Adjusted ALDA, now it shifts great?? - PeachParts Mercedes-Benz Forum

Chad300tdt · #1 07-06-2009, 08:09 PM

I was having major acceleration issues with my 1985 300CD. Once the turbo kicked in it was OK, but until then the car felt restricted.

I also have had an issue with the trans popping into 2nd gear. It didn't do it all the time and mostly if I was driving mildly. If I floored the pedal, it would shift smoothly into second most of the time.

Anyway, I decided to peel the cap off my ALDA and adjust it to gain the pre-turbo acceleration. I had already gone through other things first including adjusting all the throttle linkages.

I ended up turning the ALDA screw about 3/4 turn CCW and it eliminated the acceleration issues I was having. The CD is VERY peppy now.

As a surprise to me, the CD is shifting smoothly now through all gears.

How would adjusting the ALDA cause smoother shifts????

jt20 · #2 07-06-2009, 08:20 PM

less torque in relation to Bowden cable position.

jt20 · #3 07-07-2009, 12:41 AM

oops..

just went for a ride and realized I forgot about the vacuum.

Torque to the trans is modified by adjusting the Alda, while vacuum and the bowden cable remain the same.

Whiskeydan · #4 07-07-2009, 08:28 AM

It's a balancing act to get everything just right to suit ones driving habits.

I've been tweeking the 84 wagon's transmission stuff daily and have it real close to perfect. I'd like for it to downshift quicker though. Not sure how to do this.

After driving the Jetta TDI with it's transmission that keeps engine rpms right at its torque happiness, makes driving the MB auto frustrating. Manually downshifting alot.

Hip001 · #5 07-07-2009, 09:43 AM

Quote:

Originally Posted by Whiskeydan

It's a balancing act to get everything just right to suit ones driving habits.

I've been tweeking the 84 wagon's transmission stuff daily and have it real close to perfect. I'd like for it to downshift quicker though. Not sure how to do this.

After driving the Jetta TDI with it's transmission that keeps engine rpms right at its torque happiness, makes driving the MB auto frustrating. Manually downshifting alot.

I have similar frustrations driving my 300D.

toomany MBZ · #6 07-07-2009, 10:15 AM

I adjusted the ALDA on the SD, it now starts off in first gear, it has not done that since I've owned it. The VCV is getting and giving a different signal to the tranny. Nearly a different car.

mtbguy · #7 07-07-2009, 10:20 AM

Quote:

Originally Posted by toomany MBZ

I adjusted the ALDA on the SD, it now starts off in first gear, it has not done that since I've owned it. The VCV is getting and giving a different signal to the tranny. Nearly a different car.

Hopefully you mean that in a good way?
(I'm about to open my Alda up today if I can manage to get it off without removing the intake manifold on my 300d 2.5.)

I think I'll start with 3/4 turn CCW also- that seems to be a good start for many from what I've read.

DeliveryValve · #8 07-07-2009, 11:49 AM

Quote:

Originally Posted by Chad300tdt

...

As a surprise to me, the CD is shifting smoothly now through all gears.

How would adjusting the ALDA cause smoother shifts????

The vacuum control valve (VCV) which is connected to the throttle linkages on the IP, sends vacuum to the modulator on the transmission are sensitive to various throttle positions. After a thousands and thousands of miles on an IP, the correct calibration slowly deteriorates. The ALDA is one part that gets worn and the calibration is then off from the factory spec. With all other parts of the engine in proper adjustment, the ALDA will not allow the correct amount of fuel to the cylinders at take off. The driver then compensates the lack of fuel by pressing the accelerator further down. At this point the linkages are not in the correct position for the power that is being applied to the transmission. This then messes up the VCV adjustment by not sending the proper amount of vacuum to the modulator. Which causes the hard shifting or the shifting into the incorrect gears.

Getting the ALDA back to proper adjustment allowed the correct amount of fuel to the cylinders and stopped the chain of events in which causes the problematic shifting.

toomany MBZ · #9 07-07-2009, 11:57 AM

Quote:

Originally Posted by mtbguy

Hopefully you mean that in a good way?

I think I'll start with 3/4 turn CCW also- that seems to be a good start for many from what I've read.

LOL, I almost added that! Yes, in a good way, the car now starts off in first gear, it hadn't before since I've owned it. I have readjusted the Bowden cable too.
I am not familiar with your engine, so can't comment on what to do, yet I turned mine CCW.
DeliveryValve has a good explanation, I understand the IP goes out of adjustment and the ALDA is much easier to compensate.

tobybul · #10 07-08-2009, 08:39 AM

Quote:

Originally Posted by mtbguy

Hopefully you mean that in a good way?
(I'm about to open my Alda up today if I can manage to get it off without removing the intake manifold on my 300d 2.5.)

I think I'll start with 3/4 turn CCW also- that seems to be a good start for many from what I've read.

As far as I know, the Alda is on the driver's side. The Intake Manifold is on the passenger side. So, why do you have to take the IM off again?

tbomachines · #11 07-08-2009, 08:51 AM

The 2.5 has the funky over-the-valvecover manifold which ends up sitting on the driver's side but going over the VC to the intake on passenger side. To get to the IP and ALDA you need to remove it.

tbomachines · #12 07-08-2009, 09:07 AM

I actually have a question regarding the ALDA while this thread is active. I went to adjust the screw on top and when I turned the locknut, it turned along with the screw. I have a feeling this isn't supposed to happen and the ALDA is broken, though I didn't feel any "breaking" (woudln't surprise me to learn that the PO broke it). Am I right in assuming that the locknut should turn independently of the screw, and that if it IS turning, the internal assembly is broken? When I got the car, the cap was already off, and the car smokes quite a bit on WOT - I was actually going to turn it down, though my mileage and accel are both decent, just wanted to get it to stop smoking so bad.

tangofox007 · #13 07-08-2009, 09:24 AM

Quote:

Originally Posted by tbomachines

Am I right in assuming that the locknut should turn independently of the screw, and that if it IS turning, the internal assembly is broken?

Most likely, the locknut is just "stuck" to the screw. Put a counterhold (and maybe some penetrating oil) on the screw while you turn the nut.

tbomachines · #14 07-08-2009, 10:14 AM

Quote:

Originally Posted by tangofox007

Most likely, the locknut is just "stuck" to the screw. Put a counterhold (and maybe some penetrating oil) on the screw while you turn the nut.

So I am adjusting the screw by turning the locknut (while it is stuck to it)? How easy should it be to turn? I have heard horror stories of how fragile the screw is. Is the ALDA threaded on the inside for the screw, or is it actually jsut held on by the locknut, meaning me turning both at the same time/rate does nothing to adjust it? What are the symptoms/telltale signs of an internally broken locknut?

Sorry for all the questions!

toomany MBZ · #15 07-08-2009, 11:21 AM

I had the same thing, the entire ALDA turned, but I was able to loosen the lock nut and make the adjustment. There are two large nuts below it, clamp on to the top one, you should be able to break it loose.