TWO PIECE SPEEDO CABLE TO ONE CABLE CONVERSION

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Kolbey Baltz

Not-quite-so-new-guy
Apr 26, 2016
32
2
8
Eastern, Pennsylvania
I have a 78 Grand Lemans with the 305. my goal for this Memorial Day is to convert my two cable speedo to a single. and removing the box. first question is, what is that box? (service interval counter, cruise, etc?) and if I remove it, will it affect anything like mileage counting or of that sort. and second question is, if someone is familiar with this, what size single cable should I be looking for? haven't had the chance the measure both cables since my car is a little of a haul from my home. quick responses would be ideal cause i leave work within an hour and am looking to go pick the part up at an auto parts store. thank you everyone!
 
should be as simple as ordering a speedo cable for a car without cruise. The speedo is the same, and the trans is the same in cruise vs non-cruise cars.

Now that I think of it, the systems with the 2 cable speedo ( transducer ) may have been a dealer installed add-on. I know most of the other g's with cruise use a vacuum operated system ( I know both my 84 and my 80 had the vacuum system ). IIRC they took the stock speedo cable from the speedo to the transducer, then a second cable from the transducer back to the trans. You may be able to just reconnect the cable from the speedo direct to the trans again. Same setup in the kseries truck of that era.
 
should be as simple as ordering a speedo cable for a car without cruise. The speedo is the same, and the trans is the same in cruise vs non-cruise cars.

Now that I think of it, the systems with the 2 cable speedo ( transducer ) may have been a dealer installed add-on. I know most of the other g's with cruise use a vacuum operated system ( I know both my 84 and my 80 had the vacuum system ). IIRC they took the stock speedo cable from the speedo to the transducer, then a second cable from the transducer back to the trans. You may be able to just reconnect the cable from the speedo direct to the trans again. Same setup in the kseries truck of that era.
the cruise is in fact vacuum operated off the transducer. I had the chance to look at it just now. if I read your message correctly, I could just take the cable coming from the speedo and attach that to the transmission where the cable coming off the transducer goes? now that I think about it, it may in fact be long enough off the speedo because it has to go up from firewall, over the fender liner and up front to the transducer, then the line off the transducer goes fully back to the transmission.
 
I believe the screw-on ends are different from the transducer to the speedo bullet. I eliminated my cruise control transducer and went with the one piece cable. ATP #03160
 
are you sure you dont have a th250 and i believe that adapter works in conjunction with the lock up converter
 
I believe the screw-on ends are different from the transducer to the speedo bullet. I eliminated my cruise control transducer and went with the one piece cable. ATP #03160
where is that part number for? or is it universal? If it works for you, I'll just go with your information.
 
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UPDATE. I ordered an ATP speedo cable, model #: ATP Y-815. $12 from Advanced Auto. pulled the dash cluster out, fed it through the stock hole in the fire wall, tucked it down right to the transmission hook up and had plenty of room. no issues whatsoever. I got the Transducer removed and removed all the A/C lines and compressor. Removed and plugged the emissions canister and respective vacuum lines on the carb. car runs good. speedo works great. Pleased with my work that day. A/C box is next to be deleted.
 
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