CAB SWAP

‘79 low hump cab going on to my ‘86 high hump K-10

What do I need to know?

Also I plan on bringing over my ‘86 power locks, windows, and HVAC blower motor.

New cab doesn’t have power locks and windows and is missing blower motor.

Lastly, what do I need to know to keep ‘86 column with wipers on signal lever and use the newer gauge bezel?

Might be some clearance issues with the low tunnel, if you're planning on using the '86 front clip, you'll need to do a bit of cutting and fabricating to be able to use the hood hinges and cowl filler panel. Wipers are different between the two generations too. Starting in '81 the hood hinges migrated from the fenders to the upper corners of the firewall. The wipers use to tuck under the hood at the base of the windshield. In '81 the hood got a bit shorter, they added a filler panel between the back of the hood and the windshield, and the wipers went through that instead of tucking down out of sight.

Gonna have to swap humps.

...swapping humps...lol

Jrgunn5150 said:

Gonna have to swap humps.

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Did that in college.

Will I have to cut out and weld in from original cab?

What about all the little things like windshield washer and headlamp dimmer switch. How much is involved in transferring over from 86? What can I still use from 79? Which is parts best to keep?

I kinda figure we are going to have to cut the hump out and weld in the one from the 86. Luckily that is the one place not rusted to hell and back.

I figure we will try to keep 86 hood hinges and wiper/washer system and cowl.

What I’m not sure of is should we just try to keep all 86 dash wiring and gauge cluster? Also need 86 Heater blower. No blower on diner cab.

echo7bravo said:

Did that in college.

Will I have to cut out and weld in from original cab?

What about all the little things like windshield washer and headlamp dimmer switch. How much is involved in transferring over from 86? What can I still use from 79? Which is parts best to keep?

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Personally, I would just use all the 79 stuff and keep it simple. Alot of silly thing's changed in between, like the high beam switch, turnsignal stalk, dash pad, etc etc.

echo7bravo said:

I kinda figure we are going to have to cut the hump out and weld in the one from the 86. Luckily that is the one place not rusted to hell and back.

I figure we will try to keep 86 hood hinges and wiper/washer system and cowl.

What I’m not sure of is should we just try to keep all 86 dash wiring and gauge cluster? Also need 86 Heater blower. No blower on diner cab.

Click to expand...

On the transmission tunnel issue: If the clearance is too close - but only by say just an inch or two - you might consider using a conservative body lift kit. I will be facing a similar issue soon myself. Only in my case, attempting to mount a 2WD cab on a K30 with a TH400/NP205. After taking careful measurements (basically sticking my fist in the gap between the cab floor/transmission bell housing), I feel confident it will clear. So I am taking a wait and see approach. When the day comes to drop the cab on the frame, I'll have two sets of mounts on hand - a stock set and a 1" lift set:


What I’m not sure of is should we just try to keep all 86 dash wiring and gauge cluster?

The cluster connectors on a 79 and an 86 pin out identically (as long as you are going gauges to gauges). So you can leave the 79 dash and it's wiring intact:







Just saw your post about wanting to have a column mounted MFS, H/L dimmer, etc. If you want to drop your 86 column in the 79 dash (and I don't even know whether it will even be a mechanical fit), that changes things.

The 79 harness will only have a steering column connector for turn signals, hazard switch and horn button. As you know the leads for the wiper controls and dimmer switch will be routed elsewhere. But it is really NBFD to bring those over to your 86 column. The wiper wiring is identical and the dimmer switch is too. The only difference is that the common lead from the H/L switch to the dimmer is LT BLU in the 79 and YEL in the 86.

So to integrate the 86 column and it's additional associated controls into the 79 cab will require...get ready...cutting and splicing 8 leads. I think you can handle it.

Also need 86 Heater blower.

Blower motor - go to the junkyard.


No blower on diner cab.

Oh wow, you scored one of those rare diner cabs? I've heard about them. Those are the ones that if you open the glove box you get served cocktails and hot food. Awesome! I've seen them on Amtrak before, but never actually in a GMSB.

Jerry, I was just looking for you. Sent you a message even.

[QUOTE="chengny, post: 406665, member: 1261"

No blower on diner cab.

Oh wow, you scored one of those rare diner cabs? I've heard about them. Those are the ones that if you open the glove box you get served cocktails and hot food. Awesome! I've seen them on Amtrak before, but never actually in a GMSB.[/QUOTE]

I was thinking maybe a drink cooler actually. LOL What was rare was the factory tachometer. Will probably just part it out to someone wanting one if I keep the 86 gauges

chengny said:

Oh wow, you scored one of those rare diner cabs? I've heard about them. Those are the ones that if you open the glove box you get served cocktails and hot food. Awesome! I've seen them on Amtrak before, but never actually in a GMSB.

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chengny said:

On the transmission tunnel issue: If the clearance is too close - but only by say just an inch or two - you might consider using a conservative body lift kit. I will be facing a similar issue soon myself. Only in my case, attempting to mount a 2WD cab on a K30 with a TH400/NP205. After taking careful measurements (basically sticking my fist in the gap between the cab floor/transmission bell housing), I feel confident it will clear. So I am taking a wait and see approach. When the day comes to drop the cab on the frame, I'll have two sets of mounts on hand - a stock set and a 1" lift set:

Click to expand...

I am planning on looking at moving the cab over this weekend being that I am off for three days. I will let you know how much clearance there is in the 2wd cab on the 4wd frame and if I needed lift spacers.

I am wanting to bring over my power windows and door locks. Do you know if the harness has a disconnect or will I just have to trace back the harness and splice in the 12v and just ensure there is continuity from door to door?

echo7bravo said:

I am planning on looking at moving the cab over this weekend being that I am off for three days. I will let you know how much clearance there is in the 2wd cab on the 4wd frame and if I needed lift spacers.

I am wanting to bring over my power windows and door locks. Do you know if the harness has a disconnect or will I just have to trace back the harness and splice in the 12v and just ensure there is continuity from door to door?

Click to expand...

This was written for someone else - who hadn't yet made up his mind whether he was going to go for it. Ignore the parts that don't apply to you.



The P/L & P/W wiring is contained within a single harness. The combined harness breaks up into 3 parts

1. The cross-cab section
2. LH door group
3. RH door group

The door harness sections are fairly straight forward - they contain the connectors that plug into the window regulator motors, the lock solenoids and the associated switches. They separate from the cross-cab section at a 2 piece connector (little one for lock and bigger one for windows) out near each door.

The cross-cab section has the connectors that plug into the fuse block and also the door lock relay. The windows have no relay - just the motors and switches in the doors.

The best way to do this is to hit the junkyards or watch C/L for someone parting out an 81 - 87 truck.

Neither the locks nor the windows is a complicated system - and the wiring could be fabricated - but it is so much easier to pull an OEM harness out of a junk truck. Since you already have fully loaded doors, the only thing you would need to do the job would be a lot of wire and the previously mentioned lock relay. But trust me - even if you have to search for a while - find an OEM harness to install.

There are 4 holes that need to be drilled - for the wiring to make the transition from the A pillars to the door shell. There is also a short rubber conduit that the wiring passes through as it makes that pillar to door transition. There is a backing flange for each end of each rubber conduit where the holes are located.

Placement of the holes is critical but even if your truck never had power W/L's there are marks on the A pillar where they are to be drilled - actually there are just little dimples where the mounting screws for the flanges (for the rubbers) are to go. Just use a step drill and make a 1 3/8" hole for the wiring bundle.


That is the entire scope of the upgrade.

One suggestion:

Once you have located the harness and before installing the new doors, run the wires out to the door components and test everything. Hook a battery charger up to both leads that would normally plug into the fuse block. Run your windows up and down and cycle your locks . This is only because its much easier to repair/replace door components while they are on the bench. Plus when you finally do install the system your will have functioning windows and locks from day one.

I am doing this as we speak as well, so if you have any other questions, come on back.