722.3 Tranny. Cover me guys - I'm going in! - PeachParts Mercedes-Benz Forum

S-Class Guru · #1 07-06-2007, 12:21 PM

Well, before I drop the tranny, and go for the B3 discs, I just wanted that
warm feeling that you guys concur on my problem.
DAVID POOLE - HERE'S MY UPDATE ON THE WHITE SE TRANNY.

- Car: '91 300SE with 180k miles.
Fluid/filter changes each 30k.
Drives and shifts like new, except for the "small problem" below.

- Symptom: "rolling/clicking" noise when driving or coasting in Reverse.
Doesn't always do it, maybe 75% of the time, especially when cool.
If I shift to N while coasting, sound goes away immediately.
- Symptom: Some delay (2 seconds) when shifting Park-to-Reverse.
Park-to-D is instant, less than 1 second.
- Symptom: Sound definitely comes from inside tranny. I took it over to
our own David Poole, and naturally is was silent as a lamb (warm).
David inspected the driveline, and wisely suggested I replace the flex disc
and check the center driveshaft bearing before condemming the tranny.
Done - no help.
Yesterday I raised it up, put it in R, and got it to do it; I stuck my
stethescope on the tranny - it's definitely inside the tranny.

- DG's Diagnosis: after reading the archives, and getting an ATSG tranny
manual, I have concluded I have WORN B3 DISCS, AND THE B3 PISTON IS
CONTACTING THE K-1 CLUTCH PLATE CARRIER (click/roll).

AGREE? SOMETHING ELSE POSSIBLY?

- The fix: Pulling the tranny is no biggie - I'm retired and do silly things like
that for relaxation, when it's too rainy for golf.
1. Can I get to the B3 clutch without a bunch of special tools
(compressors, holders, seal installers, etc.)?
2. Will I probably need metal discs as well as the fiber discs, to reach
the required 1.5-2.0mm end play?
(I have never felt any slip in R - I hope I caught this really early).
3. I guess I should do the K1 discs while in there, but I am hesitant to
go much deeper, since the tranny is working perfectly, and has
never even leaked a drop!
4. So, how far can I go before I have to have some of those special $200
tools?
I know you guys will recommend a full overhaul, but I'll probably hold
judgement on that until I see how clean it looks in there.
As I said, it just works too good now, and if it failed later, pulling it
again is no real biggie. (I'm a real Sick-O, I like working on my MB!).

Thanks,
DG

david s poole · #2 07-06-2007, 01:51 PM

it is relatively easy to replace reverse clutches,front drum clutches and front pump seal.the huge piston that operates reverse probably needs the two skirt seals as well while your there OR that may be the problem[as intermittent as it is]P.S.how is the engine doing?

S-Class Guru · #3 07-06-2007, 02:49 PM

David, thanks for the reply.
If I get in over my head, I may come crawling in with a basket of parts and drop them on your desk - HeHe.

Well, motor still has the little chuga-chuga on warm start.
I got a killer deal on a pressure guage set on eBay ($26) and
ran a pressure check and leak-down:
- Pressures right on: 5.5 BAR system and 0.4 BAR differential.
Residual pressure held 40 psi overnight, so no problem there I guess.
- I suppose it's getting down to that little AHA thing?
I have an emissions inspect this month, so I think i'll get past that, and the tranny thing, then fret over the chuga-chuga again.

I love this retirement thing - so many projects to play with.

Cheers,
DG

brewtoo · #4 07-07-2007, 12:02 PM

I don't have any trans problems yet, but I have toyed with the idea of opening one up myself. Can it be worse than replacing that evaporator?

I considered buying one from a salvage yard to practice on. What special tools are required? What manual is best?

DG, you commented that removal was no biggie. What equipment do you have there at home?

Should I even consider this? It would be very satisfying to have replaced my own evaporator and rebuilt my own transmission.

Thanks

S-Class Guru · #5 07-07-2007, 06:40 PM

Brewtoo, I've done a lot of engine work and manual tranny rebuilds, but never played with an auto before. I always assumed there were lots of special tools required. Take a look in the forum tool section, pages 30-33, and you will see what I mean. Looking at the B3 and K1 clutch packs, it appears the plates can be pretty easily replaced, but the pistons for all the clutches and bands appear to require compressors to dismantle and assemble. I did a lot of motorcycle work, and many jobs could just not be done without specific tools.
So, I hope I can sneak in and freshen the B3/K1 friction plates without getting too involved or spending big bucks on special tools.

All that's required to drop out the tranny is a tranny jack from Harbor Freight, and a way to get the car up high enough to roll/slide the tranny out.
I have a set of drive-on ramps, which I raised by adding a 2 by 12 underneath them. I like these better than jacks and stands, just seem safer.
I think I paid only about $50 for the tranny jack (super bargain).
Pulling the tranny out of an S-Class with a straight-six engine is a cakewalk;
lots of room in there. Much easier than putting a camshaft in that Z06
(I usually work on my 2000 Vette in the endless search for more power that I never really use, but old Pearl needs attention occasionally I guess).

I downloaded the ATSG manual from their website for $25. It seems okay, there may be a lot missing when I dive in; but as I said, I hope I caught this
little issue early, and I can do a quick "stint" and button her back up for a few more years before the triple-bypass.

I'll dive in next week, and post my results and observations.

DG

gmercoleza · #6 07-07-2007, 08:04 PM

Please post your results as I am eager to see how things turn out for you. I did the valve body in my [now sold] 300E a couple years ago but I always wondered what it would be like to do the whole thing.

emerydc8 · #7 07-09-2007, 11:31 PM

Just had the dealer tear into mine today for the same reverse problem. The B3 friction material on the clutch plates was worn all the way down to the metal. Surprisingly, though, the rest of the clutches and bands looked so new that you could still see the writing on them (picture). We decided not to replace them. Not bad after 231,000 miles. Good luck on yours and keep us posted. My hat's off to you for attempting this one yourself.

david s poole · #8 07-10-2007, 09:51 AM

on a lot of benz trans that i see that have been serviced reg this is not an uncommon sight[reverse clutches down to the metal and the others still have the benz part # written on the friction surface].

lee polowczuk · #9 07-10-2007, 11:29 AM

ok, this begs the question---

Why does reverse wear out at that rate? i always seem to be reading that reverse goes first.

emerydc8 · #10 07-10-2007, 04:56 PM

You beat me to that question. That's the same thing I wondered. It's not like you use reverse as much as the forward gears, yet when I saw the friction plates, they were almost bare metal.

Check out the runnings scores on the inside of LB3. He said he sees this a lot.

johnjzjz · #11 07-10-2007, 06:43 PM

the gear ratio is greater in reverse and the pressure is also higher so it scrubs the disc clutches 20 / 30 percent more each and every time you engage it in reverse -- its being twisted more so to speak -- jz

C32AMG · #12 07-10-2007, 08:09 PM

The B3 friction material on the steel plates peel off, the cause was a manufacturing defect, when doing any repairs always use the up dated Green B3 fractions.

The peeling causes excessive B3 clutch clearance, allowing the B3 piston to over travel when reverse is applied, touching the K1 drum.

myarmar · #13 07-10-2007, 08:13 PM

Actually B3 wear happens when tranny is in forward gears. In reverse B3 brake is applied and there is no friction. In 4th gear half of the disks are at the engine speed and the other half is always stationary.

S-Class Guru · #14 07-11-2007, 10:03 PM

Thanks for the input guys.
I received the parts kit today, and prepared everything to drop the tranny tomorrow. I love that 6-cylinder S-Class, you can just reach in the top and remove most of the tranny bolts with a big end wrench. I left a couple of bolts in place, and dropped the pan to let it drain overnight.

The fluid in the pan looked okay, just the normal dust.
However, I cut the filter open, and I did find several little pieces of clutch material, about the size of a thumbtack head, in the filter. I assume these are the B3 clutch plates coming apart as others have mentioned.
I'll know more soon, but I have two questions:

1. These little pieces of clutch material should get trapped by the filter, and should not create a clog anywhere else, like in the valve body - yes?
everything was working fine, just the delayed R shift and the rolling/click in R.
So I guess all should be okay, really don't want to test my luck with a valve body teardown.

2. If the B3 friction plates were shelling pieces of material, will the metal spacer plates be okay? I never felt any slipping or harsh engagement.

Tks,
DG

david s poole · #15 07-12-2007, 10:02 AM

they should be.