I fitted a Fairlane cluster to my XR6 ages ago. Recently I've noticed the speedo has an issue.

As the speed increases, it appears to be out by an incrreasing amount, like an exponential error. When sitting at 60 as per GPS reading, speedo shows about 63. At 100 on the GPS, speedo shows about 108.

I've compared with two different GPS units (my HD2 and a Tomtom unit)...both of these show identical speeds, so I trust these more than my speedo atm.

So my question...can I pull the speedo unit out of my XR6 cluster and swap it with the Fairlane one?

I haven't had the cluster out for a while, so I'm not sure if they are identical?

speedos are usually calibrated from the factory to read 3km/h over actual road speed. diagnostic mode will usually show 3km/h difference from the actual speedo also.

what size wheels you running ?

Hmmm...forgot about diagnostic mode...it's independant of the speed unit, so should help determine if the speedo is in fact rooted.

I know they're a little above by default, but as I mentioned, at higher speeds, it's out by much more...and hasn't always been like that so I suspect something internal is out of tolerance.

But thanks for the diagnostic mode reminder though

Now to find the doco thats tells me how to do it...Ive been away from this site for too long

Yeah Dude, diag mode will help plenty.
So what are you replacing?? The indicator movement, i.e. the thing the pointer attaches to ??

i'd be looking at tyres/speedo gear/diff gears if its out by a %.

Well I drove home from work in diagnostic mode (big help!). Maybe I'm wrong about it being out by a %....not completely sure.

It might just be that it's over by about 6-8km/h (which is what diag mode sort of confirmed)...I'll try adjusting the needle back a little, and see if that keeps it in tol...

Ray, I initially thought movement behind the facia when it looked like it was a percentage problem...but diag mode seems to imply its a fixed speed over.

I also would think wheels/gears etc, except it hasn't always been like this...only just started happening a few months ago.

Needle adjustment will be tried first, hopefully that's all it needs.