strange things with my speedo.. i have an 1988 rx7. today i noticed it was at 100 mph. I knew that wasn't right. I then looked at my GPS speedometer and it says im doing 60 ish. Earlier in the day it was fine. and then it started doing it.

then later it read correctly after i came to a stop. the speedo and the gps are a bit off by like 2 mph due to tires i have, and that is normal. But 40 miles an hour above my real speed is crazy.. i thought if the cable came loose it would start to read slower or not at all..

Anyone know what the deal could be? TY

 

mine has been doing the same thing, anyone know whats going on? :P

 

Why would a speedometer read a Two times speed.. Is it just the NON LSD rear ends that cause this? is it a Cable? Bad dash Haunted?

 

The FC's use a mechanical spedo cable. It is possible for a different rear end or different size wheels to cause minimal discrepancies. But it should not be that large. I would try replacing the cable. It's fairly easy to do.

 

I've had a problem for some time where my speedo goes off more as my speed goes up...if I'm doing 60, it says 62, but if I'm doing 80, it says 85. Tires are original size so don't know why it speedo is off like that.

 

nvm... i need to start reading

 

my 86 na started doing this a while ago kinda. it doubled my speed precisely it seemed. it read 20 when I was going 10, 40 when 20,etc. then when I shut the car off and back on it was normal. shut it off, turned it on again and it was doubling speed again! turned out my speedometer cable came loose at the cluster. plug it back in snug and it was fixed. try that and see what happens for you OP. been working fine for a few months now. If that doesn't help then it is probably either loose at tranny side, the cable itself or (less likely) the actual speedo gear on the tranny.

 

Ill give it a try ty..