Speedometer Needle Bouncing

[prgt347]

I have a '92 GT that has had a bouncing speedometer needle for several years, gradually getting worse. I recently purchased a new cable and housing from LMR and installed it over the weekend. Installation was straight forward with no issues. Unfortunately with the new cable the bouncing is as bad or worse. I've read over JRichter's (thanks Joe, again) thread explaining the mechanics of the speedometer system but can't seem to find where the problem is.

The gear at the transmission end of the cable is not worn nor does it show any damage.

With the speed sensor and gear out of the transmission I can feel the inner gear and did not notice any damage or wear to it either.

The cable is securely locked into the speed sensor and the clip is tight. There is no movement where the cable meets the sensor.

From inside the car the cable, when not connected to the back of the speedometer, can be easily taken out of the housing and put back in with no friction. The cable spins freely within the housing until it is seated into the bottom of the housing then stays in place.

The cable snaps into the back of the speedometer cleanly with no issues.

The cable gear and transmission (FRPP Heavy Duty T5), including inner gear, were both changed out 10-15 years ago.

Any advice is welcomed.

 

[mikestang63]

I would check the actual speedo as the flywheel often goes bad...

 

[Mustang5L5]

Try lubing the speedo cable first. Sometimes they wind up and release in a rhythm seeing as the center rod is a sort of spring.

If that doesn't work, it's possibly the speedo. You can pick up another cluster on Ebay, remove the speedo, match the miles (easier than you think) and install it.

Odds are though, it may bounce as well. I'd also see if there's a local shop that specializes in speedometer repair/calibration. These may be dying out however as most cars go purely electronic these days

 

[StratTone]

I'll chime in on this one since I've been messing with this mess myself lately.

Since you got the LMR cable I assume you got the cable that came with the green grease. My guess is you don't have the cable housing greased enough. The video they have online shows them adding grease and sliding it through the tube and they never show it working so you just have to take their word for it but my guess is this way of applying the grease gets on the cable but not the housing at the bottom of the transmission because it is squeegeed by the outer housing as it is inserted keeping the grease concentrated at the top near the gauge.

I had this same problem with my cable from them. When I replaced mine with theirs it still bounced from 0-30 mph and wavered back and forth 5 mph at steady 60 mph. I took the cable back off and sprayed lithium grease down the top till I saw it come out the bottom and reinserted the cable. This did the trick for me. I have very little wobble from 0-20 and steady at 60 now.

The last little bit I may inspect at a later date but I have a strong feeling it will either be that the LMR cable has a different diameter cable that might not fit in the housing tight enough or it could be that the feral on the back of my speedo needs to be reseated tight. There is a little bit of play where it is pressed on. I need to look further into that of course to find out how much play is supposed to be there.

So give the lithium spray grease a try or apply the green grease as they do on the video from the speedo side and also do it from the transmission side to make sure it gets down there too. (didn't try this method but feel it will work)

 

[prgt347]

Thanks for the responses. I live close to JMS and called them about testing the speedometer. Unfortunately they are not aware of any way to do this. If anyone is aware of how to test this or a company that does, please let me know. In the meantime, I pulled the cable back out of the new housing and lubed it up more with the green grease that came with the kit. I didn't remove the housing so I probably didn't get enough grease into the bottom and haven't tried the lithium spray yet. The extra grease didn't do any good. Also, turns out I have the wrong gear on my speedometer cable so I just ordered the correct one for 3.73 gears today. When this arrives I'll first replace the gear and test, but really don't expect any improvement as my current gear does not appear stripped, damaged, etc. If no improvement I will remove the speed sensor from the housing, spray lithium in the bottom of the housing as suggested by StratTone and see if that works. I can get a used instrument cluster for $200 or less but just don't want to spend money until I'm fairly certain that is the issue.

If you have any other thoughts or suggestions, keep them coming. Thanks

 

[StratTone]

The way I test a speedo is to take an old cable and cut about 10 inches off from either end and spin the speedo counter clockwise with a drill. This way you can eliminate a binding issue but using only the inner 10 inch cable as the in between from drill to speedo.

Give that spray a shot it just may be your problem. I went through 2 after market cables, a cluster, taking apart my speedo and that spray really smoothed things out for me. Can't say how long it will last but going strong so far for a couple weeks. It was noticeably smoother after the spray as well. I felt very little resistance when inserting the inner cable in the outer housing.

 

[prgt347]

I installed the correct 21-tooth gear and sprayed lithium grease into the lower cable housing after pulling the cable back about a foot. Put it all back together and no difference, still bouncing around. I then removed the instrument cluster and while outside the car attached the old stock cable and housing back to the speedometer using the drill on the other end. I didn't cut it and use 10 inches, though, I used the whole thing but made sure there were no kinks or binding. Even with smooth cycling of the drill the speedometer needle bounces all around, especially at low RPM. Is it safe to say the speedometer is dead or should I try something different before replacing?

 

[jrichker]

How the speedometer works:
The indicator pointer has no direct connection to the speedo cable. It uses a drum with magnets on it to couple to the pointer. The drum turns and tries to twist the circular steel disk that is mounted on the pointer spindle. The magnetic force is all that connects the drum to the circular disk. There is very little clearance between the disk and drum, only a few thousands of an inch. Sometimes dust or dirt collects on the drum and disk surfaces that face each other. Cleaning the drum and disk with the brake parts cleaner would be the next thing to try. If that fails, Google speedometer repair and see what you come up with.

 

[StratTone]

At this point the only thing it can be is the cable or gauge. The only way left to make sure it isn't the gauge is to spin the gauge without the cable. I had an extra so I cut a 10 inch piece to do my test but you could get creative and come up with something else I'm sure. Just don't attach the drill right to the gauge. It will damage the feral.

 

[prgt347]

To follow up...the gauge was bad. I decided to replace the entire instrument cluster as opposed to just the speedometer. In addition to the speedometer issue I've been having the plastic circuit on the back of mine was warped which has been creating intermittent issues with some of my instrument panel lights. So seemed best to just replace it all. I found several on eBay for around $200 (mpsautosalvage) that are used but are in good shape and come with a new Ford lens. Installed it and everything works again. The cluster I bought had a couple of burned out bulbs but I just swapped out some from my old unit...other than that everything works perfectly.

The test that was the most conclusive was StratTone's suggestion to spin the cable with a drill. Just for comparison sake I did the drill test on the new speedometer and the needle moved smoothly up and down, no bouncing like mine was doing. Chances are my stock speedometer cable was fine but after 25 years it was probably time to replace anyways.

Thank you all for your ideas and suggestions!

 

[StratTone]

Good deal man!! Glad you got it up and running again.

I don't have a ton of experience with fixing gauges but I was able to fix mine. It ended up being the aluminum cup. Over time the press seat had loosened so I took it apart and made the cup tight and centered and it's smooth now.

Might be worth a shot if you get board to have a spare or sell to recoupe some money.

 

[fredfifty]

Try lubing the speedo cable first. Sometimes they wind up and release in a rhythm seeing as the center rod is a sort of spring.

If that doesn't work, it's possibly the speedo. You can pick up another cluster on Ebay, remove the speedo, match the miles (easier than you think) and install it.

Odds are though, it may bounce as well. I'd also see if there's a local shop that specializes in speedometer repair/calibration. These may be dying out however as most cars go purely electronic these days

how would i go about matching the miles? i recently installed a different cluster and it has 70k more miles on it.