oil leak

[Locknut]

G'day all
Well i have a NH 3lt auto lwb with a oil leak from the rear out put shaft.
I have replaced the rubber seal twice and a auto tranny dude has done it twice. He told me that he has seen worse movement in were the tail shaft goes into the extension houseing....but it still leaks.....BUGGA
Ihave looked at the inner part were the seal sits and it looks good......but when i grab a torch and look further up the extension houseing i see another "ring" approx 5mm thick to me it looks as if about the 2 oclock and 7 o clock mark there are 2 10mil grooves have been punched out,it has scrape marks like some one has driven a screw driver or similar through it??
So off to the wreckers to ava look at one and the one i looked at this "ring" is all intact the only diff is mine is a cable driven speedo (the one i looked at was electronic speedo)
Has any one noticed anything like this on there's or does some have a spare to look at for me to see wots wot?
If i change the extension houseing,will it matter if its from a manuel?
(soz for such a big post)
Gav

[Bitsamissin]

It will be the slip yoke leaking internally.
They have a welch plug inserted in them to stop the t/case oil leaking out as they are hollow from manufacturing. After a while the plug corrodes through and will start leaking oil.
New one from Mitsu is about $120 may as well change the uni joint while your at it. The old one can be sealed using an epoxy resin and kept as a spare.
Front and rear output shaft leaks confounded us for a while until we worked it out. Guys were replacing seals left right and centre, using speedy sleeves all to no avail. The only fix was to replace the slip yoke.

Frank.

[Locknut]

do you meen the yoke thats on the end of the drive shaft thst fits on to the rear out put shaft?? if so i have looked at that and its not coming from there, well i realy dont think it is i put some sealent over the welsh plug to see if it was after a new seal was put in but to me it seams to keep dribbling from the seal???
Gav

[Bitsamissin]

Hmmmm unless you have a hell of a lot of slop in the extension housing the double lipped rubber seal should not leak. The extension housing has a sort of rubber bush inside it to help locate the slip yoke. There is always a few mm of movement. The other thing is a collapsed output shaft bearing causing the output shaft to run out of round distorting the rubber seal allowing it to leak.
If there is bugger all slop there the oil seal should not leak (unless the slot it sits in is damaged) and my bet is the slip yoke. It's possible the outer face of the slip yoke is damaged or scored enough to not seal as well.
A new extension housing with bushing is about $600 new from Mitsu and yes auto and 5sp extension housings are the same.
You can also tension up the oil seal by removing the internal spring, undoing it, cutting a little off and rejoining it again.
But as I said 99% of these leaks are from the slip yoke. Very few turn out to be anything else and I hope yours isn't one of those.

Frank.

[Locknut]

Thanks for the info Frank,mite see if me mate will swap drive shafts to see if it is the yoke......hope its that.....
Gav

[pom300]

i have an nh swb and i have a leaking front tailshaft seal ive replaced it and it still leaks,but with further inspection the drip is actaully coming from the behind the uni not actually around or from the protective cowling bit what shoud i do

[hudson44]

Get a new uni. Remove the old uni and remove the plastic excuse for a welsch plug from the yolk and get a brass welsch plug from a parts store and tap it in using a bit of silicone as well. Put tailshaft back together with new uni.