HMMWV Speedometer Shenanigans

[jake20]

Hey all, figured I’d share a fun one.

I recently installed a new cable driven 60MPH speedo into my truck. The old one turned into a helicopter although the odometer was still fine.

After I installed the new one, it seemed to be working intermittently for about 2 days, then it quit working altogether.

I went down the line and checked the cable, only to find the key twisted and sheared at the transfer case. Normally the part is $15 or so to replace, though my buddy @pawski decided to have a hold my beer moment.

We cleaned up the sheared pieces and he tig welded them back together. I threw it back on the truck and 50 miles later we’re still operational


I don’t know the exact reason why it initially snapped, but I think it may have to do with torquing the cable connector going into the speedo a bit too much. I kept it on the loose side this time and it’s been perfect thus far.

If it snaps again I’ll get another key but I figured I’d share these 2am shenanigans hehe

 

[jake20]

Welp it broke again after about 100 miles, was a fun little experiment if anything lol

Should have the new keys coming in soon, but I still suspect that the cable might have a little too much resistance. If it breaks another key then I’m tempted to just pick up one of those GPS speedometers rather than replacing the mechanical cable. They look pretty neat and modern.
Anyone have a chance to play with these? https://speedhut.com/gauge-applicat...e-gps-speedometer-100mph/?dd-link=0leeg5nbtbk

 

[mccullek]

I haven’t tried one of these on my HMMWV, but I did put one on my M1078 Truck and it works great. I’ve tested it and the speeds are accurate.

 

[juanprado]

There is a civy greasing adapter made by doorman/motormite help that screws into the threads of the casing nut with a zerk fitting that you can pump grease into the casing to keep the cable happy.

 

[mccullek]

I’ve noticed my hmmwv speedometer is really jumpy at low speeds. Once I hit 30 mph or higher, it smooths out and works as expected. Wondering it this grease adapter might help that low speed jumping needle?

 

[Mullaney]

I’ve noticed my hmmwv speedometer is really jumpy at low speeds. Once I hit 30 mph or higher, it smooths out and works as expected. Wondering it this grease adapter might help that low speed jumping needle?

.
Grease on the cable that runs inside the sleeve will definitely help. Want to test that theory without spending any money? Disconnect the "high side" of the cable up at the speedometer and spray WD40 (or your favorite penetrating oil) into the cable and in a few minutes of run time - Presto! Problem temporarily solved...

 

[mccullek]

.
Grease on the cable that runs inside the sleeve will definitely help. Want to test that theory without spending any money? Disconnect the "high side" of the cable up at the speedometer and spray WD40 (or your favorite penetrating oil) into the cable and in a few minutes of run time - Presto! Problem temporarily solved...

Thanks for the tip. Will give that a try.

 

[juanprado]

In the olden days with cruise control, there was a transducer typically in the fire wall and 2 speedo cables. One from the speedo to transducer and the other transducer to trans. It was common for one of the cables to act up and that is one of the reasons the adapter was invented. Nowadays all that is done by fly by wire and electronic gizmos.

I looked and appears the adapter was discontinued.
Some on epay but here is a reference:
https://www.ebay.com/itm/115733131067?chn=ps&mkevt=1&mkcid=28
GM would be the one you are looking for.

 

[jake20]

I’ve noticed my hmmwv speedometer is really jumpy at low speeds. Once I hit 30 mph or higher, it smooths out and works as expected. Wondering it this grease adapter might help that low speed jumping needle?

I second this, mine has the same effect. Good input from everyone here, shall give some of these things a try once my new keys come in.

 

[Mogman]

As Mullaney said pull the cable off of the speedo then pull the center of the cable out and grease it from tip to tip with bearing grease and carefully put it back in, helps to have 4 hands involved.