Need a little help w/80's k20

[Bus Ted Knuckle]

Hey guys, I spend most of my time over at the 67-72 board, but I need yoru expertness (is that a word?) with my latest project.

I have a k-20 that has been pieced together.
It currently has (I think) an 84 auto trans cab on a 80ish k20 frame that has a 350 granny 4 speed combo. I have no idea what t-case or axles at this point. It is basically just all set together, the engine+ tranny controls etc, are not hooked up. I got it in this condition. The guy got frustrated and gave up on it because of difficulty in getting this low hump (?) cab to work on this standard trans. It is missing some stuff here and there, but I have a pretty good 76 c-10 parts truck I can rob off of.

Questions:

1. Is there really any difference between an auto cab floor and a standard cab floor?

2. I have a cab on my 76 that is a floor shift model and the trans hump looks totally different. Will it fit and work on my K-20 frame?

3. If the cab fits, can I use the pedal assembly etc. from the 76 (the 76 is a 250-6cyl)

4. Will I have any trouble switching sheet metal between the two trucks? It all appears to be pretty much a bolt on deal, but there is a lot I can't see under all that

5. What parts will not be interchageable between the two trucks?

6. What am I not considering having to do when I start swapping parts from my doner 76 c-10, and this early 80's k-20?

I know, I ask too much

The good part:

both of these trucks were FREE, so I can afford to put a little $ into the project.


I really want to turn this truck into my main trailer hauler to free up my 69 to be slammed and tricked out...

THANKS!!!!

Bill

[Srubydo1986]

Questions:

1. Is there really any difference between an auto cab floor and a standard cab floor?

Yes the auto floor is lower and the manual floors ar much higher about 43-4 inches higher for the transmission.

2. I have a cab on my 76 that is a floor shift model and the trans hump looks totally different. Will it fit and work on my K-20 frame?

Dont know it might if its a high hump.

3. If the cab fits, can I use the pedal assembly etc. from the 76 (the 76 is a 250-6cyl)

Dont know i keep being told the 73-80 cabs are different the 81-87 but i dont know where at.

4. Will I have any trouble switching sheet metal between the two trucks? It all appears to be pretty much a bolt on deal, but there is a lot I can't see under all that

There were two different kinds of floor set ups one that a bolt in kind for the hump and the ones that are part of the floor and have to be cut and welded in just depends if you get lucky and have to bolt kind.

5. What parts will not be interchageable between the two trucks?

You would have to be more detailed there are alot of parts that will fit it and there are some that wont.

6. What am I not considering having to do when I start swapping parts from my doner 76 c-10, and this early 80's k-20?

The cab the man swaped is an auto cab so everything that make a manual a manual must be swapped. Also was it going to be a mechanical clutch or a hydrolic clutch setup. Also make shure the title is good hate to go through all that work and have no title.

What he started is alot of work i started the same and stopped before i even took apart my rust free truck and just fixed it heres a link to it. It may help a little. What i was doing was making a auto 2wd truck a manual 4x4 truck after desiding i didnt want an auto 4x4.

Heres that link http://67-72chevytrucks.com/vboard/s...17#post2007117 And as you can see in my sig. I to have way to many cars.

[Bus Ted Knuckle]

Ok, thanks for the info, I guess I do Have a high hump cab on my donor truck. So I may just swap the whole cab. Were there any frame changes from 73 to 87 that would affect the body or bed mounts? And I have the title covered, so we are cool there.

[Srubydo1986]

well k 20 is a 3/4 so i think you would be ok there. If it was a one ton the frame in more narrow then the 1/2 or 3/4 tons. Also body mounts are different just have to get the mount that match the frame not the body. (these are the rubber one not the one that are welded to the frame.)

I dont see why it would go on i never messed with anything older the 81 (when the remake of the front end happened) but i would say the cab mont and all are at the same places.

Also nice truck in the picture you have I alway wanted a 49-54 chevy pick.
Even if your looks to be a old work/utility truck still same front parts.

(After my truck and chevelle are done i will be getting started on my greatgrandads truck a shortbed fleet side 65 pickup been sitting for about 30-40 years. But no matter how mess up it is you can always rebuild it)

[edman87]

The difference in the floor from 80's trucks was 2wd or 4wd right? As long as the floor pan is from a 4x4, it will clear. The auto trans floor is stamped for the oval cutout for the shifter from the factory. My 87 k5 was a auto from the factory, but has the stamped indention where the 4 speed would come through. I just cut it out n the line and the shift tower comes up through the floor maybe 2". I can get you a pic in a day or so if you want to see what I mean.
I believe- may be wrong on the yaer- that 83 was the last year for bolt in trans tunnel in any gm fullsize. After that they wer welded/ panelbonded in.
If the trans seems to sit about 4" too high-hits floor- the difference is the transfer case adapter. THe adapter changed in 85. The pre 85 adapter, mount and crossmenber was totally different. I can get some pics of this too if you need. I went through this also as my 4speed and transfer case were from a 84 and I had to use the 85 up adapter to mount it up. If you use the correct year parts, everything is a direct swap.

[benoit454]

One big difference in the 73-80 and 81-87 cabs is the front ends.

Old 73-80 had the cowl made on the hood and the hinges for the hood on the fenders.

The 81-87 has the cowl and all that related on the cab and holes for the hood hinges made into the cab also.

I've heard some say you can do it, just have to retro fit the 81-87 front end on the new cab by swapping the cowl pieces over and cutting holes for hood hinges.


OR.... if your 76 front end is in as good a shape or better then the 81-87 trucks, just put the 76 front clip on with the 76 cab.


Honestly I'd think you could swap the pedals, only real difference was 76 had manual linkage clutch, upper pushrod, z bar, frame bracket ball studs, and lower pushrod with return springs, 86 or whatever had hydrualic if it was factory. I'd take the 76 stuff and leave it alone since it's already in the 76 cab?

As for other things I'm not sure I'd have to think about it alot more.

Maybe it make it easier to just hack the trans tunnel out of the 76 and put it on the 80ish truck you are building. Just cut it's low tunnel out and bolt on, screw on, rivet on, glue, on whatever, weld whatever the high tunnel in the low tunnel cab.


Questions:

1. Is there really any difference between an auto cab floor and a standard cab floor?

Yes as mentioned the auto coloumn shift is a"low hump" and a standard shift or 4x4 is a "high hump"

2. I have a cab on my 76 that is a floor shift model and the trans hump looks totally different. Will it fit and work on my K-20 frame?

I'm not sure it's supposed to be a high hump just like an auto 4x4 cab or stick shift 2wd or 4x4 either one, that's how they are listed for buying carpet. If nothing else cut the tunel out of the high cab and mount it in the low cab.

3. If the cab fits, can I use the pedal assembly etc. from the 76 (the 76 is a 250-6cyl)

I don't see why not, but umm isn't the pedals already in the 76 cab? If so then yea just use them. I'd think you could.

4. Will I have any trouble switching sheet metal between the two trucks? It all appears to be pretty much a bolt on deal, but there is a lot I can't see under all that

Yea what I mentioned above about the front end. Doors should switch, beds, umm not sure depends on which is which, short bed or long, if both the same length bed then they should swap back and forth with no problems.

5. What parts will not be interchageable between the two trucks?

Well you can't mitch and match front end sheet metal, like the inner fender or outer fender, hood grille any of that. it's either use ALL the 84 stuff or ALL the 76 stuff. Then if one piece is bad, buy a replacement for said year you would be using.

6. What am I not considering having to do when I start swapping parts from my doner 76 c-10, and this early 80's k-20?

Hmm how heavy and maybe PITA swapping cabs may be,

Swapping out all the wiring, or at least unhooking it all, rerouting/running it where it needs to be, and hooking it all back up.
New bushings for it and bolts, rusted bolts, broken bolts, rounded off, or ones that have to be cut off. other then that rusted parts of the cab or other metal.

I know, I ask too much

[Bus Ted Knuckle]

Great info guys, thanks to all of you!

Scruby, I do love those 48-54 trucks too, mine is a real old time work horse.

[Russell]

Very easy to bolt 73-80 sheet metal onto an 81+ cab, not quite as easy to go the other way around though...

The 81+ fenders mount using the same bolt hole locations as the earlier trucks, so bolting the fenders on is a very easy thing, either way.

The challenge comes with the hood + hinges. The 81+ trucks have a cowl that is not part of the hood. It is bolted onto the cowl part of the cab, and have a wiper linkage that is long enough to stick through the cowl panel. The hinges for the hood are bolted to the firewall in an 81+ truck.

In 73-80, the hood and cowl are one big piece, and the hinges are bolted to the fenders. They have a much shorter wiper linkage so the wiper arms will fit under the end of the hood where the cowl section is.

So, if you want to put 73-80 sheet metal onto an 81+ cab, its a bolt on swap, just remove the 81+ cowl, and wiper linkage, then bolt the 73-80 linkage in, and pop in the old style cowl cover, then bolt the sheet metal + hood straight on. If you want 81+ sheet metal on an older cab, you have to switch wiper linkages, then figure out a way to secure both the cowl cover, and the hood hinges to the cowl / firewall of the cab.

Otherwise, the only difference between the two year ranges is the VIN plate, they are in different places on the dash, but using the approriate interior makes that a null point.