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MG TD TF 1500 - Catastrophic Tach reduction gear box failure

There I am happily driving along when I hear a clunk and something clatters out from under the car? I notice that the tach has dropped to zero. There in the middle of the road sat my reduction gearbox. The brass connector and clamp were still attached to the generator and what looks like the remains of the sheared off shaft were still in the generator. Reading the archives it looks as if this is not an uncommon part to fail? Many of the threads in the archive are older and criticize the quality of the replacement parts. Is that still the case 10 plus years later? Thanks much
Simon

S Griffin

I have had a few fail over the years, but never as spectacular as yours.

If you think about the work these gears do, and the lack of bearing support, lubrication and regular maintenance - not really all that surprising.

I now dis-assemble new gearboxes, and re-assemble with thick gear oil and 2BA screws & locknuts to hold it together. Every year it comes apart, cleaned and re-assembled with new oil. No failures since I started this process about five years ago.

Good Luck

Tony
A L SLATTERY

I am on my 4th in a year - always bought used until the fourth. Bought it from the normal supplier and it has worked fine for the last 600 miles (knock on wood. I wish Abington Spares still sold the replacement gears.
Rick

Send it to Butch Taras for a rebuild. It should then be better than new.

I think one problem with these things is that they are never lubricated properly. Maintenance is important to keep them running. I installed a NOS unit a few years ago and decided to use 600W oil which is thick as molasses. Yes it slowly leaks out but so far the gearbox seems happy. The original grease tends to dry out, and I keep hearing reports of modern greases not doing the same job the original type did. If this experiment works out well, I'll probably solder the halves together to keep the oil in permanently.
Steve Simmons

You only need enough oil to fill 1/3 of the "vertical circle" - about 15ml max. A light smear of silicone between the halves on assembly will retain 95% of the oil over a year.

The big gear does a good job of distributing the oil around when it is spinning around.

That's my experience with 3 cars running tacho boxes in my fleet.

Tony
A L SLATTERY

Simon where did the unit come from? Wondering if all suppliers are using the same source of this AM part or if these things vary in quality? Cheers
Peter TD 5801
P Hehir

Tony, this is an NOS OEM unit so the halves are already together. That's why I was thinking solder in the seam. Of course that assumes the oil could be cleaned out well enough for it to work without drilling the rivets and pulling it apart, at which point I'd definitely rather use sealer. Far easier to apply and to disassemble again at a later date!
Steve Simmons

Peter, I do not know as this was the one on the car when I tool ownership. I have a spare that came with the car, which may well be broken as well. I need dig it out and take a look.
S Griffin

The last time I did mine, I got some heavy grease and added a ½-tbls of Moly Disulphide powder. Put this mixture in so it was about half-filled.

Before closing the unit up. I carefully laid down a thin line of silicone glue to the edge, let it solidify and then assembled the unit, using nylock nuts.

So far so good with no leaks at the edge, but some minor leaking at the shafts

Gord Clark
Rockburn, Qué.
Gord Clark

Steve,
I disassemble the gearboxes from new. None of them have enough lubricant and most are just a dried hard blob of grease. I bought some 2BA Cheese-head screws and nyloc nuts for re-assembly. Once you have the screws in place, regular maintenance and re-sealing is easy.

The unit is cleaned and de-greased, and re-assembled with a thin line of silicone and a dob on each screw position. Leave the unit for 24hrs for the silicone to go off then inject 15ml of heavy oil through the greaser hole, replace the grease nipple & it's ready for another year.

If you want to have the riveted look for shows, I keep an "original spare" that is fitted when I get there. The "serviceable unit" is replaced for the trip home and all other outings.

Cheers

Tony
A L SLATTERY

The older grease does separate and what's left turns a bit hard. But you can reactivate it by adding oil back in. I do this on the NOS units before using and haven't had one fail yet. It's only been 14 years since the first one but I think that's already a pretty good run. Nothing wrong with disassembling, but I sure love seeing the original rivets in place.
Steve Simmons

This thread was discussed between 01/06/2018 and 05/06/2018

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