find a later model cab with a bolt in hump around here. So, I had to use the 78 model bolt in hump. The two floor pans are quite different.

I had to reshape the edges with a hammer against a straight edge to get the contour proper to fit the floor. Figure about 10 minutes of bumping the metal, test fit, and repeat. The floors are similar but definitely not the same. The edges on the sides of the hump had to be dressed downward to make it hug the floor properly.




Lay the tunnel into place and mark the perimeter, then remove and mark a second line about an inch inside of the perimeter mark. That's your cut line.

Hillbilly Plasma Cutter...


Resulting hole...



Now bolt the tunnel in place with 5/16 bolts and nuts with washers on the underside...


Roll underneath and weld the nuts and washer combos to the cab floor.


All in all, pretty easy. Figure an hour and a half to do the work.

[lolife99]

Thia would make a good FAQ thread.
Thanks for posting.

[N2TRUX]

Originally Posted by lolife99

Thia would make a good FAQ thread.
Thanks for posting.

I agree. Lets get it done..
Posted via Mobile Device

[4x4toy]

I have a bolt in hi hump from a 4x4 blazer, 1984 I think. Does not fit my 85 C20 very well. The rear of the bolt in floor is too high in the rear. Hope this info is of use to someone. I will mock it and try to take a picture this weekend. Now I need to find a 2wd hi hump floor.

[WigglesTheHoly]

your line is alot cleaner than mine. lol



I converted an automatic to a Granny 3..Why? Because the truck was cheap and the motor and trans were free.

[N2TRUX]

Thanks for the write up Kevin. Subscribing so I don't forget to add it to the FAQ's.

[lolife99]

Isn't the 4x4 floor area directly behind the hump taller to clear the transfer case?
So would that mean there are two different high humps?
2wd and 4wd?
Posted via Mobile Device

[y5mgisi]

Thats kinda what im thinking. I never knew there was such a thing as a 2wd high hump!

[N2TRUX]

This topic is an FAQ- "73-87 Converting a cab from low to high hump"

[lolife99]

Originally Posted by y5mgisi

Thats kinda what im thinking. I never knew there was such a thing as a 2wd high hump!

2wd 4-speed manual trucks, I assume.

[Tx Firefighter]

Yes, 2wd floor shift trucks. The 4wd high hump has a larger rear raised area for the transfer case clearance up under the front of the seat.

In my local junkyards, all of the early 4 speed 2wd trucks had bolt in humps, but the later, 80s era, trucks had a built in large hump that is not removable without cutting. I did this swap to allow a 4 speed transmission underneath a low hump (factory auto trans) cab.