Back in October last year, when I had the front diff. out to install a new VC, I noticed that the input seal was leaking. It would have been smart to replace it then, but I couldn’t wait for the seal to be ordered in. Then I procrastinated, put the job off until today. The job is quite straightforward; disconnnect the prop shaft from the front diff., undo the 24 mm nut that holds the drive flange on the input shaft, remove flange, remove seal, replace seal, replace flange, etc.
Addendum: Have a look at this thread on Yahoo Syncro list for discussion on cheaper seal. I didn’t see that thread before I bought the expensive one from dealer.
I’ll be pedantic and list the steps I took:
– chock pass. side wheels and jack and support driver’s side so that left rear wheel is off ground (you could have both wheels that side off the ground, would be easier to rotate propshaft to get at all the propshaft flange bolts)
– loosen the 3 bolts (17 mm) on the rubber mounts on front diff.
– mark the propshaft flange, the front diff. flange, and the front diff so that you can get all the bits back in same orientation.
– remove the 4 nuts and bolts holding propshaft to front diff. flange (13mm, use 2 open end wrenches), and let the propshaft rest on ground, or support with wire.
– rig up some sort of tool to hold the flange as you undo the nut (24 mm), the nut is on there tight (135 ftlb). My elegantly engineered (ha!) flange holding tool required the pass. side propshaft protection rail to be lowered a tad.
– a 2 arm puller to pull the flange off the shaft, came off very easily.
– the exposed seal can be pried out with a strong screwdriver. I was surprised at how secure it was in there. Be careful not to damage the aluminum housing.
– some oil will drip out, have a container in place to catch it
– new seal is lubed then, as the Brits say, offered up to the housing. I used a brake caliper piston to carefully drive the seal home.
– then the flange, and the washer and nut. Again you need to hold the flange as you tighten the nut.
– propshaft back up and secured.
– some gear oil squirted in the fill hole (17 mm socket head plug) just back of the driver’s side inboard cv joint.
– the diff mount bolts left loose for a few miles, then tightened up. Just to allow the front diff to settle in a happy place (a sort of horizontal self alignment).
Addendum: overview of area. 26 = 24 mm nut, 25 = thick washer, 24 = input flange, 23 = seal (22 = circlip and 20 = bearing. Both un-involved with this repair)
Here are some pics:
See the oil splash?
Propshaft removed, the 24 mm nut that holds the input flange on is revealed.
Flange held firm using homemade tool, nut loosened.
Flange off, seal exposed.
Shots of how the brake caliper piston is a good fit to use as seal seating tool.
New seal installed.
shooftie 
#1 by Scott on January 13, 2012 - 4:35 pm
You do us all a great service. Thanks!
– Scott
#2 by albell on January 13, 2012 - 4:51 pm
Thanks Scott. I neglected to talk about the seal, part number and the debate on the syncro mailing list whether another (less expensive) seal will work. I’ll get on to that.
ab
#3 by Ed on January 14, 2012 - 12:30 am
Yes, thanks for your informative and well illustrated (photo-ed?) posts which I am sure are helpful to many. (although still cursing you for the one about rebuilding the brake/clutch pedal assembly – ignorance would have been bliss)
Happy New Year!
#4 by albell on January 14, 2012 - 8:19 am
thanks Ed. How’s it going with your van? Xmas break probably taken up by other priorities 🙂
cheers and happy new year to you too
ab
#5 by Ed on January 16, 2012 - 1:16 am
yes, family matters (including a newborn a few days ago) have prevented any work on the westy for about 6 weeks. Hopefully get back to it soon…
#6 by albell on January 16, 2012 - 7:24 am
Congrats Ed!
ab
#7 by Tim Osrunn on January 15, 2012 - 7:29 pm
Most helpful and informative!
#8 by albell on January 15, 2012 - 7:47 pm
Thanks Tim. The only difficult part of the job is holding the flange while undoing the nut. Restricted room under the van for a long handled wrench.
cheers
ab
#9 by Jim on March 6, 2019 - 4:32 pm
Hi There, I am in the middle of doing this seal and have run in to something. Your photos show the original seal flush with the outside of the nose cone of the front diff, however your new seal is driven in deep. The Bentley manual says to drive it to the stop as you have done. However the seal is marketed as a dual lip. One lip on the shaft of the flange and one on the face. This making me wonder if the Bentley is wrong as when the seal is driven all the way in the face seal cant reach the flange face.
Constantly admiring your work.
#10 by Jim on March 6, 2019 - 4:45 pm
I think i may have solved it. All of the factory vw drawings show the seal at the outer edge. I think the factory seal driving tool is wide enough to stop driving the seal when it becomes flush with the outer face of the nose cone. I think the outer face seal is just to keep the dust and grime away from the proper oil seal on the shaft.