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How to: Replace the gearbox shaft selector seal (and replace the gearbox oil)


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There are plenty of threads on this but here's a summary How To guide

The gearbox selector shaft runs into the gearbox at the base of the gearbox next to the dogbone mount. The O-ring seal that prevents oil from leaking out here usually fails at some point on the Lupo/Arosa 085 gearbox and similar ones used on the Polo. You can still get the OEM part no. 085 311 113, but there are plenty of aftermarket replacement parts as well.

In hindsight I'd consider leaving this job if the oil leak isn't significant and just keep on top of topping up the gearbox oil. (Edit: The more I think about this, the more I think it is actually worth doing as preventative maintenance. There's a few of us on here now convinced the gear box maintenance and thicker oil change is what makes the boxes last. So many threads of folk looking for replacement boxes, which are hard to find, and will only get harder to come by!)

Some people are lucky and the seal pops out easily in a 20 minute job, with no need to drain the gearbox oil first even. Mine was an hour long ordeal as the seal was so welded in after 20 years. Draining the gearbox oil made it a lot easier for me, but YMMV. Otherwise once you pierce the old seal you might be fighting a steady flow of gearbox oil getting everywhere. You might as well change the gearbox oil if it hasn't been done for a long time.

Tools:

Picks & hook set, or two small woodscrews, or a small drill. 
17 mm hex bit
17 mm spanner
10mm hex socket
Funnel + hose

Method:

Gearbox oil drain

  1. Place the car up on axle stands or ramps (ramps are a lot easier for this)
  2. Remove the undertray if fitted
  3. Locate the gearbox drain and fill holes. These are two plugs that take the 17mm hex bit. The fill hole faces the bumper and is just next to the starter motor and reverse light sensor. The drain plug faces the passenger wheel and is right at the base of the gearbox.
  4. Make sure you can slacken off the fill hole first of all. If you can't get this off you'd have to fill via one the sensor holes. But you need some way of refilling the box - don't drain it without checking this first! Now take out the fill plug.
  5. Place a container to catch the oil and use the 17mm hex bit to take out the drain plug. Let the oil drain.

Selector seal replacement

  1. Place the car into first gear
  2. Remove the gear linkage mechanism that is connected to the shaft by a 10 mm hex head bolt. It should slide off the shaft and then tuck it away as best you can for access/leverage later. Don't touch any other of the other bolts/screws as these are for adjusting the linkage itself.
  3. The VW workshop manual recommends wrapping the shaft in some insulation tape to protect it at this stage.
  4. Now the joy begins. You need to get the old seal off without damaging/scoring the shaft itself. There are several methods people use:
    1. Screw in two self-tapping screws either side of the seal, then pull out the seal with the screws and some pliers.
    2. Drill a very small pilot hole (carefully!) to get a hook or pick in. 
    3. Pierce the seal with a screwdriver or bradawl, then lever it off with various hooks and picks. (This is what worked for me).
  5. Pull the seal off, clean up the opening and shaft (remove the tape), add a drop of oil to the new seal and slide it back on. Press it firmly into place as much as you can. It should sit flush with the gearbox although sometimes you find they have been pushed in a bit further and sit a bit recessed. A 17mm spanner can be used to lever it in and firm it down. 
  6. Re-attach the gear linkage mechanism to the shaft with the 10mm bolt. Check that all the gears go into place with the gearstick.

Personally, I could't see how to get screws in there, the seal is very narrow and I didn't have small enough woodscrews). There is really not a lot of room to drill in at the right angle either. It's made trickier by the fact the old seals usually have a metal ring in them, so you aren't just trying to pierce the rubber but a bit of metal too. The metal ring doesn't run right up to the edge of the seal though, eventually I managed to get a small pick between the metal ring and the inner side of the seal, right next to the shaft, and lever out from here with much difficulty. My cheapo pick set probably meant the picks themselves were softer than the shaft, which avoided scratching it. (You really want to avoid damaging the shaft!) 

That's a lot of description; again, some folk manage to pop the seal out in 20 minutes with no bother, others like me find it a nightmare to get out. There's no way of knowing until you start the job. 

Refill the gearbox

  1. With the new seal in place, and the drain plug fitted back on, place a hose + funnel into the fill hole, and top up the gearbox until it starts to dribble out (this is the only way to know that it is full). 
  2. Oil choice. 75w-90 is the official recommended oil. Some of us on here like to replace it with thicker 80w-90 to potenitally increase the longevity of the box. 
  3. Fill plug back on, and you are good to go.

 

old_seal.jpg

seal_off.jpg

Edited by decvalts
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  • 1 month later...

Currently following your Subframe removal guide (thanks!) to do a bit of corrosion removal on it for a MOT advisory, and there's a bit of a weep on my recon gearbox, and as the SDI box does not like going dry, I will be following this guide as well while i'm under.

Couple of quid for a elring seal beats a several hundred for another gearbox!

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