Is this the B2 piston problem? - PeachParts Mercedes-Benz Forum

mcneil · #1 08-01-2011, 08:38 PM

Couldn't quite figure it out from searching so I'll ask.
1983 300SD w/360k, known history, all fluids changed regularly.

Problem: First showed up as a flare in the 3-4 shift. Later it has not been engaging in any gear after coming down an exit ramp to a stoplight. I would come down from 75 to 10mph, hit the accelerator, and get nothing. Mostly, it's still driveable, since the problem is very intermittent, but I've had the car parked until I can diagnose this.

I have a 70 mile round trip commute (all freeway), and it happens maybe once every few days, and usually on the way home after heating up.

Does this sound like the B2 piston problem, or something else?

techguy512 · #2 08-01-2011, 09:45 PM

Quote:

Originally Posted by mcneil

Does this sound like the B2 piston problem, or something else?

It's almost impossible for a broken B2 piston to be intermittent.

My opinion anyway, having just pulled mine out in pieces....

ROLLGUY · #3 08-01-2011, 09:52 PM

My friend has a 1984 300D that has no movement at all in any gear. It happened all of a sudden, one minute the trans was working fine, the next- nothing. The pump is working, as fluid comes out the cooler line. Could there be some kind of piston or valve in the valve body that is going bad on the OP's trans, and gone completely bad on my friends trans?

techguy512 · #4 08-01-2011, 10:26 PM

Quote:

Originally Posted by ROLLGUY

...no movement at all in any gear. It happened all of a sudden, one minute the trans was working fine, the next- nothing.....

Your diesel fleet is impressive, so I assume you're ruled out all the external stuff (broken axle, broken driveshaft/flex disk, shift linkage, etc.)

Broken B2 will leave you with reverse working. Damaged torque converter could do it. I've heard of a rash of output shaft yokes backing out of their splines lately, could be that.

Sounds like full diagnostics are needed....

ROLLGUY · #5 08-01-2011, 11:17 PM

Quote:

Originally Posted by techguy512

Your diesel fleet is impressive, so I assume you're ruled out all the external stuff (broken axle, broken driveshaft/flex disk, shift linkage, etc.)

Broken B2 will leave you with reverse working. Damaged torque converter could do it. I've heard of a rash of output shaft yokes backing out of their splines lately, could be that.

Sounds like full diagnostics are needed....

Not wanting to hijack this thread, but our problems may be similar. If the OP's trans quits working all together, then maybe both our trans's have the same problem.
Everything short of pulling the valve body, or the trans has been done. Drained about 9 quarts of fluid (torque converter included), replaced filter and added about the same 9 qts of new fluid. Still nothing. Even checked the shifter linkage inside the trans, everything looked good. The car works in park, so I can rule out all the external stuff. I know the pump is working, because it took the full 9 qts to get the proper level on the stick.

mcneil · #6 08-02-2011, 12:10 PM

I knew there was a reason for keeping that extra 722 trans in the shed.

If it's not a readily identifiable fix, I'm going to swap for my spare trans. I'll share the results of the post-mortem on my current trans when I get it out. Probably will take a few weeks for me to get around to it, though.

ROLLGUY · #7 08-02-2011, 11:05 PM

Quote:

Originally Posted by mcneil

If it's not a readily identifiable fix, I'm going to swap for my spare trans. I'll share the results of the post-mortem on my current trans when I get it out.

We will await the autopsy, and hope it is something easily fixable.

mcneil · #8 08-03-2011, 01:06 AM

I looked in the storage area under the house and had a change of plans - this _was_ my backup transmission.

You know you have too many benz parts when you lose count of how many spare transmissions you kept.

But I did do some more diagnosis. There's an incredibly unhappy grinding-pump-sounding noise coming from the trans. Fluid doesn't look burnt, I might drop the pan this weekend to look for pieces.

mcneil · #9 08-07-2011, 01:16 PM

Update after the pan came down:

There were small pieces of bronze-colored material floating in the pan and a metallic sludge on the bottom. I had this pan spotlessly clean the last time I did a fluid change (about 40k miles ago), so all of this flotsam is recent.

Flotsam picture (the chip, not the penny)

I refilled with Castrol Dexron IV and a bottle of the Lucas transmission repair, taking pains to make sure the vehicle was parked on level ground and not overfilled. Also did an engine oil change and valve adjustment because.. well, why not?

Transmission feels better, but there's still a grinding droning sound coming from the transmission at idle. It goes away at about 2000 rpm. I took it out on the freeway and it felt better, but I still had one hiccup. Feels almost like slip, and the trans is slow to find a gear after coasting.

Any thoughts?

mcneil · #10 08-08-2011, 11:21 PM

Well, the problem is no longer intermittent.

Catastrophic transmission failure today. Whirring, banging, seizing failure. Towed it home.

Plan is now to break up the car for parts this weekend.. see what I can recover in costs from what I recently put into it. New starter, drivers seat, 205/70 michelins, oem head, etc.

ashedd · #11 08-08-2011, 11:31 PM

I have a transmission that shifts greats... but I am in Indiana. It's from my TD, so you would have to swap the tail shaft for the SD's electric speedo.

mcneil · #12 08-09-2011, 12:07 AM

Quote:

Originally Posted by ashedd

I have a transmission that shifts greats... but I am in Indiana. It's from my TD, so you would have to swap the tail shaft for the SD's electric speedo.

Tempting, but I'll pass. At 350k miles, it's not worth it.. the rear end is clunking, the suspension bearing brackets are both clunking, front right wheel bearing whines, exhaust keeps falling off, seat switches are gone.. yeah.. I'm going to miss it.

weird beard · #13 08-10-2011, 04:18 AM

let us know when you formally begin to part it out, us vulchers are hungry!

mcneil · #14 08-10-2011, 08:20 AM

It's coming apart this weekend! I need funds and driveway space for the replacement.

Part-out thread is here:
Part out 1982 300SD - blown trans

mcneil · #15 08-16-2011, 12:49 AM

The failed part in the trans turned out to be the final shim/thrust washer, in the very back.

I kept pulling out clutch packs and planetaries that looked like they were in great shape. Kept going deeper into the case hoping to find the "smoking gun" that killed the car. Finally found it, at the back of the case.

All the friction surfaces, bands, etc, looked great. Minimal signs of wear. Wish I knew why that washer decided to fail.