B2 Piston Woes (maybe) - PeachParts Mercedes-Benz Forum

mechanicalman · #1 03-08-2010, 04:59 AM

Alright, so i was stopped at an intersection to make an unprotected left-hand turn. At the opening in traffic, I floored the gas and the car started to move forward and suddenly it came out of gear and I lost all power. Luckily I made it to the curb without incident, but I couldn't get the car into any forward gears. Reverse worked just fine.

After getting a tow home, I researched the forum and it seemed like an obvious B2 piston issue. After getting the parts I started working on the piston. Unfortunately, the B2 piston was not only totally intact, but had been replaced with the newer style piston already along with the metal bushing in the piston bore. However, the seal piece in front of the bushing looked rather mangled, and didn't seem to be seated very well. Could this have caused the rough shifting I experienced prior to total failure? Unfortunately, I didn't order the black rubber seal in front of the bushing as part of this repair. I couldn't even find it in the Fastlane catalog.

On top of that. I noticed looking into the bore, that the foot of the brake band wasn't where I expected it to be. If you look at the picture, it seems to be sitting way down near the bottom of the bore. All the pictures I've seen had led me to believe the indentation for the push rod would be near the center of the opening. Did something happen to the brake band itself?

How should I proceed here? I'm pretty sure in any case, I'll need to replace that seal, but I don't know the part# for it.

mechanicalman · #2 03-08-2010, 06:43 AM

Okay, I poked around and found the part # for the seal, but fastlane doesn't have it (006 997 73 47).

I also poked around the underside of my tranny, pushed on the foot of the brake band and it feels like a totally loose part. I've never opened up a transmission to do anything more than change the filter, but I'm almost positive the brake band foot is broken off from the rest of the part. So I've got a perfectly fine B2 piston with a totally broken B2 brake band.

I'm pretty upset, I bought this car to replace the 240d that died on me only 5 months ago and now this. What do I do for this? Get a junkyard tranny? Replace the brake band? I need help guys.

DocSarvis · #3 03-08-2010, 10:40 AM

Sounds like you have done a good job of trouble shooting. I have to agree that is sounds like you have a broken band. I haven't done a band but have been into automatics before. Someone will post up with the procedure for changing the band. I would change it and run what you have. What is the mileage on yours. Unless it is super high you have just as good a chance as fixing yours for less maney than a swap from a junkyard. That is if you have the time to operate on it. As with all older stuff I run I would not do a complete rebuild. Fix whats broken and any seals and run it. Best bang for the buck. Good luck thanks

BoiseBenz · #4 03-08-2010, 10:49 AM

Do you have your free EPC membership? http://epc.startekinfo.com/epc/home.jsp You provide a CC# just to verify USA location--I have never been charged. It will change your life.

Something may very likely be haywire with the "reaction valve" (#307) and its associated "pin" (dogbone, #310) on the other side of the band. The bone fell out, the valve is jammed, that side of the band broke off, etc. All shown on page 5 of the relevant 126.120/722.303 Japan (USA 722.416 is obviously wrong

) page.

I seem to recall that, on my SDL, I had to pull off the shifter mechanism to be able to see up there to replace the valve-to-housing external seal. Perhaps the PO/shop messed that side up during the B2 upgrade and, as you've noted, it's never been right.

mechanicalman · #5 03-09-2010, 02:06 AM

I don't actually feel very good about repairing the transmission on this particular car. I got it from a mechanic that kept it from a customer that couldn't pay for (wait for it)... the transmission replacement.

I bought it because the engine had barely aged a day and I figured the transmission had some legs on it. Plus there'd be less maintenance to catch up on since the tranny fluid and filter were both fresh. But now I'm not confident that the mechanic did any part of the job correctly and I frankly have zero confidence in the transmission as is.

The fact that the brake band alone costs $300+ and a boneyard transmission can be had for maybe $400+ makes the choice fairly straight forward for me. I really don't have the money for a good rebuild, and I'm not equipped to change a transmission out, so that's really the only way for me to make it work.

This is actually the second time a mechanic has ruined a car for me. My 240D died when a mechanic reinstalled the harmonic balancer incorrectly and ruined the crank nose.

vstech · #6 03-09-2010, 08:15 AM

ouch! 400 for a jy trans?
here at pick n pull, they are 75.00
no pick n pulls there eh?

mplafleur · #7 03-09-2010, 11:28 AM

Quote:

Originally Posted by mechanicalman

The fact that the brake band alone costs $300+

Not so!

A B2 rear Brake Band can be had for $63

http://europeantransmissionscom.x-shops.com/shop/home.php?cat=745

TnBob · #8 03-09-2010, 12:44 PM

If a shop just replaced the tranny.. wouldnt there be a warranty for it ?

Its sure worth a call to them.

mechanicalman · #9 03-09-2010, 02:35 PM

yeah, i don't think there's any warranty on the tranny or the work, and i'm not even sure i want him to touch it. the transmission # was ground off the side of the case, so i'm pretty sure the incorrect transmission is in there altogether.

mechanicalman · #10 03-10-2010, 05:35 AM

hey guys, i'm having a real hard time finding the original 722.303 transmission in the SF bay area. Can anyone tell me if there are other later model# trannies that can be safely and easily mated to the 617951 engine, and also which vehicles i can find them in?

vstech · #11 03-10-2010, 08:43 AM

you could get a tranny from a 300D turbo, 617.952 and have the speedo sensor swapped over.

mechanicalman · #12 03-10-2010, 03:17 PM

which years of the 300d are acceptable for the replacement and what would their transmission numbers be?

rs899 · #13 03-10-2010, 07:18 PM

722.315 from 81 to 85

mechanicalman · #14 03-12-2010, 05:16 PM

Allright! My spirits are finally way up! A friend with a shop volunteered to help me swap transmissions and i found a suitable transmission from a 300d with front end damage for the replacement. Only problem, i've got to pull it from a self-service junkyard. Anyone got any advice for a guy without a transmission jack on how to pull a tranny from a junkyard car?

ah-kay · #15 03-12-2010, 05:29 PM

Don't know about Oakland CA. But I paid $40 for a mechanic to pull it for me a few years back on a front wheel drive car. Check with the manager at the JY. There are some day mechanics ( laborers ) around to pull anything for a very reasonable fee. They pull it real quick as they butcher up everything in the way. Call the JY to see if such service exists.