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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - TF Tach Reduction Drive Fit

I purchased a generator from EBAY a while back and it will not couple to my tach reduction drive The EBAY generator is Lucas #22258E.

The male thread on the new gen is approximately 1/8 to 3/16" longer than my incorrect one that came with the car. It was from some later model and was haywired on and destroyed the mounting bracket and the gen mount. But the drive worked.

Can anyone offer a fix beyond another generator please?






Dan Nordstrom

another

Dan Nordstrom

and another

Dan Nordstrom

You may need to return it.

Tom
T Norby


The longer one looks correct and the C39 P/N 222580 is correct for the TD. If the threads are good, the Tack drive gear box should screw on far enough to engage the slotted armature drive. Is the Tack drive gear box the correct one for a TD?
Richard Cameron


Dan, Some pictures of one of mine, I just happen to have on the bench. You can see from the rusted part vs the clean that the tack drive only screws on about half way.

Richard Cameron


Picture of tack drive P/N

Richard Cameron


Picture of Tack drive connection

Richard Cameron

To make the short threaded style work, you have to put shims or washers inside the threaded female coupler nut. If there are any, take them out and it should work. Richard is correct that the long one is proper. Check for any other modifications to the coupling assembly. Also, make sure that the new generator has the slotted shaft extending out to almost the end of the threaded part. George
George Butz

Does anybody know what is the thread size on the generator? I would think it is BSB.

Regards
Declan
D Burns

Richard, you have an original brass coupling nut- note the fine knurling rather than the straight grooves in all the repops! That is the 4th one I have ever seen!! Take good care of it and keep the pliers away. To also note: some of the older repop coupler nuts were on the short side. If the drive dog won't quite engage you can loosen the clamping collar and slide it forward a bit. George
George Butz

Thanks Richard. Your pictures tell the story.


It appears I have the correct Generator, but the wrong Reduction drive. Mine is marked with the same part number, but has a different style drive.

Guess I'm on the hunt for the correct style drive.

Anyone have a spare they wish to part with?

Thanks all

Dan

Dan Nordstrom

That is the correct gearbox. It is missing the coupler parts and the snout however. That used to be available as a "coupling Kit" from the major suppliers. George
George Butz

Hi Declan,

I don't know the thread size but think Speedy Cables will. They made up a new speedo cable for my MG M Type from scratch. I had a spare threaded speedo bush left over from a rebuild of one of my prewar MG gear boxes and used this for my alternator conversion. The threads were the same as the tacho gearbox. See arched photo.

Cheers

Jan

J Targosz

George,

If I understand you correctly, I just need a different style coupling kit. I have what appears to be the same coupler as shown in the Moss cat.

It was mounted to the old generator and appeared to work (never ran the engine to know for sure).

When looking into the drive end of the generators the incorrect one has two drive slots (for the cross pin) and the correct (new) one has only one. It seems my drive is correct for the old gen but not for the new one. I can't see how I would put a coupler onto a coupler.

Make sense?
Dan Nordstrom

Thanks Jan,
The reason I ask is that I am considering making some lookalike tach corrector gearboxes as a winter project to compliment my speedo corrector gearboxes. I suppose I could measure mine up over the weekend.

Regards
Declan
D Burns

I measured it up and it appears to be 3/4" x 26 tpi BSB-the same connection thread as on the gearbox speedo drive.

Regards
Declan
D Burns

I made a new nut for mine. My notes state that the thread is BSF 3/4-26.

With regard to the knurl. I purchased the car in '66. Unless the nut was changed before that, the nut was fully knurled with a straight knurl. FWIW its a 33 pitch knurl.

Jim B.

JA Benjamin


Dan, please post a couple of more pictures of your reduction gear box showing the side view of your coupling end. Also one of the actual coupling parts you removed. With this info, someone might help you with the correct pieces.

Richard Cameron

Here's a different shot of my red drive. Also I will include pictures of the associated generators. The one on the right is the one that this drive was attached. The one on the left is the correct unit I am trying to use.

Dan Nordstrom

and the generators

Dan Nordstrom

Jim,
I doubt it because a 3/4" BSF has 12 tpi and a 3/4" BSB has 26 tpi. I just held up a thread gauge against the remainder of visible thread and what I have looks more like 26 tpi. 12tpi seems way off. I can whip the knurl off in the morning and measure it properly. I have a 3/4" x 26 tpi BSB die here. The generator was fitted by the PO and could be a repro.

Regards
Declan

D Burns

But I said 3/4-26?



The 33 refers to the pitch of the knurl.

Jim B.
JA Benjamin

Do ya think I should just restart my thread guys?
Dan Nordstrom

Dan;
In the picture you posted, of the end of the drive, 5 posts above, the end you show seems to be missing a part.

I do not remember how mine went together. I think you are missing a part that may be pinned to the stub you show. It would have a key in it.

I will go down a see if I can see it on mine.

Jim B.
JA Benjamin

As I half remembered, there is an extension wit a key.
It is held in place with an oval head screw.
It has a bit of flexibility to allow for some misalignment.

You have the correct gen, the correct Gear box but you are missing a part.


I could sketch it up, before I reinstall, if you want.
Jim B.

JA Benjamin

Abingdon shows that part, as part of akit. 35-089 $25.75.

Moss shows a coupling kit for about the same price but I am not sure the part is in it. You would need to call.

Jim B.
JA Benjamin


Jim,
It seems you are correct. I would never have seen this. It's interesting that the PO was able to make it work. He did mention that he last drove the car during his high school days (1973). Speaking from my own experiences, we most always found a way to keep our cars on the road.

Sketch it up? For the purpose of having one made?
That may be my only choice.

I would like to shop around before going that route though.

I will give Hugh Pite a hit and see if he can help.


Thank you. Much appreciated.

Dan
Dan Nordstrom

You are welcome, Dan.

I vaguely remembered it from when I got the gear box working.

Jim B.
JA Benjamin

Dan, Yes, here's the part--- It is very corroded but you can see how its made I believe--- Yes, Contact Abingdon spares and I'm sure they will check their parts kit to confirm the item you need is in it. From the reviewing the condition of the pictured part, it looks like I can use one too.

Richard Cameron

Yep, that's what I need.

I just spoke with Abington and they do not have this specific part. I would have to a complete drive unit to get it.

I'm on the hunt.

Thank you Richard.

Dan
Dan Nordstrom

Picture of NOS coupling kit, same parts come in replacement kits, plus screw to shaft.

George Butz

Dan;
Looking at the last pix you posted. the one of the generator ends, I can see how the existing tach drive would have worked.
The generator drive shaft is just at the the ends of the threads.
The new correct generator drive shaft end is inside the threads some distance.
Inserting a short rod into the tapped hole of the tach gear box shaft so it extended out a bit on one side, it would engage the drive shaft on the older generator.

The correct shaft would have not allowed the knurled nut to tighten.


Jim B.
JA Benjamin

Jim,

That is what the PO had done to make the incorrect gen work. With the shorter end on the gen it amazingly worked. It appears he cut a short piece off an old coat hanger and slipped into the hole. The male thread on the correct generator is to long for this.

The way I see it I have no choice but to either find the fitting shown in Richards post or purchase a completely new reduction box. Or maybe have one machined.

I'm still on the hunt.

Thanks all

Dan Nordstrom

Some time ago I posted an observation that threads on Lucas products are British Association. I know the largest BA thread size is 0BA, are there other larger diameter threads using the BA specs?

I would be surprised if Lucas had a mismatch of thread profiles on their product, however stranger things have happened.
G Evans

Dan;
If you dont find something, drop me a note at mgtd51@verizon.net.

Jim B.
JA Benjamin

Dan, Seems you just need the "snout" piece, which is part of the coupling kit, no need to buy a whole reduction box. Moss lists kit for $25 or so, not sure if actually in stock. The correct fix for the short threaded dynamo was to simply fit a spacer washer inside the threaded collar to space it farther out. Then the snout fit perfectly. That spade terminal/short threaded model Lucas generator was supplied by Moss and others in the late 70s as a supersession of the original. I had the same one on my car until I restored my original. BTW, just dug through my spare bits and have parts of three couplings, but no snouts. Seems they get chewed up or something? George
George Butz

George, I may have found the piece, but want to wait until it arrives before I celebrate.


Thanks, Dan
Dan Nordstrom

MG bits 4u sell a connection kit:
http://www.mgbits.com/contents/en-uk/p7055.html

Jim,
Yes you did write 3/4"x26 tpi but 3/4"x 26 tpi is a BSB thread and not BSF. A 3/4" BSF thread would have 12tpi.

Regards
Declan
D Burns

Ah yes Declan.

I was thinking 55 degree thread, and in my mind if its not Whitworth its BSF. I keep forgetting about BSB.

Thanks

Jim B.
JA Benjamin

These pictures are from my TD but I hope they are helpful. Jud
Pic 1

J. K. Chapin

These pictures are from my TD but I hope they are helpful. Jud
Pic 2

J. K. Chapin

These pictures are from my TD but I hope they are helpful. Jud
Pic 3

J. K. Chapin

These pictures are from my TD but I hope they are helpful. Jud
Pic 4
ps: I drilled out the rivets and used screws to hold the case together. I'm not a good enough machinist or mechanic to make and install rivets.

J. K. Chapin

These pictures are from my TD but I hope they are helpful. Jud
Pic 5

J. K. Chapin

These pictures are from my TD but I hope they are helpful. Jud
Pic 6

I made a washer from a piece of gasket material to go inside the coupling to the generator and have not had and problem with the reduction drive rotating and the tach readings are very stable. Also, that Hi-tension lead no longer wraps around the radiator stay.

J. K. Chapin

Thank you JK.

Your images are very helpful.
Dan Nordstrom

Thanks for the picture too!

I'm trying to bring together all parts. I had found them in a box the preowner gave away.

The marked part in the picture is missing. Do you think a cutted washer will be sufficient or must it be hardened steel?

The grease nipple is also absent. Do you use grease or oil?

Bela

Dan, The Moss coupling kit won't work for you? PJ
Paul161


Bela, The part is not hardened, and If your making one, a cut part of a washer keyed into a slot in the sleeve should work. Silver soldering the piece would hold up I believe.

All of them I have taken apart had grease in them.
Richard Cameron

Paul,

I should see the Moss part within the next day or two. That will tell me for sure. I sent the picture and the sales guy said it was part of the coupling kit.
Mmmmmmm


Are you certain it won't work? Why?

Dan
Dan Nordstrom

Thank you Richard,

I will try and I will use grease. As a workaround until I'll find a nipple I will close the whole with a screw or a piece of tape.
Bela

Dan, That was a question, not a statement, sorry. I see no reason why the new one from Moss won't work, unless your reduction gear is not standard and has possibly been modified. PJ
Paul161

Am I right if I fill up the whole gear box with grease?

I rebuilt the missing part 1 (tongue?). An other problem was the shaft of the generator, which comes out and is not plane. An additional washer [2] in the coupling was necessary to keep the distance.

Bela

The Moss supplied coupling (with nipple) came today and everything looked great. It wasn't to be.
The nipple is to large for the generator receiver and the set screw is too big and maybe the wrong thread for the reduction drive shaft.
I'm back to square one.

So I'm still in need of a nipple and set screw - if anyone has one they'd like to part with.


George,
The nut I received looks exactly like the one you said you have seen only four of. Appears Moss is reproducing them now.


Dan
Dan Nordstrom


Bela, Nice machine work --- The manual doesn't say anything I could see about greasing of the tack gear box. However, if you over fill it, since the covers aren't sealed, grease will ooze out and make a mess when it gets hot in the engine compartment. I would just apply enough to make sure the gears get covered.

Bye the way the grease fitting appears to be a straight one with 2BA threads.
Richard Cameron


Dan, Bela, I decided to make one too just to see if it would work. I used K&S brass tubing from my hobby supplies. Just a few small pieces that telescoped together cut with a Dremel tool. I Don't know the actual sizes because they came in an assortment package already cut in small pieces.
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWFS4&P=ML

Richard Cameron


Photo of Pieces dry fit before soldering.

Richard Cameron


Completed and soldered part. I used JB Weld to fill snout on key end to make it more solid. Not as pretty as Bela's but it should work fine. At least it fits my generator tack drive and goes into the generator drive end fine.

Dan, the little screw that holds this part on the tack drive is a very fine thread screw that may be special to this application.

Richard Cameron

This thread was discussed between 02/10/2015 and 12/10/2015

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