Speedometer cable angle drive

[T Rusty]

Greetings, I have used the angle speedometer drive on the "J" type overdrive unit in my TR3A. The car is on temporary licence plates, getting ready for spring and the German TüV. The angle speedometer drive has broken three times, always after I have driven about 120 kilometers. I assumed I had done something wrong the first time but since have carefully followed instructions and it still breaks. I have had two replacements free of charge but now I would rather pay whatever amount to get this straightened out. Help! And thanks for any replies.

[AlanT]

What part of the angle-drive fails?

 

Do you know exactly what happens?

[re-hiker]

My first question would be the same, which Part failed? The short piece of Speedometer Cable that fits in the Gear Shaft in the Gearbox or are the Gears in the Angle Drive damaged. Did you checked that or have you dismantled the Gear Drive? Also try to turn the Speedometer cable fitted to the Speedometer at the Gearbox End by Hand to feel if there is to much Resistance or a Nick in the Cable. Check your Speedometer as well, I had one with a seized Gear.

 

Robert

[peejay4A]

Have you installed the copper washer that should go between the angle drive and the gearbox? Without this the angle drive can fail prematurely.

Edited March 23, 2014 by peejay4A

[stuart]

Check that there isnt a piece of the stub cable left in the gear box end from a previous angle drive breakage.

Stuart.

[TR4Geoff]

Sorry to sound negative, but I thought Angle Drives weren't fitted until the 4A?!

 

Geoff

[stuart]

Sorry to sound negative, but I thought Angle Drives weren't fitted until the 4A?!

 

Geoff

Correct, cable goes straight out and round the chassis and in through the bulkhead. "J" types didnt have angle drives fitted anyway. On a 3a though it may be needed as the cable comes out the opposite side to normal "A" type.

Stuart.

Edited March 24, 2014 by stuart

[T Rusty]

...Sorry this took so long to reply, I am also a computer genius...

 

Thanks for the answers and comments. I refer to the "J" box as if I know what I am talking about. It was advertised as a "J" box, I compared it to pictures and it looks like a "J" box to me. The speedometer drive comes out of the overdrive unit on the right hand side and there isn't enough room to screw the speedometer cable in without kinking it. Somewhere I read about the angle drive, bought one, and everything seemed to be okay. It is possible that I didn't put the copper washer in the first one but after that I certainly did.

 

The part that breaks (shreds) is the shaft (about 1 3/4") inside the angle drive that pushes into the overdrive. I took one angle drive apart and the gears were well oiled and looked as good as new. Only that little flexible shaft attached to a gear breaks.

 

I bought the recommended speedometer cable (160 inch) and installed that and had to route it all over the car, and when the next angle drive failed I bought a new short cable which fits perfectly and I assume that is not causing the problem either.

 

The speedometer was rebuilt in England along with the other gauges and when I drove the car it seemed to work perfectly with no unusual noise.

 

I'm pretty careful about not over-tightening the the knurled "nut" and it has never come loose while driving.

 

Although the angle drive seems to fit into the overdrive perfectly, I will go to my garage tomorrow and remove the latest casualty and try to see if there is anything in the overdrive that looks broken or out of place.

 

I am sure there is a reason that little shaft is flexible, to absorb torque or? The whole cable is flexible though, isn't that enough? Three of us had a prayer meeting about it yesterday and since it's my car I decided to have a unit I have apart rebuilt using a solid shaft. Do I hear booing and hissing in the back-ground!!?

 

I have run the car and the overdrive works perfectly in 3rd and 4th gears so I guess we wired it up correctly.

 

Thanks to all who answered this. I noticed somewhere that this is my second posting of a question. If that is true, I apologize to all who answered the first one. I don't know anything about it. I think I now have learned how to go on-line and get to the Tr-Register site. And, this forum stuff is really efficient!

 

Thanks again, Paul

[stuart]

If its shredding the small extension into the box and not the gears then it may well be a bit of old cable left in.It is sometimes possible to replace that little bit of drive with a bit from an old speedo cable but care must be taken when cutting as they will unravel.

Stuart.

[AlanT]

For some reason the little cable bit is too long.

 

It may be that there is something stuck in the hole but maybe this drive was intended for an A-type and so the little cable does not fit right in a J-type.

 

If its too long it whirls around in a curved shape and this causes fracture. Hence the advice about a packing washer.

 

Put something to the drive hole and try to work out how long the little cable need to be. It needs to engage but not "bottom-out"

[T Rusty]

Thanks Stuart for the idea of using the old cable to make a new "shaft". I have a lot of cable sitting around. Will look at that tomorrow. Also,I'll look into the idea that the the shaft might be too long so slightly curved. Thanks for that Alan. Paul

[stuart]

Cut the bit you want with a thin cutting disc not with a hacksaw and then carefully round off the edges with a small air grinder using 36 grit discs That way it wont unravel. If you use the end of an old cable then one end is already rounded up anyway.

Stuart.

[AlanT]

Any angle-grinder with a cutting disc will do this is you are careful.

 

You could do it on a bench-grinder too I would think.

Edited March 24, 2014 by AlanT

[T Rusty]

Tried to post this once, I was told I was not authorized...Anyway, thanks for.all of the tips. I can cut the cable with my Dremel but how do I fix it into the gear? The overdrive was completely rebuilt so I wouldn't think something is broken off in there. It's a tight fit, I'll have to use a mirror to see. The shaft being too long makes sense to me. It was so nice having the car sitting on wheels again, hate to put it on stands again. Paul

[T Rusty]

In the for sale part of the forum, Graeme Cook has a TR4 for sale. The picture shows the angle drive situation I'm faced with. The overdrive mount too close to allow using the Speedo cable without the angle drive. Paul

[AlanT]

While you are messing with this you could cut a hole in the cover, so you can maintain this area more easily.

 

This OD has been used before by who knows. A partly blocked hole is just the kind of detail a rebuilder may easily miss.

 

If you can get the broken bit of cable out you will see how to fix it I expect. Just pushes into a square hole I would think.

[T Rusty]

I took the gearbox cover off and gave it all another look. I couldn't see anything broken off in the drive. What I did discover was that there is a neat hole cut in to the chassis right in front of the drive on the overdrive...which I shoved the cable through and screed it in. The Speedo cable was a few inched too short so I 're-installed the 160 inch one and put everything back together. I have a fee ling the problem is solved. Will know in s few days as soon as weather gets better. Thanks again to all. Paul