Speedo inaccuracy, speedo drives... And you.

[RomanV]

Lets say that your speedo drive is inaccurate, and you've only got like 5 bucks to fix it with.

There are two types of Toyota speedo drives. large gear, and small.

Most are large.

So, take any large Toyota speedo drive gear, and you'll find this written on the bottom:



The top number, is how many teeth are on the shaft inside the gearbox, which spins the speedo drive.

The bottom number, is how many teeth are on the speedo drive itself.

Electric speedo drives have a short shaft, the cable ones are longer:



But if you wanted to swap the whole assembly over, you can convert to electric or vice versa easy as, they swap no probs.

From having pulled out about 20 of the friggen things from all sorts of cars at pickapart, Whether from a transaxle or RWD box or whatever, the size/shape/etc of the teeth are all the same. Same sized gear, same angle of mesh, same height, etc etc. Just a different amount of teeth.

Using GPS you can work out your actual speed vs what your speedo shows, and then work out what % you need to go up or down, depending on what you started with.

You need to know how many are in the box you are using, to calculate the percentage of difference that a different amount of teeth will make if you swap to a new speedo drive gear. But it doesnt matter how many teeth are on the gear inside the box that your new speedo drive comes from.

For example, AE111 has 35 teeth in the box, 33 on the gear.

Altezza has 10 teeth in the box, 33 on the gear.

You can use either in either type of box, and it will work just the same. The only difference is that it will have the wrong number stamped on it!

If you change to a higher final drive ratio (say 3.8 to 4:1) then you need more teeth on the speedo drive.

If changing to a lower final drive ratio, then vice versa.

In toyodiy.com, it tells you how many teeth are on a speedo drive for a particular car. So you can minimise the amount of time spent searching for one with the amount of teeth that you need.

Then you can either try your luck at pick a part, or scour trademe or whatever with a pretty good chance of finding what you need.

Swap in the new speedo drive, and you'll now have a more accurate speedo.

[OllieS]

same angle of mesh

Not necessarily, some gears are mirror images, they are just rarer. E.g. the E series boxes in AWs and SWs. I know this because I didn't pay enough attention the first time I replaced the speedo gear in my old AW - used one from a C series with the same numbers, probably lasted about 0.5 s before the diff ring chewed it - rookie mistake.

[RomanV]

Aah okay. Are they both small gear type? Ive pulled out loads of the 30ish tooth ones from all sorts of cars and they have all been the same. Na sw20 with s series box has the small type.

[OllieS]

Nah, large type, as in your picture.

Does the na SW drive go into the top or the side of the gearbox?

[Malcolm]

I would think that different number of teeth = different diameter of gear = problems with the gears meshing (and I wouldn't think there was a great deal of room to change diameters before you get bad interference or the teeth don't contact). Have you tried this yet? Actually this also makes me wonder if the reason why my speedo works intermittently is because the replacement gear I used was the wrong size and doesn't mesh properly...

[RomanV]

Yep I've tried it.

I am using a cable W55 speedo drive in an Altezza box which came with electronic speedo. I've used two non factory ratios in there with no problems. (Apart from varying speedo accuracy)

Toyota do this themselves, to make the speedo work correctly, as you could get a 30,31,32,33,34, or 35 tooth speedo just for a W5* gearbox.

[RomanV]

Nah, large type, as in your picture.

Does the na SW drive go into the top or the side of the gearbox?

Hmmm okay, weird!

NA SW20 has it plug into the top, and it uses the small gear type.

Have got one of the electronic ones here somewhere.

Via Toyodiy, says that SW20 turbo uses 30 teeth in the box, 35 for the speedo drive gear.

I guess it's not too much of an issue for a transaxle, where it's unlikely that you'd change the final drive ratio.

Just found some pictures of MR2 turbo speedo drive... It does indeed run backwards to the rest. I wonder if many else do... Bah!

[sergei]

Nah, large type, as in your picture.

Does the na SW drive go into the top or the side of the gearbox?

Hmmm okay, weird!

NA SW20 has it plug into the top, and it uses the small gear type.

Have got one of the electronic ones here somewhere.

Via Toyodiy, says that SW20 turbo uses 30 teeth in the box, 35 for the speedo drive gear.

I guess it's not too much of an issue for a transaxle, where it's unlikely that you'd change the final drive ratio.

Just found some pictures of MR2 turbo speedo drive... It does indeed run backwards to the rest. I wonder if many else do... Bah!

Isn't on transaxle the rotational speed of the speedo drive gear (the one that is driving speed sensor gear) is equal to rotational speed of wheels? Because it is located on the diff and rotating at same speed as crown and ultimately on straight line same speed as axles.

[Mr Revhead]

Toyota do this themselves, to make the speedo work correctly, as you could get a 30,31,32,33,34, or 35 tooth speedo just for a W5* gearbox.

Yeah on some vehicles it will list multiple driven gears for the same drive gear

[Rick]

I remember looking into this a while back for my car (W55) but I needed something like 40 teeth on the speedo drive which I dont think they ever made one or I couldn't find one, so it not that easy if you a running higher diff ratios.

[Malcolm]

Isn't on transaxle the rotational speed of the speedo drive gear (the one that is driving speed sensor gear) is equal to rotational speed of wheels? Because it is located on the diff and rotating at same speed as crown and ultimately on straight line same speed as axles.

Yep, also I was wondering how the number of teeth on inside the gearbox worked, when numbers around 30-40 are being talked about but the gear in the transaxle gearboxes is massive. I realised this is because it's effectively a very truncated worm gear, so it's the number of teeth that move axially along the gear in a full rotation, rather than radially, that matters. I found a pic that helps illustrate this:

(stolen from thegreatestben)

[ebgamer]

you guys seem to know tonnes about speedo drives, don't want to hijack the thread but what would be the difference between an electronic speedo cable and analogue? I managed to pickup a digital dash from a wrecked ae82 fxgt to put in my sedan but the gearbox and fuel tank were gone so I couldn't get the associated parts to plug it in.

[loose_unit]

Just digging this thread up again. Just doing the same thing in my Hilux. Ive changed ratios from 4.1 to 4.8 and i have a 31/10 speedo drive currently in the transfer case, and have calculated that a 33/11 will be the closest match. Will the 33/11 go in and mesh properly?

[strx7]

that thing is going to be NUTS to drive in 2wd in the wet with a 4.875 in the back of it!!!

[RunningRich]

Be careful not to strain that blue gear in the gearbox. My ST165 once had a speedo drive cable failure that must have put undue load on it so it failed.

Good thing though as I then had the gearbox disassembled, my spare ST185RC gearbox disassembled and the two merged into one all under warranty. Wouldn't get that service out of an aftermarket warranty these days!

[evil_si]

Good info, knew id seen it somewere awhile ago.

This should be make tech faq!!!

[gt4dude]

wonder if the reason why my speedo works intermittently is because

the electric contacts between the loom and speedo drive need some CRC and compress air to blow out grease shit

it fixed mine anyways