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So years ago when my dad did the LS swap he didn’t plug the analog speed cable back in but plugged the computer speed cable in. He wired the LS harness into the factory Olds harness but I don’t think the speed cable was included. So I have a non working speedometer, which I imagine also means I have a non operating mileage counter. And you can only plug one in. What do I do? Please help.
this is a photo my dad took when I was driving years ago post LS swap. If you look you can see the needle resting in the photo, this was while I was doing maybe 10 mph. So I don’t think the speed cable is connected at all.
Last edited by 442hurstolds; June 27th, 2024 at 01:55 PM.
If the trans came w/ the LSx, it won't have a place to attach the mechanical speedo cable. You must use an adapter to "translate" between the electrical signal produced by the LSx's transmission and the mechanical speedo cable. The other option would be to retrofit your dash w/ a digital speedo that is compatible w/ the transmission. Its hard to tell from the late model plastic harness and electrical tape to see if that is an appropriate adapter, I suspect not since your dad didn't hook the mechanical speedo cable to anything, likely because there was no place to.
If there is a chance I've misunderstood your post and your trans is an old-school (TH400) trans that has a mechanical speedo connection and it is just "occupied" by the adapter your dad used to provide feedback to the LS PCM, that's a different issue. Not sure if they sell a "speedo cable splitter" gearbox adapter (kind of like those ratio adapters used frequently on cars w/ 4.xx rear ends). That would allow connection of both the speedo cable and the PCM adapter box.
The "Zero depreciation for mileage mod":
Last edited by JohnnyBs68S; June 27th, 2024 at 05:21 PM.
If there is a chance I've misunderstood your post and your trans is an old-school (TH400) trans that has a mechanical speedo connection and it is just "occupied" by the adapter your dad used to provide feedback to the LS PCM, that's a different issue. Not sure if they sell a "speedo cable splitter" gearbox adapter (kind of like those ratio adapters used frequently on cars w/ 4.xx rear ends). That would allow connection of both the speedo cable and the PCM adapter box.
I run a 2007 4L80e it is a junkyard drive train. Yes you are correct but not for a th400. The connection is occupied by the PCM cable and not the mechanical cable. Is there an adapter plate for both the mechanical cable and the electric wire?
I run a 2007 4L80e it is a junkyard drive train. Yes you are correct but not for a th400. The connection is occupied by the PCM cable and not the mechanical cable. Is there an adapter plate for both the mechanical cable and the electric wire?
Speedhut sells a "Speedbox" that uses GPS to detect your car's speed and generates a rotational speed (via a stepper motor presumably) that is proportional to that speed which is then connected to and can drive (spin) your mechanical speedo cable. This would be a separate system from your transmission connection and would be independent of any gear ratio and tire size concerns. Not cheap, but probably the most elegant solution.
It appears that the Speedbox can also connect to the vehicle speed sensor (VSS) in the transmission, but since you already have your LSx PCM adapter device connected to the VSS output, you'd probably need to "Y" in that connection somehow. Fortunately, it appears that a connection to the VSS is optional.
Last edited by JohnnyBs68S; June 28th, 2024 at 06:44 AM.
Speedhut sells a "Speedbox" that uses GPS to detect your car's speed and generates a rotational speed (via a stepper motor presumably) that is proportional to that speed which is then connected to and can drive (spin) your mechanical speedo cable. This would be a separate system from your transmission connection and would be independent of any gear ratio and tire size concerns. Not cheap, but probably the most elegant solution.
will the mileage count work if I get the speed box? Also how would I get the “Y” connection to the transmission.
will the mileage count work if I get the speed box? Also how would I get the “Y” connection to the transmission.
1) Yes, since your factory speedo measures mileage by counting the revolutions of the cable.
2) Good question, I don't know the answer. Personally, I'd just skip it since it is optional to connect the Speedbox to the VSS. I'm guessing that the Speedbox includes this VSS input in case you don't want to mount the little antenna for the GPS. I guess that connecting the VSS would also keep your speed (and mileage) accurate when going through tunnels where the GPS connection would drop. I would recommend visiting some Chevelle sites where LS swaps are much more popular. There may be a "Y" cable adapter for this situation, but I didn't see anything like this on the Speedhut site. Another thought is to check the LS PCM adapter you have to see if maybe is has a VSS connector pass-through / output for this exact purpose. I suspect that it has to have the ability to connect to a digital speedo in the OEM application, although that "connection" may be in PCM firmware and not a physical connection. I just don't know enough about LS PCMs used in swaps to speak with authority on this topic.
Last edited by JohnnyBs68S; June 28th, 2024 at 08:51 AM.
1) Yes, since your factory speedo measures mileage by counting the revolutions of the cable.
2) Good question, I don't know the answer. Personally, I'd just skip it since it is optional to connect the Speedbox to the VSS. I'm guessing that the Speedbox includes this VSS input in case you don't want to mount the little antenna for the GPS. I guess that connecting the VSS would also keep your speed (and mileage) accurate when going through tunnels where the GPS connection would drop. I would recommend visiting some Chevelle sites where LS swaps are much more popular. There may be a "Y" cable adapter for this situation, but I didn't see anything like this on the Speedhut site.
okay, thank you, if I come up with anymore questions I’ll ask here. The speed box is going to be taking a backseat for a while because I’m more focused on getting the car running. I’m prioritizing the interior and the drum to disc brake conversion right now, thank you.
June 27th, 2024, 01:48 PM
