Speedo Angle Drive

[glemon]

I just read an online discussion with someone suggesting that perhaps the smiths angle drives used on Tiumphs etc. might come with different ratios, as my speedo reads about 25% too low this would be very helpful if there were such a thing in that range, but I thought they were all 1 to 1 ratio.

Anyone have any further knowledge of this?

 

[HerronScott]

Greg,

I'm pretty sure they're all 1:1 for Triumphs but I certainly don't have any definitive knowledge here. I thought I recalled us discussing your overdrive probably being one from a Volvo which was the cause of the speedometer being off? Something was different about it than a TR6 J-type but it's been a while.

Scott

 

[Deleted member 8987]

This outfit makes all sorts of drives with whatever reduction/increase you need:
https://www.speedograph-richfield.com/html/minature_gearbox.html

 

[hondo402000]

there is a roll test you can do to figure out if your spedo is off, and with that information you can send your spedo off to the professionals and have it recalibrated. I think you can get the directions for the roll test from Nisongers site

Hondo

 

[glemon]

But it is so far off recalibrated will only get me right speed, odometer will be way off, they can fix this too, but it becomes much more expensive, that sis why I am looking at ratio adapter options which will fix both problems.

Yes, I must have a different drive ratio in my J type O/D.

Thanks for the site supplied looks promising, I have been looking at US sites for the adaptors, but many don't seem to be familiar with "our" cars.

 

[TR3driver]

FWIW, my local speedometer shop offered to build a custom in-line ratio converter for around $100. That was a few years back, so the price may have gone up.

Another thought, you might be able to get close by just changing the driven gear in the OD. Probably have to drop the rear crossmember and lower the OD, but I think it could be done without removing it from the car.

 

[HerronScott]

Quantum Mechanics sells the parts needed to modify the Volvo J-type overdrive to have the speedometer ratio. It involves disassembling the overdrive though. :frown:

Quantum Mechanics TR overdrive parts

This kit contains all the parts you need to convert a Volvo J type overdrive into the correct ratio and connection to fit into a TR6. It contains a new “8 start” speedometer drive worm gear for the mainshaft, a new, correct length, 20 tooth speedometer pinion driven gear, a new speedometer bushing with new seal and o-ring, a new ferrule and fork, and a new 90 degree drive for connection to the stock TR6 speedometer cable. You must disassemble the Volvo overdrive to install the “8 start” worm gear on the annulus. This kit not only enables you to connect to the TR6 speedometer cable but gives the correct ratio for the stock TR6 speedometer. This kit will fit all Volvo J type overdrives with the mechanical type speedometer assembly. It will not fit the electronic speedometers as the Volvo J type rear casing is not bored for the speedometer assembly. Price is $235 + $8 shipping in the USA.

Scott