JimBob951

Well, tonight the shark stopped moving forward! Still has reverse. Thinking in may be the B2 piston. It had been slipping slightly when starting, but the shift cable was loose. Fixed that, but when the wife took it out for a ride, it stopped going! Drove out where she was at and confirmed it was broke! Waited almost two hours for a truck.

Jim

Roger

Jim...

Today, I just got my 87s4 running after 4 years. I was told by one of the big 3 that the transmission was shot (there were many circumstances which led me to believe that it wasn't the B2) but It turned out to be a bad piston for the B2 brake band. Had too many things going on to be able to justify a $3k rebuild, so I let the car sit, and sit and sit.

Here are some really helpful links:

https://rennlist.com/forums/928-forum/250248-automatic-transmission-b2-piston-replacement.html

http://web.archive.org/web/200410260...s/b2piston.htm

http://articles.mbz.org/transmission/b2/


These are the parts needed:

B2 piston - 107 270 043 2 $175.96 (new design)
Bushing - 126 277 085 0 $7.54 (plastic vs metal)
Red O-Ring - 005 997 704 8 $6.96
Black Ring - 006 997 734 7 $6.67
Pin (longest) - 126 277 747 5 $10.50 (you will need this since your tranny has been slipping)
Pan Gasket and Filter Kit - 126 270 0298
2 gallons of ATF

Read all of the information on the links provided above. The MB documentation states that the large o-ring should not be removed, but can easily be replaced on a 928. The most difficult think to do is to replace the metal bushing (actually it's the black o-ring that's difficult) because the valve body has to be dropped (don't worry, ***** and springs will not fall out). Remove and drain the front oil cooler...there's about a quart of fluid there.

Everything is still very fresh in my memory...so fee free to ask any question.

Good luck!!!

Roger 87s4

mpesik

btdt.
if u need help pm me.

I had the tranny and all it's bits on the basement floor.
If you love your car, you'll find a little bit of fun somewhere in all that frustration.

JimBob951

Thanks for the info guys! Yeah this is gonna be fun! So where is a good place to get the parts from? On-line? I saw that Rixters company, DC Automotive had them, but I guess those are used take offs? Not sure.

Jim

rixter

Jim,
we carry used units... right now I have an 87 with under 100k just in and it has lsd, have another unit that has just over 100k, no differential, also have a parts unit, had main pump fail and fried tc and a couple other parts

Roger

I would suggest that you purchase new parts. For the transmission parts, call several local MB dealerships so you can compare prices. The local MB dealers can usually get the parts in 1 day vs. the Porsche dealer. In addition, prices are cheaper through MB vs Porsche. If they ask you the type of car, just tell then it's for an 87 420 SEL.

I found an online store which had the B2 piston for $114, but I wanted to look at the part prior to payment to ensure that I was purchasing the most recent design (I have seen 3 different versions / designs of the B2 piston)

For the filter and gasket, call one of the big 3 (when possible, we should support the ones that support us). If I remember correctly, the gasket has been beefed up to prevent leaks.

Regards,
Roger

JimBob951

OK, I think I am finally going to get around to pulling the B2 this weekend. Anything to watchout for/look for? I have searched some old posts, so have a general idea. Also what to look for in the new replacement part? You guys said there were three different versions? All with the same part number? I am gonna check local MB dealers too, but I have seen the parts with good prices on-line also.

Jim

Roger

Jim,

Torque converter:
When draining the torque converter, you may need turn the engine until the drain plug is visible. If turning manually, only turn the crank clockwise. Once you've aligned everything, use a marker or some paint to mark the 12:00 position on your crank pully. In the future, when you have to drain the converter, you wont have keep crawling under the car to see if the drain plug is position correctly...you'll just have to align the paint mark to the 12:00 position.

Sleeve
Once you have dropped the valve body and have removed the B2 band guide (tan plastic), you will need to use a hammer to tap out the sleeve. The black (metal reinforced) o-ring is actuall what's holding the sleeve in place.

B2 Piston:
Part number - 107 270 043 2 is the latest part number/version. I suggested going to MB because they will always provide you with the latest part vs. the discount shop that will sell you what they have.

I've seen 3 versions of the B2 piston:

Version 1: Small think plastic ring (like a piston ring) around the outside edge of the piston. The other side has a cast 6 sided star.



Version 2: Thick plastic ring around the outside edge of the piston. Thick plastic ring covers the entire surface of the piston edge. The other side has a cast 6 sided star.

Version 3 (newest): Thick plastic ring around the outside edge of the piston. Thick plastic ring covers the entire surface of the piston edge. The other side has a beefy 4 sided star (less prone to breakage).

I has version 2 which broke at the 6 sided star.

Hope this helps.

Roger

JimBob951

Well I pulled the B2 piston. Sorry don't have picks yet, can't get the thing in focus with my stupid digital cam!! Anyway, it doesn't appear to be broken, and it looks like the version two. It does look somewhat scratched up on the end that goes into the metal bushing/ring. (kinda like the one pictured in another B2 thread) Is that bad enough to keep the car from going forward? Was expecting it to be in pieces! I will replace the metal with the newer plastic ring also.

Jim

JimBob951

Well I guess it wasn't the B2 Piston (or not just the piston) I looks like the pin on the other end of the piston came loose and bent the band a little and fell out! Is there a way to fix it? Or will it need replaced?

Jim

Roger

Jim,

Would it be possible for you to post larger versions of the pictures? Just to clarify, is this the pin that insets into the B2 piston?

I wonder what caused the pin to fall out in the first place.

Roger

JimBob951

OK, was able to get some bigger pics, looks like the pin one opposite side of the band from piston got loose some how. I found it laying on top of the plastic guide. Appears that it bent the lip of the band some.:

borland

Jim,

Sorry to hear it. Maybe Steve has seen this type failure before.

Looks like a material defect that finally gave way under heavy torque of the engine. That pin and pressure unit counter hold the brake band from rotating while in the B2 piston forces the band in the engaged position. The plastic guide keeps things in place, so the pin can't fall out or get dislodged.

The only way to replace the B2 band is to remove the tranny from the car. The WSM details the complete transmission disassembly/reassembly procedure. B2 band requires almost a complete disassembly.

I overhauled the 4 speed automatic on my 90' S4. Hardest part is removing the pinion nut while counter holding the transmission case. 400 ft-lbs torque to get it off. 3/4" torque wrench to reinstall a new pinion nut (275 ft-lbs). Overhaul gasket kit from Mercedes is about $125. The B2 band is about $200 from Porsche. You'll likely find other worn parts to replace, so it could get expensive.

Steve Cattaneo

You do have a B2 failure; it’s the band, internal. Did you remove a plastic guide from the band. Your pictures are small, can you post bigger pictures, include the B2 piston and bore.

JimBob951

Well here are some pics of the B2 Piston. You see a little scoring on the end: