GKN overdrive oil sucking problem

[Marco]

Hi, for some reason my GKN overdrive is filling up with EP oil from the transfer case. On the run down to the South of France all went OK but on the way back the overdrive started to fill up. It's not the first time this has happenend. It first happend after 13000km.

Innitially I was thinking the transfer box breather was blocked (cleaned all pipes after first filling up) but I now expect the overdrive unit to suck in EP oil.... Does anyone have had a similar problem? I'm using the clutch for all gear changes incl. overdrive in/out.

I actually do consider to loop back the overdrive breather pipe into the transfer case. Not the best sollution as EP is not the right lubricant but at least the EP might stay in.

Or take off the unit.... but I do like the low revs so much..

Cheers

Marco

[yellow]

Check the breather on the OD unit as well. I ad a similar issue, which was linked to a blocked OD breather pipe.

[Kev Baldwin]

The type of oil transfer you describe is a common fault on the GKN. They just don't like being run for long periods of time when they can get hot. GKN no longers makes/sells the OD because of faults like this and others.

Take the OD off. Secondhand value of the GKN will probably pay for a Disco 1:2 T-Case gearing swap.

[Marco]

The type of oil transfer you describe is a common fault on the GKN. They just don't like being run for long periods of time when they can get hot. GKN no longers makes/sells the OD because of faults like this and others.

Take the OD off. Secondhand value of the GKN will probably pay for a Disco 1:2 T-Case gearing swap.

Thanks.... but is it pressure inside the transfer case or a vacuum inside the overdrive? I do expect a vacuum as the LT230 breather is fine and not spitting oil. Disco gearing is unfortunately no option for my 200TDI 130 station, it's just to heavy. I do need the normal 5th gear ratio.

Will probably run the OD on EP now as it is taking it in anyway, no clue what that will do to the unit as it is much thicker... at the moment the breather is spitting out an EP mixture into the engine bay, bad smell and very messy, need some kind of expansion tank or loop back into the transfer case. As the LT230 is a recon unit from Ashcroft I do n ot want to mess up that one due to the current overdrive failure.

Looking at other GKN posts I do not expect much from contacting GKN....

[western]

has your OD got the little white translucent plastic expansion bottle at the OD end, like mine in this picture, early ones just had a vent hose to the outside.

[Marco]

has your OD got the little white translucent plastic expansion bottle at the OD end, like mine in this picture, early ones just had a vent hose to the outside.

Yes it has, or better that one has collapsed already so I've fitted a new expansion bottle (= basic fuel filter) on the other end of the tube inside the engine bay. Just to make it easier to monitor any leakages (+ oil being transferred into the bottle). It went fine for about 1500km but on the long run back home it started to fill up + drip out EP oil. Not sure if this has been a slow cumulative process.

As the oil level of the transfer case is below the overdrive unit I expect some kind of vacuum inside the overdrive is causing the unit to fill up with EP.

[western]

I'd be making sure the breather hoses are clear & the OD oil level is correct & the shaft seals at the joint to transfer box are intact & undamaged, I do lots of 240 mile drives at 50 to 65 with my OD engaged & ddon't have any oil lose or transfer.

[Marco]

I'd be making sure the breather hoses are clear & the OD oil level is correct & the shaft seals at the joint to transfer box are intact & undamaged, I do lots of 240 mile drives at 50 to 65 with my OD engaged & ddon't have any oil lose or transfer.

Hi Ralph,

Breathers have been cleaned and checked after the previous oil transfer. It's not pressure inside the transfer box, that breather pipe is not dripping oil. Seals, expect a problem because oil is getting in.

Speed, running speeds of the OD have been up tp 70-80 Mph / 2-10 hours. Thursday I've been doing 675 miles / 1080 km.

Will drain the unit and refil with ATF but that will not solve the problem.

Does anybody know the part number of the shaft oil seal(s)?

[gus]

Hi Ralph,

Breathers have been cleaned and checked after the previous oil transfer. It's not pressure inside the transfer box, that breather pipe is not dripping oil. Seals, expect a problem because oil is getting in.

Speed, running speeds of the OD have been up tp 70-80 Mph / 2-10 hours. Thursday I've been doing 675 miles / 1080 km.

Will drain the unit and refil with ATF but that will not solve the problem.

Does anybody know the part number of the shaft oil seal(s)?

Welcome to the GKN problems club.

I had the same problem traveling to Moroco 16 months ago.

But my feel is that I have solved the problem for ever, i hope.

Make the tranfer vent hole biger.

Replace the big bearing in the GKN with another orginal bearing. Only the original NTN orange color will run ok, don't try SKF or other brand.

And install another seal and a o ring in the GKN, like you can see in these photo.

One travel from Madrid to Tunisia, and 20.000 km after, my GKN is working ok still, only with a small mix of oils between tranfer and OD.

[Marco]

Hi Gus,

Thanks for your post and images, have been studying the pictures. It does sound like the right way to go for me.

The parts used, it would be most helpful if you've got the part numbers for me. Are these standard items?

Thanks

Marco