1983 700R4 auto to 1976 SM465 manual transmission swap

[Rick1972]

My son and I are planning on doing an auto to manual swap in his 83 C20 from our parts truck which is a 76 C20. The transmission crossmember was destroyed when it was parted out.

Questions
1. Is the crossmember specific to the SM465?

2. Will the cab need to be lifted to install the manual clutch z-bar linkage?

Any other advice?

We do have an NV 4500 out of an OBS available. Would that be more difficult to swap in. We have a fresh 350 V8, that is slightly modified.

I attached a picture of the current state of the truck.

 

[Strick]

The crossmember should work and the holes for the Z-bar chassis mount should be in the frame already. The floor is going to be the issue with the swap. The pan should unbolt from the 76 and I would cut the surrounding floor and graft into the current cab to make the install easier. I did this on a 2WD cab several years back when putting on a K10 truck.

Strickland

 

[Rick1972]

We sold the cab to help fund this.
Maybe we can buy a cover off a boneyard truck. I understood the 83 trucks would have been hydraulic clutch - would that Z bar have been necessary then?

 

[Catbox]

Manual transmission floor as referenced above...

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This was as we were stripping the inside so we could clean and paint the floor with rustoleum.
It looks much better than this photo shows.

 

[bucket]

The crossmember is not specific to the 465, however, there were two different styles of crossmember, depending on the year and if the truck had dual exhaust originally. Either will work, but you may need to drill new holes in the frame.

'83 (and '84) were still a mechanical clutch linkage. Everything should transfer over from the parts truck.

You will need a high hump floor cover, like what Catbox posted. However, sometime in the 80's, the floor stamping changed, so that may not be the exact cover that you need. @TotalyHucked posted a bunch of great info regarding the floor stampings, I'll see if I can find that thread.

Lastly, the z-bar linkage. Hopefully your frame already has the holes to mount the support bracket. Otherwise, it may be a royal pain to drill those holes with the cab mounted.

 

[CalSgt]

I’d bet you need a longer drive shaft so hopefully you got that from the donor. It’s much cheaper to have a shaft shortened than lengthened.

Do automatic trucks come with the clutch pedal bracket in the cab? That part is a PIA to get out, it’s the whole dang steering column support, brake pedal bracket, brake master cylinder/ power booster bracket.

We made the opposite swap when I was a kid, we removed the clutch pedal and just shimmed that section of the assembly with a piece of pipe. We also robbed the wide Auto type brake pedal from a donor truck, it fit the manual bracket just fine.

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The Z bar linkage can be installed with the cab in place but not sure about the support bracket, @bucket sounds right on about the holes in the frame. If they’re there should be fairly simple.

Here’s the best picture I have of the support bracket on my older K10 frame, your newer 2WD frame may have different holes and landmarks but should give a rough idea of how and where it goes.

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Here’s the approximate location of the clutch rod hole in the cab (looking from underneath) there should be a few dimples for the screw hole locations (orange arrows). There is also probably a center divot for the hole itself. 2” hole IIRC.

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Did you get the column out of the manual donor truck? You should be able to unhook the neutral safety switch for the automatic (top of the column near firewall) and figure out how to hook it to the NSS for the SM465.

You’ll also need to wire your reverse lights up to work with the SM465, the automatic uses the same NSS for back up lights and starter safety. Each has their own harness plug on the NSS on mine.

I don’t suppose anything needs to be done with the lock-up torque converter wire on the brake light switch. It just grounds out when the brake pedal is pressed, just terminate it and tie the wire up somewhere out of the way.

That’s all I can think of at the moment