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MG TD TF 1500 - Lazy Tach

I started up the TF yesterday to warm everything up, which went well with the exception of the Tach acting goofy for the first time ever. Holding the engine at a steady RPM, the Tach would climb slowly to the desired RPMs and sometimes pass the mark and climb a few hundreds RPMs higher, then slowly drop below the point where it should have stopped. Ths generator pulley is not slipping, the gear reduction is working fine and the cable seems perfect. Also when I let it idle, the tach would slowly drop to almost zero, a little increase in RPMs it would start climbing again. I think it's in the tach, what do you fellas think? PJ
PJ Jennings

Paul,

Might be time for a tach cable lube?

Jim
James Neel

PJ, are you sure both ends of the inner core on the cable are still connected? If so, both ends engage the female receiver when the cable is installed?

When was the last time your tach was cracked open? Gearbox serviced with modern, correct lube?

Regards, Tom
tm peterson

So Tom …

What lube should I use in the tach drive on back of my generator?

My TF Operation Manual says to use 90 gear oil. My case is spread apart (probably from the pressure that I created by pumping chassis lube into it). So gear oil is gonna leak right out.

Side note: The manual recommends the same gear oil for the gearbox as the diff. Do I put Redline MT90 in the diff like the gearbox? Or do I put Sta-Lube GL-4 85W90 hypoid gear oil in the gearbox like the diff?

Strange what you learn when you read the manual!

- Lonnie
LM Cook

Hmm. I have always put lithium grease in mine and it still oozes out. I would think gear oil would stream out of all the cracks.

I guess I have been doing it wrong for 50+ years. :-(

Having said that I wonder if your problem could be in the instrument itself. I think I need to lube both my rev counter and speedo because both dance around quite a bit.

It's been 20+ years since they have been lubed.
Christopher Couper

It might just need waking up as well PJ. Take it for a 20 or so mile drive and see if it settles down. Cheers
Peter TD 5801
P Hehir

Thanks guys for all the good suggestions! I have checked the cable and it's ok, now I'm going to pull the tach out open it up, clean it and lube it. I thought of using clock oil, possibly Mineral oil?? Not a clock guy, so help on what to lube it with would be appreciated. I use white lithium on the cable. PJ
PJ Jennings

Just ordered a bottle of clock oil for old clock works, hopefully that will do the trick. PJ
PJ Jennings

If that works you can come to my house and lube mine too. :-)
Christopher Couper

PJ,

Clock oil is good but if you use it without cleaning the old grease and gunge, it won't help. Before doing anything you should start by removing the gauge from the car and test it. The best method I have found for testing is to use an electric screwdriver and a cotton bud (qtip) put the bud in the chuck of the driver then push the other end in the square drive. Use different speeds to check the reaction of the gauge. If it is bad then it would need to be taken apart, cleaned and re-oiled best way to clean it is with isopropyl alcohol.

John
J Scragg

Thanks John, as soon as the weather warms up a bit I'll pull the gauge out and see how it reacts. Thanks for your suggestion. PJ
PJ Jennings

I use lithium grease in my case as well...clock oil for the innards on the tach as posted here.

Regards, Tom
tm peterson

Found out it wasn't the tach at fault, it was the tach cable. A replacement cable, it has a plastic collar on the tach end of the cable and it split allowing it to slide up against the tach drive causing the tach to become very erratic.Replaced it with a "supposedly" copy of the original drive cable for 60+ bucks and it is like a wet noodle with no stability in the casing at all. If I had an original outer casing I could rebuild it. Such is life! LOL! PJ
PJ Jennings

But the real question is does the wet noodle cable work properly?
Christopher Couper

Chris, we'll know today how well it works.
PJ Jennings

It was the old cable causing the issues with the Tach. The Tach is works perfectly and is steady as a rock! The new cable is tight on the drive housing and tight on the Tach as it should be. PJ
PJ Jennings

OK. Thanks for the update.

My tack and speedo bounce all over the place and seem to be getting worse. I have lubed the cables and made sure they were aligned and connected properly.

Next step is to get a drill out and run them direct and see how they behave.
Christopher Couper

This thread was discussed between 04/02/2020 and 07/03/2020

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