Overdrive filling from transfer box

[Boothy]

Just stuck an overdrive on a lightweight and it seems to overfilling with oil from the transferbox.

I'm sure I've heard of this before but couldn't find it on a search or a trawl through.

It was straight swap from one series to another and was not a problem before.

Any thoughts please.....

Chris

[secondjeremy]

I've got the same problem - I'm wondering if its due to a slack bearing in the overdrive allowing the shaft to move back and forward and pump the oil in. I suppose one solution would be to remove it and drill a hole in the side of the seal at the appropriate level so that the oil drained back when the thing was stationary.

I should add that I think the transfer box is breathing correctly. I had to change the main box and was very careful when I built it to make sure it vented properly - and did the same when I fitted it to the transfer box. Overdrive is still taking the transfer box oil and chucking it out.

[Snagger]

The overdrive sits well above the transfer box's oil level, so the only way oil can get into it is by being forced in. Unless you have a curious spiral groove somehow worn into the output shaft (one is actually machined into Roverdrive shafts to create this pumping action), the only way in which this forced migration can occur is the transfer case breather being blocked.

It's not normally the upper, visible part of the breather that is the problem; it's the slot between the empty vertical rectangular void under the breather cap and the gear box main shaft, just above the main shaft oil thrower - it fills with gunk and debris which settles like fine silt and mud and completely blocks that slot, so transfer box pressure can't react the big void and cap.