[Vwdiesel] very leaky driveshaft seal

[James Hansen]

Evans Antoniou wrote:
> hi all,
> 
> i have an mk3 jetta 1.9TD AAZ engine.
> 
> about 8 months ago i had the seal changed due to
> prevention as i was doing the clutch work at the
> sametime. now there is a large leak from the
> driveshaft seal where the hub (cup) attaches to the
> tranny (5sp).

Okay, you changed which seal, same one as is leaking, or the one that is 
hidden when the motor is mated to the trans?
> 
> i brought the car to the local transmission shop and
> they thought it was a bearing in the tranny causing
> the  oil leak but they did not even drive the car
> (only assumption) and i had to rebuild the tranny - i
> think this is BS because the tranny drives great,
> there is no rattle, no funny noises - tranny has been
> driving the same ever since i purchased the car. i
> tranny might have around 250 000 km.

If it is an output driveshaft seal you are referring to, then yeah, you 
can tell without driving it.  you go underneath, and grab the cv shafts, 
then try to wiggle them up and down.  If they move LOTS, then the seals 
will be leaking because of worn bearings on the crown gear, the one that 
the output shafts are coupled to via the differential gears.  yeah, I 
know, lots of words if you are unfamiliar with it, but the last bearings 
on the way out of the trans on either side of it that support the shafts 
that the CV joints bolt to wear prematurely if the trans is ran low on 
oil.... the diff is the highest thing in the case, and the bearings 
starve if the oil level is low.  Only way to actually repair the trouble 
is to replace both bearings.  changing seals is a stop gap measure, and 
they will fail again if there is excess play.  Excess meaning you can 
discernably wiggle the shafts up and down, and you could measure this 
free play with a tape measure, not a dial indicator.
> 
> now i am new to troubleshooting tranny issues but does
> the tranny misfunction in any way due to the leak
> except more noise if there is no oil left?

Less oil equals more noise- you hear the crown and pinion gears howling 
in pain, and the bearings that support them wear.
> 
> is this a huge job?

Huge enough if you are new to it.
Just get it fixed, and try to watch over someone's shoulder if they are 
cool with that.  You can learn lots for next time that way.
A minimum you need a bentley manual before tackling the job. Remember 
that these are factory manuals and that they are not step by step do it 
yourself home handyman manuals either. They ASSUME you already have 
enough mechanic skills to be working in a shop.  It's something like, it 
will say "remove transmission from car." without including a step by 
step procedure to accomplish this.  But, that said, when you do get to 
the model specific stuff, or the dirty little tricks that the designers 
like to pull on us to get stuff apart, they will usually make mention of 
the trick you need to do the task at hand.
> 
> i have a 1.6L diesel (non turbo)  tranny and is this a
> direct swap?

No, not really.
It can be, but with some effort.
All vw stuff is backwards compatible, but not forwards.   That is, new 
stuff fits into old, it has all the mount holes etc.  New stuff wasn't 
invented yet when the old stuff was made, so you will be lacking 
mounting holes etc, on the older 1.6 tranny.

In my limited experience, it is waaaay better to rebuild what you have, 
then you know what you have when done. If you rebuild it to as new 
condition, then you have a tranny that is as good as new.   Getting a 
different used one in many instances, is just buying someone elses's 
stuff that needs fixing, and you wind up diving into it eventually anyway.

Yeah, I'm a bit cynical
-james