I'm in the process of changing my gearbox oil. I've just opened the gearbox fill plug and a little bit of oil is draining back out. The gear oil has not been changed for 4 or 5 years & 6K miles (car hasn't moved for a year) & when I've done this before (several times) when I've filled it I've put a spirit level on top of the plenum so I have a known amount of oil in there i.e fill it though the xfer case till it starts coming out the gearbox fill plug then adjust the jack till the back of the car is level & leave it there till it stops dripping, then button it up. It looks like about 70-100ml has come out so it's not huge amounts but how destructive is it? There is obviously the possibility that it wasn't 100% level last time but I think it was. I also have a vague recollection of doing the job quite quickly so could be I left it a little on the full side. So the thought is to do it carefully & dead level this time, leave it till it stops dripping out the fill plug & then run it for 1000 miles & see where it's at, or is that a bad idea? Anyone experienced this thing failing & if so any idea roughly how much oil went past the seal into the gearbox & then how much it takes before it will damage the gearbox, or is it not going to hurt it? Sent from my SM-A505FN using Tapatalk
My internal seal leaked a few years ago. I became suspicious because shifting suddenly became difficult. I checked the engine oil and noticed it was about a quart low. My engine does not use oil. That's when I checked the level in the transmission by opening the filler bolt. About a quart came out and it was the color of engine oil instead of red like it should have been. The engine oil level is higher than the transmission oil level so if the seal leaks, there is transfer with the car stationary.
Iain, I have some of the X seals (thanks to TommyA in the US.) Send me your address and I'll post you two. Warm them up with hot water, stretch over something round, cool in freezer, they’ll stay bigger for a while making them easier to fit.
Do you know when the seals were last renewed? Is there any leak or weep on the external shaft seal, usually you would see them both start leaking around the same time. Possible for the internal one to leak while the external one does not, but if the external one is leaking that would be a sign to renew both. It does not seem like enough excess gear oil has come out to me, when you do the level fill, it can take a long time for the oil to work its way through and come out the filler hole. The cheater method of filling the gearbox is what I do as well, but it may be that this gives a slight overfill compared with the factory method as set out in the manual. A slight overfill is I recall suggested to be a good things by some Fchat experts, for greater certainty lubrication under high g forces. I would do a gear oil change that is due, wait a suitably long time when the car is level, like a couple of hours, to let the oil run out to the correct level so you have no guessing as to the correct fill level, and then do a check after a couple of months of driving, and then see if you have the excess oil coming out. Also, measure your oil level in the same manner before and at the next gearbox level check, and see if it is going down at all. If both gear and oil levels are not where you would expect, that would be a clear enough indicator to get on with a shift shaft seal project. fyi, my understanding is a 10W40 engine oil is about the same viscosity when warm as an 80w gear oil (gear oil uses a different vis scale, both act as about a 40W oil when warm). The popular Redline gear oil MTL is a 75W80 I recall and quite a surprisingly thin viscosity when you pour it. So while these oils have different formulations for their intended uses, I doubt some 10W40 engine oil in the gear sump is going to do harm to the gearbox over a short period of time. Conversly, getting gear oil in the engine would probably not be great, but the higher oil sump tends to be the one that leaks into the lower gearbox sump.
I would delay the change for 500-1000 miles and keep an eye on your engine oil level. Then check the gearbox level again. You'd probably feel the difference in shifting before any damage is done.
Thanks for the suggestions & info. The seals were changed in 2011 with quad seals at around 36k (now 49500). I use 0W40 Mobil 1 & a mix of 1xRed Line 75W90 with the rest 75W90 NS in the gearbox. I've changed both & will check the gearbox level in a few hundred miles. I filled the gearbox through the drop gear case & let it drain back overnight so its definitely dead on full. The oil that came out the gearbox was distinctly tan in colour but it was clear. New Red Line is Orange bordering on Yellow. The amount of oil that drained back overnight was surprising given how long it took to start coming through, it really does take 20+ minutes after you top it off via the transfer case. Maybe 150ml came back out. I don't recall exactly what I did the last time but I have a suspicion that I didn't let it drain for long enough. We shall see. Will try & remember to report back in due course once I've run it for 500 miles or so Derek , I'll pass on the seals for now till I know whats going on, but thank you very much for the offer. Given the space I now have to work in I'm not sure its a job I would do myself if it needs doing.
