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Low tech question square body floor pan to frame clearance

Squamch

Squamch

Canadian
Joined
May 19, 2020
Member Number
93
Messages
1,644
Loc
republic of Vancouver island
Buddy is LS/4L80E swapping a 78 gmc 3/4 ton. I was under it helping lay out where the 2wd floor pan needed to be cut to clearance for the trans, and noticed that he only has 3/8" to 1/4" between the floor pan and the frame, with new energy body mount bushings in place. Seems like not enough to me, or am I out to lunch?

Pic of one of the first times the motor went in, just for fun.

1000002558.jpg
 
Mine is about 1/2" towards the back of the foot area then gets tighter up towards the pedals. Looks about 1/4"

You ain't trippin :flipoff2:
 
When I get a minute, I'll check my 86. I put a 2wd cab on it and left the low hump floor. I do have a 1" body lift, but can still measure and subtract that.
 
Might be a good idea to pilot drill holes thru the flat shelf behind the seat from underneath where the rear cab mounts bolt up, with a bolt with a 1/4 hole so you can drill a hole saw hole in that flat back of the seat spot.

As its pre ordained that the 1/2 bolts that hold the cab to the frame will rust solid inside under that unreachable spot.
 
toomany said:
When I get a minute, I'll check my 86. I put a 2wd cab on it and left the low hump floor. I do have a 1" body lift, but can still measure and subtract that.
Click to expand...

Sometime in the early 80's the tunnel changed shape and didn't unbolt anymore. Probably to do with packaging of OD transmissions and aluminum tcases. '91 crewcabs and 2500 Burbs had a factory 4L80E.
 
1983 was the last of the removable transmission tunnel cover sheetmetal in a civilian chevy truck.

Unless you have a m1009 chevy blazer cucv, those are most likely removable up to the end of that series of the 1.250 ton cucv which was from memory 1987.

u2slow said:
Sometime in the early 80's the tunnel changed shape and didn't unbolt anymore. Probably to do with packaging of OD transmissions and aluminum tcases. '91 crewcabs and 2500 Burbs had a factory 4L80E.
Click to expand...
 
My 74 is removable. My 84 was not. I still have a piece of the 84 floor pan to replace my 74's rot holes. They did change the dimpling but, PAE is probably spot on for the year change.
 
My 78 gmc sheet metal was also removable, made it real easy to R&R the manual transmission.

Early panel was (front to rear) shorter than later so early does not interchange with later.
 
PAE said:
1983 was the last of the removable transmission tunnel cover sheetmetal in a civilian chevy truck.
Click to expand...

Sounds about right.... my 87 and 91 crewcabs (4wd & SM465) didn't have removable tunnels.
 
u2slow said:
Sometime in the early 80's the tunnel changed shape and didn't unbolt anymore. Probably to do with packaging of OD transmissions and aluminum tcases. '91 crewcabs and 2500 Burbs had a factory 4L80E.
Click to expand...

Correct. 2wd auto and column shift 3spd got the low, non removable floor. All floor shift and 4wd got the high hump. Removable or not depends on the year.


I don't know the exact year of the cab I used. It still has wiper switch in the dash, so late 70's early 80's. The high hump came from a 76. It fits, but you can see the gap at the back. Once the carpet went on you can't notice it. The low floor is still there, crammed some sound deadening between the two of them.

IMG_20190825_191250.jpg


IMG_20190825_191912.jpg



I'll look in the morning and get an exact measurement. But from this picture it doesn't look like there would be much body/frame clearance without the 1" body lift in there. FWIW, I'm running a 4L60E/241 and don't remember there being any clearance issues.

IMG_20190914_191045.jpg
 
Depends only exactly where youre looking aswell.

I remember my 86 2wd not having much more than that 1/4" ish where the frame rises under the seat hump. And yes, the cab and bed were still lined up.

But there is a bit more at the forward cab mounts.

Ill be next to my crewcab tommorrow so i can get pics.
 
I have a 91 v series quad cab if it helps you out...
It is buried tho, so I hesitate to look.
 
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