Reverse or PNDL switch problems w C6
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Reverse or PNDL switch problems w C6
I put a brake pedal assembly including the brace from the firewall to the dash from a '79 F250 Supercab Camper special into my '77 F250 Supercab camper special. You may ask why...well the '79 produces more line pressure than the '77 at the same pedal force, plus the '79 sits a little further off the floor and is a bit more reassuring when pulling a trailer.
I measured the line pressure on the '77, and it gives about 800 psi front line pressure at 100 lbs pedal force, while the '79 gives about 950 psi. Both measured at idle vac in neutral. I also swapped the booster, and the '79 booster mounts. So this is great, but the column mounted PRNDL switch on the '77 won't clear newer '79 brake pedal. Arrgh..
My plan is now to try the auto trans mounted '79 PRNDL switch on the '77. Only problem is the '79 C6 shift shaft has two grooves in it for the switch, and the '77 does not. If I drop the trans pan and valve body, can I swap the shaft without further hassle? The brakes are much better now, so I really don't want go back to the old pedal assy.
I measured the line pressure on the '77, and it gives about 800 psi front line pressure at 100 lbs pedal force, while the '79 gives about 950 psi. Both measured at idle vac in neutral. I also swapped the booster, and the '79 booster mounts. So this is great, but the column mounted PRNDL switch on the '77 won't clear newer '79 brake pedal. Arrgh..
My plan is now to try the auto trans mounted '79 PRNDL switch on the '77. Only problem is the '79 C6 shift shaft has two grooves in it for the switch, and the '77 does not. If I drop the trans pan and valve body, can I swap the shaft without further hassle? The brakes are much better now, so I really don't want go back to the old pedal assy.
Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
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From: Hesperia, CA
I am trying to remember what I went through trying to get the shift lever out of mine to replace the seal. If I remember right the shaft hits the drum and will not come out with out a complete disassembly of the tranny. It is messy as heck to find out. The valve body has to come of and the darn fluid leaks out of the orifices forever and drips all over every thing. You might move this over to the tranny section and get a more definitive answer.
Personally I wouldn’t take it apart. I would put a back up light switch on the dash, wire past the neutral switch and just be careful and always start the darn thing in park.
Personally I wouldn’t take it apart. I would put a back up light switch on the dash, wire past the neutral switch and just be careful and always start the darn thing in park.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
My plan is now to try the auto trans mounted '79 PRNDL switch on the '77. Only problem is the '79 C6 shift shaft has two grooves in it for the switch, and the '77 does not. If I drop the trans pan and valve body, can I swap the shaft without further hassle? The brakes are much better now, so I really don't want go back to the old pedal assy.
The NSS mounts to the outer manual control selector lever, which has a hole thru the center of it that the inner downshift lever passes thru.
This inner lever has a threaded end. The NSS mounts to the outer lever, the nut and washer that retains it, threads onto the end of inner lever.
The manual control selector lever can be removed without removing the pan.
I know the manual control selector lever's oil seal (D5AZ7B498A) can be replaced without removing the pan. The manual control lever has to be removed to get at that seal.
Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
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From: Hesperia, CA
Bill he is asking about the shaft, not the lever. I pulled mine apart a couple of years ago, but just can’t remember for sure. I believe that the shaft hits the drum and will not come all of the way out. That is why I told him that this should be in the transmission forum. I am sure somebody there knows.
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Yes, it's the outer control lever which needs to be swapped out. I think the inner kickdown shaft is the same on both trucks. It's starting to look like the gear selector lever on the '79 may also take a longer link from the lever on the column down to the trans., as the lever has a quite different shape?? I sort of recall a nut on the inside of the trans case which holds it into the case. Could also mill grooves in '77 shaft for the switch if it comes to that. It's been about 15 years since I had one apart. Don't want to get into a total trans thrash, as the trans I'm pulling the lever off of is in good shape as well, and if that was required I would just swap the trans. Of course that goes down another path...the trans in the '79 has a US Gear overdrive on the back and I want to install a Gear Vendors OD thats been stting under my bench for two years. Both take a different driveshaft length I believe. The US Gear unit is almost new, (they had an upgrade program a few years ago), but the Gear Vendors can shift on the fly under full load which sounds real nice.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
DOAZ7D261B .. Downshift Lever
Fits: 1970/89 all C6's, car & truck.
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The gear selector lever from the came out of the '79 and installed in the '77 without issues. The valve bodies did have to be removed, but with a box wrench, the nut retaining the shaft can be removed, the shaft can be slid out and both the gear selector and kickdown shaft can be removed without further dissassembly. At this point the shaft seal could be replaced also. The trans mount PRNDL switch works fine on the '77. Thanks Guys.
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