722.3 No Reverse, No Forward gears - PeachParts Mercedes-Benz Forum

1985 300SD Sady · #1 12-02-2010, 04:01 PM

1985 300SD approx 235,000k
722.303 approx 200,000k
- fluid level normal Blood red, no burnt smell (checked while idling on level ground)

Symptom-

acts like it's in neutral while in R, D, 3, or 2. will not move forward or reverse, engine just revs.

Currently-

-Linkage is intact. Locks into park, reverse lights work, and shifter operation feels completely normal.

-No engagement of gears ie. car does not squat like normal when you put it in gear.

-Fluid and entire transmission is cold when engine is fully warmed.

-Will engage once rolling, has no off the line.

Nitty Gritty / History-

Tranmission swapped in 2007 - no trouble until...

A few weeks ago my B2 piston failed. Put in a new B2 piston, cover seal, tranny filter, K1 kit, and pan gasket. I drained the torque converter. I refilled everything with fresh fluid - it was a whole new car!

I had driven it a dozen or so times since this recent maintenence - and began to notice it sometimes being slow to engage into gear, slipping when I first started off from a stop.

Trouble-

Yesterday afternoon I checked the fluid level when at operating temp, idling, on level ground and it was low (still registered on the dipstick) I figured I had found the slipping problem and topped it off. Shut the car down without a test drive.

Last night I start it up, put it in gear - all systems go. A half mile from home as I'm coasting down a hill (foot off accelerator) I go to speed up and it acted like it was in neutral. Engine revs, no forward gear. I slowed to a stop.

Checked the fluid level and it's high. Must have added too much, so I correct it (drained some into a container) and still no go. I had left the engine idling (and the heat on, as it was snowing) so by the time I was draining the fluid the engine was almost at full temperature, and the transmission was stone cold. Even the fluid was cold.

Once it gets rolling it engages. That's how I got it home without a tow. On level ground, with the car in drive, I gave it a big shove. It moved easier than I thought it ought to. With it rolling I hopped in and with a lot of slipping it finally engaged (2nd gear?) shifted (into 3rd?) and ran fine until I stopped. I believe it was the grace of God that I got all green lights back to my driveway.

Checked again this morning, still nothing. After searching here and elsewhere - it just seems like the front pump died? or perhaps the torque converter? Do I need to do a pressure test?

I'm sick of all this maintenence.
Can anyone offer some hope? An idea of something to check?

Please help!

mach0415 · #2 12-02-2010, 04:23 PM

Good info provided, but what condition was the fluid in when you pulled the pan off last time? If it was burnt smelling or black, you have severe clutches/steels damage from an internal hydraulic leak, causing clutch pistons to engage lower than specs and allowing clutches to slip.
You need to remove a cooler line (from the trans to the cooler) and insert it into a clear jar or jug. Have someone start the car and see if fluid comes out at a decent rate. If so, the pump is working, but the torque converter may have come apart inside, causing no forward/rearward movement. There was a recent thread about a similar problem a few weeks ago. Search my profile and posts, as I commented on them.
Another possibility is that the filter may have come loose, causing no fluid pick-up, unless on an incline, since fluid level, relative to the pickup, is artificially accentuated. Also check the trans filter seal - usually an o-ring.

Good luck, I hope this helps

Diesel911 · #3 12-02-2010, 05:51 PM

There is 2 Transmission PDFs in the below link. There is also some symptoms and what causes them at the PDF sites
http://www.peachparts.com/shopforum/showthread.php?t=99833

1985 300SD Sady · #4 12-03-2010, 05:59 PM

I drained the fluid just now and pulled the pan. Fluid is blood red, with no burnt look or smell. I noticed no metal particles or foamed fluid. The K1 piston plate was intact and the screws are tight. The filter is still tight. Anything else I should check while I'm in there?

It seems to me like its the TC or the pump. I supposed I'll button it back up and unhook a cooler line while it's running to see if there's pressure.

Thank you for any suggestions

mach0415 · #5 12-03-2010, 06:09 PM

That is the next thing I would do. If you get steady flow, I would zero in on TC. You will not get much heat if fluid is simply being pumped. Friction will, though. Did you read a thread started by jimandsuzy about his 85 SD - same concern was TC.

1985 300SD Sady · #6 12-03-2010, 06:19 PM

Quote:

Originally Posted by mach0415

That is the next thing I would do. If you get steady flow, I would zero in on TC. You will not get much heat if fluid is simply being pumped. Friction will, though. Did you read a thread started by jimandsuzy about his 85 SD - same concern was TC.

Yes, I read through that thread. Thanks for the advice! Will update soon.

1985 300SD Sady · #7 12-04-2010, 12:13 PM

With fluid back in the transmission I started the car and unhooked one of the transmission cooler lines at the radiator. There was only a couple drips

must have been the residual fluid in the line, no flow whatsoever.

Could the shock of new fluid ruined the pump or seals? When the B2 failed, could that have done other damage?

What would you do, in my shoes?

kerry · #8 12-04-2010, 12:32 PM

Replace the pump?

loepke72 · #9 12-04-2010, 04:08 PM

Sounds like front pump failure. These transmissions have a small pump in the rear that allows for push starting, so that explains why the transmission seems to work when the car is rolling. Since you'll have the transmission out to replace the pump you might just want to remove the old one and disassemble it for inspection to see if something is actually wrong before $pending hundred$ on a new pump.

dude99 · #10 12-04-2010, 04:14 PM

If you do disassemble it and repair it take some pics, I don't think there is a how to on it yet.

whunter · #11 12-04-2010, 05:21 PM

Quote:

Originally Posted by 1985 300SD Sady

With fluid back in the transmission I started the car and unhooked one of the transmission cooler lines at the radiator. There was only a couple drips

must have been the residual fluid in the line, no flow whatsoever.

Could the shock of new fluid ruined the pump or seals? When the B2 failed, could that have done other damage?

What would you do, in my shoes?

Install the transmission from the local wrecked 300SD.

If you are interested:
We could meet half way or I will try to pick up the damaged unit for diagnosis/repair in January 2011.

mach0415 · #12 12-05-2010, 07:22 AM

One other thing first! The torque converter could still be the root cause IF the slotted ears on the hub of the TC that engage the pump are sheared. In which case the TC may still be the only fault, but that is IF the pump input interface is not buggered up as well. I agree with Roy. I would line up a good used trans first and investigate as I pull the trans for inspection. You may still have a good trans, but a bad TC.