1978 Toyota Corolla Wagon goes over 130mph!


#1

at least that’s what the speedometer reads when cruising with highway traffic during regular commutes to and from work.



when accelerating from a stand i.e. at a light, the speedometer immediately starts reading 40-50mph and is already past the 130mph marker when i’m barely going about 30mph.



the car has the original 1.6L 2TC engine and is an automatic. it’s not a muscle car with any sort of power modifications.



what i’d like to know without spending all sorts of money is what would the problem be most likely attributed to: the speedo cable, the speedo gear in the transfer case and or the gauge cluster? Thanks in advance for any help.


#2

It isn’t the cable. That cannot gain speed on its own.

My guess is it’s the cluster; however I’ve never torn these apart so I’m guessing. There should be a clutch mechanism withing the cluster that converts the spinning cable to a stable speed output rather than a rotating output, and my guess is that the clutch mechanism is binding.


#3

I would think the trouble is within the gauge also. You may be able to prove it by disconnecting the cable connection at the tranny and drive the end of the cable using a varible speed drill motor.


#4

i’ll go ahead and try that. if it does turn out to be a mechanism in the gauge cluster, i guess i’ll have to cross my fingers and hope the dealership has one on the shelf somewhere collecting dust. thanks.


#5

What’s wrong with checking out the salvage yards? I doubt a dealer will have a 30-year old part lying around, but you may get really lucky with some internet factory suppliers. I just doubt you’ll find a NOS (new-old stock) part for a '78 Corolla.


#6

Probably a very weak or broken hair spring on the speedometer needle. This means trying to locate a used instrument cluster at the salvage yards (could be difficult on one this old) or pulling the cluster and sending it off to a speedometer shop for repair.

You could do a net search for speedo repair shops in your area.