1984 300D. I installed a brake booster today on my car and when I went to go take it out for a drive. It felt like the car was driving in neutral I wasn't gaining any speed so I decided to head back. As I was heading back hitting the accelerator on the road didn't seem to do anything I pulled in a street parking turned off the car. I tried turning it on again it wouldn't budge I'd hear *click*, so I put her in neutral just so I could push it in all the way in the spot the car wouldn't even shift into neutral. I finally got the car on idk how I shifted it from L to D and it fired right up. I still can't shift in between gears even though I feel the transmission shift in all of the gears when I'm shifting.


Update: car goes in all the gears just fine now. Idk how I didn't do anything to it except let it. However it struggles to go past 40 mph and their is this small emitting from below coming from below. Transmission is shot? It riffles through all the gears 1-4 just fine
Any ideas

Ely,

The shifter handle won't move normally OR the shifter handle goes into position but the car does not move?

Was everything ok until the brake booster replacement? Was anything else done to the car?

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

a little bit of both. At first the car would go in position but it wouldn't move I even put it in neutral and no matter what I could not push it. I let the car sit for a little bit came back and it wouldn't start so I riffled it through gears and put in on "P" it started instantly.


Car has been sitting for a month and the only work I've done on it is brakes/brake booster and master cylinder


It struggles to past 40. I can smell burnt transmission fluid from below

Sounds like two different problems.
The shifter not moving properly and the car not starting sounds like the neutral safety switch may have started to seize and or the shift linkage bushings are bad.

About not going over forty and smelling burned fluid could be low on fluid due to a leak or trans failing. Did it shift into fourth gear?

Check the fluid level. How does the fluid look and smell? If the fluid looks really bad you could try servicing it, i.e., new filter and fluid.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I will check it out tonight. It shifted out of fourth gear just fine. The transmission would shift out of 2000 rpms and go on to the next gear.

Closely examine the area where you worked to install the booster for disconnected or cracked/broken vacuum lines.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

When I was working on my Car unknowingly disconnected the Vacuum Line from the transmission vacuum modulator.
The care up shifted nearly normal but the down shifts were extremely sudden and harsh. Reconnecting the line fixed the issue.

Notice that lack of vacuum did not stop it from shifting.

When you were having the forward shifting problems could you still shift into reverse.

I agree with the poster that mentioned the shifter bushing. There is 2 large ones at the top and one or 2 smaller ones on the outside linkage. The good news is the generic replacements don't cost much.

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84 300D, 82 Volvo 244Gl Diesel

To me this kind of sounds like its something simple and u are just thinking worst case scenario.

So it's still kinda of unclear as to if the car has these problems before you put the booster on or if not?

You said it had been sitting for a month? Did you drive it regularly before then? Did you just recently buy it? Etc

__________________

There is a small vacuum hose shaped like an elbow on top of the injection pump. Examine it closely, mine was bad on the '85 and the car was SLOOOOOW!

Check all other vacuum hoses in the area where you worked. It is common to knock one loose or crack/break one.

Look on the firewall near the booster for vacuum hoses that control the turbo boost, they go to a small black switch/valve.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Per Diesel911 - "When I was working on my Car unknowingly disconnected the Vacuum Line from the transmission vacuum modulator.
The car up shifted nearly normal but the down shifts were extremely sudden and harsh. Reconnecting the line fixed the issue.

Notice that lack of vacuum did not stop it from shifting."


Diesel911 - for a long time I have been mentioning that the tranny really does not need vac to upshift, only to downshift. Technically it does but the vac bleeds down to zero so fast when you hit the throttle (at least on my SD) that there is almost always no vac at upshift. - I personally tested this by disconnecting the VCV and connecting a mityvac to the vac modulator. With no vac it upshifted fine and had clunky downshifts; however by pumping up the mity vac after reaching fourth gear, the downshifts were very smooth coming to a stop. I have received a lot of grief for relaying this information but your statement just serves to confirm my experience.

You receive lots of grief for your claims because you keep repeating the same information ad-nauseum without ever learning when someone tries to explain how vacuum relates to shifting on the 722.3 transmission.

Vacuum is not required for any shift. Up or down. Shift points are controlled by road speed (governor) and throttle position (control pressure cable).

The vacuum is provided by the VCV to fake a manifold vacuum signal as you'd have in a gasoline engine, the entire point being to refine the shift quality. You should have full modulator vacuum at zero throttle, reducing vacuum up to approximately 1/4 throttle, and zero vacuum thereafter.

The vacuum is there to modulate the shift for smoother engagement, much like slipping the clutch in a manual transmission car. Without the modulation, the shift is abrupt and rough under low load conditions (meaning less than 1/4 throttle when accelerating), and when decelerating/coasting (zero throttle), much like simply dumping the clutch in a manual car.

Vacuum problems will not cause a failure-to-shift problem. They will cause a refinement (harsh engagement) problem. Too much vacuum results in sluggish, extremely smooth shifts that will rapidly wear the clutch packs in the transmission. Too little vacuum results in a car that feels like it's being driven by a teenager learning to drive stick. When the VCV is adjusted properly and the modulator pressure adjusted properly, the 722.3 transmissions should have a firm, but not harsh shift when going up the gears and be completely unnoticeable when shifting back down the gears during a coast or braking event.

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1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

You need to mention that the full modulator vacuum is not the full vacuum present in the Vacuum Line coming off of the Vacuum pump. There is a restricted fitting that reduces the vacuum before the vacuum valve and the vacuum valve itself leaks off vacuum so what the modulator gets is much lower then what is in the main vacuum line.

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84 300D, 82 Volvo 244Gl Diesel

Yes, I agree with both of you. Vac in my SD comes off around 20 and is reduced to something between 12-15 by the VCV.

Diseasel300. For some reason you will just not admit that the tranny will upshift almost perfectly with no vacuum even though that is not the design. I know from personal experience. And now it appears that Diesel911 has experienced the same thing. Again I am talking about the quality of shift, I am not talking about the shift point - only the quality of shift. Maybe I have not been clear about. And we can continue to disagree; nothing wrong with that.

Correct. The modulator vacuum for any given year or model is given in the FSM. Modulator vacuum is typically 12-14".

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

Because if the transmission is set up correctly, at 1/4 throttle input or less, the transmission will shift hard on upshifts. If it doesn't, you have the modulator adjusted too soft. Above 1/4 throttle input you should notice no difference since vacuum is already bled off. Below that point, YOU SHOULD NOTICE. Exactly the same behavior as downshifting without vacuum, abrupt and rough.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]