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MG TD TF 1500 - Gearbox Mystery

Good day to all,
I am in the process of restoring my TD. A few months ago I rebuilt my gearbox, using gear oil as lubricant on all parts, but didn't fill the gearbox with oil.
This week I decided to fill the gearbox with oil and noticed that the drain plug had leaked a little. So, I took off the drain plug to check seal and found this. See photo.
The first thing I did was to remove the cover and check for the 3 shifter balls (all there), and then remove the middle shaft part way to reveal the two balls hidden in the case (both there). This extra ball is the same diameter as the 5 shifter balls.

I don't see any way that a ball could have been left in the case during cleaning because case was cleaned and then glyptol painted inside. This ball is perfectly clean, and I shouldn't have any extra parts. I didn't replace any balls with new ones, so I shouldn't have an extra one.

I did replace the 3rd-4th sliding hub, but it was reassembled on the bench with all bearings, so I can't imagine any way a ball could have been missed. Even if I had somehow missed a ball, how would it have ended up here? I did not disassemble the 1st and 2nd sliding hub.

Where did this ball come from? I really don't want to disassemble the gearbox and check the 3rd-4th sliding hub because it is a pain to get the balls back in. However, I don't see any alternative to complete disassembly if I can't solve this mystery some other way.

Advice?

Jim Smith TD17744


JV Smith TD17744

Jim, I have no idea where the ball may have come from nor any other potential solution to your mystery. Nonetheless, should you decide to disassemble the tranny to solve it, you may find this jig that my neighbor (TD 10879) cobbled together for me useful in getting the sliding hubs back together. I'd be happy to lend it to you.

Jud




J K Chapin

Advice? The box has to come apart. Sadly.
Regards, Tom
tm peterson

Hello Jim. The first place I would look is the balls that are in the case to prevernt two shift rods from moving at once. The two balls sit in the csae between the shift rods. It's easy for one to slip out when you are putting the shift rods in. Also checking is not as invasive as removing the main shaft.

Butch
R Taras

Thanks Butch,
I had hoped that was the issue, but both balls were in place.

Tom, I am afraid you are right. I was hoping a BBS Santa would bring me another solution.

Thanks Jud, If I can't find another solution, and I take the 3rd-4th sliding hub apart, can I contact you to arrange a loan? I managed to get it together using a hose clamp and some finishing nails to depress the balls, but it was sketchy at best.

Jim
JV Smith TD17744

I still can't figure out how I could lose only one 3rd-4th ball in the case. The 3rd-4th sliding hub was reassembled earlier in the process.

Is there another ball that could have dropped into the case during reassembly? There is a single locating ball on one of the gears to align to the mainshaft, but I think it is peened over.
JV Smith TD17744

Jim, sure. Contact me on this forum or directly at jchapin3 at aol dot com.

Jud
J K Chapin

Jim, Butch's suggestion of the interlock balls is a good one, Have you checked them or are you saying they were there when you assembled it --You'd have to remove the selector shafts to check
You'd think if it were synchro balls they would be out on the workbench or floor maybe instead of in the housing
Maybe if you removed the selectors you could have a feel of the 2 sliders and check to see if they feel like they still have the balls ,maybe by sliding each in turn into gear and get up along inside the slider to check with a small piece of wire to have a feel to check if all balls are present
William Revit

For the location of 2 more balls, check the Moss catalog transmission blowup for balls 20 & 38 or workshop manual 80 & 123.

Check the reverse gear selector for the missing ball. That should be accessible under the shifter cover.

Hard to imagine one in the shift support bracket could find its way into the trans.

You didn't say whether the trans was installed or if the bell house is attached.

JIM N

By the way, on page Q4 in the workshop manual, there is an illustrated description of creating your very own Synchomesh Assembly Tool 18G325 from a junk first gear. The internal splines can be beveled 20 degrees for easily compressing the sliding hub balls out of the way.

However, machining the internal splines is not for the faint of heart. That gear is HARD, in capital letters. My first attempt at boring the splines was not pretty. There were sparks everywhere and the tungsten carbide was not cutting it. Seriously. On top of that, the splines set up a chatter, no, a rumble, that was rattling my heavy 8' bed, 7hp German lathe. I took it out and played an oxyacetylene rosebud on the gear for quite a few minutes keeping it cherry red to anneal it softer but the old limey steel still put up a helluva battle with the splines still generating a horrid vibration. After removing the desired portion of splines, the cut was butt ugly due to the chatter. I spent another 15 minutes with a die grinder smoothing it out while spinning on the lathe, so it was a success after all.

JIM N

Easy way to check if the selector lockout balls and pin are correctly fitted is---with the top off the box slide the centre selector shaft in either direction 3rd or 4th until the gear is selected, then with it like this try and move each of the other selector shafts---If it's assembled correctly neither of the outer shafts should move much and certainly nowhere near enough to select a gear, they should be held by the interlocking balls---if they're there
willy
William Revit

All,

To assemble the sliding hub, there is another trick which was suggested by Dave DuBois, I used his method, it works really well.

copy pasted (again) from archives.

"For holding the balls and springs in place, I got a tip from an old transmission mechanic for doing that. Use a center punch and punch a dimple on either side of the holes for the detent balls, very close to the edge of the holes. This will swage the edge of the holes enough that you will have to force the balls into the hole (be sure to put the springs in place first - a favorite omission of mine). Once past the swaged edge, the ball will stay in place without tie wraps or hose clamps. Better, if you ever have to take things apart again, the balls won't go shooting all over heack and gone."


John
J Scragg

A clarification update. I did open the box, slid the 3rd-4th selector shaft out far enough to see the two balls safely in the case. So, all 5 selector balls were/are in place.

Jim, is ball #20 under the reverse plunger? I can't tell for sure from the Moss exploded view. I don't see where else it could be. I didn't disassemble the reverse selector, so if it is under the plunger, is should still be there. I could be wrong, but my memory tells me ball #38 is smaller than the than the others.

The gearbox is on the bench, not in the car.

Jim
JV Smith TD17744

The 5/16" ball with spring is the detent under the reverse plunger, inside the reverse selector.

Going by memory, if the bell housing isn't attached, you should be able to slide the shaft forward a few inches to remove the reverse selector, after loosening all the setscrews on the shaft. When you removed the shafts, that ball could have shot out the side of the selector in a heartbeat. The plunger rod has a twisted wire I suspect is only there to secure it for preassembly before installation. I can't see it acts as a positive stop for the life of the car.

Ball 38 is a smaller but might be mistaken for one of the 5/16" balls in hurried reassembly. You can probably see it in the shifter mechanism so it isn't a factor here. I recently looked at an old shifter and the ball was missing, only the spring was there extended out of place.

Good luck!
JIM N

I should've said, that ball could've shot out if you removed the plunger from the reverse selector.

It looks to me like that wire prevents the plunger from drifting out and losing the ball before it is installed.

Of course, the plunger shaft must be inserted with the notch to the ball. If someone overlooks this detail, there's just a 1 in 4 chance it'll go in correctly.
JIM N

I'm curious about the "wire" on the reverse selector plunger. Mine has a cotter pin in it and I never disassembled it, never removed the cotter pin.

Jim, is it your opinion that this cotter pin, or in your case the wire, should be removed after assembly? Or should this really be a cotter pin that remains on the plunger?

In my ownership, which has been since the early 70s, my gearbox has never been disassembled until I did it a few months ago. So, I assumed that the cotter pin was original and should remain.

Jim
JV Smith TD17744

Glancing at the Moss catalog, they illustrate but don't really identify the cotter pins. The trans I have open has a wire in place of the cotter pin. Either way, it looks like the only purpose is to keep the parts together before assembly as the plunger cannot exit the reverse selector thanks to the spring loaded ball. That assumes the shaft is oriented with the notch down to engage the ball.

I don't believe I put that wire on the selector shaft, but I do very often use a few inches of stainless steel welding wire in place of cotter pins. May it is because I'm a welding engineer. I bend the two ends into an S configuration to prevent rotation. Either way gets the job done.

There's no reason to remove the cotter pin.

I just wanted to point out a location that has a ball that could possibly be the orphan you discovered in the bowels of the transmission. If the reverse selector wasn't disassembled, then that ball should still be in place and not your nomadic ball bearing.

One can a good idea of whether the ball & spring are present and the plunger is oriented correctly. Exert significant force against the plunger. It should resist movement at first and then abruptly snap back. IF the plunger moves freely against the spring, they may post a thread on how easily it shifted from third into reverse at 50 mph!


JIM N

Happy Holidays,

Well, the mystery is solved, if not yet corrected. One of the 3rd/4th sliding hub balls is missing, see photos.

The only thing I can figure is that sometime during reassembly, I moved the shaft before installing the circlip that prevents it from moving too far back. It's still odd to me that only one came out. I will inspect it more closely when I disassemble.

For those of you who may need a similar inspection, I found out that you can see all of the sliding hub balls without dismantling the gearbox. By putting the shifter in the 3rd gear position, you can see all of the 3rd/4th balls by rotating the shaft. By putting the shifter in the 1st gear position, you can see all of the balls in the 1st/2nd sliding hub. This was actually very helpful in diagnosis. If all of the balls had been there, I wouldn't have had to dismantle the sliding hub to look.

Thanks for all of your help and advice.

Jim





JV Smith TD17744

Jud,
I sent you an e-mail.
Jim
JV Smith TD17744

Jim, I got the email. The gadget will be in the mail tomorrow. Jud
J K Chapin

Thanks to Jud of the jig to compress the balls.

This was extremely easy. All I had to do was press the jig onto the gear, over the ball bearings. I slid it just far enough into the tapered area to slip the errant ball in from the side. Then slid the sliding dog on and all done.

Thanks, Jud, for the Christmas loan!

Jim

JV Smith TD17744

This thread was discussed between 08/12/2021 and 29/12/2021

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