speedo problem

[Tremblor]

when my truck is cold my speedometer reads quite a bit above what is suppose to be at. For instance, when the truck is warm, the tach reads 2000RPM in 3RD gear and im doing exactly 60km/h. When it's cold the speedo says 80km/h at the same RPM and same gear. is there a way to fix this. Also i think it's causing my odometer to increase faster as well. Or am i wrong?

 

[Foxracin]

Mine has done the same thing ever since I swapped t-cases to the manual case. That shouldnt cause it though.

The colder it is the faster it reads until it warms up then its fine. Im not sure at all what is the cause but mine does it it and I have wondered why. Mins was fine before I swapped t-cases.

 

[little x]

Mine does it as well. There have been one or two threads on here about it over the past few years. But to my knowledge no one who has had the problem has ever figured out the cause, or a solution.

Can someone describe exactly how the speedo works, then maybe we can think it through? I know that there is a gear in the t-case which turns a gear at the end of the speedo cable. I am assuming that the faster this gear turns the more it pulls the cable (some how) and then on the cluster side, as the cable is pulled the needle turns. Is that it? What actually tightens the cable as the gear turns faster?

 

[explorerguy89]

thats extremely odd

 

[thanatos9]

Mine does it too. The first time i noticed it I looked down at the speedo on the freeway and it was pegged. I got to the store, ran in quick and jumped back in it, it was back to normal for the trip home.

 

[Tremblor]

It's not that the speedo is pegged, it's that the colder my truck is the more is increases over what it really is. as it warms up it gradually comes down to what it is suppose to read.

 

[ifergusson]

Mine does that too.When it is -30 or so I can be doing 10mph and the speedometer will be pegged.If it is less cold then it might only be off 10 or 20 km/h.I usually gauge my speed by the tach untli it warms up.

 

[tgorle]

Mine does this too... thought it was only during cold spells when it started happening a few years ago (it also appeared to be intermittent based on colder outside temperatures, and would read correctly after the car was warmed up).
Now, it's constantly off year 'round, usually reading about 35 when I'm going about 20-25, and it reads about 5mph over at freeway speeds.
Very strange, and no obvious reason or cure.

 

[BigRondo]

This may or may not apply. I remember years ago that the cars had mechanical speedometers and often times the cable or the gear on the transmission would wear out. When the cable was wearing out and it was cold out it would make a screeching noise and give false readings, or not work at all until it warmed up. We all know that the cold weather will have an ill effect on the metal cable and plastic gear. Apparently this is magnified when the cable is worn/stretched and the plastic gear is worn.

Just my $.02