Lost 2,3,4th gears in 300D... All of a sudden - PeachParts Mercedes-Benz Forum

JamesDean · #1 08-04-2012, 09:10 PM

Hey everyone

was just taking the 300d down to get some food and was met with only first gear.. Max speed...25/30 mph.. Yesterday I drove the car around the block without problem soo this might be b2.. But I though that was isolated to early 80s cars... Is there something electronic or throttle linkage related that might explain this.. Somehow I doubt it.

DeliveryValve · #2 08-04-2012, 09:32 PM

What chassis and year is this 300D?

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JamesDean · #3 08-04-2012, 09:43 PM

91 124.128 300D 2.5 Turbo. My bad, must update my sig.

I checked the dipstick and it seemed to be low.. I added quite a bit because every time I checked it, it looked low, actually I didnt even see a clear line on the stick. I added about 1.5 QTs...to no avail. I decided to stop at that point as I dont think adding more would do any good.

mach0415 · #4 08-05-2012, 08:27 AM

Look at the kick down switch under the go pedal to see if its stuck. Mine was.

vstech · #5 08-05-2012, 09:36 AM

there are a few things that can cause this... however, the problem may be internal, requiring a rebuild.

first, check your bowden cable. verify it's not stuck fully extended...
next, unplug the kick down switch under your accelerator pedal.
my 87TD will not shift out of first unless I let up off the pedal. if I hold it to the floor, it'll max out the RPM's and not shift. lift my foot, and it shifts normally. the bowden cable does this, and mine needs a tweek, but I don't drive with the pedal floored much, so it's not an issue for me, if your cable is broken or jammed fully extended, it would behave the same way.
good luck!
low fluid, and constant low fluid is a bad sign though. it indicates a leak that could EASILY damaged a drum/band/clutch preventing shifts.

JamesDean · #6 08-05-2012, 10:05 AM

Quote:

Originally Posted by vstech

there are a few things that can cause this... however, the problem may be internal, requiring a rebuild.

first, check your bowden cable. verify it's not stuck fully extended...
next, unplug the kick down switch under your accelerator pedal.
my 87TD will not shift out of first unless I let up off the pedal. if I hold it to the floor, it'll max out the RPM's and not shift. lift my foot, and it shifts normally. the bowden cable does this, and mine needs a tweek, but I don't drive with the pedal floored much, so it's not an issue for me, if your cable is broken or jammed fully extended, it would behave the same way.
good luck!
low fluid, and constant low fluid is a bad sign though. it indicates a leak that could EASILY damaged a drum/band/clutch preventing shifts.

Cable verified to be operating normally.

Kickdown switch disconnected.

I drove the car, up the street, no up shifting. However, I did notice that if I pull the gear selector down to "2" there is what feels like a downshift. But when I take the selector back up to 3/D I dont feel an upshift. It feel similar to my 420 when you take the selector all the way down and then click it over to the right (I forget what its actually called).

I'm not sure on the fluid. I have never been able to successfully read AT dipsticks. It did just come back from the shop middle of last week and I think they would have told me if it was low on fluid..

I was going to attempt to pull the B2 piston today and see if that is it.. Any one else think that it might be?

BoiseBenz · #7 08-05-2012, 10:45 AM

It is absolutely not the b2. That keeps the car from moving forward. it's more likely valve body, governor, stuck kickdown solenoid, etc.

JamesDean · #8 08-05-2012, 10:51 AM

Quote:

Originally Posted by BoiseBenz

It is absolutely not the b2. That keeps the car from moving forward. it's more likely valve body, governor, stuck kickdown solenoid, etc.

I beg to differ. Here's my past experience with my 300SD..

I supposed I could check the kick down solenoid though, How does one check to see if its stuck exactly? I've disconnected the switch for it.

300SD Transmission Dead...

From the ATSG Manual:

B2 is engaged during 1,2,3 gears if I'm reading that correctly..

rstl99 · #9 08-05-2012, 11:08 AM

Not sure this applies to 300D, but my 240D had the same symptoms some years ago after some routine maintenance done underneath. Ended up being a vacuum line disconnected at the transmission. Once reconnected, it worked fine and has since.

Stretch · #10 08-05-2012, 11:17 AM

Quote:

Originally Posted by JamesDean

...
B2 is engaged during 1,2,3 gears if I'm reading that correctly..

Indeed - but if you had a 100% dead B2 piston then wouldn't you be saying "I can only get reverse"? First gear works doesn't it?

JamesDean · #11 08-05-2012, 11:26 AM

Quote:

Originally Posted by Army

Indeed - but if you had a 100% dead B2 piston then wouldn't you be saying "I can only get reverse"? First gear works doesn't it?

I was re-reading my 300SD post and it seems that I was able to eventually get the car into 2nd gear? I dont remember this but I wrote it..

First gear and reverse work fine. Quick to engage and responds fine.

Maybe the Kickdown solenoid is stuck? How would I go about freeing it? I don't have any spare to install in its place... I've disconnected it at the switch end.

I'll double check the bowden and vacuum cable connections at the transmission end however I doubt its the vacuum since I've had the 300SD disconnected a number of times for diagnostic purposes and the transmission has always upshifted fine. Hard and firm, but fine.

Also found this thread with some good information:
'91 300D trans stuck in 1st gear...

I'm thinking maybe I could cobble together a gauge and check out the trans pressure.. Maybe like the above linked thread something is up with the regulating pressure/governor?

I believe I read in another thread that its either 8mm or 12mm. Someone else posted that the banjo fitting from the 617's boost line to alda would work..

Is the "shift valve housing" the valve body? I can't seem to find the charts/tables they are referring to with regards to regulator pressure hm..

JamesDean · #12 08-06-2012, 08:04 AM

So it looks like from all the data I've gathered that it *might* be the worm gear on the governor or something on the governor.

I'd like to check the governor's regulating pressure before pulling the thing out. I believe there is a port on the front driver's side of the transmission for doing this.

I believe the hook up is a banjo bolt.. 8mm or 12mm, I'm not sure, can anyone verify this size. I'll probably have to get a fitting, bolt, hose and gauge still.

After that I'll hook it up and see what it says. Now, when I hook this up...I'm assuming ATF going to come into the hose and go to the gauge right?

I forget what the specific number that I'm supposed to be seeing is but I think it said if I see nothing than thats a gov problem..

JamesDean · #13 10-15-2012, 12:21 PM

updating this thread.

1) governor had cracked gear. plastic gear that drove governor was missing pieces too.
2) disabled secondary pump by removing the two metal gears AND the shaft piece inside the pump.
3) used 50mm deep snap ring pliers. they were $30 welllll spent.