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09-30-2011, 05:24 PM
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#1 |
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Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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speed-o-meter issues
so I recently bought my 79 and have been fixing all the little issues. My cluster I believe is a later year cluster, at least I know my bezel is for sure. It has a tach on the left and speedometer on the right. Neither work! I had my truck up on stands to change the rear end oil and thought id crawl around and look at the tail cone to see if the cable was hooked up. The cable is a 2 part cable that runs down into this little gear box lookin thing. Everything is in place but the box is loose to the transmission. When I wiggle it, it leaks tranny fluid alittle. Does anyone recognize this box? p.s. sorry about the funny angle, i was on my back in an awkward position! Thanks in advance!
  
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09-30-2011, 05:28 PM
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#2 |
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Moderator
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,977
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Re: speed-o-meter issues
It's a speedometer ratio adapter.
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09-30-2011, 06:06 PM
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#3 |
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Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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Re: speed-o-meter issues
is it supposed to be kinda loose? The small bolt and plate at the base are tight so Im not sure how its supposed to secure it. What would be the issue if I removed it and just screwed the cable to the transmission?
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09-30-2011, 08:37 PM
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#4 |
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Moderator
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,977
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Re: speed-o-meter issues
It's not supposed to be loose.
The speedometer gear housing in the transmission or transfer case has O-ring seals on the outside and inside. Replace those seals and the leak will stop. If you remove the adapter both speed and mileage will be off by the gear ratio of the adapter. The ratio could be from +50% to -50%. Removing a +17% ratio adapter will make the speedometer read 17% low so a 55mph reading on the clock is actually 66mph... That's bad. |
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09-30-2011, 08:42 PM
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#5 |
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Registered User
 Join Date: May 2009
Location: Weymouth Ma
Posts: 489
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Re: speed-o-meter issues
Looks like you are missing a bolt on the trans mount also.
__________________
03 GMC Yukon XL 2500 Quadrasteer, wife`s DD 84 Chevy K30 CC SRW 55 Chevy 210 2dr post |
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09-30-2011, 11:40 PM
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#6 |
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78K & 79C Jimmys
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
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Re: speed-o-meter issues
"tach on the left"?
not the right? my 78,79,up to 89 are all like that is the cable even hooked up?
__________________
John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350 |
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10-01-2011, 12:40 AM
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#7 |
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Registered User
Join Date: Sep 2011
Location: Clackamas, Or
Posts: 139
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Re: speed-o-meter issues
my bad, tach on the right! Yeah its hooked up and the cable itself is in good shape. Maybe I should pull the ratio adapter and see if its missing something
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10-01-2011, 10:48 AM
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#8 |
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Registered User
Join Date: Nov 2010
Location: Windsor Locks
Posts: 628
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Re: speed-o-meter issues
when I got my truck the speedo didn't work and it ended up being that ratio adapter was stripped out inside. you can remove it and hook up the cable straight to the trans just to see if it works.
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10-02-2011, 11:14 PM
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#9 |
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Registered User
Join Date: Feb 2003
Location: Mulvane, Ks.
Posts: 756
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Re: speed-o-meter issues
I have the same type of adapter on my 83 dooly. However, I have been told mine is worn out and needs to be replaced. I've found a site on the internet called Speedometer World. Has anybody used them and what is your recommendation?
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