LT77 Strange Gear Selection Problem

Hi,

I `ve just fitted a replacement gearbox to my defender. To be fair, it is off unknown quantity, but i was told that it was removed froma running car and was working fine.

The problem is that, i`ve just fitted and put my gear selector back on (the whole gear shift and diff lock mechanism together by the 4 bolts on the rear of the gearbox).

I have no oil in the gearbox or transfer box yet, but thought i`d check the gear selection. The selector centres on 2/3 and I can select 1,2,3,4 and reverse, but 5th is no where to be seen. It just comes to a stop when trying to select it. I ve removed the selector unit and get the same result by selecting it manually without the linkage.

Now the strange thing is where you would expect a 6th gear (if there ever was one), i can select a gear there - ie. - if you pull back from 5th, you get a gear there.

The lt77 is an ex MOD recon unit if that helps. My old gearbox is a 50A suffix G and the new box is a 51A MOD box.

Could the linkage on the 50A be different to the 51A?

I checked the old and new box - without the selector mechanism, 5th gear is definitley different on th etwo boxes. On the 50A box, the selector has to be pushed all the way over to the right, then forwards. On the 51A box, it has to be pushed all the way right, then backwards.

I did notice that the stick appears to have been welded at some point - i presume to be fixed as it may have snapped in the past, but maybe not?

Thanks, Mike

Attached pics of the selector mechanism

have you tried by moving the selector shaft itself under the gearbox top ,its possible tops fitted wrong or grub screw under gear stick is loose or by your description 5th gear synchro hub fault

Hi,

Grub screw is tight in the unit itself. Yes, i removed the whole selector unit from the top of the box so i could access the selector in the top of the gearbox.

On my old 50A LT77, the selector moves all the way to the right, then slots back into what i presume is 5th gear. On the 51A, it moves all the way to the right, then the selector in the gearbox will only move forwards into what i presume is 5th.

The box has obviously been use in the past as it still had the slave cylinder in the bellhousing and was a a bit dirty - was a recon unit fitted in 2009 by the mod according to the seller.

Here`s the link to the original ebay ad - you can see the selector mechanism in the box in one of the pics, if you use the enlarge faciltiy. Anything look fishy in there?

http://www.ebay.co.uk/itm/lt77-Gear...D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

if you look at the pics you willl see a collar with a raised center you have to ensure the slotted peg on underside of g/box top sits over it as well as lining up selector quadrant

Thanks - i`ll check that tomorrow night (or morning before work maybe!) - hopefully thats what it is. I did only only line the selector quadrant up and wasn`t sure about the raised collar.

its the 5th gear interlock

Thanks - i had a closer look in the light this morning and it looks like that collar should slot into to the selector(?).

This is mine - the selector is pushed all the way over to the right. I tried to lightly push it back, but it felt pretty jammed and i didn`t want to break anything.



You can see on this pic i found where it slots in. On the pic from ebay, you can just see its all aligned correctly, so it must have come out somehow and then attempting to select 5th has pushed the selector ring back and jammed it.


Should it come back easily or can i rotate, the collar, etc and then pry it back with no damage?

Thanks, mike

Just a quick update as i think i have hopefully sorted it.

I have no idea how the interlock cam disengaged from the selector, but i ended up carefully removing the circlip on the selector, then sliding the collar back. I could then push the selector back into position and re-engage the peg form the interlock.

Pushed the circlip back on and with the linkage back on, everything seems to be moving how it should be.

5th seems a little sticky/stiff, but hopefully with some oil in the gearbox, it will get a little freer

mike1978 said:

Just a quick update as i think i have hopefully sorted it.

I have no idea how the interlock cam disengaged from the selector, but i ended up carefully removing the circlip on the selector, then sliding the collar back. I could then push the selector back into position and re-engage the peg form the interlock.

Pushed the circlip back on and with the linkage back on, everything seems to be moving how it should be.

5th seems a little sticky/stiff, but hopefully with some oil in the gearbox, it will get a little freer

Click to expand...

usually by moving gear stick with the collar not held by the slot in the retainer on gear box top,