Toyota Starlet c52 speedo adjustment via swaping the speedometer driven gear.

[MrDoors]

Hi Guys, as you know I have done a conversion on my Toyota Sera.
The conversion consisted of a Toyota Starlet EP82 4E-FTE with an accompanying C52 gearbox.
My problem is I want to run a R17 225/40 tire opposed to a R14 185/60 tire.
The rolling diameter will be slightly off.
My question is can I simply change the speedometer driven gear without taking apart the gearbox and correct it.
If so how do I go about finding out what gear I need and where to get it.

The Starlet SPEEDOMETER DRIVEN GEAR is listed below.
33403 GEAR SUB-ASSY, SPEEDOMETER DRIVEN (MTM)
33403‑19285 歯数=31, マーク 31:35

Rather change the gear than getting one of those adapter boxes.

Cheers guys.
Any info would be greatly appreciated.

[4th surf]

Right well changing the driven gear is easy. Just follow the speedo cable down to the gearbox, undo the 10 or 12mm bolt that sits on top of the box next to where the cable goes in, pull the cable up and out of the box (which will come up with the housing that it screws into) slide the driven gear off and slide the new one on, put it all back together and you're done. A point to note this is a good "cheat point" when doing gearbox oil changes too (take the fill plug out and put a funnel in the speedo drive hole and fill her up until oil leaks out of the fill plug...can't go wrong). Not that you'll achieve much by doing this as the EP82 has only but one choice of driven gear. The way that I see this as I quite simply cannot remember the equation to calculate the overall rolling radius of the tyre and work out replacement tyre size for larger rims is one of 3 options.

1. when you go to get your tyres I remember that when we had a Bridgestone outlet attached to our workshop back in NZ we actually had a "Cross reference chart" which gave you corresponding tyre sizes for larger rims to keep the overall gearing correct, this was designed for "Idiots" so you started with the original size and went across the chart to the desired rim size and that was what was fitted.

2. Go to the wreckers and grab a selection of driven gears from some FWD Corollas and perhaps look at a few Camry ones to see if they will fit. Grab your GPS and keep changing them over until come up with a combination that is PDC. I actually did this myself when I did the V8 conversion on my Surf and fitted the 180kp/h V6 4runner speedo and larger tyres. At 100 indicated she is doing 102.

3. This would be the best option as back in the day the cops and also taxis had to have it done regularly for legal reasons and that is when you have fitted your desired wheels and tyres to have the speedo re-calibrated and certified as accurate. I'm not sure what this costs now but the savings on those "funny photos" and bits of paper from "those peeps that drive vehicles with funny roof racks and wear blue shirts" may more than offset the initial costs in the first place. Someone like Asiat instruments may be able to help there or contact the technical department of the RTA and ask them where you can have it done. A point to note here is we had to have this done in NZ to pass compliance where the EP82s would come into the country with a TRD instrument cluster fitted.

Hope that this helps but remember this is based on my experience from working on them in the past so while 6 years ago now might be a bit out of date