Hey I need some help here.

Car 1983 300SD
285K miles

delayed engagement into R or D (3-5 seconds)

Good shift at 1/3 or less throttle, or when the accelerator pedal is floored.

Flares (2-3 and 3-4) when throttle is between 1/3 and full throttle.

tested vacuum to modulator and it appears to be 10" at idle and 0" at full throttle.

Where should I start?

Well, for the delayed shifting, you've got to start with the filter and fluid.

The flaring would be typical with a trans of that vintage. You might get some success in dropping the vacuum from the VCV down lower at idle. The curve shifts to the right and firms the shifts somewhat.

I've never done the modulator pressure increase, but, it sounds like that one might benefit from turning the modulator up a bit. Usually it's done with a gauge. If you try it, please post your procedure and results.

Some folks have recently bought a shift kit that has successfully corrected the flaring.

Alternately, you could replace the K1 piston and spring, but, this will only assist the 2-3. The problem with the 3-4 would remain.

It does sound like you're on borrowed time with the described symptoms and the mileage.

Well I did some tinkering, and here's what I got:

I cannot adjust the vacuum any lower, as the vacuum control valve starts to hit against the stop. It didn't look like it was hooked up right, but I compared what I have to a vacuum diagram, and it appears to be connected properly.

I'm starting to wonder if all the adjustments in the world wont fix internal low pressure on the tranny.

I adjusted the vacuum modulator counterclockwise 3 spots, and I might have gotten a littel harsher shift, hard to tell, overall I would have to say that I got nowhere.

One thin g I forgot to mention in my origial post is that the car seems to shift better after it gets to temperature.

Any other suggestions?

Marty

Well, I suppose that the result is not all that surprising.

Disconnect the vacuum line to the transmission and run it with no vacuum..........just for grins.......let's see if that helps anything.

If not........you've reached the end of the road with it.......unless you want to take a $50.00 shot at the spring kit.

Yeah, 250-300K seems to be about when these trannies need some attention, I replaced mine right around 275.

WEll I continue to drive the yellow jacket, Funny rhing is, when she's floored, it shifts PERFECTLY, just the way I would like it to. 1-2 3500 2-3 4000 and 3-4 4400 not a single flare. but mid throttle flaring occurs. Looks like I'll just keep driving it like a bat outta hell. Chirps tires in the 1-2 shift on WVO/RUG combo.

Seriously considering adding Propane injection to make her SCREAM.

And after her final sting, it'll be time for parts.

Marty

before you just thrash it to death, work your way upstream from the tranny vac modulator and check/replace all the vaccum connectors. Have you plugged the EGR valve lines? Mine sounded very similar to yours and it was caused by vaccum leaks and crappy connections....fixed for about 40 cents worth of vaccum line.

Delay going into reverse seems to be pretty normal for these cars. I don't drive like a bat outta hell, (chirping the tires is driver error on my part)...as someone once told me..."these are luxury cars, drive them luxuriously"...in other words, ease this ole gal around the dance floor! She may just keep right on dancing.

__________________
Mark
1983 300TD Wagon
Even a broken watch is right twice a day

The most IMPORTANT reason that I drive like a "bat outta hell" is to keep the injectors clean. Driving 'luxuriously' just dont cut it when I'm burning Waste Vegetable Oil.

mespe,
I have not located and/or studied the vacuum diagram for your particular YR/model but my limited experience to date tells me that the various restricted orifices in these beasties are critical to proper vacuum balance and of course this changes with age/miles [ for us humans too!].

I recently obtained all 6 of the different sizes of M-B's in-line orifices.
I mention this because this could be a way to further lower the vacuum range your modulator is seeing. As the tranny ages I think [even though a newbie]... I think many here accept the premise that it is pretty much an art form to adjust the vacuum system/modulator in order to squeeze out a few more miles from these trannies. I just turned 300K on my 1980 300D[na] with a 722.1 and yes it flares too. But I have not given up yet.

Back to your situation:
Q1 - Have you found [with some assurance] the proper vacuum diagram for your car?
Q2 - Does it show any "in-line" orifices, orifices built into "Ts" , or orifices in vacuum "dashpots" or whatever other names they go by?

Not all the vacuum diagrams identify what size orifices are specified and in my case my M-B dealer's parts counter did not even know about or have a way to come up with the P/N(s) for these "cheap" but critical parts! Let know if you want P/N(s) for the in-line orifces! Their mechanic had the PN(s) written down on an old parts envelope... that's where I got my numbers!

Orifices - wherever found, and by whatever name can easily become clogged… and keep in mind that many [if not most] of these cars have an open vent line hanging under the dash.
Sidebar - On this let me relate to ALL that my mechanic showed me how he often installs clear universal fuel filters in the vacuum lines of these car’s engine/tranny vacuum systems.
One on the vent line under the dash to filter out debris from being sucked in!... and
one on the line to the diesel shut-off valve on the side of Injection Pump to give an early visual warning that your shut-off valve diaphragm is leaking oil!

Sam

Try tightening the Bowden cable 1/2 or 1/4 turn at a time and take a test drive to see if it improves anything...the trans may perform as though it's at WOT, even when it isn't