View original topic: Rear Main Seal Shim Question
ddye Mon Oct 19, 2020 9:21 am


I am in the process of replacing the rear main seal on my 88 2.1 Westy and a question has arisen. Note, I have watched the Boston Bob video and read several article but am not finding my answer.

My question is this; If I am replacing the rear main seal, is it necessary to replace or do anything with the shims that dictate end play? I will not be replacing nor resurfacing the flywheel. I am thinking it is ok to just clean the shims and replace but I am not certain.

Thank you!

Vanagon Nut Mon Oct 19, 2020 10:32 am

I've only played with those shims once but I'd say that if the end play is still within limits and the shims haven't seen excessive wear, no need to replace them.


MarkWard Mon Oct 19, 2020 11:11 am

Generally, you’d check the endplay before you remove the flywheel. Assuming it was in spec, you’d be fine to reuse the same shims. In fact, if you found excessive endplay, it wouldn’t be a good idea to tighten it up without knowing why it’s loosened up. So, you are likely good to go. Don’t forget the flywheel O ring.

ddye Tue Oct 20, 2020 10:28 am

Thank you for your quick responses. Very helpful!

Wildthings Tue Oct 20, 2020 11:22 am

It is good to inspect the shims for damage as they can wear over time. Make sure you uses some grease to hold the thrust washer, shims, and funky washer in place until the flywheel is installed. With a 2.1L engine you should be able to reshim the endplay if need be, unlike earlier VW boxer engines where reshimming could cause the thrust bearing to seize to the crank. If the end play is excessive then it would be good to figure out why it's loose before throwing everything back together though.

dhaavers Tue Oct 20, 2020 5:31 pm

^^^ Yes: grease/oil for install, but check endplay with everything DRY... :?

- Dave

ddye Fri Oct 23, 2020 6:18 am

Welp, I took my flywheel in to be turned and it turns out that it had been turned so many times previously I needed to order a new one. Guess I'll check the end play when the new new FW comes in and add/remove shims as needed.

MarkWard Fri Oct 23, 2020 7:02 am

You’ll get the “cleanest” measurement with no seal or O ring. Once you have it adjusted, then install the seal and O ring. You can recheck to be sure something didn’t dislodge during assembly, but expect it to measure slightly tighter.

scottydub Sat Oct 24, 2020 8:07 pm

When you check the end play, are you supposed to pull back on the flywheel and then let it set itself, then push forward and let it set itself, and then get the difference? Or are you measuring any movement that you can create by pulling and pushing with your hands? When I pull back on the flywheel it goes back and then re-centers itself as soon as I let go. It returns back about 10/1000s of an inch. So, I add that to the forward movement, or is the place
It returns to the place I start measuring from? Thanks

Abscate Sun Oct 25, 2020 3:33 am

If it’s 0.010 inches with no shims it will come into spec with the right combination of three , that’s one, two, three , shims

Btw...from one of the common no no.

It is not necessary to have three shims. VW could have designed the system to only take one, like some Porsche engines use. For whatever reason, probably production related, VW chose three as the magic number. However, in some cases it might be necessary to use only two, o

Three shims.that shalt not go to four, nor 2, unless Thou proceedest directly to three

MarkWard Sun Oct 25, 2020 6:27 am

End play would be total movement. Think of it as if you could insert a feeler blade between the flywheel and the thrust bearing face. You are setting the “gap”.

The more of these you do, the more of a feel you get, that you can’t really get from reading or watching a video.

You don’t want it too tight or too loose. Good luck.

scottydub Sun Oct 25, 2020 9:57 am

Ok, so any amount of movement that I. An create by moving the flywheel is what’s measured? It doesn’t matter where it settles of what position it would naturally rest in. Thanks

Abscate Sun Oct 25, 2020 10:57 am

The end pints are prised out and pushed in. If it is squishy or not reproducible it tells you something is wrong inside

Wildthings Sun Oct 25, 2020 3:15 pm

If your shim pack is degraded with one or more shims being bent or having odd wear, it is hard to get a repeatable reading. Having thick cold oil on the shims doesn't help with getting a good reading. Remove the flywheel and the seal and then inspect and clean the shims. Reinstall the shims and flywheel leaving the the seal out, torque the flywheel lightly and check your end play.

Bulli Klinik Mon Oct 26, 2020 8:03 am

And don't worry if it's two or four. The flywheel won't know the difference.

If you live in a cold climate, I'd avoid the low end spec of .003 and bump it up to .004-.005.

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