• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Toyota tranny users-Speedo

Share this page

prb51

prb51

Luke Skywalker
Country flag
Offline
Has anyone had a speedo adjusted to work properly with the 82-85 Toyota tranny?
I've done the calculator thing and am close by watching the rpm etc but it would be nice to have a real speed reading and specifically mileage.
I was wondering if a stock TR3 speed could be gutted and a Toyota unit put in place...or has anyone sent one off for 'retooling' by a gauge company?
 
I cringe at the idea of gutting an old Smiths speedo to fit a Toyota speedo head.

If you're willing to go to that trouble, contact a local speedometer shop and discuss ratio boxes with them. These are small inline gearboxes about the size of a pack of cigarettes. You provide them some new speedo cables, an indication of where you want the box mounted along the cables, and you give them some speed/distance measurements. They will build you a little gearbox that will match your Toyota gearbox to the Smiths speedometer.

I'm not suggesting the people in the link below... they are just the first hit I got when Googling:
https://www.texasindustrialelectric.com/speedo.asp
You'll see pictures of the ratio boxes about 1/3 way down the page. They put those 7/8" threaded ends on the cables you supply and build the gearbox based on the numbers you provide.

See these links that are better:
https://www.speedometershop.com/ratio.html

AND... much more importantly see these guys as they support Smiths gauges.
https://www.gaugeguys.com/ratioadapt.htm
 
Hi Pat, You need to know if your speedo is slow or fast? Then you can remove your speedo gear from your transmission and according to the color (in most cases) take it to your Toyota dealer and have him order you a new plastic gear that is either faster or slower than your gear depending on what you needs are. Good Luck, Bill C.
 
Thanks Bill. That sounds all to easy but a friend explained that to me via telephone. He said it was easy to change out the one gear.
The stock TR3 is 15 to 18 mph slower than actualspeed based upon the rpm/gear ration calculator and that seems correct by seat of the pants and observing traffic too.
 
prb51 said:
Thanks Bill. That sounds all to easy but a friend explained that to me via telephone. He said it was easy to change out the one gear.
The stock TR3 is 15 to 18 mph slower than actualspeed based upon the <span style="font-weight: bold">rpm/gear ratio calculator </span>and that seems correct by seat of the pants and observing traffic too.
Click to expand...

That calculator was cool. I plugged in my tire size as 205/60-15, 2300RPM "red line" and 5th gear calculated just under 60. This is also our speedo reading and verified by my bother's Passat. So ours is pretty darn close as-is. BTW, Herman has a cable made up that fits both the Toyota and the speedo. But no conversion was needed with mine and 205/60s.
 
Peter,
Good deal.
I've no problem with the cable. Bill takes an MG angle drive and adapts it to the Toyota tranny and you plug your stock cable into it. The stock cable is routed above the Tranny behind the engine block and down to the passenger side to the angle drive. It works better than the stock routing as there are less (no sharp) bends and my speedo bounce went away as soon as we did that route.
But, since I'm running 165/80 15's 25.39 diam. we're at the same diam as stock and the TR3 speedo ratio is off.
Since both tranny's have a 1.0 ratio for 4th gear you can figure the dif in speedo error. Mines about 15/18 mph for whatever reason.
Peter, did you use an angle drive on yours and how is it routed if not?
 
In the Manual that comes with the HVDA kit are the instructions for calibrating the speedometer. Mine is off by about 15 mph and I'll be doing this shortly. Basically, you mark off 1/100th of a mile or 52'9-1/2". Remove your speedo and put a piece of tape on one of the flat sides of the speedo cable. Center your rear wheel on the first mark and drive the car until your rear wheel is over the finish mark. While you're moving you have to count the number of revolutions that cable makes. On the front of all Smith speedos is a number like 1120. If you had your stock tranny, rear end and original tires, the cable would have turned 11.2 times or 1120 divided by 100 because you only went 1/100th of a mile. So now any good speedo shop can adjust the speed and odometer, Herman recommends West Valley Instruments in Reseda CA 818-758-9500. I called and spoke to Morris who knew exactly what I had and what I needed to do. $125 to rebuild and calibrate the speedo and another $60 for new odometer gearing.
 
Good info Bob, my speedo has an 1180 coefficient. You might check the response above by Doug.
The guys making the conversion boxes would keep your speedo stock, fix your speed and odo, and save you about 30 bucks.
But if they are completely refurbishing your speedo it sounds like a good deal.
 
prb51 said:
Peter, did you use an angle drive on yours and how is it routed if not?
Click to expand...

I have two different angle drives adapters, both attach at the gearbox and both are Toyota issue. One is a bent tube that forms a sweeping 90deg. and the other is a true right angle unit. I was told that many Toyotas use angle drives and they are pretty much universal amongst the models that use them. The right angle unit came with the last Supra tranny and I purchased the tubular unit from Toyota parts (for $70).

The 3A uses the tubular adapter. The cable routes 1) up away from the exhaust although I added ThermoTec cool-tube over it 2) forward and over the top of the gearbox towards the driver side 3) then out from under the battery box and 4) finally back through the firewall to the dash. I think that the original actually went through a hole in the chassis next to the gearbox then forward up and over as described above.

I don't have part #s handy - it would take some time to find them.

Here's the 3A with the tubular adapter:

-PK
 

Attachments

  • 14307.jpg
    14307.jpg
    59.5 KB · Views: 198
Peter,
Thanks for the picture but I'm gonna bug you some more.
I've called some Toyata parts guys and they just give me a 'duh'???
Could you locate a part number?
Thanks,
Pat
 
Well I did the speedo revolution test as described above on a quiet paved street after inflating the tires to the proper setting.
Pretty easy actually, to drive slowly and count the revolutions (blu tape flag on the cable-hand held), from marker to marker.
My stock 1180 speedo (marked on the face) turned 10.5 revs rather than the 11.8 it would normally.
The odometer is off 1/10th mile turning 9/10ths in a mile.
I'm enjoying this endeavor, fun to figure this stuff out.

Toyota sells the proper plastic speedo gear for the 85 Celica....I was wondering if replacing the stock gear with the Celica unit if that would work.
It would be easy and inexpensive...might just try that.
 
Pat,

I don't have the time to look right now. I'm trying to finish the addition to my shop before winter sets in so I can get the cars in. I'll look after the holiday.

-Pete
 
prb51 said:
Toyota sells the proper plastic speedo gear for the 85 Celica....I was wondering if replacing the stock gear with the Celica unit if that would work.
It would be easy and inexpensive...might just try that.
Click to expand...

From what I understand, you can not change just the gear, much like the ring and pinion in a differential if you change the size of the speedo gear you need to change what it meshes with in order to give you a different output. I am running a Toyota transmission with a 4.1 diff gearing this equates to a 10% error. I hope someone can prove me wrong on this because I would love to change the gear out to get accurate readings. But from the Toyota boards I check out, I believe this problem has not been corrected via just a single gear change.
 
I've a friend that has done just that experimenting with dif primary gears for the unit.
It is kind of a hit/miss thing but he's had luck doing that and has a box full of assorted gears to try out.
Depends upon how much accuracy you want ...exact or almost. If the speedo is slow a gear with one more tooth (etc).
 
Back
Top