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Oil leak in Tail shaft???

Started by _Squarepants_ , May 09 2009 03:59 PM

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7 replies to this topic

#1 _Squarepants_

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Posted 09 May 2009 - 03:59 PM

I have an oil leak around the back of my gear box.
I'm pretty sure it's coming through the centre of the slip yolk on the front of the tail shaft.
Posted Image

There looks to be a welsh plug or something similar in the centre of the slip at the yolk (uni) end. Can anyone tell me if that's correct?
Has anyone had this problem before?
I have changed the seal in the rear of the extension housing, the oil flicked off the tail shaft onto the floor pan seems to line up with the uni joint and the inside of the dust cup cover on the slip is completely dry. The slip was brand new when I had the tail shaft built 4-5 months ago, it is to suit a Celica 5 speed.
If it was coming through the seal and being flicked off by the uni the dust cup would be soaked inside.
I'm pretty sure I've found the leak, I just find it hard to believe that's what's actually going on, so I'm after some second opinions please.

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#2 _kingy_

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Posted 09 May 2009 - 04:08 PM

shine a torch inside the yoke and have a look in, if you can see any witness marks youve got problems. Meaning, tailshafts too long and when the suspension compresses, the output shaft is hitting the "welch plug"

How far can you push the yoke in to the box when the rear uni is disconnected?

Ideally you want about an inch or a tad more.

It could also just be a leaky yoke, try a bit of silastic wiped around the rear "edge" of the welch plug, its possible theres just a weep there.

To test that, you could stand the tailshaft verticle, clean all the oil off, pour some gearbox oil into the yoke, and come back in half an hour and see if its leaked.

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#3 _chrome yella_

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Posted 09 May 2009 - 04:09 PM

yep, i had quite a few cars that i have wrecked over the years that leak thru the welsh plug in the back of the yolk, some had silicon smeared everwhere, but i think there would be neater ways to fix the problem.

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#4 _Squarepants_

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Posted 09 May 2009 - 04:18 PM

shine a torch inside the yoke and have a look in, if you can see any witness marks youve got problems. Meaning, tailshafts too long and when the suspension compresses, the output shaft is hitting the "welch plug"

How far can you push the yoke in to the box when the rear uni is disconnected?

Ideally you want about an inch or a tad more.

It could also just be a leaky yoke, try a bit of silastic wiped around the rear "edge" of the welch plug, its possible theres just a weep there.

To test that, you could stand the tailshaft verticle, clean all the oil off, pour some gearbox oil into the yoke, and come back in half an hour and see if its leaked.

It's definately not bottoming out, but good call. There is about an inch clearance there as you said.
I will try the test you have mentioned to confirm, again, good call! :clap:

I really don't want to start smearing silicone all over it as I paid good money to have this thing built properly by the "so called" experts, so as far as I'm concerned, it's their problem. I'll take it back to them next week and get them to fit a new welsh plug with some sealant.
Thanks guys! :spoton:

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#5 Struggler

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Posted 09 May 2009 - 07:55 PM

This is a fairly common problem. The plug is not a welsh plug as such but a spun in disc. The proper fix is to braze around it so to seal it up but the silastic works as well. Personally I use an epoxy adhesive (araldite or JB Weld) as I couldn't be bothered heating it up.

Make sure the yoke is spotless before appling the epoxy (from the outside), I use carbiclean and compressed air.

JMHO

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#6 _NURVUS_

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Posted 09 May 2009 - 08:07 PM

Had the same thing. Replaced the seal in the box, shortened the tailshaft half an inch and had the yoke plug "tested". All back together and it still leaked, tied a rag around the slip yoke and oil was on the tailshaft side. Ultra blue sealer over the yoke plug and it's been fine for 6 months.

As far as i know there's no real way to test the plug, a shop filled mine with crc and compressed air and it didn't leak, put it back in the car and it leaked straight away.

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#7 _ljharbsy_

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Posted 10 May 2009 - 10:49 PM

Also check out in the extension housing the aluminium bush they wear and can cause leaks, drop the rear of the shaft off the diff and see if there is much movement, also the felt seals can be damaged. Have seen the welsh type plug leak before too. To replace the bush you would need to remove the box and take the rear housing off the box, if you are in sydney pm me I can help you out.

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#8 _Squarepants_

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Posted 11 May 2009 - 04:21 PM

Also check out in the extension housing the aluminium bush they wear and can cause leaks, drop the rear of the shaft off the diff and see if there is much movement, also the felt seals can be damaged. Have seen the welsh type plug leak before too. To replace the bush you would need to remove the box and take the rear housing off the box, if you are in sydney pm me I can help you out.

Thanks for the offer mate but I'm in Brizzy. The new seal I fitted had a new felt wiper in it too. I will inspect that bush before I bolt it all up.
I pulled the slip yolk off the tailshaft and filled it with metho. Leaked like a sieve(sp?). I used metho as it's thin and would clean out any oil residue from around the plug. I bead blasted the paint off, washed it again and silver soldered it up. Haven't tested it again yet but I'm pretty confident
Thanks for the advise all. :spoton: