second opinions on my transmission 2nd to 3rd problem, help needed..

[body_infinity]

Ok guys need a second opinion on my transmission. After taking my 1971 (early mod) 280se 3.5 (m116) to a couple of trans EXPERTs the same answer, that its just normal for the type and age of car, so left it there but after reading a few posts here I was wondering if I can have some views on my specific problem, ok my symptoms:

She seems to change very quickly from 1st to 2nd, you don’t even feel the change very quick and very smooth (is this normal?)

2nd gear to third very very slow, I don’t have a rev gauge (i do have yellow lines on the speedo but?) but it seems to rev for a long time before it changes over to third? And a funny thing I have noticed…….as I drive in second revving like crazy if I slightly take my foot off she bucks and seems to change into 3rd hmmm

3rd to fourth seems smooth.

so its just 2nd to third where my problem is so here is what I have checked so far:

vacuum leak…only found the metal pipe from engine down to trans but no rubber hose, wanted to check the hose but can not locate it, anyone have a pic or diagram??

Note I do have a vacuum leak in the central locking which I am working thru just waiting on the master door valve!

Trans oil is fine clean and no burnt smell etc
Any help here again is greatly appreciated.

[RAYMOND485]

1984 300d Turbo 141,000
Repair The Vacuum Door Leaks And The Trans Need The Extra Vacuum

[Cephallus]

Is the door lock system on the 280se really driven by the engine vacuum system, not a separate pump like other MB's?

The symptoms are a classic modulator problem. Proper vacuum function of the trans modulator system is vital for correct shifting.

I'd be skeptical of your 'experts' credentials if they dismiss poor shifting as normal behavior. Take the car to someone who really knows about MB transmissions, and how to properly verify the function of the modulator/linkage.

[250 Coupe]

I'd say either vacuum modulator problems or if you have one, the link from the throttle linkage down to the tranny.

If you have a bit of white smoke or are loosing tranny fluid, the modulator diaphragm may have given up. I don't know how the metal line transitions to the intake and the tranny so I can't help there.

On my 1976 450SEL, M117 the linkage from the throttle to the tranny was way out of whack and caused the tranny to shift oddly. It should be adjusted so that with the throttle valve closed and the linkage gently moved fully to the rear, the ball stud on the link snaps directly on without any side force.

Michael

[body_infinity]

Originally Posted by 250 Coupe

I'd say either vacuum modulator problems or if you have one, the link from the throttle linkage down to the tranny.

If you have a bit of white smoke or are loosing tranny fluid, the modulator diaphragm may have given up. I don't know how the metal line transitions to the intake and the tranny so I can't help there.

On my 1976 450SEL, M117 the linkage from the throttle to the tranny was way out of whack and caused the tranny to shift oddly. It should be adjusted so that with the throttle valve closed and the linkage gently moved fully to the rear, the ball stud on the link snaps directly on without any side force.

Michael

Hi michael and thanks for the info, I dont get any smoke or fluid loss - vacuum modulator had a look in my manual but it does not cover the tranny and dont want to go back to the experts has anyone got a pic or diagram of what it looks like?

re the linkage from the throttle to the tranny .... let me know if I am wrong but I dont think the D-jet was setup like this? tried to look for this but nothing just saw a metal pipe going from back of the m116 engine to the tranny and on the right there was a bunch of wires thats about it I think?

[rg2098]

The modulator is on the passenger side of that transmission at the end of the metal pipe, it is not adjustable. Fix your door lock leak as a first step. Second, I would look into a possible K1 spring kit.

[senorunimog]

For quick diagnostic purposes you could just put a vac plug over the nipple where the connection to the central locking is. Thats how I'm currently running my 280. You also should check your timing, if its off it will change the vacuum curve, and hence the shift points.