TimCo

I have an '83; it's been running pretty well. I drive it 100 miles a day RT to work and back. It hasn't even hickuped in the last 9 months.

But, last month on the way home ... it wouldn't shift into high gear ... but it soon did and I wondered if I wasn't hallucinating. A week went by and I was paying attention and then noticed ... that 2nd gear wasn't shifting up at 2000 rpm as it usually did, it was sticking in gear (like you would drive a manual in traffic) and shifting at 2800. Then it happened again (sticky); and again ... and it became a regular occurrence with all the gears. The 1st to 2nd shift was getting kind of sloppy (not crisp). Then today at a stop sign ... instead of going, it just sat there - it wouldn't go forward in any gear. It had reverse (but I found that out later after I pushed it back out of the intersection). But, none of the forward gears were there. It was like it had neutral and reverse.
I had it flatbedded home. The driveway has a slight slope but I jacked up the rear of the car so it was pretty level and checked the fluid. I was suprised when I took off the cap and fluid started burbling out like a spring. It must be overfilled. The fluid appeared RED but when I drained some out into a glass ... it was more of a brown. It didn't smell burnt; it had no smell.

What do you think? Is this thing gone? Can a fluid change and a filter do any good at this point?

I would appreciate any suggestions. There were no noises; no grinding; no banging; no boom; just acted like the shift lever was accidentally pushed into neutral.

Tim

Steve Cattaneo

Sound like you have a B2 problem, do a search, target B2

rjtw

I had a similar problem on another make of car many years ago that was due to a clogged filter. Good luck and please let us know what you find.
Rick

TimCo

Steve, Rick, ...
Thanks for the replies.
Tim

Rich9928p

Here is another thing to check - coolant mixed with the A/T fluid. If the A/T cooler in the radiator has developed a leak the higher pressure engine coolent can get in the tranny. Not a pretty sight!

Garth S

The engine must be at temperature and running BEFORE taking the reservoir cap off: some say that the fluid will gush out if the engine is not running ... .
Steve has accurately called the B2 piston; however, brown fluid is never as good as red .... and it cannot hurt to correctly check the fluid level. It is more likely to be low than overfilled, even prior to the 'burbling spring'. At this stage, just add sufficient to get between the marks, and go through the gears to see if there is any engagement.

TimCo

I had to wait to the weekend to work on this. I didn't have the correct 5mm hex wrench so I couldn't drain the transmission oil pan before dropping it down. It was a little messy but I had one of those 3ft x 5ft x 1" sheet metal pans underneath so it wasn't really a problem. Other than that, the pan came off easily by removing the (6) 13mm bolts.
The filter looked like it was restricted because it was drawn into the exit hole a little bit. I don't know if that is normal or not. I was hoping that the filter was the problem because there wasn't a spec of dirt/metal/debri in the bottom of the pan. I replaced the filter, pan and added about 3 1/2 quarts of fluid.
I replaced about as much fluid as I took out. The level is probably not correct but should be close. It's interesting after looking at it; that the oil pan needs to be level and you're filling to about the top of the transmission oil pan.

But, I started it up a couple of times while still jacked up in the back. I still have REVERSE but I have no forward gears. I'm going to take it back down; level it out; check the level; idle it; warm it up and see if anything changes.

I found the B2 access (middle round; approx 3" diameter cover). How do you get that circular clip off? It's not a circlip where you can pinch it together. I wasn't able to extract the clip to get the cover off and pull the B2 piston.

This is an 83. It's stamped as an A28/01 type. There is a reference to mercedes p/n's. A local dealer can get me those parts in 2 days. I have the parts microfiche and also found a nice transmission section in the manual (section 37 and 38). I found reference to shimming the piston.

Steve, if you can recommend the parts needed to replace the B2 piston, let me know. I'd be glad to buy them from you.

Tim

TimCo

I was able to get the circular clip off with a sharpened/pointy pick. The cover was marked "MERCEDES BENZ 126 277 09 03. The Piston was marked R 126 277 0538.

It seems to be ok. What part of it goes bad?

Steve Cattaneo

That part number is the first design piston, the one that often fails. remove the piston and the band pin. Check the piston bore for any ridges/ excessive ware by running your finger across it. You can buy all the parts from MB. Can you post a picture of the piston.

Some times it breaks; at other times the thin sealing ring on the piston just wares, less surface area. The updated piston and seal is more robust. Parts need to do a professional job

107 270 04 32 ___B2 Piston
005 997 70 48 ___B2 Piston Seal Ring (to the cover)
126 277 08 50 ___Plastic Bushing for Updated B2 Piston
006 997 73 47 ___Seal that holds in the bushing

TimCo

Thank you Steve.

I have six photos of what I think is the B2 piston; some photos may be redundant. One was of the clip, cover, piston and pin. Other photos were different views. I see some wear on the piston shaft - light scrubbing but I can't interpret it ...

This car had 65000 miles on it when I got it. I'm the 3rd owner. It was always serviced by the dealer. After getting it running (FI was gummed up - thank you guys for the help) ... I've been driving it 100 miles a day RT to work 5 days a week for the past 7+ months with no problems at all - without skipping a beat ... unitl the trans went on the fritz and then stopped "working" altogether.

If you'd like a photo of a certain view, let me know.

Tim

Tails

Tim,
If you send my your e-mail address I will forward a report on my repair of my B2 Piston.

The report included mods done by MB and many web sites on B2 Piston replacement.

Please reply by return as I leaving tomorrow for three weeks holiday.

Tails 1990 928S4 Auto.

Steve Cattaneo

Tails

Why not post your report on rennlist, so the group can benefit from your experience.







Tim,
The inner piston seal is worn, the update is a package; let me know when you have all the parts. Also buy a piece of red scotchbrite.

TimCo

Hello Steve,

I'm attaching a closeup of the B2 Piston. Are you looking at those grooves which apparently were made by the seal? So, the piston is bad and the seal is bad ... ?

Great, I'll order parts tomorrow and I should have them in 2 days. I'll install them Sat morning.

There is a section in the manual that refers to different sized pins ... that are used to adjust the B2 Band. Question: Do I need to order a few of those in case?

And, ... do you think the patient will live?

Tim

Steve Cattaneo

The fluid is clean , no metal in the pan, it looks good.
We are doing what an experience transmission diagnostician would do; the early B2 piston is the number one cause of a no forward movement. Measure the pin with a dial caliper and email me the measurement at mastertech@mastertechtrans.com

BC

This is great. Lets continue this thread as much as we can.