When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm currently chasing the cause for a bouncing speedometer in my 1971 LT-1. After reading some prior discussions here, I've pulled the entire cable from behind the dash for inspection and lubrication with graphite. The cable looks perfectly fine, and inserts back into the sheathing with very little effort. However, the cable seems to bind-up with about 4-5 inches remaining and I'm not sure why. Once it gets past this sticking point, it goes in pretty easily the rest of the way and spins by hand with very little effort (before seating into the transmission).
My question -- what could be causing this binding right near the transmission? There is a 90 degree turn in the transmission tunnel, but there no visible kinks that might be an obvious cause. However, it does seems like this is where the cable is getting bound up.
I know on GM speedometer cables..and I do not know exactly what year GM began using it...but there is a special curves aluminum sleeve that aid in holding the cable housing at a curve when it comes out of the transmission area.
I do know that heat can mess up your cable housing.
I would attach a drill to the end of the cable that goes in the transmission and spin it and see if the gauge bounces. If the gauge does not bounce that would at least let me know I am not having to go into the speedometer fitting and gears in the transmission and heck them.
I know on GM speedometer cables..and I do not know exactly what year GM began using it...but there is a special curves aluminum sleeve that aid in holding the cable housing at a curve when it comes out of the transmission area.
Thanks -- I do know that the sleeve holding the cable sheathing is intact and there is a gentle curve into the transmission housing. My primary concern is the resistance that I'm getting while re-inserting the cable into the sheathing about 4-5 inches from the end -- the cable inserts effortlessly until that point.
Hi rb74,
There are 2 'clips' on the transmission tunnel that help 'guide' the cable on it's way to the transmission.
Are they they and were they used? PERHAPS they weren't and the 'tightness' you're feeling in the cable at that point is the result of them not being used at some time in the car's life?
Also there's a special guide/bracket the the cable runs through to help turn the cable into the transmission connection. Is that there?
Regards,
Alan
Most of it is hidden by the cable. It's about 6 inches long.
There are 2 'clips' on the transmission tunnel that help 'guide' the cable on it's way to the transmission.
Are they they and were they used? PERHAPS they weren't and the 'tightness' you're feeling in the cable at that point is the result of them not being used at some time in the car's life?
Hi Alan -- I was under the car yesterday and recall seeing a couple of clips holding the cable fast against the tunnel. I could slide the cable back/forth a bit through these clips. I'm also wondering how hard it would be to "twist" the cable sheathing 180 degrees as a test to determine if the outer portion of the inner sheathing is worn (giving the cable a new "surface" to run against).
Hi rb74,
I added another photo after you posted… is that 'bracket' there?
I THINK it might actually be part of the cable itself since it's not shown as an ITEM on the AIM page. UPC12, Sheet 2.5
Regards,
Alan
I added another photo after you posted… is that 'bracket' there?
I THINK it might actually be part of the cable itself since it's not shown as an ITEM on the AIM page. UPC12, Sheet 2.5
Yes -- the bracket is there. If it is indeed part of the cable itself, that nixes my idea of cable rotation as a test. I will take a closer look this afternoon to be sure.
As like I wrote....I use a drill and spin the cable and see what happens.
The bracket was a part of the cables when you bought them from GM... then they stopped adding them with it and you would have to transfer over the original bracket to the new cable.
Quick update to close the loop on this -- I never could get the speedo to stop bouncing with the old cable, so I just opted to replace it wholesale. After looking around, the closest match I could find was a BALKAMP 615-1612 from NAPA. Just a bit shorter than original, but I was able to get it to fit just fine and now I have a steady speedo for my efforts.
speedo cable question
