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Speedometer gear

  • Thread starter Thread starter j69302
  • Start date Start date Feb 25, 2011
J

j69302

Active Member
Jan 31, 2006
325
1
29
Feb 25, 2011
#1
  • Feb 25, 2011
  • #1
I am looking for a 15 tooth speedo cable gear that will work in a TKO600. Smallest gear Modern Driveline offers is a 16 tooth which is what I have and my speedometer reads 10 MPH low across the entire range, and over a 133.2 mile trip (GPS and google earth measured) the odometer shows 127.6 miles. Which is 4.2% on the low side.

The weird thing is it constantly reads 8-10 MPH low when comparing it to my GPS, as well as gear ratio vs RPM calculations. My understanding is the difference should get worse as speed increases.

Is it possible the speedo itself is out of spec? either with the return spring or the magnetism of the drag cup?

I can get the the ideal ratio by switching to a 8tooth DRIVE gear and a 17 tooth speedo gear.

What is involved in changing the drive gear?

I recently removed the speedo to oil it which fixed the needle from bouncing all over the place. I noticed there seems to be quite a bit of end play in the drag cup, and can hear a very faint noise that sounds like the magnet is rubbing on the cup. I am considering sending it out to get rebuilt.

Has anybody had any luck with having them rebuilt? Has anyone tried the reproduction speedos? Are they any good?
 
2

2+2GT

10 Year Member
Apr 25, 2009
3,333
10
79
Southeastern Pennsylvania
Feb 25, 2011
#2
  • Feb 25, 2011
  • #2
The Ford gears were 16-21. There is also a rather delicate aftermarket 23.
 
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