27 replies to this topic

[Purple Tom]

Hey

Have just put a new gearbox onto my MG Metro engine, as the second gear synchro was knackered on the old one. The new one engages all gears lovely, except the selection is very stiff. When in neutral its really hard to waggle it side to side, but once you have it in the right place it selects the gears fine. It only does it from side to side too, ie:

First to second - fine
second to first - fine
second to third - really stiff
third to second - really stiff
third to fourth - fine
fourth to third - fine
neutral across to reverse - really stiff

The gear selector box top steady bar bush (the one that fits into the diff housing) was knackered on the box that went in, so I removed it, and for the time being have bodged a 'bush' out of a bit of rubber hose and some penny washers. Do you think it could be this thats causing the stiffness, in that its not allowing the bar to move enough?

Or is it more likely to be some sort of problem within the box itself??

I hope not

[vasi]

Judging by the photo, it appears that you've mounted the engine about 5 feet away from the car, this will in itself make it surprisingly difficult to engage the gears.

[Purple Tom]

lmao!

Seriously though, some help would be much appreciated..... :grin:

[Guess-Works.com]

pml @ vasi

But seriously, the 'side to side' on the gear stick is converted to a rotation on the gear selector shaft. Had you tried pulling the gear lever out, and greasing the connection, If it's not that then there is only two pieces in the box which moves, the selector shaft and the interlock spool. These fit into the levers which connect to the selectors and it sounds like these are either missaligned or incorrectly fitted.

When you say 'new gearbox' do you mean a reconditioned unit, or one you had lying around ? If it's reconditioned, I would be having words with the supplier.

But if it's not the gear lever, then it's engine out.

Piccie of bits ( highlighted in red )

[Guess-Works.com]

ooh... just thought of something...

When putting a gearbox together, until the 1st motion shaft is torqued up to the correct amount, the 3/4th synchro will be slightly missaligned, as it is being pushed towards 3rd gear by the 1st motion shaft.

[Purple Tom]

hmmm

When I say 'new' i mean one that was lying around. It has been covered over, and it engaged all the gears fine without any stiffness when I removed it from the Metro it was in, but that was in august last year.

Could those components become misaligned during normal use??

Thanks very much Guessworks

Tom

[Guess-Works.com]

only through wear, but that normal goes the other way ( ie sloppy )

The only other thing is that dirt or corrosion has set in where the shaft enters the box, but I would expect this to also affect the lateral gear selection.

[Purple Tom]

I think i'm going to put the proper bush into the top 'steady bar' of the rod change part, I just have a feeling it could be this thats causing the problem.

When i removed the engine the car was high up on axle stands, and the whole rod change mechanism was hanging low down onto the floor from the rear mounted bush (behind the stick). Is there a chance that this could have in someway damaged the internals of it?

[Dan]

There's pretty much nothing inside the selector housing to damage, the only real way to damage it would be to damage the housing itself and deform it which would be visible externally.

It could well be your steady rod bush causing this. If the housing is allowed to twist side to side when you move the stick then it will be harder to twist the rod far enough to get all the way through the interlock spool. The steady rod controls the location and alignment of the housing so if it's not properly fixed then it won't do the job. I seem to remember you need a pair of these bushes and they are dirt cheap but it's been a while since I changed any now.

[Dan]

Oh, now I remember.


One bush at the gearbox, two to hold the housing to the car.

[Purple Tom]

yeah, I needed one on the 1275 in the clubby. I ordered one today, should be here tomorrow morning. My thinking was similar, basically I have used a bit of rubber hose sliced down its length to form a rubber sleeve where the bush would be, then some penny washers between the diff housing and the 'fork' of the top steady bar. I think whats happening is when I move it across in neutral it just flexes the rubber hose and doesn't rotate the selector shaft properly. That'd explain why it moved laterally easily, but not across, as Guessworks said.

I'm going to change the bush tomorrow night, at the same time as my steering column bush, and putting some shiny wiper brightwork on, so i'll let you know.

thanks for the time and advice - and especially for the images Guessworks.

fingers crossed!

Tom

[Purple Tom]

I have changed the bush in the diff housing, its made no difference at all. I took the bottom out of the selector box, and made sure it was fully greased.

I took the stick out, and put some mole grips on the rod to see how stiff it was. It isn't actually too bad, its stiff in neutral in the forward gear part, but move it over to the reverse part of neutral (if that makes sense?), and it rotates freely. There's still no lateral stiffness at all.

Any ideas? Could this be the problem Guessworks was referring to? Is there any way in which the problem he described could be caused by normal driving?

Thanks

Tom

[Cir-clipalot]

is it possible the bit of the selector shaft that sticks out the gearbox, and to which you attach the main selector rod with the roll pins, has become bent? for example if the box has been lying around its kinda easily tread-on-able?....

[Purple Tom]

hmmm, its possible that it could get bent, but it would have to be a severe impact to bend it I think. And i'd expect it to affect shifting in all directions really?

[Guess-Works.com]

When you rotate to the reverse, and it looser, this suggests that the part which is making it stiff is no longer in contact, which actually could mean an issue with the interlock spool, but at this stage, any more investigation would essentially mean box out.

Thinking about it, it would be possible to withdraw the selector with the box in the car, but could be messy, and getting it back in maybe problematic if any of the selector plates moved ( reverse would be the most likely to do this ). Not something I would want to try in a hurry.