Speedometer or cable making a noise?

[mcintyrederek]

Hi,
Finishing a "get it going" restoration on an '86 Silverado C10 with TH400 trans.  Has the original speedometer and cable with 209 K miles.  When it got a little cooler last fall I noticed either the speedometer or cable is making a noise, so I just disconnected it from the transmission until I got closer to finishing.  Your thoughts please, it is more likely the cable making the noise or the speedometer and its internals?  Forgive my ignorance, but does the cable only come out one-way (through the dash end??)  I tried sliding the cable out on the transmission end and it wouldn't pull out.  I've heard of people oiling the cable with grease, etc.  Your recommendations please.  Thanks, Derek.

[DrDaryl]

It's probably the cable.  Loosen the cable where its attached to the transmission and the firewall so you can pull a little slack in it as you remove the dash assembly that holds your speedometer and other gauges.  Should be able to get your hand behind the speedometer; there is a tab to release the cable from the speedometer.  I just pulled the metal cable out a good bit, lubed it and slid it back in and have had no troubles. 

[rich weyand]

On my K-10, there is a doodad on the transmission/transfer case end that has a tang on it that is driven by the speedo connection.  If you pull the cable out at all, it will fall off and then you have to open up the other end to put it back on.  This may be specific to 4WD models.

Just use some Silikroil or some motorcycle cable lube on the top end.  Squirt it into the cable housing; it will work it's way down.

[ScottD]

I had a similar problem with my 85.  The speedometer made noise, but also jumped around and would vary +/-10 mph.  I took out the dash and pulled the speedometer cable off the back (need to disconnect from the tranny first to get some slack) and I sprayed white lithium grease down the cable.  Since its thick I did it multiple times over a weeks time and also connected my cordless drill to the cable to run it down.  Good news is the jumping completely stopped and it now runs perfect.  Bad news is the noise is still there.  The noise must be from the gauge itself, so I'm not sure if there is a lubricant point there or not.

[mcintyrederek]

OK, I will disconnect from speedometer end and try to lube.  We'll see how it goes.  Thanks much for the quick replies.
Derek.

[mcintyrederek]

ScottD, How many miles do you have on your '85 ??

[Captkaos]

Disconnect the trans end and pull the cable out.  If it isn't kinked check the casing to see if it is crushed.

[mcintyrederek]

I tried pulling it out from the transmission end but it wouldn't seem to come out.  How much force and with what to pull it out?  Needle nose pliers?  The cable isn't kinked anywhere that I can see.  I just figured it only came out one way, and that was through the dash.  But if it will come out the transmission end, that would be much easier for me.

[bd]

Derek, remove the cable from its casing from the speedometer end.  There's a brass or plastic ferrule tightly crimped onto the cable at the speedometer that prevents cable removal from the transmission end. 

Unthread the cable assembly from the transmission (or the speedometer ratio adapter, if used), so the cable doesn't bind as you pull it from its casing.  As Rich Weyand posted, be careful not to lose any steel drive keys from the end of the cable or ratio adapter - the drive keys are easily dislodged (usually when you aren't looking).  Inspect the drive key to make sure it isn't bent.  Disconnect the cable from the back of the speedometer head as DrDaryl described.  Use a pair of needle nose pliers to grasp the end of the cable and remove it from its casing entirely.  Carefully wipe the cable clean and inspect the full length of the cable for any bends, kinks, broken or frayed strands, distortion/rounding of the stamped square cable ends and/or any noticeable cable wear.  Remain alert to potentially sharp metal strands while wiping the cable clean!  As Captkaos pointed out, if the cable appears in excellent condition, carefully inspect the full length of the cable casing.  Any permanent bends or distortion of the casing will cause needle jump.  The only practical solution for a damaged casing is replacement of the complete assembly.  If the cable and casing appear in good condition, liberally coat the entire length of the cable with a high quality, medium viscosity lithium grease.  Lay clean rags or newspaper on the floor of your truck to keep the cable clean while feeding it back into its casing, then apply grease to the cable as it enters the casing, but do not over-grease the final ~2" at the speedometer end or you may flood the gauge head.  Reconnect both ends and road check it to see if the symptoms disappear.  Don't forget to reinstall any drive keys that you removed during disassembly.  For additional information read Common causes of "bouncy" speedometer needles in our Technical Pages.

Edit:
The cable casing should be flexible with its plastic sheath intact, not damaged from exhaust heat or pinching.  Sweeping bends in the casing are unavoidable and of little concern as long as the casing isn't rigid and hasn't taken on a set shape.  Rigidity of the casing that results in a set shape, coupled with a dry cable, accelerates wear and can cause cable rattle or slap that transfers directly into the speedometer head.

[rich weyand]

Like bd said.  The only other hint I've ever heard is to coil up the cable in a coffee can over night and cover it with a light oil.  Let that soak in overnight, pull it out, wipe it down, then grease the cable with lithium grease.  That makes sure the interior spaces of the cable are lubed, preventing corrosion and internal rubbing as it rotates where it goes around bends.

[mcintyrederek]

Hi,
Again, thanks tremendously for the detailed responses.  I will try that this afternoon when it warms up some.

[rich weyand]

And here's one stupid simple thing to try.  Mine made a little noise when I put the dash back together after changing out light bulbs and putting a new fuel gauge resistor in.  I simply grabbed the cable housing and pushed it toward the gauge to relieve tension on the cable housing.  End of noise.