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Post by Gasket on May 24, 2005 23:14:27 GMT -5
The speedo in my 77 K20 has not worked since who knows when. Odometer obviously doesn't work either. Old owner said the cable was disconnected at the tranny, but when I looked at it, it was hooked up. I haven't ripped the dash apart yet to see if it is connected behind the guage cluster, but I found a part in the cab that I am confused about. At first I thought this was just a part off of another vehicle, since I found it buried in a huge pile of crap that the previous owner left for me in the cab, but now I'm not sure. It appears to be some kind of transducer, and it says "Borg Warner" on it. It has a place for a speedo cable to go in and one for it to go out. In my experience, I have usually seen speedo cables go directly from the tranny to the dash, unless the truck has cruise control. My truck does not have cruise. Is this a part that is off the truck? I'd sure like to have a working speedo, since ticket prices are going up...
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Post by Bent on May 24, 2005 23:50:22 GMT -5
Does it look like this?
 This is a ratio adapter used to correct the speedo if the axle ratio has been changed or tranny regered so on. If the adapter was used, then the cable is probably disconnected where the adapter used to be. 
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Post by Gasket on May 25, 2005 17:13:55 GMT -5
Yes, that looks like it! Thanks for the help. Next time I get an opportunity I'll try to reinstall it. I don't think the gears were ever changed in the truck, nor the tranny. Could this have been a factory part?
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Post by 19_Chevelle_69 on May 25, 2005 20:55:17 GMT -5
My '77 4x4 had one from the factory.
It could be a number of things. Best thing to do is pull the cable off at the speedo, and take it for a short run to see if the cable is actually spinning.
Also, you should be able to pull the center cable out from the dash end to see if it has frayed and possibly the squared end has rounded off.
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Post by Gasket on May 29, 2005 22:19:49 GMT -5
Thanks, Don and Bent. I removed the speedo from the dash this weekend to take a closer look at things. I originally thought there might be two separate cables due to the ratio adapter, but found only one. It is connected at the transfer case tail and at the speedo. The cable end did not look frayed or rounded. I'll probably take it for a spin tomorrow to see if the cable actually spins. My feeling is that the gear inside the tranny tail is broken, since the cable does not appear to be broken.
My truck's gear ratio is 4.11, as it was from the factory, and the speedo cable appears to be factory (it "looks" like it's 28 years old). I also found yet another ratio adapter in the glove box. Like the other, this one says Stewart Warner on it, but looks much different. It is longer and the input and output ends are directly across from each other. I really have no clue which one is the right one to use, if either. Any ideas?
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Post by Pontiac1976 on Jun 11, 2005 12:38:10 GMT -5
The pic shown looks new from dealer I had to get one about 7 month ago . You may need it or not depending on gears tire size trans gearing . If the speedo is ok and cable then it in the side on the trans where the speedo attaches . The small plastic gears are worn 'en or striped. If you truck biggest tires were 205\75\15 you wanted 235\75\15 your speedo would read say 60mph but really be going 65-70 IE. , so the ratio adapter fixes that all so   hope this helps mine was a 305chev 77 1/2 Ton 350 trans 3:08 gear changed to a 77 454 1/2 Ton 350 trans 3:08 gear now changed back to a 85 SS 305 in a 77 1/2 Ton 350 trans 3:08 gear think cost me from dealer $130.oo Canadian duo |
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hope this helps