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MG TD TF 1500 - Tachometer Gearbox Lube

While returning from Middlebury last Saturday Lazarus' tachometer abruptly quit registering. The pin that goes into the generator split where the locking screw attaches it to the gearbox input shaft. Received a repair kit from A/S yesterday and installed the pin. The gearbox is an original Smith's that has been rebuilt with the case halves riveted together (tightly). I see a problem. The grease fitting doesn't function very well if there's no way for air to get out of the casing.
I suspect that the gears have not been getting greased. I'm considering inserting the typical small red tube of a pressure can of lubricant into the grease fitting hole and filling the casing that way. Any suggestions about grease? How about lithium?
Another option is drill a small hole in the case to allow air to get out when grease goes in. Could get messy when it gets warm. Bud
Bud Krueger

Bud it would be highly unusual for the gear box to be air tight. The grease can escape at either of the cable ends, the rivet points and the joint of the case halves.

Right or wrong I use a couple of pumps of moly out of my grease gun. I've never seen it harden up like the stuff from days of old.
MG LaVerne

Lithium is a good choice. Regards, Tom
tm peterson

I also pump a bit of lithium grease in mine too. I have a riveted one and the grease seems to seep out of every crack and needs to be wiped down frequently.
Christopher Couper

Right on, Deerslayer. I mean LaVerne. Put the handgrip toy away and got out the lever greasegun. As is heard in My Fair Lady, "... oozing charm from every pore he oiled his way across the floor.." Bud


Bud Krueger

Unscrew the fitting and you can see whats in there.
If you want you can shovel grease through the hole, into the cavity while turning the gears.

Now there is an issue with grease compatibility. Grease is formed by subjecting oil to the action of a BASE. Sometimes Lithium, some times Sodium, sometimes other metallic hydroxides. In effect the oil is turned into a soap.
Some of the bases are not compatible and the result is a hard abrasive mess. Different bases should not be mixed. Since you don't know what has been used, I would suggest you clean out the stuff that's in there first.

I used a pressure can of KROIL with the tube sticking in the fitting hole while turning the shaft under power, on the lathe. A drill press would work also, as would a hand drill.
When the effluent runs clear you are ready to start over.

Jim B.
JA Benjamin

Bud - Check the wear on your generator rear bushing. Excessive wear on that bushing will put a strain on the pin from the tach gear box, causing it to split. Cheers - DAve
D W DuBois

Jim, I cleaned it out with a good licking from a pressure can of Kroil. Filled it with moly from the grease gun.
Thanks for that, Dave. I have about 15,000 miles on that bushing. To get a replacement pin I had to buy an A/S repair kit for about $40 w/shipping. Bud
Bud Krueger

One little bump and you get branded a killer for life.. :-)
MG LaVerne

"Dave. I have about 15,000 miles on that bushing."
How tight do you run the fan belt in you car - should be at least 1" deflection between water pump and generator pulley. Should also be a segmented belt. I think that I went through couple repair kits before I woke up and smelled the coffee and got a proper segmented belt. Cheers - Dave
D W DuBois

See http://www.ttalk.info/Holcombe.htm Put the segmented belt on in Feb '05. Definitely have the deflection there. In fact, David Sander checked it out when I opened Lazarus' bonnet on the visit to his place in May.
I suspect that the cause of the pin breakage was lack of lubricant in the gearcase. Bud
Bud Krueger

Hi, Bud. I had similar problems with my tach gearbox. The lube in mine was all dried out and hard. I tried the solvent method to clear it up but I found I just could not clean it properly without disassembly. I ultimately decided to take it apart and when I did I found considerable dried gunk and swarf inside which I never would have got out any other way. When I was done it spun like a new one. I used conventional light bearing grease upon reassembly.

Over on the MG Experience I posted a thread with photos of my repair:

http://www.mgexp.com/phorum/read.php?46,2700992

And I'll quote what I wrote there in hopes it may help you or others down the road:

"I disassembled the case by crimping in the rivet flares and then gently driving the rivets out whilst supporting the underside with a small ratchet socket. I cleaned it in the parts washer, lubricated it with light bearing grease and reassembled it - it looked and worked like new.

As for the case assembly, I wanted to do the best I could to make it look at least reasonably original upon reassembly. The rivets are a bit hollow at the ends, making it very easy to drill them with a #43 drill (being careful not to drill all the way through the rivet head) and then tap them with a #4-40 thread. After they were drilled and tapped I filed the ends of the rivets down so they were just slightly longer than the thickness of the case. To assemble the case I used period-correct cheese-head screws and the original rivet washers, which located nicely on the bit of rivet extending from the case, and used a touch of Loctite blue to ensure they stay put."
Kevin McLemore

Oh, and in my case the reason for failure was because the tiny gearbox shaft fixing screw backed out and seized into the brass coupling sleeve, locking the shaft and snapping the coupler shaft.

Here's photo #1 of my completed repair:



Kevin McLemore

And photo #2:

Kevin McLemore

Kevin, there more I think about what I saw the more I think that I joined your club.The screw was not seated in the countersunk surface. Bud
Bud Krueger

Yeah, Bud, I put a little Loctite blue on mine when I reinstalled it to prevent it backing out in future.
Kevin McLemore

This thread was discussed between 26/06/2014 and 29/06/2014

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