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MG TD TF 1500 - Gearbox output shaft hard to turn

I replaced the rear felt seal in a club member's TD gearbox. Bolted the rear case onto the main case and lightly tightened the flange nut. The output shaft became hard to turn. The more that I tightened the flange nut, the harder the shaft became to turn.

What am I doing wrong?

>> Method: (pardon the long description)

The gearbox with bellhousing attached is sitting vertically on a WorkMate.

The gears are in neutral.

I installed a new well-oiled felt seal into the rear case. I inserted progressively larger sockets through the seal until one matched the diameter of the shaft of the flange. Then I pushed the shaft through the seal until the flange touched the rear case. The seal is securely trapped in the groove in the rear case.

I stuck the guard plate (Moss #441-440) and the spring plate (Moss #441-170) to the center bearing on the mainshaft (Moss #127-000) with tacky grease so that it wouldn't move as I attached the rear case. The guard plate (the one with the smaller I.D.) is against the center bearing. The spring plate is againt the rear case.

The rear bearing was on the output shaft and firmly against the distance tube. I greased the outside of the bearing so that it will easily slide into position in the rear case. I sat the bearing guard onto the bearing so that the raised center was against the center of the bearing. With the guard in place, the bearing spins freely.

I held the flange securely inside the rear case as I sat it onto the output shaft and against the main case so that the felt didn't get trapped between the end of the flange and the bearing guard.

I moved the rear case onto the output shaft and almost against the main case. I had to use the attachment nuts to pull it up the last 1/8" against the main case.

I screwed on the flange nut finger-tight. Then snugged it up with a wrench ... no where near the 60 ft-lb torque required. It is very hard to turn the output shaft. Gets harder the more that I tighten the flange nut. Gets easier when I loosen the nut.

Thanks for your help,

Lonnie
TF7211
LM Cook

Maybe its binding on the nose, one of the needle bearings inside the 1st motion shaft?
mog

Hi guys, "Chicken Little" here.

I guess the sky wasn't falling after all. I tighten all of the bolts and torqued the flange nut. The shaft turns easier than it did before. Still has a lot of drag.

Maybe the edge of the felt seal got caught in the scroll between the flange and the opening in the rear case. I had been turning the shaft in reverse. I noticed that a few felt fibers had worked out past the rear case. It's a tight fit between the flange and the case. Don't know if the fibers could have bound up the flange as much as I was experiencing.

> mog: I hope that it isn't a needle roller or bearing. The owner didn't want a full tears own. I replaced the layshaft (which was needed), but no rollers or bearings except the rear bearing.

FYI - the felt seal is a thick white one from Abingdon Spares, not the thinner dark gray from Moss.

I don't want to pull off the rear case for the fifth time, but if you see a glaring error on my part, I will. I haven't lockwired the selector bolts or speedo drive yet.

Lonnie
TF7211
LM Cook

Auto spell correct on an iPhone makes some funny substitutions. My reply above states: "The owner didn't want a full tears own." Should be "... a full tear down." Maybe tears is a more appropriate term in this instance!

Lonnie
TF7211
LM Cook

Knock the input shaft & output shaft with a soft hammer.
Len Fanelli

Thanks Len,

I whacked the input and output shafts with my plastic hammer. No change. Input still turns easily. Output remains difficult to turn.

What did you hope to change by hitting the shafts? Is there something that I should look for?

Lonnie
TF7211
LM Cook

Lonnie,

You will get this issue if you have installed the 3rd/4th sliding hub back to front. The problem is that you can't see it once it is assembled. To check this out,I would remove the rear casing and reassemble everything (spacer bearing,flange, nut etc.) without the rear casing. if the rear bearing stays in the casing on removal, then use the old bearing for the test. If the output shaft is still jammed, then that is your problem.

I had this exact problem on a box I was given which just had a rebuild by an "expert".

John

52 TD
J Scragg

Neil mentions the 3rd gear cluster as well - http://www.mgccyregister.co.uk/technical-information/the-xpag-files/xpag-rebuilds/xpag-gearbox-rebuild/part-five-gearbox-assembly/
mog

Maybe Chicken Little was right.

I torqued the flange nut to 60 ft-lb, then backed off half of a flat to insert the split pin. I pounded on the input and output shaft with a plastic hammer as Len suggested. Neither moved in/out and no improvement.

This morning, I touched a mechanic's stethoscope to various places on the gearbox case while I turned the output shaft. I can hear a scuffing sound near the rear opening of the rear case. Can't tell if the flange is scraping against the case or if the sound is near the rear bearing. (Wonder if the "fat" felt seal from A/S is flexing the bearing shield against the bearing?? I believe that the seal is trapped within the groove in the rear case.)

The bearing is a new Moss rear bearing. Spins freely when not installed. The bearing shield is installed correctly. I can see with a mirror that the ball retainer is moving correctly and that the bearing is not slipping in the rear case.

The flange and the distance tube press against both sides of the bearing hub. I can't see how that could make the output shaft difficult to turn as the flange nut is tightened.

Looks like I may need to pull the rear case again and install another bearing (which I have) just to be sure. I'll pull the flange out of the felt seal and rear case to make sure that the seal is positioned correctly.

> John and mog - Thanks. I did not take the entire gearbox apart. None of the gears in the main case including 3rd gear and 3-4 sliding hub were touched. I replaced the layshaft, but not the needle rollers. I can't see how the layshaft could cause the problem.

Still looking for suggestions,

Lonnie
TF7211
LM Cook

Lonnie,
Try a trial assembly without the felt seal and see what happens.

When you are refitting the rear end casing you have to be a bit careful with the felt seal. I install the felt seal in the casing and then push the gearbox output flange in twisting as you go and from the inside push the felt seal over the flange with a long drift so that it sits correctly and snugly inline with the bottom of the flange and is not distorted. When in position I fix a cable tie around the flange to stop it moving or sliding down into the casing. Then slide on the casing and flange as one unit.

Regards
Declan
D Burns

Pull the flange off, and look and see if any of the seal felt was squished between the flange and bearing. If so, that is likely the problem. George
George Butz

SUCCESS! The bolts and flange are properly torqued in my friend's TD gearbox and the output shafts spins freely.

I removed the Abingdon Spares white felt seal that was in the rear case and replaced it with a dark gray one from Moss.

The Abingdon Spares seal was a little thicker and stiffer than the Moss seal. It had mushroomed out of the groove in the rear case and wedged between the shaft of the flange and the opening at the rear of the case. It was not trapped between the end of the flange and the bearing guard.

I had trouble installing a white A/S seal in my gearbox earlier this year. Not saying that there is a problem with the part, just saying that I find the Moss part easier to install.

Thanks, everyone, for your suggestions.

Lonnie
TF7211
LM Cook

This thread was discussed between 10/11/2015 and 19/11/2015

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