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Just got the gearbox for my latest restoration and I am having the usual hassle trying to get the pinion nut off. Why do they always seem to be torqued far more than the 150 ft-lbs specified?

Is it beneficial to apply any heat to the nut in this case? I'm not sure if that would help or not but I really don't want to break any gear teeth on a 333 box!

I have selected 4th and second to lock it up. Seems like first looks a little delicate. Should that work ok?

I hate doing this part of the disassembly...

You shouldn't need to warm the pinion nut but, if its been put on with Loctite, like what happened to a gearbox I had to pull apart (that had been built by the Mini gearbox guru), then I'd say some gentle heat to warm the Loctite is essential. Nothing more than gentle though.

Locking in 1st and 4th should be OK, not sure about 2nd but would think it still does the same, then use a 3/4 drive bar on the socket. Sometimes an extension to the bar is required until it cracks off !

Another way to lock up the Mainshaft is if you have an old Idler Gear you can sacrifice, weld a handle on to it that's a L shape such that it can rest against a part of the case when fitted up. Then select 4th gear only and undo the Pinion Nut. This will only work though for undoing that nut and for doing up the 1st Motion Shaft Nut.

Have you guys ever broken teeth by locking up the gears internally? This seems to be crazy tight

I haven’t Gary and yes, they can seem really tight and sometimes go with a Big Bang when they crack off.

Gary Schulz wrote: ↑Fri Nov 20, 2020 5:32 pm Have you guys ever broken teeth by locking up the gears internally? This seems to be crazy tight

I broke teeth in my youth stripping a box, but I think I locked 2nd and 3rd instead of 1st and 4th.
I'm always relieved when the pinion and first motion shaft nuts come undone without any damage!

I’ve done loads of boxes and only broken teeth once. That was a box that’d been sitting open in a shed and there was grit and dirt between the gears. I always lock 1st and 4th.

I do find you need to hold the box with something I usually put it under the car trailer and lower that on to it (protect top and bottom with wood).

Engaging first and top gears is the best option, if you use the other gears it becomes very 'springy' on the torque wrench or knuckle bar. if you have an old laygear of the same spec you could temporarily fit that if you are worried about the teeth breaking.
I made a plate which fitted in place of the end cover which had a hole to properly locate the socket and extension and this was bolted to a long piece of aluminum angle which you can stand on while undoing or torqueing up. The angle was reversed to suit. It made a big difference as all the force was on the nut and you weren't chasing the 'box around the floor.

Gary Schulz wrote: ↑Fri Nov 20, 2020 5:32 pm Have you guys ever broken teeth by locking up the gears internally? This seems to be crazy tight

I too haven't, but I've had a few where I've done a few hail merrys before leaning on the bar. It does also make me worry that while the teeth may not have broken at this point, has it induced a stress in to that tooth that's taking all the load ?

The other thing is, and I know most here wouldn't, is NEVER use a rattle gun on them.

I struggled with a box last year. Tried everything, even put a mini on it but all i did was lift the box. My friend of this parish took it to a friendly g/box re-conditioner and he undone it with an impact gun, he did not even bother to lock the gears! No idea how he did it. Another box was easy to undo with just me standing on it!

Paul

I always love Bob's solutions to pretty much everything. It is really elegant to maintain the concentricity of the socket/extension on the pinion side using that plate. Anytime you need an extension you wind up putting on unfavorable bending moments that do nothing to get the applied force where it needs to be. I love it. Yes, it seems very springy which is why I hate doing this job. I guess I will just go with locking first and fourth to see if that makes it more rigid.

I found a way to not have to chase the gearbox around the shop by "gently" clamping it under one of the ramps on my lift. I don't drop the full weight on it, just enough to keep it in place. Also use several pieces of 2x4 between the ramp and the bottom of the box.

Even with that extension on my bar I haven't had enough luck or courage to budge it! Of course this is showing the first motion shaft side which eventually came apart

I had a bench made for workshop with bottom shelf 1/2 ins taller than a gearbox. Ideal way of not having to chase it round the floor.

Seeing Bob's elegant holding bar and socket support reminded me to post this up. It's probably more of a novelty these days than anything useful, but might be helpful to some. These are some plans from our Local Factory for Building a Hold Down Jig, in this form, it only suits those with rubber couplings, but with a little imagination, it could be adapted for any drive outputs.

I have an 1 1/2 deep impact socket, 1/2 inch drive. And a CP rattle gun. I grip the socket with one hand and squeeze the trigger of the gun with the other. I have never, ever not been able to undo a nut, and I have stripped 1000s of gearboxes. EDIT - No need to ever lock the mainshaft.

Spider wrote: ↑Sat Nov 21, 2020 5:02 am Seeing Bob's elegant holding bar and socket support reminded me to post this up. It's probably more of a novelty these days than anything useful, but might be helpful to some. These are some plans from our Local Factory for Building a Hold Down Jig, in this form, it only suits those with rubber couplings, but with a little imagination, it could be adapted for any drive outputs.

I think I like this solution the best because it puts all the nasty loads right on the pinion. In the case of this 333 gearbox the pinion is probably the most expendable gear if it breaks. Some of the others inside the box are a little hard to come by.

So using an impact driver is OK?

I normally use a ball joint spanner with a length of tube over the handle for undoing the pinion nut, nice straight pull on the spanner.

Gary Schulz wrote: ↑Sat Nov 21, 2020 2:55 pm So using an impact driver is OK?

From the damage I've seen, no.

Thing is, it won't damage the Pinion, but the larger problem with using an Impact Driver here is the Gearbox internals are quite dry of oil, and many parts have case hardening - Bearings, Shafts and the Gear Teeth. The action from the Impact Driver on these can fracture these Cases and if not picked up, later in use flakes off. The Bearings may not be a big deal, as they would usually get replaced, but I think items like the Gears, the Mainshaft, the First Motion Shaft and Laygear are a different story. The tighter the nut is, the worse it will be on all these parts.

Imack's Ball Joint Spanner I feel is a good idea. I have an Open Ended Ring Spanner that I have used from time to time. When using the Socket, if I have troubles keeping the Socket square on to the Nut, I've just put a packing piece under the Ratchet Head, though Bob's solution is nicer.

The fixture you have shown only stresses the ring and pinion and nothing else, correct?

I may actually fabricate something like this...

I am looking closer at that drawing and it is unclear to me what the items marked 4, 5, 6 and 7 actually engage with or hold down on the gearbox. The rod doesn't seem to locate adjacent to any part of the gearbox that I can tell based on the dimensions.

In any case I get the point; hold the drive flanges still and apply torque to the pinion nut, pinion and ring. All the gears stay safe in this case. I'll come up with a variant of this concept that makes sense to me.

Does the rod sit across the top of the front fins?

GraemeC wrote: ↑Sat Nov 21, 2020 8:34 pm Does the rod sit across the top of the front fins?

That's what I thought at first but when I make measurements of the box sitting on the bench the position is in mid-air. It is the right idea though so I will just adjust accordingly to get the right effect.

EDIT: Took a closer look and it does appear that the rod goes above the fins on the front. The dimensions are referenced to some odd places in the drawing but I guess it makes sense. Time to order some steel and hope I don't destroy the final drive.