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1Back to top Go down   I really need you guys Empty I really need you guys Fri May 03, 2013 1:25 am


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I know this is slightly "off Topic" as it relates to automotive gears, not motorcycle. Still, I hope it has relevance because out bikes have similar final drive gears. I have a Used Chevrolet Differential on the bench & I'm attempting to prepare it (CHEAPLY) to replace the one on my vehicle. Following is the narrative of what I have and the help I'm asking for.
The object is dependable not necessarily "whine free" I'm replacing few if any parts.
Hypoid Gear set adjusting
This differenial gear set has NO backlash.
There is no history known on who may have installed the gears/bearings (if at all)
No road test was available before inspection.
It seems obvious that because there is NO backlash, that something has been replaced and
is not factory original.
The object of this repair is to adjust the gear(s) positions to create suitable backlash while
achiving the best comprimise of mesh pattern.
There are 6 Gear pattern Photos below.
Photos 1-4 are of the drive side of the Ring Gear.
Photos 5 & 6 are on the coast side of the ring gear.
To me it appears that on the drive side, the pattern is running very low on the gear tooth,
almost off the bottom and slightly deeper in the gear than optimal.
Conversly, the pattern on the coast side of the same teeth is running High up towards the
outer circumferance of the ring and about proberly centered in the depth of the gear tooth.
I have to move either the ring gear out (left) away from the pinion or I need to move the pinion
gear forward away from the ring to create backlash. I do not have the exact spec yet, but I will
look it up in the book. I'm guessing (with no professional knowledge of gearing) that I'm
shooting for about 3 to 6 one thousanths of an inch backlash, measured at the ring gear outer
Now, I really need some help on this from some of you down under engineer types that
understand the exact relationship between hypoid gears and how movement of either effects
the other.
Obviously, If it works out the right way, the ring is easier to shim left away from the ring than
the pinion is to remove the inner bearing & crush sleeve to change the pinion depth.
Please help me decide which way to move what.
Thanks ahead of time.......ibj...
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2Back to top Go down   I really need you guys Empty diff Fri May 03, 2013 5:11 am

sven k100

sven k100
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are the bearings(i presume taper roller type) being replaced ?. if so, then this could restore the original positions of the gears in relation to each other.My understanding of a correct wear/scuff pattern is central on the tooth, tapering to an oval at the edges of the scuff.


3Back to top Go down   I really need you guys Empty Thanks Sven Fri May 03, 2013 1:48 pm


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Thanks for your input. I should have been clearer on my original note. I made my living before retiring as a professional fleet maint. mechanic. That said, Rear end gears happened to be a job we either sent out or replaced "rebuilt" as a unit, due to the often times special tools & skills required to set them up correctly. Hence although I'm very familiar with these, I lack the actual hands on experience when it comes to getting the mesh patterns just right. With these particular ones, If you have to change the pinion gear "depth" the inner pinion bearing needs to be pressed off & on again to change the selective shim. Doing that requires a very specialized bearing press adaptor if one wants to be able to re use the same bearing during possible multiple R&R's until the correct shim is derived. With methods available to me at home, I can r & r the inner bearing but I would ruin the cone and need a new one. Due to variances in actual bearings this can be a difficult process. They make measuring jigs & tools to establish which shim is in the correct range, but those are prohibitively expensive for a home user.
So, I know how to do the job, but I lack the experience to be absolutely sure which of 4 directions to move which gear in order to generate the needed backlash while maintaining the correct mesh. One adjustment always changes the needs of the opposite one.
Currently, studying my manuals, indicates that I need to start by moving the ring gear case away from the pinion about 0.015" to get .007 in back lash. If that leaves my pattern ok, I'll be good. If not, I'll have to move the pinion out (forward) .005 and then determine again how much to move the ring.
Hopefully someone here can "Read" the actual pattern photos and tell me which way to move what & how much.
As to your direct question about replacing the bearing, That is what I'm attempting to avoid. Generally, if the bearings were "worn" the backlash might be too loose, but never too tight. Hence, I suspect that the last guy did it wrong.


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