4 speed gearbox output shaft

[david.g.chapman]

Can anyone tell me where the end of the splined output shaft is in relation to the rear of the extension housing? Does it poke out a bit, or is it recessed in the housing so you can get a hooked seal puller in there to extract the rear oil seal with the output shaft fitted?

Dave Chapman.

[john.p.clegg]

Dave

Mine sticks out approx 0.685" and the last time I had to remove the oilseal it was hammer and chisel job..

John

[david.g.chapman]

Thanks, John.

I think I will leave the rear oil seal until I pull the gearbox/engine for something more important....

Dave.

[bcmc33]

The spline sticks out 20mm
The seal will be a real pig to change in-situ.

[RichC]

uh oh !
I kidded myself my recent gearbox oil leak was a factor of my overfilling ....
Having put the front end on axle stands , the next morning i found a lake of gearbox oil which i believe must be emanating from here as its dripping out of the chassis drain hole near the back
is it really an 'engine & gearbox out' job?
I'd like to know if anyone here has tackled replacing the output shaft oilseal 'in situ'.
Tips would be welcome if so.
happy new year !

[Orsom Weels]

Hi Rich,
It could just be the welch plug missing from the propshaft yoke. Prior to my ownership, my S4 had a dreadful 'gearbox' oil leak, after it had been fully rebuilt by Graham Bolton. If you jacked the front of the car, oil would literally just pour out. On closer inspection, we could see nothing wrong with the gearbox or it's seal, but there was a ruddy great hole through the middle of the prop UJ yoke. Graham told us there should be a plug in there, & swapped it for another propshaft he had lying around with the said plug in place. No more oil leaks, but a lot of work to find we could have just removed the propshaft

Regards, Tim

[HAIRY]

A front-end shunt can result with the gearbox spline pushing-out the 'core-plug' in the prop shaft,

[RichC]

this is REALLy interesting !
I would never have guessed ... and of course I had the mother-of-all rear end shunts before the rebuild so maybe that's it!
i imagine the welch plug, if it has pinged off, will be sitting in the chassis tunnel somewhere .
will do some checking.... thanks HAIRY
RichC

[RichC]

....and Tim , thanks also !

[RichC]

So as predicted I found the Welch plug missing and you can see the output shaft I think!
Took me a while to scan around with my iPhone to locate the Welch plug....i thought it was likely to be aft of the UJ. You can see in the first picture it was right at the front of the chassis so I was able to get my big hand up past the exhaust pipe and reach for it.
Next question is how to tackle putting the Welch plug back in with least hassle!!!!

[mbell]

I've just replied one of the coolant ones on my engine and invested in a special tool

https://www.amazon.com/gp/aw/d/B000XSGK ... ref=plSrch

Pretty sure I couldn't have done it in situ with out it. Might not be much use for yours thou.

[miked]

deleted

[RichC]

Welch plug back in .

Bit of a faff getting propshaft out but followed forum tip elsewhere taking it out with differential and gearbox in situ.
Bit of a squeeze .. All I had to do with the diff was loosen the top mountings just little in order to get the propshaft back enough to come off the gearbox output shaft, and then remove the gearbox mountings , jack up the gearbox and pull the propshaft out underneath the starter motor.
Awaiting new uj and gearbox mounting as the rubber was split...
Oh , and as I had a tube of superglue handy I ran a bead round the Welch plug!

[rgh0]

There are two types of plugs that are commonly used in automotive service
i.e

A cup style plug that seals on the sides of the cup as it is driven into a smooth bore until the top lips of the plug are flush with the casting

A dome plug ( the true welch plug I believe). The plug fits against a step in the hole bore and is expanded by punching in the centre of the dome

I am going from memory from about 20 years ago when i had the same problem and the plug got pushed out so I may be wrong but i believed the tail shaft used a domed type plug and had a step in the bore for it to sit against ???

A cup style plug may go in to deep and be pushed out by the gearbox output shaft when refitting?

cheers
Rohan

[RichC]

Hi Rohan,
This is the original plug. It fitted fine for many years.. There is a small step and it clicked home with just a light touch.
I too have a concern that if I am too rough in refitting the thing might pop out again. That's why I ran a bead of superglue afterwards.