TR2/3/3A Unconventional TR3 Speedo Fix...Is it Doable???

[karls59tr]

Pulled onto the highway the other day and there was a sign indicating the speed of your car. Sign said 45mph. Tr3 speedo said 60mph. I'd like to adjust my speedo to correct reading but I have a TR6 trans and an OD diff. so I'm thinking that getting the speedo professionally calibrated wouldn't work. I know that the speedo dial indicator is easily removed so would it be possible to gently reinstall it further back till I get a correct reading?(possibly lifting indicator slightly to bypass the dial "stop").I know it would be trial and error. Anyone have an idea as to how much the indicator would have to move back in order to lose 15mph on the dial???

 

[TR4nut]

Karl-

I did this on a speedo that I used on my TR4 and was partially successful. If you haven't done so, take a look at Tony Rhode's writeup on speedo repair.

He has a section how to move the pointer. There is a chance you could do it without taking everything apart, but you would need to grasp the spindle firmly without damaging it and then move the needle - Tony's method which requires pulling the innards out of the case first sounds more involved but safer.

Randy

 

[karls59tr]

Thanks for the info Randy.

 

[TR3driver]

The thing is; if the problem was caused by your TR6 gearbox, then the error will not be a constant 15 mph. Moving the pointer could make it accurate at 45 mph, but then it would read too low at lower speeds, and too high at higher speeds. Moving the pointer will also not correct the odometer and trip meter.

To really fix the problem, you need to either change the gear in the tranny, or install a ratio adapter.

BTW, I advise extreme care when trying to pull the pointer off. It's easy to snap the shaft, making the whole thing useless.

 

[Geo Hahn]

I have calibrated mine using Tony's instructions. I drive with the speedo losely in place and usinga GPS (and my wife with a clipboard) I call out the speed and she records it vs actual (GPS).

Pull over, pop out the unit and calibrate some more. After a few stops iti is really good.

Note -- I don't think the OD have any affect on the speedo -- but age and use will call for some adjustment.

Note (2) -- you may find the error is not linear, i.e. you may only be able to get it really accurate in a particular range but not exact elsewhere. I just picked a range where accuracy was most important to me (45-75 mph).

 

[BobbyD]

After installing a Toyota 5 speed and a Nissan diff, my speedo was way off as was my odometer. I wanted BOTH to be accurate.....I wonder how many guys get great gas mileage because their odometer is way off?..........anyhow, I decided to send the speedo out to be re-calibrated for speed and to have new gearing installed for the odometer. Herman van Den Akker recommended West Valley Instruments as they specialize in just British Gauges. After talking to Morris at West Valley, I sent him my speedo and cable which were returned within 10 days for exactly the cost quoted. BTW.....a lot of the speedo and tach cables being sold have improper tip dimensions which can damage your gauge. Since then a bunch of guys in 6-Pack have sent their gauges to West Valley and everyone has been very pleased with the results. My site has a write up on the data you need to provide to get your speedo calibrated as well as the cable specs. Paul Rego sent all of his gauges to West Valley and has an extensive write up on his site.

 

[martx-5]

After installing a Toyota 5 speed and a Nissan diff, my speedo was way off as was my odometer...

Interesting, after I installed the Toyota box in my TR3 (no Nissan rear obviously), but I did change the tire size from 165-15 to 185/70-15. I went out for a drive with my GPS, and the Jaeger speedo registered the <span style="font-weight: bold">exact</span> same mph as the GPS...I mean, it wasn't off one mph over the whole range...well, up to 85mph anyway... :laugh: I found it hard to believe, but there it was.