Gearbox mystery

[Daniël Bos]

I've a gearbox issue I don't understand.

When cold, all is fine.

When warmed up, it's very hard to select gears, I have to really slam the stick to get the bugger in gear, changing up and down once moving is fine.

 

I thought, maybe the clutch gap was so small that when warmed it was expanding and thus engaging slightly, even with the pedal pressed down. So I adjusted the clutch, easy job as the slave has an adjustment nut and is easily accessible.

Made no difference, even when adjusted to the point of not properly engaging with the pedal released.

 

There's no (obvious) leaks from either master or slave, not losing fluid.

 

There's no clutch slippage.

 

Don't think it would be synchro rings as when idling and warm it's the same in all gears?

 

This particular gearbox has a reputation for the exact opposite, stiff to operate when cold.

Could it be that a previous owner experienced that and used a lighter oil in the box, perhaps even added a friction modifier thus making the oil so slippery when warmed that the synchro doesn't have enough friction to spin the gear when meshed?

Probably not a bad idea to change the oil anyway, but are there any other suggestions of possible issues that would make it misbehave like this?

 

Sent from my E5823 using Arbtalk mobile app

[Timber Man]

I had a similar problem with a Discovery years ago,it was fine for a few miles then gear selection became hellish.

Garage stripped it down after loads of checks ,fitted new clutch whilst in there...30 miles up the road no better....300 miles later it just came right.

Someone in the know said it was an hydraulic problem which would come about when the system became pressurised,...take from that what you will.

[aspenarb]

99.999999999999999999% certain that clutch drag is your problem, it may not be the clutch itself but its in that department. Aside of the clutch itself drag can be caused by the center plate jambing/sticking in the input spline and things like pilot bearings dry or seizing. Pull it apart and all will be revealed.

 

Bob

[Daniël Bos]

99.999999999999999999% certain that clutch drag is your problem, it may not be the clutch itself but its in that department. Aside of the clutch itself drag can be caused by the center plate jambing/sticking in the input spline and things like pilot bearings dry or seizing. Pull it apart and all will be revealed.

 

Bob

Not excited by that...big cast iron lump on the back of a 6l straight six..

Seems likely though.

Don't think it's the clutch plates dragging, as when I adjusted them way past disengaged the problem is still there.

I don't know how sticky mechanisms or bearings would be worse when warmed up though?

 

Sent from my E5823 using Arbtalk mobile app

[Daniël Bos]

I had a similar problem with a Discovery years ago,it was fine for a few miles then gear selection became hellish.

Garage stripped it down after loads of checks ,fitted new clutch whilst in there...30 miles up the road no better....300 miles later it just came right.

Someone in the know said it was an hydraulic problem which would come about when the system became pressurised,...take from that what you will.

I ruled that out by adjustment and testing.

 

Sent from my E5823 using Arbtalk mobile app

[aspenarb]

Not excited by that...big cast iron lump on the back of a 6l straight six..

Seems likely though.

Don't think it's the clutch plates dragging, as when I adjusted them way past disengaged the problem is still there.

I don't know how sticky mechanisms or bearings would be worse when warmed up though?

 

Sent from my E5823 using Arbtalk mobile app

 

Think of it like this and assuming there is no problem with the clutch itself. Clutch pedal is pushed down and all things be equal the plate slides back off the flywheel on the spline and there is a gap between the drive plate and the two surfaces of the flywheel/clutch cover. Clutch is released so no problem.

 

Bring on condensation,rust,mud and general crap that gets into our sort of 4x4`s from wading or off roading , spline gets cacked up and the clutch plate cannot get back on the gearbox spline to clear the flywheel hence the drag.

 

A seizing pilot bearing can do the same.

 

Bob

[ashtree]

How far along its engaged travel does the gear lever move before it goes solid.

 

When trying to engage is there any noise from the box.

 

If you try to engage gear without pressing the clutch do you get a ratcheting sound.

 

Is the problem the same in reverse.

[Stock]

Mybe an internal leak in the master cylinder...................

[Breezeblock]

I've had that problem on an old car it was the synchros that were worn it was cured by changing to a synthetic oil in the box

[woody paul]

No oil in box??