TR4/4A Speedometer and Angle Drive

Hi

I hope this may be of interest/help to some others. My saga has been four failed angle drives in 20 years due to speedometer binding. Initially, I had suspected poor quality angle drives. I had the speedo rebuilt twice (2004 and again in 2014). Upon inspection after this latest failure I identified the issue as cracked odometer drive gear. Apparently when rebuilt, they used or installed NOS gears which (at this age) develop a hairline crack in them. Once the gear cracks, the teeth no longer nicely mesh with the worm gear - causing binding in the speedo head - which then results in a snapped angle drive.

I did some searching online. Came across this: Odometer Gears Ltd.
https://www.odometergears.com/
https://www.odometergears.com/produc...-Smiths/All/37

I spoke to Jeff at Odo Gears this last Monday and he was super knowledgeable and helpful. I ordered two 32 tooth gears, one to replace the odo drive and one to replace the trip-odo drive. These are newly manufactured gears (direct injection plastic) made from Celcon which includes graphite in the material and supposedly self lubricating. Not cheap ($25) but, better than $175 to rebuild the gauge with NOS parts which will only fail (again) and blow up my angle gear (again). Not to mention angle gears cost $45.

I got it all repaired and installed in the car last night. Everything functions normally again. Here are some pics (original gear is red, new gear is white). You can see the hairline crack in the old (red) gear:


Regards

Bob

Thanks, good to knwo a source of quality repalcement gears.

RJS said:

...I hope this may be of interest/help to some others. My saga has been four failed angle drives in 20 years due to speedometer binding...

Click to expand...

My experience too. Clever of Jaeger/STC to use a $80 angle drive designed to fail if the head binds and save you from breaking that $5 cable.

Glad it worked...the gage is still in very nice shape.

Bob,

Thank you for the feedback. Anytime I can help further, please call anytime. Great photos.

Jeff

This came at a timely moment as I'm surveying three speedometers last week and this week to decide which one will go in to a car we hope to complete by the end of the year.

One of the speedos has a red gear and binds something fierce when (slowly) spinning it up with a drill on the bench. Even hand spinning it gets 'draggy' and then downright tight. It has the same telltale crack like the one that can be seen in photo #1.

Is there a preferred method for removing the cracked red one and refitting the new one?

--Jake

Jeff - thanks and you're very welcome.

Jake - the red gear is a press on. I used a tiny eyeglass screwdriver to slowly but surely pry it up and off. The mounting pin is 5mm. The hole in the new gear is tight, perhaps 4.6mm. So, easy fix. I used a sharp 3/16" drill bit and slowly used it (by hand) to open it up (took my time over ~45mins). Once I could get it starting to press-on, I used a pair of channel lock pliers (with plastic protection on the teeth) to very gently press it home.

Not hard, just be patient and work carefully

Bob

Thanks Bob, good info on the fitment. I had no idea the red gear was the culprit until I read your post yesterday and then the light bulb went on. The world makes sense again!

--Jake