928newb

So the next thing I am going to do is to replace the tranny filter, fluid, and gasket. I understand that there is a vacuum hose on the tranny that can cause issues when it becomes brittle. Where is it located, and is there anything (not obvious) that I should know before tackling this?

Thanks in advance

Mrmerlin

Hi 928newb, it would be most helpful if you would click on user CP at the top of the page,
and then click on edit signature,
then please add the year and model and trans type of your car.

To answer your question , in general the the vacuum line comes off the rear of the engine
its located under the aircleaner lower housing,
the line starts off at the 6 way splitter on 85 86, S4 and later cars,
and has an aluminum line off the the intake on the spider intakes.

The short flex hose connects to a hard line that runs down the top side of the TT,
to just in front of the trans axle/ TT connection,
then another flex hose is connected to the hard line to the vacuum modulator,
its best to replace both of the flex lines.

928newb

I could only locate one vacuum line, connected to the modulator. It does run on top of the TT towards the engine, but it`s not short. The whole length I was able to see/ touch was that flexible braided variety. Where does it connect to the hard line?

Also, what do I replace it with? The same cloth covered hose or will a silicone hose do the trick?

Mrmerlin

sounds like the system has been modified there should be a metal line running down the TT

NOTE if they replaced the whole line with another flex line and it looks like its in good condition then you may want to leave it alone.
you will have to remove the air cleaner to find out where this line attaches since its not original your going to have to hunt for it

grepin

Hi I am looking into a similar issue with hard shifting. I will get the car in the air and start tracing things soon. However on an 84 16V model does the vac line for the trans go through the fire wall or out the side of the left rear engine bay T.

Thanks

FredR

The vac line goes down the front of the firewall and onto the top of the torque tube where it picks up the solid tubing section. I got some materials from the local MB dealers to do the flexible tubing at the rear and the nylon tubing section on the front end. I also used the flexible tubing to make transition connectors. Make sure the solid tubing is not blocked and is not leaking.

grepin

Yeah i just jacked it up and started the engine with the vac line hooked up to my mighty vac and can see consistent vacuum. But confused as whilst it was disconnected I hooked up my mighty vac to the two lines exiting the engine bay and they held vacuum....with trans disconnected. Anyway it may be the modulator setting. I have no history on the car as I am resurrecting it.

gazfish

There’s a single line running over the top of the torque tube for the transmission, was it a typo?

grepin

No. Happy there is a single line. But I was trying to find where it terminates at the other end. Where does it get vacuum from in the engine bay. Hence I should be able to go to the other end somewhere and put vacuum to it and check it doesnt leak. There are only two options that I can see and both held vacuum with the line to the trans disconnected. Anyway I have confirmed by running the engine its getting Vac.

grepin

It just dawned on me its the hard line off the top front of the manifold. I feel a little dopey. I was trying to make sense of it coming off the brake booster vac system through the one way valve and out the fire wall.