My speedometer needle always seemed a bit weak in that it moved down/up when you drive over bumps or rough pavement.  Is that just how these speedometers are?

I have a dash cap on meaning the speedometer can't/won't come out.  This is just a general question.

 My 71 speedo was always steady. I'd check the speedo cable and sheath for defects. The flexing of the sheath when going over bumps may be related.

57 minutes ago, Mark Maras said:

 My 71 speedo was always steady. I'd check the speedo cable and sheath for defects. The flexing of the sheath when going over bumps may be related.

A defect would mean a tear in the sheath outside of the cabin?

You could also check were the cable attaches to the transmission.

59 minutes ago, chaseincats said:

A defect would mean a tear in the sheath outside of the cabin?

Possibly but it could also be a frayed cable that catches on the inside of the sheath when it flexes. I'd remove the sheath and inner cable from the car. pull the cable, clean everything, lube, and reassemble if there's no damage.

@Mark Maras Hey friend would it be easier to disconnect the speedometer housing from the transmission, slide the cable out, inspect, and add some lithium grease and give that a shot first? Wanted to get you’re thoughts on that.

3 hours ago, siteunseen said:

You could also check were the cable attaches to the transmission.

That part should be good - I replaced that pinion gear housing/seal a few years back and the cable there looked good - the issue is probably further up the line

2 hours ago, Mark Maras said:

Possibly but it could also be a frayed cable that catches on the inside of the sheath when it flexes. I'd remove the sheath and inner cable from the car. pull the cable, clean everything, lube, and reassemble if there's no damage.

Can you do that without removing the speedometer?

1 hour ago, Yarb said:

@Mark Maras Hey friend would it be easier to disconnect the speedometer housing from the transmission, slide the cable out, inspect, and add some lithium grease and give that a shot first? Wanted to get you’re thoughts on that.

Is the issue only at the ends (speedometer and transmission connectors) or can the issue be anywhere within the sheath?  

The issue could be anywhere in the sheath.

Yes I believe you can pull the drive cable all the way out towards the transmission end. Getting it back in and all engaged might be a trick though. IDK

 I've removed the cable only from the transmission end. There was a frayed wire in the center of the cable. You'll have to turn the cable while pushing on it to get it to line up with the speedometer connection.

1 minute ago, Patcon said:

The issue could be anywhere in the sheath.

Yes I believe you can pull the drive cable all the way out towards the transmission end. Getting it back in and all engaged might be a trick though. IDK

Yeah, the re-installation was my main concern haha

I believe the speedo end is just a square end on the cable. If it pulls through easy, it should go back just as easy. Now when it gets to the top you will have to rotate it to get it into the the speedo drive hole. As long as the inner cable comes out at close to the right angle it all aught to go right back together, Worst case you have to remove the cable from the speedo and then reattach by feel. It's do-able...