Wandering Speedometer Needle at Highway Speeds - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**pjmoreland** · 11-11-2020, 04:47 PM

At speeds under about 40mph, my speedometer is stable, but it drifts around at higher speeds, as seen in this video:

https://youtu.be/5TxuNPqF8_g

I swapped in another speedometer I had, and it was even worse, but acted basically the same way. It seems like bumps in the road are causing the needle to move around. What can I do to fix this? Do I need to get a new/reproduction speedometer?

LS short box · 11-11-2020, 05:24 PM

Try lubing the speedo cable. Doesn't cost any thing and it may help.

**pjmoreland** · 11-11-2020, 05:28 PM

Quote:

Originally Posted by LS short box

Try lubing the speedo cable. Doesn't cost any thing and it may help.

I did lube the speedo cable last night and it had no effect. It is a new cable, although the speedo acted the exact same way with the old cable.

Andy4639 · 11-11-2020, 07:25 PM

Quote:

Originally Posted by pjmoreland

I did lube the speedo cable last night and it had no effect. It is a new cable, although the speedo acted the exact same way with the old cable.

Take the cable loose at the transmission and look at the plastic gear head it goes into. It's more than likely worn out. Take it out and buy the same gear put back in it. This is just example picture. Look into the end opisite of the gear that is where the cable goes. It should be nice and square like the cable and fit's pretty tight.

**pjmoreland** · 11-11-2020, 07:54 PM

Quote:

Originally Posted by Andy4639

Take the cable loose at the transmission and look at the plastic gear head it goes into. It's more than likely worn out. Take it out and buy the same gear put back in it. This is just example picture. Look into the end opisite of the gear that is where the cable goes. It should be nice and square like the cable and fit's pretty tight.

Here's my gear. It's a 44-tooth out of a TH400. Looks pretty good to me, but I will replace it anyway

Andy4639 · 11-11-2020, 08:33 PM

That gear looks OK. It could be the end of the cable that goes into the speedometer head also. Are the cable end going to the gear itself. How do they look?

geezer#99 · 11-12-2020, 11:09 AM

What did you lube the cable with?
Did you pull it apart and clean it inside plus the cable.

**pjmoreland** · 11-12-2020, 11:18 AM

Quote:

Originally Posted by geezer#99

What did you lube the cable with?
Did you pull it apart and clean it inside plus the cable.

I used a Teflon based light grease that is designed for bicycle cables. I pulled the cable out of the housing, wiped it off, applied the grease and reinstalled. I didn't clean the housing.

geezer#99 · 11-12-2020, 11:44 AM

I clean them out inside and the cable with acetone.
Then use white lithium grease for lube applied sparingly.
Make sure the cable is held in place along the lower firewall too.

**pjmoreland** · 11-12-2020, 11:46 AM

Quote:

Originally Posted by geezer#99

I clean them out inside and the cable with acetone.
Then use white lithium grease for lube applied sparingly.
Make sure the cable is held in place along the lower firewall too.

I'll give it a good cleaning with solvent. I have it fastened to the firewall with the original clip.

Willys_MB · 11-12-2020, 12:33 PM

Sheesh, mine always wanders like that and I never really thought anything of it. I guess I have another thing to fix.

**pjmoreland** · 11-12-2020, 01:22 PM

Quote:

Originally Posted by Willys_MB

Sheesh, mine always wanders like that and I never really thought anything of it. I guess I have another thing to fix.

That's what I'm wondering. Maybe this is common simply due to the age of our trucks. This is my fourth C10, and none of my previous trucks had this issue, but the last one I had was 13 years ago.

**'68OrangeSunshine** · 11-12-2020, 04:13 PM

I have used graphite dust to lube the speedo cable, but the most reliable ground speed indicator is a GPS device on the dash.

Davidf · 11-12-2020, 04:55 PM

I think cable issue is the most likely cause of a bouncing speedometer. I would remove the cable, pull the inner cable out of the sheath and a suitable lubricant (i.e. not lithium grease) such as:

https://www.amazon.com/Ags-Kable-Eas.../dp/B000ZO0EA2

Willys_MB · 11-12-2020, 05:06 PM

I just put this new cable in and lubed the heck out of it, as did the OP, so I don't think it's the issue here

Davidf · 11-12-2020, 06:19 PM

How the routing, do you have a sharp bend in the cable. Maybe disassemble the speedometer and lube the part of the cup/magnet part that the cable spins. Maybe it is binding due to hard grease at the housing.

**pjmoreland** · 11-12-2020, 06:42 PM

Quote:

Originally Posted by Davidf

How the routing, do you have a sharp bend in the cable. Maybe disassemble the speedometer and lube the part of the cup/magnet part that the cable spins. Maybe it is binding due to hard grease at the housing.

The routing seems good to me, and there are no sharp bends. I already put a drop of light oil on the speedometer input shaft.

Astro-Balls · 11-12-2020, 07:19 PM

When I pulled my cable and housing out, Cleaned the inside of the housing and could not believe the grit and gunk that came out of it.
after a couple of good cleanings to the housing and cable, lubed with speedometer cable lube and good as new.

**'68OrangeSunshine** · 11-12-2020, 09:45 PM

I have found those offset spedometer correction boxes [used when you have bigger than stock tires] tend to amplify the bounce.

**pjmoreland** · 11-27-2020, 03:16 PM

I sent my speedometer to TBONE1964 and he ended up replacing the entire speedometer head with good used unit. The speedometer is drastically improved over my old unit. It is rock steady most of the time. It still swings around if I hit a bump or dip, but that seems unavoidable. Here's a video of it in action.

https://youtu.be/Cvvz8rQTz_E

**'68OrangeSunshine** · 11-27-2020, 03:47 PM

My rig just rolled over 400,000.

**pjmoreland** · 11-27-2020, 04:23 PM

Quote:

Originally Posted by '68OrangeSunshine

My rig just rolled over 400,000.

Nice! That would explain your signature. I have no idea what the mileage is on mine. Probably less than that.

**pjmoreland** · 11-30-2020, 06:22 PM

After driving my truck a few times with the replacement speedometer installed, I noticed that it was off by 4mph at all speeds. Normally speedometers are off as a percentage due to incorrect drive/driven gears in the transmission, not a fixed offset, but this wasn't the case with mine. I selected the drive/driven gears using the TCI calculator, and I measured my tire circumference by placing marks on the ground as I pushed my truck forward one revolution of the wheels. I tested my odometer out on an eight-mile straight stretch on the interstate, and it was dead on compared to the mile markers. I noticed my speedometer wouldn't move away from zero until I was going about 4mph. Anyway, I took the speedometer apart and discovered an adjustment bar on the return spring. I did a little trigonometry and came up with needing to rotate the bar by 11 degrees CW (toward the 100mph end of the speedometer) to increase my speed reading by 4mph. This translated to moving the end of the adjuster bar by .164". I just got back from a test drive, and the speedometer is dead on now from 0 to 70mph. I compared it to the actual speed displayed while running Google Maps navigation on my phone.

11-11-2020, 04:47 PM	#1
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,039	Wandering Speedometer Needle at Highway Speeds At speeds under about 40mph, my speedometer is stable, but it drifts around at higher speeds, as seen in this video: https://youtu.be/5TxuNPqF8_g I swapped in another speedometer I had, and it was even worse, but acted basically the same way. It seems like bumps in the road are causing the needle to move around. What can I do to fix this? Do I need to get a new/reproduction speedometer?

11-11-2020, 05:24 PM	#2
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 2,147	Re: Wandering Speedometer Needle at Highway Speeds Try lubing the speedo cable. Doesn't cost any thing and it may help.

11-11-2020, 08:33 PM	#6
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Wandering Speedometer Needle at Highway Speeds That gear looks OK. It could be the end of the cable that goes into the speedometer head also. Are the cable end going to the gear itself. How do they look? __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-12-2020, 11:09 AM	#7
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Wandering Speedometer Needle at Highway Speeds What did you lube the cable with? Did you pull it apart and clean it inside plus the cable.

11-12-2020, 12:33 PM	#11
Willys_MB Registered User Join Date: Apr 2017 Location: Boise, ID Posts: 856	Re: Wandering Speedometer Needle at Highway Speeds Sheesh, mine always wanders like that and I never really thought anything of it. I guess I have another thing to fix. __________________ 1968 GMC C2500 Long Bed Fleetside

11-12-2020, 11:44 AM	#9
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Wandering Speedometer Needle at Highway Speeds I clean them out inside and the cable with acetone. Then use white lithium grease for lube applied sparingly. Make sure the cable is held in place along the lower firewall too.

11-12-2020, 04:13 PM	#13
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,536	Re: Wandering Speedometer Needle at Highway Speeds I have used graphite dust to lube the speedo cable, but the most reliable ground speed indicator is a GPS device on the dash. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

11-12-2020, 04:55 PM	#14
Davidf Registered User Join Date: Nov 2014 Location: Austin Posts: 749	Re: Wandering Speedometer Needle at Highway Speeds I think cable issue is the most likely cause of a bouncing speedometer. I would remove the cable, pull the inner cable out of the sheath and a suitable lubricant (i.e. not lithium grease) such as: https://www.amazon.com/Ags-Kable-Eas.../dp/B000ZO0EA2

11-12-2020, 05:06 PM	#15
Willys_MB Registered User Join Date: Apr 2017 Location: Boise, ID Posts: 856	Re: Wandering Speedometer Needle at Highway Speeds I just put this new cable in and lubed the heck out of it, as did the OP, so I don't think it's the issue here __________________ 1968 GMC C2500 Long Bed Fleetside

11-12-2020, 06:19 PM	#16
Davidf Registered User Join Date: Nov 2014 Location: Austin Posts: 749	Re: Wandering Speedometer Needle at Highway Speeds How the routing, do you have a sharp bend in the cable. Maybe disassemble the speedometer and lube the part of the cup/magnet part that the cable spins. Maybe it is binding due to hard grease at the housing.

11-12-2020, 07:19 PM	#18
Astro-Balls Registered User Join Date: Feb 2019 Location: Nor Cal Posts: 822	Re: Wandering Speedometer Needle at Highway Speeds When I pulled my cable and housing out, Cleaned the inside of the housing and could not believe the grit and gunk that came out of it. after a couple of good cleanings to the housing and cable, lubed with speedometer cable lube and good as new. __________________ 1968 C20 Fleetside 396 4sp PS PB AC CST . https://www.youtube.com/watch?v=RWK8GgWD4uA

11-12-2020, 09:45 PM	#19
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,536	Re: Wandering Speedometer Needle at Highway Speeds I have found those offset spedometer correction boxes [used when you have bigger than stock tires] tend to amplify the bounce. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

11-27-2020, 03:16 PM	#20
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,039	Re: Wandering Speedometer Needle at Highway Speeds I sent my speedometer to TBONE1964 and he ended up replacing the entire speedometer head with good used unit. The speedometer is drastically improved over my old unit. It is rock steady most of the time. It still swings around if I hit a bump or dip, but that seems unavoidable. Here's a video of it in action. https://youtu.be/Cvvz8rQTz_E

11-27-2020, 03:47 PM	#21
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,536	Re: Wandering Speedometer Needle at Highway Speeds My rig just rolled over 400,000. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

11-30-2020, 06:22 PM	#23
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,039	Re: Wandering Speedometer Needle at Highway Speeds After driving my truck a few times with the replacement speedometer installed, I noticed that it was off by 4mph at all speeds. Normally speedometers are off as a percentage due to incorrect drive/driven gears in the transmission, not a fixed offset, but this wasn't the case with mine. I selected the drive/driven gears using the TCI calculator, and I measured my tire circumference by placing marks on the ground as I pushed my truck forward one revolution of the wheels. I tested my odometer out on an eight-mile straight stretch on the interstate, and it was dead on compared to the mile markers. I noticed my speedometer wouldn't move away from zero until I was going about 4mph. Anyway, I took the speedometer apart and discovered an adjustment bar on the return spring. I did a little trigonometry and came up with needing to rotate the bar by 11 degrees CW (toward the 100mph end of the speedometer) to increase my speed reading by 4mph. This translated to moving the end of the adjuster bar by .164". I just got back from a test drive, and the speedometer is dead on now from 0 to 70mph. I compared it to the actual speed displayed while running Google Maps navigation on my phone. Attached Images



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