series 3 1st gear not holding in

Hi All,

opefully someone can help.

I have rebuilt the engine on my Ex Military 109 (1980) - and have run it in.

However when i select first gear, you have to hold it fully forward until you start moving, otherwise it jumps out straight away.

Once moving, it will hold in OK, until you take the power off and then it jumps out.

Having removed the brass plug above the detent spring and ball bearing, you can see that to get the lever fully forward to 1st gear, you are moving the detent fully back and then a little more on top - so the spring and ball bearing when allowed to, move he shaft back to where it should be - but this is now not enough to hold in first gear.

Is this some sort of spacing / thrust washer wear in the gearbox ?

Please help if you can. I have found the rebuild challenging
(not a mechanic !!!) but want to get this sorted.

If you have good engagement in the detent and the spring/ball bearing is ok then I'm afraid it's something in the box.
Possibly selector fork worn which can can changed without box removal. But most likely worn gear or sychro cones both mean box has to come out.

peter109winterised said:

Hi All,

opefully someone can help.

I have rebuilt the engine on my Ex Military 109 (1980) - and have run it in.

However when i select first gear, you have to hold it fully forward until you start moving, otherwise it jumps out straight away.

Once moving, it will hold in OK, until you take the power off and then it jumps out.

Having removed the brass plug above the detent spring and ball bearing, you can see that to get the lever fully forward to 1st gear, you are moving the detent fully back and then a little more on top - so the spring and ball bearing when allowed to, move he shaft back to where it should be - but this is now not enough to hold in first gear.

Is this some sort of spacing / thrust washer wear in the gearbox ?

Please help if you can. I have found the rebuild challenging
(not a mechanic !!!) but want to get this sorted.

Click to expand...

Bear in mind that on these boxes the 'detent' springs are not the same as the 3rd and 4th gear cluster which are a flat type of spring, on the lower gears they are a small coil with a flat square block and ball bearing.

If one or more of the springs are broken or have lost tension then you will find it is not as positive to engage, it will go in very easily without much resistance that the spring puts on the ball to lodge it in the space it rests when in gear.
That ball in part also keeps it from jumping out under load or over run.

It may be the gear mesh on the synchro cluster, badly worn teeth.

Which leads me to suggest that perhaps it is the slider gear itself having worn shoulders that have become tapered through plain old wear and tear, just like the bow of a small boat.
If that is the case the box has to come out and parts replaced with new ones.

If the synchro is worn then it would crash on engagement coming off neutral and on changing down.

Series gear boxes are not that hard to work on with the most difficult task for a newcomer being the removal of the lay-shaft bolt before the bell housing comes off.

If you take the selector top off and have good look inside with a very powerful light then you should be able to determine if the gear is worn or the springs are fecked...

It's not a difficult job to break the boxes apart, but it is time consuming, and you will need a good engineering knowledge to know what to replace, and the parts alone make it uneconomic, might be cheaper to get an exchange unit!

Enjoy ...

Series III gearbox rebuild - Series Forum - LR4x4 - The Land Rover Forum

peter109winterised said:

Hi All,

opefully someone can help.

I have rebuilt the engine on my Ex Military 109 (1980) - and have run it in.

However when i select first gear, you have to hold it fully forward until you start moving, otherwise it jumps out straight away.

Once moving, it will hold in OK, until you take the power off and then it jumps out.

Having removed the brass plug above the detent spring and ball bearing, you can see that to get the lever fully forward to 1st gear, you are moving the detent fully back and then a little more on top - so the spring and ball bearing when allowed to, move he shaft back to where it should be - but this is now not enough to hold in first gear.

Is this some sort of spacing / thrust washer wear in the gearbox ?

Please help if you can. I have found the rebuild challenging
(not a mechanic !!!) but want to get this sorted.

Click to expand...

check nut on rear of main shaft ,either gear has too much end flot or dog teeth are worn on first gear