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-   -   Measuring gearbox end-play (http://www.advrider.com/forums/showthread.php?t=796697)

DiabloADV 06-03-2012 09:13 PM

Measuring gearbox end-play
 
I spent 3 hours Saturday trying to get the shim measurements right after an overhaul of my 5sp gearbox. We had the right plates and a handful of depth measuring gadgets. I (and about everyone else there) kept getting different measurements. The box would get closed up, and be too tight. Then, do it again and the output shaft shim (which is visible before the seal goes on) would be loose. One guy had been at it for 4 hours by that time. I finally gave up and had to get home. I think using those indicators takes more skill than most of us at the tech day possessed.

Today, I tried a method I'd read about. Place little pieces of hollow-core solder so the ends sit across the outer races. Heat the cover and install and torque. Then take the cover back off. Measure the squashed solder, subtract 0.05mm, and you have your shim specs.

http://i1138.photobucket.com/albums/...k/ed610c3f.jpg

It worked perfect, and took 15 minutes instead of the tedious afternoon of ultimate failure. Plus you don't need a $70 flat plate and a $100 indicator. Or much skill.

DiabloADV 06-03-2012 09:16 PM

Also...here's why you don't use the kick starter on a '74 90/6...

http://i1138.photobucket.com/albums/...k/af11db53.jpg

Those gear nubs are almost completely worn through.

Rucksta 06-04-2012 06:11 AM

Thank you.
It seems to make perfect sense.

hardwaregrrl 06-04-2012 06:13 AM

Wow!! Thats nuts!!! Thanks for the pics!


Quote:

Originally Posted by DiabloADV (Post 18831259)
Also...here's why you don't use the kick starter on a '74 90/6...

http://i1138.photobucket.com/albums/...k/af11db53.jpg

Those gear nubs are almost completely worn through.


ozmoses 06-04-2012 06:25 AM

Why subtract the 0.05 mm?
 
Being mathematically challenged, my first reaction when numbers are involved is to panic :eek1.


Is the .05mm a tolerance or...?

Wirespokes 06-04-2012 06:50 AM

Correct!

The thickness of the solder is the exact distance between the bearings and case. The .05mm (.002") is the clearance needed.

Airhead Wrangler 06-04-2012 07:11 AM

Hmmmm. That's pretty slick. I've never rebuilt a trans before, at least not on an airhead, but now I kind of want to just try that trick. Cool. :clap

DiabloADV 06-04-2012 07:40 AM

Quote:

Originally Posted by ozmoses (Post 18832804)
Is the .05mm a tolerance or...?

Yup. That's what gap is left over so it's not tight and oil can circulate.

DiabloADV 06-04-2012 07:41 AM

And...I bet this would work on a crankshaft. Place the solder, torque up the flywheel (with the old bolts). Remove flywheel, measure solder, install proper thrust washer/shim and install flywheel with new bolts.

supershaft 06-04-2012 08:42 AM

I advise people to do that with pistons and valves all the time and I had never thought about doing it in the tranny. I work on them semi-regularly. I might try that next time. I always look up the specs but I think they go to zero. For my own nit picky self, I think they shift better shimmed to the bare minimum. IMO, with all the right stuff and a lot of experience the measurements are still a bit of a guess for measuring the bearing height. I measure them from the inside race but you are never quite sure if the gauge isn't rocking.

Flywheels? I will probably stick with a dial indicator but you could do it that way. It's real accurate and a real time saver with pistons. If everything is right you don't even have to take it back apart! I do it all through the spark plug hole. I think it's a much more solid measurement than clay.

Bill Harris 06-04-2012 09:23 AM

So this will give you a clearance of .002" at 'room temperature'. Has anyone ever reckoned that clearance at operating temperature? That is, at the temperature of the gearbox while running, the steel gearshaft will heat up and expand in length, the aluminum case will will heat up and expand in length, and the delta-length will be more fo the aluminum than for the steel (different "coefficient of expansion" of the metals, about 3x more for the aluminum than the steel). For example, the .002" cold clearance may be ~.009" hot.

Just curious. Been meaning to do the same figurin' for the crankshaft endplay. But if some (other) techno-geek has beat me to it, I'm no glory-hog... :rofl

DiabloADV 06-04-2012 09:57 AM

Quote:

Originally Posted by Bill Harris (Post 18834034)
Has anyone ever reckoned that clearance at operating temperature?

Yes...and I know exactly who....

The engineers at BMW that decided that 0.05mm was the right number. :wink: They get paid to think about such things.

100RT 06-04-2012 11:31 AM

Quote:

Originally Posted by DiabloADV (Post 18834285)
Yes...and I know exactly who....

The engineers at BMW that decided that 0.05mm was the right number. :wink: They get paid to think about such things.


Are they the same guys that eliminated the output shaft circlip and then put it back on years later?

Wirespokes 06-04-2012 11:34 AM

:rofl:rofl:rofl:rofl

Who knows? The guys who designed the transmission may have been long gone by then!

Bill Harris 06-04-2012 11:43 AM

Nah, I suspect that the old guys who designed the tranny retired and came back to the office for a visit, found out what the whippersnappers had done with the circlip and screamed "vat vur you tinkink???" and got it put back in.


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