Gearbox main shaft pinion nut - undo

[rufusruffcutt]

Guys, anybody got any good ideas for undoing a very stubborn gearbox main shaft nut.
As you can see from the photo, we've got the box well lashed down, a 4ft breaker bar with a
scaffold pole over and it still won't budge an inch.

Lock tabs are flattened.
Gearbox is locked into 2 gears as per manual.
Input nut is still done up. Should this be undone first?

First off I'm not being a Muppet here and trying to undo it wrong way am I?, it is towards
the front of box (anti-clockwise as you look at the nut through the side of the box)?

Can we put heat on it?

Cheers in advance for any help.

[rww]

I have got a couple of procedures with this problem, which is the unstable nature of the gearbox when you put a large turning force on it.

1. Remove the diff assembly(if not already off) and put a steel bar in through the opening as a lever to turn against. This sometimes works.Invert the gearbox and get someone to stand on it's base whilst you attempt to undo the pinion nut.

2. Put the engine block back onto the gearbox and bolt it up. Lay the block/gearbox down on the floor and then attempt the main shaft nut again. Get someone to stand on the block as well if necessary. This has always worked for me and I have never applied heat.

[guru_1071]

i always lay the boxes on the face (on a bit of card or plywood) as they dont worm around as much, then i have a 6 foor long hunk of timber that i jam under the bench and rest on top of the gearbox, this acts like a lever, so once the balance is right the case cannot move.


make sure you have it locked into first and fourth gears, any other combo can pull teeth off the laygear


having to use such a long bar (without any joy) suggests that either some goliath animal has tightened the nut up in the past, or locktight has been used.

if you have to use heat to get the nut off, i would be wary of using either the nut or the mainshaft again.


there is nothing special about either of the threads, they are both normal 'lefty-loosey - righty-tighty'

[rufusruffcutt]

Thanks for all the above advice, we tried the second one rww, and still couldn't shift it!!

So rather than going down the heat route and more swearing, it was easier (brutal) to grind
a corner off, even then it still put up a fight before finally turning.

Just to confirm it is an anti-clockwise thread for future reference to anyone searching this out.

Whoever built the box -not me I might add! did it up way, way more than the prescribed 150lb ft.

Photo of the offending nut after removal. No damage to the main shaft threads.

[guru_1071]

ive had to cut them off before!


ive also seen them where they have been done up so tight that the mainshaft has broken off between the pinion and the nut!

[rww]

Glad to see it is off and well done for not damaging the main shaft threads.