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Posted by: bondo Feb 20 2006, 08:33 PM

On page 5.1-5/3 of the factory manual, bottom right, it says: "NOTE The values are always rounded off to the next 0.05 mm."

My adjusting dimension is 63.35mm, and after adding .3mm of gasket the measurement comes out to 63.32.

Do they mean I should always round UP to the next .05mm (63.35), or do they mean I should round to the NEAREST .05mm (63.30)? I suspect that this clarity issue comes from a translation from german.. but maybe not.

I can only add or subtract gaskets in .05mm increments, so I can either leave it at 63.32mm or I can make it 63.37mm. What do I do?

Posted by: bondo Feb 20 2006, 08:43 PM

Perhaps I should clarify my need for clarification..

To me, "rounding off" means subtracting, or perhaps rounding to the nearest. But the "next" in there makes me think they mean adding, as in the next higher 0.05mm. Anyone know german and have a german manual to check?

Posted by: alpha434 Feb 20 2006, 09:02 PM

.05 mm is minutia. .05 mm= .00196 inches. Thats 2 thousandths. A plus or minus two thousandths tolerance on an assembly is very tight.

Meanwhile. I would round down if it's the side plates, because that is only setting preload. If it's the intermediate plate, then I would round up, but check your lash at the diff afterwards. Knock knock. If it's gear spacing, then just make sure that everything has clearence when it goes together and the numbers don't matter unless there isn't clearence. If ths is the tolerance on the differential spacers, then I would round up. I hope that helps. All I've got handy is the 741\c manual. Good luck.

Posted by: bondo Feb 20 2006, 09:20 PM

Thanks!

I just remeasured with my 12" calipers (they actually fit around the measuring tool better, but aren't digital or metric) and then did the conversion.. I got 63.36mm that way.. looks like I'm pretty much spot on and have nothing to worry about.

Posted by: alpha434 Feb 20 2006, 09:46 PM

Iyeee!!! You have actual vernier scales that you are trying to do trans work with?!?

I always use micrometers. Or I'll measure a piece with a digital heighth gauge. But most people don't have that luxury. But use a mic.
Here's ISO rating scale

Vernier w/in .005
Calipers w/in .002
Micrometer w/in .0005
Digital Mic w/in .0001

This scale is REGARDLESS of the most accurate markings on the tool. Good luck. There isn't any real reason to worry, but if there turns out to be a problem, this might be why.

Posted by: bondo Feb 20 2006, 11:35 PM

Hehe, not vernier.. Dial calipers, advertised as accurate to .001". I don't have a micrometer, and if I did it probably wouldn't be big enough.

The tool I'm using to measure pinion depth isn't that great either. It's a big shaft the bearings go on, with a spring loaded pin, like a bore gauge. It has a knob on the end that releases and re-locks the pin once it's sprung against the end of the pinion. Then I have to take out the tool and measure it. It's not as nice as the porsche tool, but I'm sure it's much less expensive.

Posted by: alpha434 Feb 21 2006, 12:18 AM

Calipers are only good to w/in .002, regardless of advertisement. This is based on my personal experience and training as a machinist. The other tool you are using will work well, as long as you are very careful to not bump it or change the measurement in any way.

Good luck. If it all goes together fine, and the lash is correct and everything, it should work great. Porsche trannies are really easy to work on. I'll have my 10 year old brother working on them by the end of the summer. Haha.

Good luck. Feel free to pm me if you need any help/advice. I'm not so bad- even if I am just a kid.

Posted by: bondo Feb 21 2006, 12:25 AM

Whelp, now that that's all taken care of, I now seem to have too much backlash.

Manual says it's marked on the ring gear, but I can't find it (maybe it's on the back, I didn't take the ring gear off the carrier). The manual says the backlash tolerance is .12 to .18 mm. I measure .5mm. There is a .25mm shim I could move to the ring gear side of the carrier, but would that send it too far the other way? About how much do I need to move the carrier to get the backlash into spec? My options are limited as I don't want to mess up the preload, and I don't have all the available shims.

Posted by: alpha434 Feb 21 2006, 12:29 AM

Do you have shims for the intermediate plate?

Posted by: alpha434 Feb 21 2006, 12:31 AM

What size shims do you have available?
For the inter. plate and the carrier?
Whats the carrier size?
Distance between carrier bearings?

Posted by: bondo Feb 21 2006, 12:38 AM

QUOTE (alpha434 @ Feb 20 2006, 11:31 PM)

What size shims do you have available? For the inter. plate and the carrier? Whats the carrier size? Distance between carrier bearings?

I have .1mm and .2mm gaskets installed under the int. plate, with a .25mm left over. That's all done, I'm satisfied with my pinion depth measurement.

I have a 3.0mm shim on the ring gear side of the carrier and a 2.9mm and a .25mm shim on the other side. The total 6.15mm thickness gives a perfect preload, so I need to keep that.

I have a 2.6, a 2.7, two 2.9s, a 3.2 a 3.3 and two .25mm shims available, in addition to the ones installed. .

Posted by: bondo Feb 21 2006, 12:38 AM

Oh, and I don't know what the distance between the carrier bearings is.

Posted by: alpha434 Feb 21 2006, 12:45 AM

put the 2.6 and a .25 on the ring gear side. put a 3.3 opposite it. Check your lash again and get back to me.

The reason I asked about the intermediate plate is because you can back it out .1 or so and get the right lash. But it's better to have the right spacers for the carrier instead.

Posted by: bondo Feb 21 2006, 12:46 AM

What it seems like to me is that I need a 2.8mm and a 3.1 mm shim to be able to do the next two possible steps of tighter backlash, before the third step of just moving the .25mm shim to mthe other side. I guess I'll try moving the .25mm shim and see where I'm at.

Posted by: bondo Feb 21 2006, 12:47 AM

QUOTE (alpha434 @ Feb 20 2006, 11:45 PM)

put the 2.6 and a .25 on the ring gear side. put a 3.3 opposite it. Check your lash again and get back to me. The reason I asked about the intermediate plate is because you can back it out .1 or so and get the right lash. But it's better to have the right spacers for the carrier instead.

Isn't that backwards? I have too much backlash, and that would move the ring gear farther away from the pinion.

Posted by: alpha434 Feb 21 2006, 12:49 AM

Right. Backwards. I'm sorry.

Posted by: alpha434 Feb 21 2006, 12:52 AM

I got mixed up, not having it in front of me. You would move the plate forward .01 not out.


It's a real B$%@ having to bolt it up and unbolt it, isn't it? I just did a 741 last night. Big hassle. Similar problem with the lash, but I've got all the shims, too.

Posted by: bondo Feb 21 2006, 01:15 AM

QUOTE (alpha434 @ Feb 20 2006, 11:52 PM)

I got mixed up, not having it in front of me. You would move the plate forward .01 not out. It's a real B$%@ having to bolt it up and unbolt it, isn't it? I just did a 741 last night. Big hassle. Similar problem with the lash, but I've got all the shims, too.

Yes, it IS a pain. to do all the unbolting/rebolting. Ok, I now have .28 mm backlash after moving the .25mm to the other side. It's heading in the right dirtection, so I think it's gonna work out. Hafta sleep now though.

Thanks for the help Chris!

Posted by: alpha434 Feb 21 2006, 01:20 AM

No prob, man. Like I said. Feel free to pm me.

Posted by: bondo Feb 21 2006, 07:20 PM

Sho-nuff, using micrometers (at work) I got a different number.. 63.373mm.. So I think I'll switch to one .25mm gasket and then do the backlash all over again and see if things line up better with what shims I have. (my latest attempt gave me too little backlash, only .002")

Posted by: alpha434 Feb 21 2006, 07:36 PM

Yeah. That's what I said....

Posted by: bondo Feb 21 2006, 08:15 PM

Sigh.. Spec is .005 - .007 inch backlash.. With the shims I have and with fudging between the two options of pinion depth I can use, the closes I can get is .002" and .010". What's worse, too little or too much?

Posted by: alpha434 Feb 21 2006, 08:27 PM

too little.

When the metal expands from heat, the gears will grind. But if it's too loose, then the gears will hit too hard against each other.

Posted by: bondo Feb 21 2006, 08:38 PM

QUOTE (alpha434 @ Feb 21 2006, 07:27 PM)

too little. When the metal expands from heat, the gears will grind. But if it's too loose, then the gears will hit too hard against each other.

Neither option sounds good.. I have one more trick.. I'm at the high end of the preload target.. so I have one more option if I use .05mm less preload. Hopefully that will get me the backlash I need.

Posted by: Headrage Feb 21 2006, 08:41 PM

I think this is the longest thread I've ever seen with only 2 people involved.

Posted by: alpha434 Feb 21 2006, 08:51 PM

Yeah. That would be fine. Or like I mentioned a while ago, you can move the intermediate plate, just a little bit.





And Headrage, here ya go.

Posted by: Headrage Feb 21 2006, 09:01 PM

Posted by: bondo Feb 21 2006, 09:15 PM

YES! Nailed it.. .006"!

I had already moved the intermediate plate as much as I was comfortable with (calculated pinion depth fell nearly right between two gasket options, I tried both). The only thing left to mess with was preload, and that got me exactly what I needed with the shims I had. Of course this would have been much easier if I had 2.8mm and 3.1mm shims, but I didn't. I ended up using a 2.9, a .25 and another .25 as S1 and a 2.7 as S2. Theat gave me a total of 6.10 instead of 6.15, so slightly less preload (but still within my target range).

Allan: I could have taken this to PMs, but then this info wouldn't be available for any others who are nutty enough to do this. (I won't ever do this again.. from here on out all critical parts come from the same trans.. but I'll make an exception if I ever get an LSD)

Posted by: alpha434 Feb 21 2006, 09:20 PM

Hey! Congrats! Trans work is easy. It's all easy, really. It doesn't start to get tough until you start playing with Ti connecting rods, right?

Haha. Put this thread in the classics section. It mentions ALL the tricks for getting the lash correct.

Posted by: kwales Feb 22 2006, 09:50 PM

Hey Alpha,

Ever sat down with a GOOD set of digital calipers and a box-o-precision gage pins?

My Starret calipers are dead nuts accurate.

Ken