83CD Tranni Vacuum help needed

[bigsky]

Bought a 83CD last week, have been looking for a turbo. Picked up the 83 with new MB installed motor 20K miles ago. Motor runs great, but tranni has vary hard shifts. Replaced tranni filter/fluid, made shifts a little more consistent. Also did diesel purge on IP. Today started tracing vacuum/lines. Found that I do not have any vacuum going to tranni. Traced lines to the 2, 3/2 valves on top of valve cover, and found that two of the lines were broke off. Questions:

1: Have done much research, and it looks like many just delete this whole setup, should I delete it, and if so where can I find a good write up??

2: Should I just order the new 3/2 valves and get it running/shifting correctly before doing EGR delete?

3: The 3/2 valve set up on the valve cover, uses 4 vacuum ports, but I only have 3 vacuum lines going to it. Am I missing a vacuum line some where??

Tried to upload Pic, but failed

[Alec300SD]

Originally Posted by bigsky

Bought a 83CD last week, have been looking for a turbo. Picked up the 83 with new MB installed motor 20K miles ago. Motor runs great, but tranni has vary hard shifts. Replaced tranni filter/fluid, made shifts a little more consistent. Also did diesel purge on IP. Today started tracing vacuum/lines. Found that I do not have any vacuum going to tranni. Traced lines to the 2, 3/2 valves on top of valve cover, and found that two of the lines were broke off. Questions:

1: Have done much research, and it looks like many just delete this whole setup, should I delete it, and if so where can I find a good write up??

2: Should I just order the new 3/2 valves and get it running/shifting correctly before doing EGR delete?

3: The 3/2 valve set up on the valve cover, uses 4 vacuum ports, but I only have 3 vacuum lines going to it. Am I missing a vacuum line some where??

Tried to upload Pic, but failed

Congrats on the new acquisition

Vacuum from the VCV atop the rear of the IP regulates downshifts.
The bodwen cable regulates the upshifts.
This thread should help: http://www.peachparts.com/shopforum/diesel-discussion/158216-its-critical-how-you-set-your-transmissions-vacuum-system-your-diesel-mbz.html
I used a drip irrigation needle valve to have a on-the-fly adjustable vacuum orifice instead of trying to hunt down different sized color-coded MB vacuum orifices.

1) Yes, it's not a complete DIY write up...but take a look at the EGR delete pdf in the linked thread. http://www.peachparts.com/shopforum/diesel-discussion/385092-mystery-solved-egr-switchover-valve-causes-throttle-linkage-binding.html

2) No, the switchover valves only affect the EGR valve operation (under different load conditions).
If the EGR is deleted, also delete the switchover valves.

3) No, only three lines connect to the intermediate piece (item 74) on the EGR - Engine system vacuum jpg in the linked thread. (First photo)

[tdhawk]

Although I am learing from experience and this forum that all sorts of vacuum leaks can cause hard shifts, I have recently found another vacuum leak/cause of hard shifts that is easy to diagnose. I have an 85 300TD.

During the summer when the weather was warmer, I was experiencing intermittent hard shifting combined with slow engine shut off. Haven't had any trouble all winter. The other day, for the first time in many months, it was warm enough I wanted to use the center air vents. AS soon as I punched the center vent button on the climate control, I had immediate hard shifting and slow shut off, and no air to speak of coming out of the center vent. I'm fairly certain it a leaking vacuum pod for the center vents. Probably have a problem with floor vents too, since I don't have much heat down there.

The entire egr and arv circuits on my car have been deleted.

It's simple to check whether the climate control is the/a culprit on my car, an 85 300TD (same climate control as yours, I think) If I take off from one stop light with either the defrost or defrost vent and floor (the two left buttons) it shifts as it should. The next stop light, if I push either button for center vents, it shifts very hard.

Might be worth the simple test.

[bigsky]

Made EGR cover plate, completely eliminating EGR system. Found that I have vacuum leaks in every system, except climate control, bypassed all leaking systems for the time being. Have 15 at vacuum line going to tranny, at idle, drops to 0 as throttle is applied. Tested tranni fluid pressure at the modulator, and had 1 psi, after making a key adjusted pressure up to 42 psi. Still had hard/harsh shifts. Got back to shop and re-checked psi at tranni modulator. It was high, so checked vacuum going to tranni, it would not hold vacuum. So, then I replaced the tranni modulator, a real pain in the a$$. Had to replace tranni mount, so did the modulator at same time, still vary little room. Adjusted new modulator to about 38 psi, was shooting for 42 psi. 1st shift is still vary hard, other shifts are acceptable. For a smoother fisrt shift should I raise, or lower the psi, checked through the banjo fitting, by the modulator.

[Mesalm]

My experience has been that lower pressure is softer shifts, higher is firmer shifts

[bigsky]

Have the modulator at the tranni set at 33 psi right now, shifts are still a little hard. Especially the 1st shift. Going to order some of the vacuum restricting orafices from MB, and try to get the vacuum going to tranni from 15 down to about 10. Then reset the modulator at the tranni.

[Alec300SD]

If you use a drip irrigation needle valve you can vary the vacuum orifice size with a twist of the valve handle.
Here's a link to a photo of my setup in my 83 W126 300SD

http://www.peachparts.com/shopforum/attachments/diesel-discussion/141631d1491110554-81-300sd-hard-shut-down-needle-valve-place-standard-orifice-reducer.jpg

[tyl604]

As I remember you turn the trans modulator clockwise for a sharper shift. Seems like folks recommended only turning a max of 1/4 turn at a time and then testing.

[bigsky]

Today spent another 4 hrs adjusting tranni, found that the pressure at the tranni modulator, needs to be set with engine at 1200 RPM, not idle. Modulator was running at over 50PSI, lowered the PSI to about 38PSI at 1200 RPM, First shift was still harsh, second shift was perfect, third shift has a slight "clunk". Lowered modulator PSI down to about 25 PSI/1200 RPM, with 15 vacuum going to tranni, at idle. This eased the harshness/clunking slightly. Then adjusted bowden cable in small increments, tranni is now shifting at about 2800 RPM at all shift points. Still slightly harsh 1st shift. Think this is as good as this tranni will get

Have noticed that the tranni seems to shift great when cold, got down to 25F last night, this morning tranni shifted all three shifts perfect. If it shifts better tomorrow morning, thinking of using a tranni additive to thicken tranni fluid. Any opinions??? Afraid this tranni may be on its final legs.

[Diseasel300]

Did this car sit a lot and is the fluid old? You might dump some Trans-X in there and drive it like you stole it for a few hundred miles then do a fluid/filter change. Certainly helped my SDL that felt like a circus chimpanzee was in charge of shifting.

[bigsky]

Originally Posted by Diseasel300

Did this car sit a lot and is the fluid old? You might dump some Trans-X in there and drive it like you stole it for a few hundred miles then do a fluid/filter change. Certainly helped my SDL that felt like a circus chimpanzee was in charge of shifting.

Do not have much history on car, but do not it has ever sat for any extended periods. Odometer is at 488125 KM, engine was replaced by MB dealer on the west coast, 5 yrs/20K miles ago. Do not get much history on a $450 car.

Re-adjusted tranni modulator, with vacuum line disconnected (proper way to check) Adjusted modulator to 40 PSI. Tranni still shifted vary hard at all shifts. Then started adjusting modulator PSI down, counter clockwise, 1 turn then going for a road test. After about 11 turns, and jacking/crawling under car 11 times. Tranni now is at about 80%, 1st shift is perfect, if I completely lift throttle at 2000 to 2500 RPM. Shifts perfect into second, at all RPM's. Third to fourth shifts perfect at 2800+ RPM, lower RPM shifts are a little firmer, but not a clunk. This is close enough for me. Down shifts are all smooth, and kick down shifts are all firm. Will crawl under car, and see what PSI I am running at the tranni modulator, just for future reference.

[tyl604]

Wow. Eleven turns. I suspect your foot will get used to working with the tranny and you will not even notice it. Good luck.

$450 - wow again. Wish I had the time and talent to take on a project like that and bring it back. Save every one that you can.

[vwnate1]

Wow ! .

I can only dream of a Mercedes this cheap .

Any chance of you posting photos of your bargain car ? .

Good to hear the shifting is O.K., I pulled my hair out doing it on my '78 and '80 Diesel Coupes .

[bigsky]

Originally Posted by vwnate1

Wow ! .

I can only dream of a Mercedes this cheap .

Any chance of you posting photos of your bargain car ? .

Good to hear the shifting is O.K., I pulled my hair out doing it on my '78 and '80 Diesel Coupes .

Can not upload pics on this forum, but plenty here More Fun, 1983 300CD - Mercedes-Benz Forum

[bigsky]

pic of 83, this is a test, trying to figure out how to load Pics to this forum.