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Speedometer Repair

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BobbyD

BobbyD

Jedi Knight
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Last year I installed the Toyota 5 speed and the 4:08 Nissan diff along with a lower profile tire so my speedometer was off by about 12-15 MPH. This winter I sent it out to West Valley Auto Electronics in Resada CA for a rebuild and recalibration. There's a little exercise you have to go through before sending it out which determines how off it is. They rebuilt it, calibrated it, installed new odometer gears and replaced the cable guts in 10 days for $225. Today I hooker up my GPS unit which also shows MPH and went for a ride around town and on the highway. The speedo and the GPS were dead on up to about 50 MPH. Above 50, the speedo read about 3 mph higher than the GPS. That's pretty darn good in my book and the speedo is as smooth as it can be. Now I need to find a measured mile to test the odometer.
 
Bob,
I went thru the same exercise with the 5 speed/speedo. West Valley auto did mine too and a nice job they did.
I seem to be about the same as you 2 to 3 mph slower than indicated (I'm sure it was my calculation that was a hair off) but alot better than the 15+ I was before. My speedo needed a rebuild anyways and they did a great job, very smooth and registers even a few mph when crawling along on my dirt road.
 
Bob, I have seen a measured mile on Route 159 in Windsor Locks. It has been years since I last noticed it, however, it may still be in place. I don't travel this area often but will keep it in mind to check for it next time I'm near the area. It happens to the the stretch of road called South Main Street and was located between Hayden Station Road and Lawnacre Road and was posted with very small signs along the edge of the road for northbound motorists.

I know this would be a little bit of a drive from Wallingford but maybe on a nice day it would be worth it.

Hope the link works

https://maps.live.com/#JnE9eXAuV2luZHNvci...S05OS4xNDA2MjU=
 
Aren't the mile markers on 95 and 91 exactly one mile apart?
 
Take a stop watch to the measured mile, run at indicated 60 mph, one mile in one minute and you can check the odo at the same time.
 
If you're sending this to a speedo shop for re-calibration, they will have forms to submit when you send in the unit. They will basically be asking for the equivalent of an odometer reading over a known measured distance.

If your speedometer is otherwise intact, consider having the speedo shop build you a ratio converter box instead of changing your gauge's odometer and speedometer calibration. The ratio box will mount inline with the speedo cable and it will convert the actual rev/mile in to the revs/mile that the speedo needs to be accurate. I think you'll find they are less expensive than a complete speedo conversion and recalibration but obviously the shop will be able to explain the merits of each method.

For info on ratio boxes, see the folks at APT:
https://www.gaugeguys.com/speedcorrect.htm
 
There are steps you have to take before sending your speedo in and I've documented them here. I thought about the "ratio converter box" but the cost was wasn't all that cheaper and I didn't want a "box" hanging under the car. What impressed me with West Valley was that he asked for a measurement on the cable tip to determine if it was protruding too much. I also figured that after 34 years it was due for a complete tear down and rebuild.
 
I've actually used them on 91 south just out of being bored and they seem to be right on the money.
 
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