[TR] HVDA 5-speed in TR6--speedo gear

Fri Feb 10 08:09:34 MST 2017

Update:

I've been working on a recalibration of my TR6 speedometer after doing the HVDA Toyota tranny conversion some years ago.  I wanted to do the most basic (and cheapest) fix that would actually make my gauge accurate.  I may have finally met success with option 7 in my list, exchanging the driven gear in the speedo gear assembly.  What follows is an extension of what I originally posted for that option.

I took the driven gear out of the TR6 (with Toyota tranny) so I could get a tooth count.  It has 31 teeth and was stamped with an 11 that indicated a drive gear with 11 teeth. According to my earlier calculations that meant I needed to get a replacement gear with 28 teeth (for a drive gear with 11) to get my speedo very close to accuracy. I went looking on Toyota parts sites, but they are difficult to use (maybe all modern parts sites are?). If you don't already have a part no. you have to enter a vehicle model and year or a VIN. I fiddled around for a long time trying out various models to see if a 28:11 driven gear would show up, but I got discouraged. The closest I got was a 27:11 on a 4Runner truck, and I decided that I would settle for that if I could be sure it would fit my W58 tranny. I signed up on a Toyota forum and asked if driven gears from one tranny could fit another, but no one seemed to know. One guy suggested I go to a junk yard and pull a gear or two from 4Runners and compare to my current one. I looked online at the Toyota truck inventory at a local yard, saw a lot of non-4Runner Tacomas, checked online to see if the 27:11 gear came on those trucks, and just by luck found a 28:11 gear for a W59 transmission on Tacomas. Wikipedia says that the W58 and W59 are similar both externally and internally except for the specific driveline gear values used, so I have some confidence that the 28:11 I need will fit my car! I just placed the order, $22.83 plus $10.50 for shipping. 

I'll post again when I get the part and see if it really fits. If it does fit, I'll test drive it first to see if I really achieved what I want. Fingers crossed. 

Tim

On Feb 5, 2017, at 9:06 AM, Tim Gaines <mtgaines at presby.edu> wrote:

I have found several possible solutions in my quest to calibrate my TR6 
speedometer after making the HVDA Toyota tranny conversion.  Thanks go out 
to several members of this list and several on the Triumph Experience forum. 
Here is a summary of those solutions.

1.  Keep using a GPS or a phone with a GPS-speedometer app and forget about 
the actual gauge on the dash.

2.  Use a GPS to calibrate the speedo and mark new lines on the gauge face 
or glass with a Sharpie.

3.   Classic Automotive Innovations has an ingenious solution.  A gps 
controls a motor that spins the speedo cable (disconnected from the tranny) 
at just the right (adjustable) speed.  The current price is $275.

4.  As Herman van den Akker recommends, send your speedometer to a shop that 
will replace gears for the speed and odometer mechanisms that will 
accurately recalibrate the gauge.  This requires some accurate measures on 
your part of the number of turns of your present cable per 1/100 mile.  I 
just got a quote from Palo Alto Speedos for $295 to do that calibration.

5.  Buy a speedo ratio adapter for $60 - $120 that attaches to the tranny 
between the speedo gear and the cable and adjusts the cable turns per mile 
(TPMs) to match speedometer calibration.  Different speedo gauges require a 
different number of TPMs.  Whereas most American gauges are standardized at 
1000 TPMs, mine is 1120, and I have heard of another TR6 one being 1180. 
Maybe there are even more values out there.  The advantage of this solution 
is that there are right angle ratio adapters that will help alleviate the 
problem of the tight turn in the speedo cable from the Toyota tranny to the 
TR gauge.

6.  An in-line ratio adapter that connects via cables to both the tranny and 
the gauge.  It does what the above device does.

7.  Find a replacement speedo driven gear with the proper number of teeth to 
change the ratio to match the speedo gauge.  The new driven gear must be 
matched to the number of teeth in the drive gear.  From what I have read, 
that number is 10 or 11 in the W58 Toyota tranny that is often used for the 
HVDA conversion and the value should be stamped on the shaft of the current 
driven gear.  The driven gear can be removed fairly easily from under the 
car by removing a single bolt that holds the gear assembly in place with a 
small metal tab.  I have found only one online site that lists driven gears 
with details about the drive- and driven-gear teeth.  I have emailed to ask 
if all of the Toyota driven gears will fit the W58 transmission, but I 
haven't heard back yet.  I would think that there is a standard for the 
speedo gear assembly across tranny models.

http://parts.lakelandtoyota.com/showAssembly.aspx?ukey_assembly=519949&ukey_make=1060

There are some calculations that must be made to find the right gear, and 
there is a helpful site that guides you through it.  Keep in mind that this 
guide assumes (without saying so) that the speedo gauge uses the US standard 
1000 TPMs.  At the stage where the guide says to divide by 1000 (or 1001), 
you divide by your own gauge value.  That can be found at the bottom of the 
gauge face, partially hidden by the chrome rim around the gauge.

http://www.celicasupra.com/forums/showthread.php?67982-The-end-to-speedometer-gear-questions

I have not been able to find the precise driven gear I need, but I did find 
one that should get me much closer to an accurate readout.  The price of the 
driven gears is about $25 - $35.

Art Liefke sent me the url for a site that explains in detail how the 
British speedometers work and how to calibrate them.  I have only briefly 
skimmed it at this point, but it looks to be a good explanation of all the 
things (and more) I pieced together in several days of looking and reading 
online.

http://www.westnet.com/~mfrank/Speedometer/Smiths.html

Tim Gaines
Clinton, SC
1974 TR6
1980 Spitfire

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