Here We Go - Trans Shimming Doubts

[ME 109]

Why not install the plate with the gasket and torque to spec. Then take your measurement? I recently got a shim plate from cycle works and I think it says to do this in the instructions.

That's the way to do it.
Then, it doesn't matter a hooterfenanny how much the gasket compresses.
There are other things that will vary shim measurements such as cover plate warp.
Even torquing the cover plate bolts/screws/whatever, will induce warp in the cover plate.

[Duane Ausherman]

The rear covers can warp and a few times we removed the junk and lapped them down flat again.

[Ray from Indiana]

Ok, take my shimming plate and squish the gasket by torquing to spec before taking measurements. I get that.

Just hope the gasket seals afterwords. Because if I use the second gasket I bought its thickness will be a little different.

Did anyone look at the BMW manual example? Their example doesn't make sense to me because they subtracted teh gasket thickness so I'm going to ignore it and use the calc I showed in blue.

Jeff - Is that how you did it?

The reasons I'm doing it myself:
1. I wanted to see the damage with my own eyeballs if there was any after finding 2 small metal cubes approx 1/32" in my drain pan on last oil change.
2. If I send it away and spend a minimum of $700 ( what they charge these days) for a basic rebuild, I learn nothing except how to depend on other people.
3. I've rebuilt gearboxes before, just not a BMW box. Last I checked its still just a gearbox. So its gearbox vs engineer. Hope I win and I think I will with patience as Duane noted and a lots of research and learning. I don't expect to be an expert nor do I want to be. My post here was just about some confusion cause by looking at that BMW manual example.

Thanks guys, I'll be back for more.

Opened the box up today without any drama. I used arm power and a couple of lengths of 1" sch 40 pipe to take the output flange nut off - leverage is your friend. I kept the impact gun away from the box.

While I was waiting for some stuff before beginning I put some penetrating oil in the cavity around the output flange nut. That was about 3 days ago. When I put the flange puller on and started the socket with an 18" breaker bar, the flange lifted! Did so with only about 25 or so foot pounds!

I thought - "Oh crap, someone didn't have the flange on tight enough - or did the penetrating oil do some good?" Well there are no signs of spinning or galling on the output taper so the oil must have helped.

I'll post some pics when I get them organized. Removal of the shafts for cleaning and inspection is next task.

thanks

Ray

[Duane Ausherman]

The oil didn't loosen the flange, it was just not tight. You were very lucky to not have it spin and ruin both parts of the taper.

[ME 109]

You'll be fine Ray, just take your time and don't force anything, and when measuring for shims check and re-check.
I used the gasket under the shim plate and used said gasket upon assembly. No leaks.
Some folk don't use a gasket and use a sealant instead, apparently without trouble.
The bmw manual contains several mistakes throughout.

Some folk also say to measure from shim plate to bearing i.d. next to shaft. My problem with doing so is that the i.d. doesn't run against the shims, and in my case I measured a step up to the i.d. from the o.d.
That may well have been the result of the bearing 'hanging' off the inner race....

Anyhowz, torqued shim plate with gasket to bearing, minus depth of pocket in cover, minus .05mm endplay = shim stack thickness.
Take several measures around each bearing, measure cover plate pocket depths with parallels ideally, measure each shim thickness.

If the shim stack/s are too thick, the input shaft will go from 'loose' with a loose cover plate, to stiffening once the cover plate is torqued.
If this occurs, cover plate must be removed and shim stacks reduced by .02mm and retried.
It may only be one stack that causes a stiffening input shaft, but you won't know which one.
So that's where the 'measure and re-measure' comes in.

A slight stiffening of the input shaft (Gidday ZM! ) can be cured by a wack on the end with a plastic/copper mallet.
If the input shaft stiffens up well before the cover is fully torqued/tightrened, Off with the cover again!!

[Ray from Indiana]

The oil didn't loosen the flange, it was just not tight. You were very lucky to not have it spin and ruin both parts of the taper

I can say that the nut took full back breaking grunt with 3ft lengths of pipes over the flange holder bar and my breaker bar to get the nut loose but when I pulled on the breaker bar only when using the puller tool it was cake. My conclusion was the flange must have been on the taper tight by the amount of torque required to get the nut off

[ME 109]

I found both Airbears and my output flange retaining nut not so tight, but both flanges took quit a bit to 'pop' off.

[esman100]

Ray, I used the same method ME109 did including the "wack with a soft mallet" to set the bearings. The first box I did has over 40k trouble free miles and both run cool and quiet. I can't view the manual file with my DROID, but you know as an engineer that manuals are written by non technical people and are quite often full of mistakes. So, read what ME 109 wrote and Zen and the Art of Motorcycle Maintenance and with the right tools you will see how easy it is.

[esman100]

Ray, I used the same method ME109 did including the "wack with a soft mallet" to set the bearings. The first box I did has over 40k trouble free miles and both run cool and quiet. I can't view the manual file with my DROID, but you know as an engineer that manuals are written by non technical people and are quite often full of mistakes. So, read what ME 109 wrote and Zen and the Art of Motorcycle Maintenance and with the right tools you will see how easy it is.