Final Drive revisited

[marty mayer]

A lot of you might remember my rants last summer when my final drive went south on my 04 GS Adventure on my way home from the UN and The MOA. Got nowhere with BMW and I still believe there is a design flaw. Luckily i had a spare bearing and seal with me. BMW of Sturgis SD. rebuilt it for me. Made it home, but didn't trust it at all. The final was running extremely hot with about a 10 mpg drop in mileage. Long story short a very good friend of mine is a retired machinist. The guy can fix, repair, rebuild or fabricate just about anything. I trust him way more than any BMW mechanic that I have ever dealt with. Well he kept bugging me over the winter to get the final drive off and to him. He wanted to take a look inside. He found that the big bearing was shimmed 15 thousandths to tight. Sturgis BMW probably didn't have any shims or the know how to shim it properly, and just reassembled it with my existing shim.

Also while he was in there he didn't like the fact that there was a tapered roller bearing on the other end of the assembly in there. He feels that that would constantly be putting additional side load on the big roller bearing. He ended up putting just a plain roller bearing in place of the tapered roller bearing. Not sure how he did this but he did. He said that when BMW went to the 1200 models they changed from a tapered bearing to a roller bearing. Thus greatly reducing final drive failures. So far only a couple of hundred miles but it is running much cooler and seems ok. Has anyone ever tried this and if so How did it work for you? Best of all he says it's guaranteed. If it fails he will come and get me. Doesn't care where I am.

Marty

[dirtrider]

Morning Marty

 

I guess we’ll have to wait a few thousand miles to see how yours works out.

 

I question the need or even the desire of going to a free floating R/H bearing in the 1100/1150 final drive as the original tapered roller bearing was part of the system of maintaining proper ring to pinion backlash. The original L/H (crown) bearing is a deep grove bearing so is designed to work with a side load as well as radial load.

The 1200 hexhead does free float the R/H side but is also set up with a different L/H crown bearing as well as a hollow inner axle.

 

One of my biggest worries on free floating the 1100/1150 spool is then the ONLY thing holding and maintaining the proper gear backlash and spool lateral position is a light press fit of the crown bearing in a rather soft aluminum cover. On the 1200 hex that crown bearing is held from sliding sideways by a rather robust snap ring (the 1100/1150 doesn’t have that and I believe not enough extra bore to even machine the cover and add one.

 

I guess I can’t see any harm in the free floating the R/H bearing on your final drive short term. Long term I just don’t know, as your new L/H deep groove wears it will start to allow fluctuation in the gear back lash as well as the gear tooth contact position.

 

Keep us posted in about 10,000 miles on how yours works out.