What causes the speedo to seemingly "bounce" up and down as youre driving? Car is a '63 F-85 with the cable driven speedo. None of the other gauges currently work but that is next on the project list as I think some of the copper ribbon on the back of the gauge cluster is broken so Ill be repairing that. But could that be causing the speedo to act this way? The ground supply on the back of the speedo cluster maybe? I also will randomly hear a sort of grinding noise while driving from the cluster, Im assuming its coming from the speedo since that cable is the only thing rotating and that is the type of noise it is but it comes and goes, not consistent or at idle.

 

Well, if it's the speedo cable it stands to reason there should be no noise whatsoever at idle. Time to remove the speedo cable (I suggest a complete removal) entirely, remove the metal shaft from inside the black tubing, clean the inside of the black tubing, clean the metal cable, then grease the entire metal cable and lightly grease inside the black tube housing. You have 60 years of gunk residing w/in. It's not a bad job at all honestly, just needs to be done.

 

Hi speedo cable was replaced, it was converted to a Chevy 350/350 before I got it which didn’t come with a cable so I installed a new greased cable. That’s how I found the broken copper lines in the back of the gauge cluster

Sound is definitely in the back of the cluster area since I can hear it in the cabin while driving.

 

So, I'm guessing here but help me to ensure I have this correct. The vehicle is a 1963 Oldsmobile F-85 with a Chevrolet 350 small block attached to a Chevrolet TH-350 transmission in the vehicle.
Does the vehicle possess the original 1963 Oldsmobile F-85 dash panel instrument cluster?

 

Yes Chevy 350 motor and turbo 350 trans, everything else is original Olds

yes still has original ‘63 F85 gauge assembly.

 

You researched this enough to know whatever year (you don't say) Chevy 350 trans you have the speedometer cable will interchange with a 1963 Oldsmobile F85 instrument cluster speedometer gauge? What Part # speedometer cable did you use? Maybe others can provide some assistance. I don't know if a Chevrolet 350 trans speedometer cable will interface correctly with a 1963 Oldsmobile F85 speedometer gauge. If you're hearing a grinding noise &/or the speedometer is bouncing up/down I'd first suspect the incorrect speedometer cable. Others may offer some assistance. What Part # speedometer cable you use?

 

I was thinking as long as the ends were compatible the speedo cable would work. Meaning the thread size and pitch for each endcap nut, as well as the square end of the inner cable itself fitting, which all did, and that the only adjustment that might be needed would be the driven gear in the trans so the gauge would read accurate speeds.

The cable I got is ATP Automotive ATP Y-804

 

IMO, that cable should work as it's listed compatible for both Chevy & Olds of the models years accommodating your gauge and trans. Although, I'm always suspect of ANY vendor's advertised compatibility indices. Especially when I see the original cable for your car was listed for the 1963 and 1967 models years. I'm at a loss....hopefully others will chime in. Good Luck.

 

I had the exact same bounce with a Ford several years ago. I finally sent it off for repair and it needed a jewel replaced at the speedometer needle.

 

I hope it isn't the panel cluster speedometer gauge as I know they're hard to locate for a '63 F85. I suspect the next course of action would be to remove the cluster gauge and validate the speedometer move freely. To get up to speed I "guess" you could use a hand drill on one end of the cable to get it to rotate fast enough.

I'll mention I did find a 1963 F85 panel speedometer gauge cluster on eBay just now. I really didn't think I'd find one anywhere. Good Luck.

https://www.ebay.com/itm/374521169172

 

My Dad's 1964 Buick Wildcat developed a bouncing speedo - they replaced the cluster.

 

I think I have an old harley speedo cable laying around if it fits I could rig that up on my drill and test the cluster once I remove it. I just need my wife to get her hands up in there to remove a couple of those bolts on the cluster that I cant reach haha.

Thats funny Vintage_Chief I have that very cluster saved in my ebay already and have been debating on pulling the trigger. The circuit board back looks intact and in better shape than mine but the fact that its listed as "untested" and they wont confirm if any of it worked makes me hesitant.

 

If my ‘66 big cars are any guide the highest probability is the speedo cable is meeting some kind of spinning resistance which is keeping it from spinning at a consistent rate to be a good input to your cluster. I’ve found the actual speedometer gauges to be very reliable over the years.

The wound cable inside the casing may be fraying, or the cable and/or casing may have a kink in it which keeps the cable from spinning consistently at wheel speed. It might even have more than 1 kink.

I’d pull the inside cable first to see if there’s any obvious kink or fraying there. If not, I’d look at removing the cable casing from the car at least to clean & grease it. At that time you can also look for kinks in the wound casing.

If you need replacement, know the length of your original get the closest-length replacement you can find. An inch or 3 longer won’t be a problem. An inch short might even work.

If yours, like mine, connects to the left front wheel dust cap, you also want to check the condition of the nylon squared off nut that the inner cable goes into. Usually when these go, the speedo stops entirely, so this is likely not your problem.

These aren’t usually too bad to fix, but it can sometimes take a few tries.

Hope that helps
Chris

 

OP stated he installed a new greased cable in Post #3

 

Anyone know what the axle ratio is for the 6.5” rear end in ‘63?

I’m trying to confirm I have the proper driven and driven gear combo in my TH350 trans and this info is part of the calculator.

 

There were only three options: 3.08:1, 3.23:1, and 3.36:1. The ratio code will be stamped on the cover adjacent to the RH axle tube. A, B, or C are the codes, respectively.

 

Thank you. I’ll take a look at the tag.

 

It isn't a tag. It is stamped right into the cover near one of the bolts

 

I was just getting to hit "Post Quick Reply"...you beat me to it.

 

Yup I found it.
C-234. Looks like that would be the 3.36. So I have that and my wheel height of 25.5”. I think I can use that to calculate which gear combo I would need

 

If you find you need a speedometer head, I have one that don't bounce. I would for sure investigate the cable first.

 

Thanks Eric
im going to take the circuit board out and fix the breaks in the copper ribbon and get all the other gauges/lights working with good grounds and get the correct gear drives combo, then see if it’s still bouncing. If so I’ll be reaching out to you haha

 

Sounds good. My circuit boards are bad but I do have a good speedometer if you do need it.

 

Chris, inside the dust cap, how is that nylon squared off nut attached to the cap?
Steve

 

I just went through this. The nylon nut which retains the squared off end of the speedo cable in the wheel is held in place by a steel strap that's welded to the inside of the dust cap. Once the nylon nut snaps off from too much resistance or age or whatever, you're on the hunt for a new dust cap. Which are now rare. Check the classic car bone yards and get replacements there if you can find 'em.

But - there's a fix.

You can get dust caps for some early to mid-60's Chevies which have the nylon nut, then cut it out & put it in your olds. If I remember right it was a Nova part or maybe a Chevelle up to 67 maybe. Sorry to be vague. Figure out which Chevies from what years had wheel driven, and not transmission driven speedo cables. They will very likely use the same nylon nut which may have snapped in your car. Get a couple of these parts new, you will be destroying them to capture the nylon nut whole. Let's call the Chevy dust caps the "donor" and your Olds cap the "recipient".

Get your Dremel & cut the nylon nut out of the donor cap. This won't take long. You're trying to defeat the welded strap that holds the nut to the donor cap. Remove the nut and set it aside. Toss the Chevy dust cap, it won't fit your big olds anyway. You just want to save the nylon nut. And maybe it's retention strap - consider the dust cap packaging & discard it.

Now drill out the welds on the retention plate in your "recipient" cap in your Olds. Do this with a cotter-pin-sized drill bit that will defeat the welds, you don't want to destroy your dust cap. For best results your drill bit should be the same size as commonly available cotter pins. Once the welds are busted with your cotter-pin-sized drill bit, carefully remove the retention strap in your Olds. It needs to keep its shape, so don't bend it any more than you need to. Your dust cap should now have 2 small holes 180 degrees apart. Your retention strap should have those same holes. It should also have a square opening in the middle where you'll push the nylon remains out to make room for the donor nylon nut.

The next problem if you can't weld, like I can't, is how to retain the nylon nut and drilled out retention strap to the dust cap. I used cotter pins in each dust cap hole of the exactly right outer diameter to match the weld-drill holes. The wide (rounded) end of the cotter pin goes on the _inside_ of the dust cap the "legs" go outward. Then get the cotter pins hammered down as tight as you can make 'em on the outside of the dust cap. It's better to weld I'd think, but I don't know what to do about the heat which would probably melt the nylon nut anyway...

That's how my Starfire is today. Works fine so far, probably a 500-600 miles in, no weird noises or ill effects that I've seen.

Still, if you can find a good original cap, that's probably a better solution. This was a "well how do I make it work again" solution. For what it's worth, I asked my tire/suspension guy if I should worry about it and he said "I don't know what can go wrong".

Cheers
Chris

 

Good advice above, just don't ignore the cable. Even though it's new it can still be poor quality. They usually work better with graphite powder instead of grease or oil.