Bouncy Speedometer Needle?

[iruyle]

Hey, all.
After a search for "speedometer" I read through about 2 dozen posts and found a ton of folks with totally inop speedos or speedos that were out of calibration but nothing that addressed this specifically:
I have an 86.5 manual that I bought back in '91. Sold it to my boss in 2003 and got it back recently. Never saw this issue back then and guages have never been altered. The tranny was removed and built (bearing went bad) about 2 years ago and now the needle wavers wildly when accelerating, maybe +/- 10 mph vs. actual speed. It evens out somewhat at highway speed and always stays consistent with rate of travel, just spasmodic.
Where do I start with correcting this?

 

[57trimMKIII]

My needle has bounced around under 20 MPH since I bought my car, you're not the only one.

I've heard this problem is caused by the speedo' cable, but I've never bothered with it. :dunno:

 

[xzeror]

mine does the same stops bouncing after 20.

 

[jg5899]

I've heard that this can be caused by an old dry worn cable.

As far as my own personal experience I had a 4runner with the same issue and all it took was lubing the cable, lube acts as a dampening agent for the cable. Not sure if it would be applicable in our cars though. Might be worth a shot

 

[Nick M]

Rule of thumb: Bounces to start and smoothes out is the speedo head. The wound up spring has lost some tension. As the drum spins faster the spring is wound tighter and it stops bouncing. If it bounces consistent all the time at all speeds, that is the cable.

 

[shipkiller]

if it's a constant but very very very small bounce, like a vibration in the needle let's say.

that would be the cable and overtime would it become worse?

 

[iruyle]

Rule of thumb: Bounces to start and smoothes out is the speedo head. The wound up spring has lost some tension. As the drum spins faster the spring is wound tighter and it stops bouncing.

Thanks for the info. Is there a fix less drastic than a new cluster or shall I just leave it be?

 

[f00g00]

Things you can check are the short cable coming out of the speedo gear housing on the transmission. The gear itself,if they are slightly worn it can cause a bounce. You will have to get under the car though and make sure the front of the car is higher or you could have tranny oil pouring out of the holé if the rear end is jacked up. On my car I have to run hot spotz tape around my cable or my 3" downpipe melts my cable which lets my speedo bounce for about 30 seconds, then it seizes and I have to change it and the nylon gear.

 

[destrux]

Every import car (toyota or not) that I've ever worked on that had a bouncing speedometer had old gummed up/dried up grease in the speedometer cable assembly. It makes the cable stick and then "pop" rather than spin smoothly. If you don't fix it, eventually the cable will snap or the speedometer gear in the trans will break or strip. You can usually slide the inner cable out and clean it, and the housing it goes through, with carb cleaner. Then grease it up with the proper grease (I like to use high temp wheel bearing grease, but that's probably not OEM approved). I've fixed at least a dozen cars by doing this, and it lasts for years till the grease dries up again.

 

[Nick M]

On some models (Cressidas and Supras rarely came in the shop) I would spray white silicon grease, and the cable would move smoother. If it bounces early and smoothes out, you don't need a whole cluster. A speedo shop (if you have one in your area) can rebuild it. You will have a sticker inside your door saying the speedo was repaired at xxx,xxx miles. There are too many liars, cheats, and thieves in the US, it has to be done that way.

 

[Skeezix]

I somewhat enjoy the slight bounce in the speedo lol, that's how you know you are driving an antique vehicle

 

[iruyle]

I somewhat enjoy the slight bounce in the speedo lol, that's how you know you are driving an antique vehicle

LOL. I suppose it's a little tough for me since I got the car when it was 5 years old. It's kind of sad to see it, like seeing the old dog you got as a puppy limping around the yard with arthritis and cataracts...

 

[ImperfectSupra]

Would the small bouncing of the needle cause a jerky acceleration with light pedal pressure on gas, due to speedometer gauge sending out an uneven speed signal to ecu?

 

[757_supra]

Every import car (toyota or not) that I've ever worked on that had a bouncing speedometer had old gummed up/dried up grease in the speedometer cable assembly. It makes the cable stick and then "pop" rather than spin smoothly. If you don't fix it, eventually the cable will snap or the speedometer gear in the trans will break or strip. You can usually slide the inner cable out and clean it, and the housing it goes through, with carb cleaner. Then grease it up with the proper grease (I like to use high temp wheel bearing grease, but that's probably not OEM approved). I've fixed at least a dozen cars by doing this, and it lasts for years till the grease dries up again.

This actually confirms what I was thinking. My speedo needle bounces only on very cold days, so I figured it was something that got hard in the cold,such as old grease. So this is near the top of my list to fix, as it bugs the hell out of me. Good info. Many thanks.

 

[supraguy@aol]

Would the small bouncing of the needle cause a jerky acceleration with light pedal pressure on gas, due to speedometer gauge sending out an uneven speed signal to ecu?

No. The engine/ ecu doesn't really care/ know what the speedo is doing.

 

[ImperfectSupra]

No. The engine/ ecu doesn't really care/ know what the speedo is doing.

I hadnt notice that the acceleration was a bit bouncy during low rpm gradual acceleration until I noticed the bouncing speedometer. Maybe its a coincidence.

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[jetjock]

No. The engine/ ecu doesn't really care/ know what the speedo is doing.

Actually the ECU does know and care but you're right in that it won't matter in this case.

OP: Clean and lube the thing now or you'll be replacing it...

 

[ImperfectSupra]

Actually the ECU does know and care but you're right in that it won't matter in this case.

OP: Clean and lube the thing now or you'll be replacing it...

Thanks

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[supraguy@aol]

Actually the ECU does know and care but you're right in that it won't matter in this case.

OP: Clean and lube the thing now or you'll be replacing it...

I know that the ecu gets a speed input, but it comes from the speedometer itself?

 

[jetjock]

Yep. Input signal #6:

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=044

Reed switch (4 pulses per rev iirc) in the combo meter except for the digi-dash in which case an optical encoder is used...