TA Rear Spring Trunnions

[Rob Reilly]

Yet another anomaly is discovered with this TA.
I went to put in the new trunnion bearings from Frame Up. They are a cylinder with a slot cut in it, and are too long by .375 inches (8mm) and are different from what came out, which was two half cylinders. Why are they different?
The old design had a steel end bearing disc on the outboard side. Examining further, I see there is an inboard end bearing disc inside the spring mounting shaft.
I suspect it is supposed to come out, but is it pressed in there?
How thick is it?
And how am I to get it out?
Have I interpreted this design correctly?

Here are all the parts I removed.

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Closeup of the old and new bearings.

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View of the end of the spring mounting shaft with some kind of disc inside.

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[ferricsteed]

Good day Rob. I do not have a definitive answer. However, my TB trunnions looked exactly as yours, two half cylinders so you are not alone.
I suspect you do not need to pull out the bearing disc but if you wish, you screw in a bolt or screw into the center and pull. Usually there is a hole in the center for lubrication. Just make sure it is a bearing disc and not a plug.
I suspect you file to fit the new bearings to a zero clearance to the width of your spring. Doug probably make them overly long to accommodate none standard (wider) springs that may have been installed over the years on some cars.
Regards, Tim Bloomfield

[Rob Reilly]

Thanks, Tim, it's good to know mine is not some weird DPO concoction.

There is no hole in the thing for a screw. I don't know what the thing is, whether a bearing face that is supposed to rotate, or a plug that is pressed in. I don't know what is behind it.
The new bearings from Frame Up are 3/8" (8mm) too long, the slots don't line up with the main spring leaf so I can't install it, and with the two other round pieces installed I can not get the hex cover piece on.
Something is wrong.
I have sent an email to Frame Up but no response yet.

[Rob Reilly]

Success!
I had been thinking this spring mounting shaft might be a solid bar with a counterbored end, but looking at the round bearing surface it looked too smooth to be counterbored, so I concluded it must be a separate piece. And if a separate piece, the only reason to make it a press fit would be to prevent grease getting in there. But it's a small space relative to the large space around the spring leaf, so I concluded it was not a press fit, just stuck with rust.

There was about 1/16" sticking out, just enough that I could get the tips of some channel locks on it. I squirted some penetrating oil in there, wiggled it with the channel locks, and after a little while got one out.

The cross tube is hollow all the way through, looks like probably all one piece, with a couple of small pins sticking up inside that are probably to locate the inboard rivet flanges for brazing. I stuck a long piece of wood through and knocked out the other end plug with a few taps of the hammer.

To recap for future folk faced with this puzzle:
The cross tube is bored 1" diameter to about 2-1/4" depth, then counterbored 1-1/16" diameter to 9/16" depth. The internal parts beginning inboard are a steel plug 63/64" diameter x 17/64" thick with ground surfaces; next the half round bronze bearings 63/64" diameter x 1-1/4" long; next another steel plug 63/64" dia x 11/64" thick with ground surfaces and a hole for grease; next a steel plug 1-3/64" dia x 9/16" high with a tapped hole for the grease fitting extension and a 1/4" dowel in the side to prevent rotation.

I note that because of the 1/4" dowel, when removing parts one should remove the grease fitting extension first, then the big hex cap. Conversely when installing, one should tighten the hex cap first, then install the grease fitting extension.

[Rob Reilly]

So the two slotted bronze bearings from Frame Up replace four original parts (the two half round bearings and the two end plugs). I test fitted them all to be sure, then removed them and greased them up.

New parts trial fitted.

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Assembly order is important.
1. Put the rubber sleeve boot on the spring end first, so you don't forget it.
2. Put in the first slotted bronze bearing, which may have to be tapped in the last 1/4" or so with a hammer against a socket with an extension.
3. Turn the slot parallel in line with the slot in the mounting shaft.
4. Slide in the spring end with the boot, the end catching the slot, and at the same time put the front end on it's stud.

First bronze bearing in place, spring end inserted in slot.

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5. Put in the second slotted bearing.

Second bearing in place.

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6. Put in the thick plug with the side dowel and tapped center hole. It has no chamfers so it may have to be tapped in with a small hammer.

Plug with side dowel and tapped center hole in place.

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Lord Nuffield probably saved twopence not putting chamfers on this part, but the line workers got back that twopence when it took them 10 seconds longer to put the part in. It should be about even with the end of the outer tube.
7. Install the big hex cap.
8 Install the greaser extension.
9. Install the grease fitting. The lock washer is important here because otherwise the end of the grease extension would be up against the bronze bearing.

Done. One of my caps was already stamped LEFT so I stamped both of them LEFT HAND THD.

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10. Grease it up.

I think the first bearing ought not to have a center hole, so the grease doesn't get into the center of the cross tube, and the second bearing ought to have a larger center hole for the grease to pass through into the spring end chamber.

[TC9800]

My TA (2841) had the bronze trunions in two halves as others have stated. However the rear trunion was geased as part of the central lubrication system, perhaps yours has been changed?

[Rob Reilly]

No, mine is TA1271 and never had the central lube system. That began with TA2253.
But thanks for the confirmation on the two half rounds design. I have not found any mention of any change to the trunnion bearing design in any of my MG books.