I searched and searched the forum but I do not really find what I need.

83 300SD 422K miles, unknown miles on transmission. The car runs like rust. EVERYTHING works(all vacuum etc).

When it's really cold outside, my car lives outdoors, my car shifts fine. Normally it flares BAD on the 3-4 shift and flares pretty good on 1-2. I ALWAYS have to feather the pedal to get it to shift w/o flaring(good thing I proof read... it shifts fine at low throttle settings). Reverse works great and it "kicks down" the way I think it should.

I personally believe there are no major vacuum leaks.. when it was warm out I inspected the vacuum lines under the hood and replaced some stuff. I have never tested the vacuum because I would need to buy more stuff, I am not rich. I still feel the vacuum system is working very well. I have made bowden(?) cable adjustments and got it dialed in where I think it needs to be. It seems a little tight though... if I loosen it up the flaring is worse.

I keep reading about the VACUUM MODULATOR adjustments. I have searched and find lot's of talk about it. However, no one seems to mention where to find it OR how to exactly adjust it. I assume it's part of the transmission itself. I also assume I need some sort of tools to make the adjustments.

I have read about the K1 thingy... again no real description/pictures. I realize that my transmission is more than likely old and tired and needs a rebuild very soon. I just want to make whatever adjustments I can to improve the flaring. If I end up needing the K1/K2 thing that would be fine too. A tranny rebuild is NOT on the agenda right now.

I would like to get this resolved before my 555 mile trip to Virginia for Army stuff.

Thanks for any help and sorry for the long winded post.

How is the 2-3 shift?

You still need a Mity-Vac. Rich or not, it should be the first tool bought to work on these cars.

Flaring can be caused by worn clutch packs, too much vacuum, etc. Too little vacuum and the shifting and the shfting is quite abrupt.

The modulator is on the driver's side of the tranny. It adjusts by using little "t" stored under the rubber cap. IIRC, counter clockwise makes the shift firmer.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Thanks I will look for the modulator. I mis-spoke before. 1-2 flares mildly and 2-3 flares bad. 3-4 is ok I believe.

And some more info:

My car has what I consider fatal rust so I am not looking to restore it. I would much rather find a southern car sometime in the future. I do however want to resolve the flaring issue the best I can for now. Thanks

At the risk of appearing to be an incredible smart alex, are you absolutely sure that the fluid is high enough? You can get those exact symptoms if you're low. SteveBFl says to check it in neutral, at operating temperature, and treat the line as being the first point at which the fluid goes all the way across the dipstick.

If that's good to go, as mentioned above the modulator lives on the side of the driver's side of the tranny. It a long vaccum tube that leads all the way back into the firewall. IIRC it's green, but will look black from all the dirt. G'luck.

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Tjohn

82 300 SD
77 450 SL (gone)

Do you have an Autozone near you. My local store has a mighty vac in their free loaner program. Check it out.

Here's a link for adjustment procedures with pics.
http://articles.mbz.org/transmission/adjust/.

John

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Certified Registered Nurse Anesthetist (CRNA)
2002 F250 powerstroke with Plantdrive WVO conversion
1983 300SD 190K miles ,sold
2006 E320 CDI

I will check the fluid as you describe. I checked it months ago and didn't think much about it since it doesn't leak anything. And I would have checked it in Park. Lemme give that a try.

It's snowing like crazy here so I did not crawl under it today to look at that modulator.

THANKS I will check autozone out. There is one so close that I could walk in a few min's.... if it wasn't snowing.

The AutoZone near me didn't loan out a MityVac but had the plastic one for sale about $25 iirc.

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1985 300D Turbo
"Evolution is God's way of giving upgrades" Francis Collins

Still have not got a mityvac yet.

I messed with the modulator.... For some reason I thought the T key was going to loosen the entire modulator and then I could turn it CCW. I quickly figured out the T key WAS the adjustment. Who knows what its set at now.

It shifted a little better. I followed some vac lines and decided to plug the one I thought went to the climate control. I removed and plugged the black/red(?) one and VIOLA no flaring.

I feel I still need a mityvac so I can set that modulator properly. Soooo I am guessing dash pot's????

mitivacs have a little pump that you can pull on vacuum lines to see what the gage reads when you pump them down and how long they bleed down. You can achieve same effect by pulling and plugging lines one at a time, and driving the car, but it takes a lot longer that way. Vacuum solenoids under dash can be bad, vacuum door locks can be bad, vacuum seat adjustments can be bad, injector pump components can be bad, any line can be disconnected under the carpet, all affect transmission shifting. See the diagram somebody gave you, vacuum is the worst feature of the mercedes diesel.

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'80 240D biege "Mercey Bird"
'80 240D light blue "Slug"
'80 300SD dark blue "Theodin"

You didn't look in the DIY section!
RESOURCES > DIY ARTICLES:

• Transmission Vacuum Modulator Adjustment
• Vacuum leak Isolation
• Transmission Vacuum Control Tuning

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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