called? I've spent the greater part of the last two days searching(to no avail) because I remember reading a post about replacing the two plastic levers there. Mine are worn completly off and I would like to know what to ask for when ordering. This is for my '81 300SD.

Thanks for any answers.

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car

TDC amplifier?? -- if you can open Adobe files and will PM me your e-mail address I will send you a 46 page document with all the components in you 81 SD

__________________
BENZ THERE DONE THAThttp://www.peachparts.com/shopforum/...c/progress.gif
15 VW Passat TDI
00 E420
98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
(o\|/o)

Are you referring to the black box on the top of the valve cover?

This box houses the EGR switching valves for "most" vehicles. They leak vacuum and cause shifting problems.

You can probably eliminate the problem completely by disconnecting and capping the one supply vacuum line to the black box. One line is the supply vacuum. One line (black) is the vent. One line goes over to the temperature switch for the EGR.

The only line you are interested in is the line that is the supply vacuum. It normally Tees into the line coming from the vacuum pump.

http://www.peachparts.com/shopforum/showthread.php?t=118408
This maybe the thread you are thinking of.

http://www.peachparts.com/shopforum/showthread.php?t=121418
http://www.peachparts.com/shopforum/showthread.php?t=121049
Here are a couple more threads with good, maybe better information.

Is this what your looking for:

Click Here
You should verify that these valves do not effect your transmission before you disconnect them.

Danny

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination

There's a good xplanation of what and how on dieselgiant.com.

Doesn't this "black box" also send differing pressures of vac. to the modulator on the tranny? That would explain why there is 2 lines going to it (vac supply and modulated vac out) and 1 going to the EGR.
I think the reason the people replace those levers is becuase their shifting gets messed up due to the things wearing thin...not becuase they start leaking.

I wouldn't just toss it and cap it off unless you have recently done a stickshift conversion

Of the three lines, one goes to the EGR valve, and is the only one that sends a vacuum signal from the 2/3 valves. The second is the vacuum supply line, which connects to the same line that feeds the transmission valve on the back of the injection pump. The third line is actually a vent line.

Think of it this way: a 2/3 valve sends a vacuum signal to the EGR, causing it to open. When the 2/3 valve closes, there is still vacuum in the line. If the line is completely leak free, that would make the EGR valve stay open forever! There needs to be a way for the circuit to bleed off vacuum to allow the EGR to close, hence the vent line. When the EGR valve is open, the vent line is blocked off. Unblocking (opening) the vent valve empties the vacuum from the circuit, which is what allows the EGR valve to close.

If everything is working as the factory intended, the 2/3 valves should have no affect on transmission shifting. The vent line and vacuum line are never open at the same time, and the amount of vacuum it takes to open the EGR is negligible. The reason that the 2/3 valves eventually affect transmission shifting is because they start to leak. This means that the supply line is also now a vent line. This decreases the vacuum signal going to the vacuum control valve on the back of the injection pump, making the transmission think you're pressing the accelerator when you're not. This low vacuum condition leads to firmer-than-needed shifts. This can be remedied by buying new 2/3 valves, but if you're not using EGR, that's a bit like buying a $60 golf tee.

__________________
1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K

This is absolutely spot-on for most of the 617 vehicles. I'm positive it is 100% correct for all 1981-1984 SD's.

There may be the odd 617 or 616 that has these valves providing some control over the transmission. But, I've only seen one member post about it, and it's pretty rare.

I dunno bout that.

My 300D has intermittantly clunked when coming to a stop ever since I have owned it. I just learned to live with it. Then, based on some discussions here a few weeks ago, I decided to replace the vacuum switches. No change still clunks. For the hell of it, I mityvaced both old switches and both new switches. One of the new ones leaks on the normally closed port and one of the old ones leaks on the normally open port when held closed. Installed the 2 non leaking switches (one old, one new) with the 2 new levers and PRESTO!!! No more clunking. It only took me 7 years to solve this problem.

Viva la manual transmissions!!!!

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Palangi,
Of course, using good switches will stop the vacuum leak, which is what caused the hard downshift (clunk). This is because the leak reduced the vacuum signal being sent to the vacuum control valve. This does not mean that the good 2/3 valves are doing anything to to affect the vacuum signal to the transmission aside from plugging a leak. I'll bet that if you disconnect the supply line to the 2/3 valves and plug the 3 way fitting with a golf tee or something, you'll notice no difference in the way the transmission shifts.

__________________
1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K

The vacuum source is shared by the transmission controls and the EGR controls. The vacuum line that is shared by these systems is also limited by an orifice. If there is a leak in either system it can cause problems by side effect in the other system.

Note that some of the lines are vacuum lines and some of the lines are vent lines. MB uses controlled leaks to regulate vacuum. I have never convinced myself whether there is a controlled leak in the vacuum valves on top of the valve cover that is intended to reduce the vacuum to the transmission controls under some throttle openings on some cars.

That link is in the first thread that I linked to above.

I have seen one vacuum diagram for one variation of a 240 that looked like it works this way. For most cars the line that you refer to as modulated vac out is a vent line. I think that 240 diagram is in one of threads that I linked to above.

Cateaux, thanks for the good explanation.

This fits completely with the theory.

If the vacuum switches for the EGR are leaking, they cause a drop in the transmission vacuum. If you were to disconnect and plug the vacuum supply line to those switches, you would get the same result as you now have with new (not leaky) switches.

VERY havd shifts into low gear. Hooked all back up, test drove, could barely feel down shift to low.

In the pic(IF i get it here) there is a very short piece of vac hose between what looks to be a one way valve and the plastic unit on the IP. This hose is deteriating and needs changing. I pulled a bit on it but don't want to break something. Is it just a piece of hose-or part of the plastic unit on the IP?

Attached Thumbnails

 

__________________
Jim

'49 170?(donated to church in Darmstadt '58)
'58 220S(crusher, after '73 fire[San Antonio])
'72 280SE 4.5
'77 240D
'81 300SD
'83 240D parts car