Today, I changed the transmission fluid and washed the engine bay of my 1987 300TD. Now I am feeing slightly later shifts than before the fluid change and wash. The fluid level seems to be OK.

What could be the possible causes of this?

Look for vacuum hoses you could have knocked off while cleaning or spraying around in there.

turbodiesel:

Any particular areas to look for? It is similar to your 300SDL.

I am still learning this car.

Thanks.

Most of the vacuum lines are on the drivers side, near the firewall/engine area. There is a whole load right there, you probably knocked one off accidently.

On the way back to home from work, it seemed it shifted OK except a slightly delay from 3 - 4. Maybe my foot was too heavy after changing the transmission fluid in the morning.

My tach does not have the shift points indicated. Does anyone know the rough RPM ranges for the shifting points on a 1987 300TD?

Will also check for vacuum hoses and lube a few places when daylight arrives.

Thanks.

There are dots on the speedo where it is the maximum speed for that gear.. on my 300SDL its..

. (31mph)

.. (50mph)

... (84mph)

Should shift like 10mph before those points at WOT (wide open throttle (floored))

Thanks, turbodiesel. I see them now. I was looking at the tach (wrong gauge).

Shift timing on this car is controlled by a bowden cable connected to the throttle, not by vacuum modulation. To locate the bowden cable, start at the bracket where the throttle cable is mounted to the intake manifold - there's a big white knob for adjusting throttle cable tension there.

Go down and toward the firewall a bit - look for a cable exiting toward the back of the engine and heading down the transmission tunnel. That's the one. There is a threaded adjuster for setting tension on the bowden cable - uses a wrench, but I can't recall which size. Merecedes spec is to just take up all slack with the throttle closed. A little bit either side is OK too, if you like your shifts sooner or later. Loosen it too much and you'll get klunky 4-3 downshifts. Too much tension and it might hang up in third gear.

This car also has vacuum modulation to the transmission; it controls only shift quality - firm vs. soft. The Vacuum Control Valve (VCV) is mounted on the side of the engine near the injection pump. It can be adjusted by loosening two 10mm nuts. Again, adjustment is a bit of a personal preference. Too much vacuum and the trans will flair, too little and you'll need a kidney belt.

To make things even more complicated, there is also a circuit to soften the transmission shift quality when engine temperature is below 50C. This system utilizes a three way switchover valve mounted on the forward firewall quite near the washer bottle. It causes the vacuum amplifier (round blue thing on drivers fenderwell) to provide more vacuum amplification until engine coolant temperature reaches 50C.

After changing to synthetic trans fluid, I found the trans flared on shifts when the softener circuit was engaged. So I unplugged the electrical connection on the three way valve and all is again well.

More than you ever wanted to know...

- Jim

Thanks, Jim.

I have your post printed out and will trace and locate the cable tomorrow morning.

I read your post several times. So my slightly delay from 3 - 4 is caused by a too tight Bowden cable?

Do you have an explanation why a fresh fluid change can cause the slight delay?