Speedometer differences

S

shawn bennear

New member
May 25, 2007
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My speedometer in my 77 PB is acting up. I have a spare, but the one in the coach is a 85 mph one, and my spare one is the 120 one. Is there something
I need to change other than the speedometer, or is it just simply changing the speedo?

Shawn
--
http://www.gmcmotorhomeworld.com

1977 Palm Beach, 403 V8 w headers.
 
> My speedometer in my 77 PB is acting up. I have a spare, but the one in the coach is a 85 mph one, and my spare one is the 120 one. Is there
> something I need to change other than the speedometer, or is it just simply changing the speedo?
>
> Shawn

Either speedo will work. Standard is 1,000 revolutions per mile on the drive cable so the odometer and speed indication will be the same.
--
Wally Anderson
Omaha NE
75 Glenbrook
Megasquirt III injection
Bob Stone hydroBOOOOST
Manny reaction arm system
Branscombe Kelsey Hayes park brake
http://wallyandsue.blogspot.com/
 
Wow, 3 23'ers.. I believe the speedo gears are the same and you should be able to swap heads as in your 2nd coach.

> My speedometer in my 77 PB is acting up. I have a spare, but the one in the coach is a 85 mph one, and my spare one is the 120 one. Is there
> something I need to change other than the speedometer, or is it just simply changing the speedo?
>
> Shawn

--
C. Boyd
76 Crestmont
East Tennessee
 
Shawn,

I have a careful caution for you.

If your speedometer is acting strangely, it is often the cable. Particularly with headers, the cable gets too close to the exhaust heat.

So, before you do much else (and you might as well anyway), disconnect both ends of the lower cable and confirm that it spins freely in the housing.
If it does not, lube it NOW.

Just so you know, if the cable jams up, it can take out the governor gear and then you are stuck in first gear until you remove the left header to get
at the gear and change it out for the spare that you should carry.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
"acting up"?
Bounce tracking with vehicle speed is cables
Swing with road bumps or maneuvers is loss of damping in speedo itself.

--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Sounds like a 40+ year old instrument that is in need of being cleaned,
lubricated, and adjusted by someone with delicate hands, good vision, and
knowledge of instrument repair and maintenance.
It also needs its cable(s) carefully removed from their sheaths,
lubricated, and routed well away from header heat. If you freeze up a
cable, it almost always strips out the nylon governor gear. If that
happens, you will be driving home in low gear. If you do have headers, most
often the drivers side will have to be removed to accomplish this. This
many times results in broken manifold bolts, stripped threads, etc. Grease
is cheap and easy to use. Your choice.
Jim Hupy
Salem, Oregon (presently at the GMC CASCADERS Christmas rally at LaConnor,
Washington.)

On Fri, Dec 6, 2019, 7:32 AM Shawn Bennear via Gmclist <

> Its really kind of odd... it bounces at lower speeds, then seems to float
> around at higher speeds (50+)
>
> --
> http://www.gmcmotorhomeworld.com
>
> 1977 Palm Beach, 403 V8 w headers.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
 
Best to do the lube thing and tie the cable away from the exaust.
Keep eye on the cruse control as well as they do present a problem.

On Fri, Dec 6, 2019 at 7:51 AM James Hupy via Gmclist <

> Sounds like a 40+ year old instrument that is in need of being cleaned,
> lubricated, and adjusted by someone with delicate hands, good vision, and
> knowledge of instrument repair and maintenance.
> It also needs its cable(s) carefully removed from their sheaths,
> lubricated, and routed well away from header heat. If you freeze up a
> cable, it almost always strips out the nylon governor gear. If that
> happens, you will be driving home in low gear. If you do have headers, most
> often the drivers side will have to be removed to accomplish this. This
> many times results in broken manifold bolts, stripped threads, etc. Grease
> is cheap and easy to use. Your choice.
> Jim Hupy
> Salem, Oregon (presently at the GMC CASCADERS Christmas rally at LaConnor,
> Washington.)
>
> On Fri, Dec 6, 2019, 7:32 AM Shawn Bennear via Gmclist <

>
> > Its really kind of odd... it bounces at lower speeds, then seems to float
> > around at higher speeds (50+)
> >
> > --
> > http://www.gmcmotorhomeworld.com
> >
> > 1977 Palm Beach, 403 V8 w headers.
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmcrvparts.com
1-800-752-7502
 
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