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GKN O verdrive fitted to a 5 speed V8.


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Just bought a V8 110 with a 5 speed box.Its fitted with a GKN overdrive unit which lights up but wont engage.

The gear box is fine and smooth in reverse and 1-4 gears.It selects 5th nicely ,but on release of the clutch makes a noise like a machine gun.

Is the box knackered,or could it be something to do with the overdrive unit perhaps.

If thew box is knackered can I fit a discovery R380 unit .

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Had a similar prob with my V8 and GKN. Check that the overdrive unit has not vibrated loose, can't remember if it is 3 or 5 countersunk screws that hold it in place, we simply locktighted the buggers. Being a bit loose, someof the gears were a bit chewed up, but a quick clean up with a sanding disk sorted that out. No probs since then (well other than the engine going off with a bang).

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I fitted a GKN O/D to an R380 - the thrust washer thingy shatterd after a very short time, so it was replaced under guarantee. The new one refused to stop leaking at the gasket joint, until we noticed that the face of the O/D was bent :(. Shortly afterwards there was always an awful transmission clunk that couldn't be identified (new gearbox and Trans box recently fitted). Removal of the O/D cured all problems immediateley. I don't know about the GKN O/D - they take a bit of a knack to engage/disengage, are very expensive, and seem to have one problem after another.

Les.

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got a GKN on my R380, only problem I've had is the speed sensor failing, cured by fitting a new one, been OK for a few year now, it gets regular fluid changes, & when selecting/deselecting keep the power on, don't lift off or use the clutch.

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I hear a lot of comments from a LR mechanic friend and his colleagues about these units burning out their bearings, solenoids failing and general poor mechanical ruggedness. It doesn't sound much like they were ever any good If you already have one, it's probably worth putting right if it's not an expensive repair, but costly repairs or a new purchase (if you can find one) are probably not worthwhile.

I suspect that tuned engines and infrequent fluid replacement have a large influence over the units' poor longevity, though.

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got a GKN on my R380, only problem I've had is the speed sensor failing, cured by fitting a new one, been OK for a few year now, it gets regular fluid changes, & when selecting/deselecting keep the power on, don't lift off or use the clutch.

I engage my gkn under power, but get some dreadful transmission clunks if i disengage under power! Because of this, i always dip the clutch when disengaging. I change the oil every service time. It only takes ~600ml and cooling is not good for the OD, so i think that regular oil changes will be beneficial (GKN reccomended it every 50K IIRC!!). I have also put a deeper (higher capacity), finned sump on my transfer box in order to increase cooling there in order to try and stop the OD getting as hot.

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