Trans won't shift/lost vacuum locks
 

Hello,
I am new to the forum. I just bought a 1984 300sd. I like the car a lot. I got the car and had the valves adjusted, changed all fluids and filters etc. I have all of the rocords back to the window sticker.

THe problem is that the other day the car stopped shifting out of first. At first I thought maybe the trans had gone out, but when I went to lock the car I discovered the vacuum locking system was no longer working as well. I am assuming some wort of vacuum system problem is the culprit. The trans fluid is in the correct place and the transmission shifted before without flaring etc outside of a slightly stiff first shift. Where should I start or what should I test? WHat are thpossible problems?
- Bad Vacuum pump?
- Bad vacuum modulator?
- just a single loose hose?
- Bad shift control valve? (Is this what it is called?)

Anyway. I work on my own cars volvos, vws etc...
I have a mightyvac...
Thanks for your help,
Benjamin

Your gonna need a mity-vac kit, or something like it.

The W126 chassis 300SD's use an electric central locking pump that has nothing in common with the engine vacuum systems...

The trans will still shift with the vacuum disconnected..just a harder shift.

sd
 

did you change the trans fluid and filter[and drain torque converter]? david poole european performance dallas tx.

Trans Fixed
 

The bowden cable was sticking. It took some lubricant to fix the issue. Thanks for the recomendations.
The vacuum locks are still non functional and the climate control vents aren't working properly either so I still must diagnose this problem. Strange that both problems started on the same day at the exact same time.
Benjamin

Mighty Vac
 

I have a mighty vac kit as stated in the initial post. I am wondering how to apply it to my vacuum problems. Which lines do I tap into and how do I test for vacuum? Is there a relavant thread someone can point me to?
Thank you,
Benjamin

We were fortunate to have a forum member (WHUNTER) organize our DIY Links and articles. They are on the tabs at the top of your screen.

DIESELGAINT

had a great writeup on vac. systems, including the CLS system.

Fixed problems
 

Thought I would post since I stumbled upon this post. The transmission wasn't shifting because the bowden cabled or "kickdown" cable going from the throttle linkage to the transmission was stuck. I added some cable lube to the cable and got it unstuck and now the transmission shifts well.
THe problem with the vacuum locks was simply a fuse.
THanks for the help,
Ben

I believe that the '83 300SD uses the engine vacuum pump for this, and the '85 uses the electric pump. I do not know what's in the '84.

I think that the 84 is in fact the electric pump, so my worry about vacuum was unfounded...