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2 speed rearend quit working on 77 Chevy C60
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69zfarmer
Posted 1/30/2010 17:46 (#1049567)
Subject: 2 speed rearend quit working on 77 Chevy C60


North Central Alabama
I have a vaccumn operated 2 speed rearend that has been trouble free till now.I also have some parts on this truck that i do not know their purpose.One part is on the firewall that the speed odometer cable goes through it also has a wire to it (see picture)The 2 speed switch on the gear shifter has a cable that goes down to the valve that sends vaccumn to rearend to operate the high and low it also has 2 wires going to the same switch along with cable.What do wires do?What purpose do these 2 vaccumn canisters serve?Also i tried to plug the vaccumn line to the govenor and the throttle blades would not open.Whats missing on the govenor?

Edited by 69zfarmer 1/30/2010 17:51




(986,1845c,holley carb,heads,truck vaccumn parts 001.jpg)



(986,1845c,holley carb,heads,truck vaccumn parts 005.jpg)



(986,1845c,holley carb,heads,truck vaccumn parts 004.jpg)



(986,1845c,holley carb,heads,truck vaccumn parts 002.jpg)



Attachments
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Attachments 986,1845c,holley carb,heads,truck vaccumn parts 001.jpg (79KB - 262 downloads)
Attachments 986,1845c,holley carb,heads,truck vaccumn parts 005.jpg (72KB - 231 downloads)
Attachments 986,1845c,holley carb,heads,truck vaccumn parts 004.jpg (53KB - 216 downloads)
Attachments 986,1845c,holley carb,heads,truck vaccumn parts 002.jpg (63KB - 199 downloads)
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Marv
Posted 1/30/2010 18:20 (#1049592 - in reply to #1049567)
Subject: RE: 2 speed rearend quit working on 77 Chevy C60



Milford, Illinois
If I was guessing, I'd say the vacuum actuator on the rear axle has a hole in the rubber diaphram.  That happened to a '63 Chevy C60 of mine.  Parts were not easy to find so I took a rubber inner tube and made a new diaphram.  Worked fine for several years and now it's gone so I don't know anymore.
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Dave Cen.Ia
Posted 1/30/2010 19:13 (#1049653 - in reply to #1049592)
Subject: Marv ?



Nevada, Iowa
Just curious, were you able to get a hold of 5 star?
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Marv
Posted 1/30/2010 23:06 (#1050013 - in reply to #1049653)
Subject: RE: Marv ?



Milford, Illinois

I got busy last week and didn't get him called, but I will for sure this coming week.

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jddriver
Posted 1/30/2010 18:57 (#1049637 - in reply to #1049567)
Subject: RE: 2 speed rearend quit working on 77 Chevy C60



Greenwood Mo
1977 trucks had points and not vacum.The piece on the firewall is the adapter for the two speed for the speedometer.NUMBER THREE IS THE VACUM BRAKE BOOSTER.
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tj_farms
Posted 1/30/2010 19:10 (#1049648 - in reply to #1049567)
Subject: RE: 2 speed rearend quit working on 77 Chevy C60



Delaware, Ohio
If you remove the two hoses on that rear end vacuum pot, one should have vacuum with engine running. Switch the gear shift switch and should change vacuum to the other hose. If it does your problem is in the axle mounted pot as above poster said. If not then the problem is in the vacuum switch, or rusted out air lines, collapsed rubber hose, etc. The two canisters on the firewall are just vents for the vacuum hoses, maybe a check valve inside to release vacuum when not in use.

The governor hose if disconnected, not plugged, governor will not limit RPM. Plugging that hose will only let the engine idle. unplug that small hose and if engine does not rev up then there is a problem inside the carburetor.

The little gear box in the speedometer cable is a 2 speed gearbox to change the speedometer at same time as rear end is shifted to keep speedometer accurate.

I didn't think 77 Chevy's had vacuum 2 speed shift, but your pictures are definitely vacuum 2 speed. Mine are electric shift 2 speeds. I did have vacuum on a 1964 Chevy C60.

Edited by tj_farms 1/30/2010 19:17
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seedcleaner
Posted 1/30/2010 19:32 (#1049675 - in reply to #1049567)
Subject: Re: 2 speed rearend quit working on 77 Chevy C60


Mid-Missouri
nuelle 4x4 has the parts for the rear axle. higginsville MO. saw them two days ago
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Red/Green
Posted 1/30/2010 21:15 (#1049846 - in reply to #1049675)
Subject: Re: 2 speed rearend quit working on 77 Chevy C60


Elizabethtown,KY
I had a '68 C-50 that had the rubber diaphram go bad as a previous poster said.
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Von WC Ohio
Posted 1/30/2010 23:45 (#1050065 - in reply to #1049567)
Subject: RE: 2 speed rearend quit working on 77 Chevy C60



Check the cable that runs from the push pull button on the shifter that goes down through the floor underneath the truck. I had mine separate under the truck that was allowing the whole thing to move instead of just the inner wire of the cable. I bent up a special piece of metal with a series of clamps on it to hold the outer jacket of the cable in place. Works perfectly and has shifted this way for years now. Mine would shift into high but would not go back into low without crawling underneath and holding the outer sheath and moving the inner wire on the shift cable. Hard to describe and it took a while for me to find exactly what was going on but I fixed the problem with the new bracket and hold down clips. 

 

 

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s_fritz
Posted 1/31/2010 00:00 (#1050078 - in reply to #1049567)
Subject: RE: 2 speed rearend quit working on 77 Chevy C60



South Central IL
We had a 74' C60 that had the vaccum 2 speed. If the above ideas don't solve your problem, ours was converted to an electric 2 speed. Our local mechanic did the work a long time ago. I don't believe the conversion was that expensive and worked perfectly. I think he got the parts from a salvage yard.

Edited by s_fritz 1/31/2010 00:01
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c2gleaner
Posted 1/31/2010 00:09 (#1050085 - in reply to #1049567)
Subject: Re: 2 speed rearend quit working on 77 Chevy C60


S.E. IL
1. It's probably a 67' not 77'
2. "JDDRIVER" photo #3 is not a VACUUM BRAKE BOOSTER, it is a two speed rear axle vacuum shifter
3. Likely it does have a hole in the diaphram. Take the diaphram to NAPA I'll bet they can order you one.
4. I have seen them do as Von suggested with the outer housing moving instead of the inner.
5. Good luck!!
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69zfarmer
Posted 1/31/2010 08:28 (#1050241 - in reply to #1050085)
Subject: Re: 2 speed rearend quit working on 77 Chevy C60


North Central Alabama
I am pretty sure it is a 77 i have the title somewhere.So what do the vaccumn canisters do in photo #2?In photo #4 the govenor has a hose barb in the back which has a vaccumn on it when truck is running.You can't see in the photo but it does not have anything hooked to it.Does this small vaccumn leak at the goveror hurt performace of the 350 engine?
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dondozer
Posted 1/31/2010 19:13 (#1051254 - in reply to #1050085)
Subject: Re: 2 speed rearend quit working on 77 Chevy C60


NW Ohio,near Findlay
I didn't know that option was on a 77 C-60, but there it is. Good luck, probably pancake at rear. Maybe time to update to electric, not that hard, speedo control is hardest to find.
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