ray77vette

what causes the speedometer to bounc, and even better what needs to be done to fix this?

thanks

blademaker

My speedo bounced really bad, right before it quit. A new cable didn't fix the problem, so I had it rebuilt.

78whtshark

My 77 GMC truck did that and it was the gear in the side of the transmission. Replaced the gear and speedo is fine every since.

Aflac

The speedo system on C-3's isn't too complex.. It's the Gear, 2 cables, xducer, the speedo head and the gear in the trans....I noticed that my lower cable acted stupid and that made mine flop. I repositioned it for a good angle and secured it. GTG no more flop

ray77vette

thanks now i know where to start

ductape

Believe it or not, a bad u-joint'll do it too :yesnod:

mrvette

I fail to see how a U joint could make the speedo bounce....assuming it's in the rear suspension, not some addition to the speedo cable....

I will assume no cruise controll...pull the speedo cable, and examine for any signs of wear....it only pulls from one end, the other is fixed in place by an adaptor....usually up top....the cables themselves are common and easy find in a parts house....
the shroud needs cleaned out and any carbon/graphite lube or old dried oil needs be cleaned out, I just use carb cleaner and a air jet...blow it out....

if it's still acting up, you need do the nasty...pull the speedo head....and fix that....it's fairly easy....do a search and find my previous posts on how to do this....

GENE

turtlevette

lubricate the speedo cable.

comp

man oh man, for a u-joint to throw off the speed-o, the bind and release would ge un real :banghead: :banghead: like gas.brake,gas,brake
i'd think you would feel or hear :eek: the joint before it could bind so bad as
to send that much harmonics back threw the driveline :eek:

kenko74

Recommend you replace the speedo cable (my '74 had a two-piece cable). My speedo didn't bounce, but it sure did squeek. The new cables fixed everything. A lot easier than pulling your entire speedo, too. Hope that will fix your problem. I'd avoid squirting any lube in the old cable, or any additional lube in the new cable. The cable spinning sometimes acts as a pump and works any excess lube right up into your speedo, and gunks it up, plus looks bad with goo spots in your dash's centerpiece. A cable's not very expensive, and should last 20 years.

BSeery

I had the same problem and it was the cruise control transducer that was causing it. So, after you lube the cables, if the problem does not go away, look at the transducer and see if it is stiff to turn.

Mine locked up and tore the end of the cable.

mbeeman350

My speeometer use to bounce on my 72. Pulled the cable off at the transmission end and sprayed some penetrating oil in the end. I held the cable above the car, higher than the head piece in the dash. All in an attempt to satuate the cable as far as I could w/o removing or replacng it. Then I lowered it and let it drain. Did this a few times and you would not believe the gunk that came out. The cable was dry, dirty and rusty. After letting it drain over night I sprayed some white grease into it. No more problems, quiet and steady! WD 40 or 30 wt oil would work OK.
A note of caution, you do not want any oils or solvents to enter the head or speedometer housing, so be careful when trying to satuate and re-oil
Good Luck
Mark :party:

gliot1

Speedo cable. I bought the lube device from Mid America and it cured mine.

Kingt

As BSeery said, "if you have a cruise control check the transducer." That's what caused mine to bounce.

comp

do you know if the transducers are all pretty much the same(chevy,cars&trucks)

mga1x

i pulled one out of an '80 olds...it was the same as my vette.

all of the above was good advice: check cables for tightness at transducer and lubricate upper cable. problem should go away.

Neo Fender

To add to what has already been stated: If you have cruise control, you'll have two cables, an upper (CC transducer to speedometer) and lower (CC transducer to transmission. If you find out that the lower cable is your problem, about 90% of time it's caused by a bad transducer binding and not allowing the cable to turn at one end while the transmission is trying to turn the opposite end.

The CC transducers are a universal GM item. Some may have add ons for dashboard lights, etc. but these can easily be removed. Salvage yards have them for about $20 - $25.

Aflac

mine did the same thing... still isnt working right... think i stripped the cable end of the tranny gear :cuss


[Modified by Aflac, 4:40 PM 12/17/2003]