Tranny vacuum leak

[DannyBNH]

I was looking to hopefully replace the vacuum hose that runs from the modulator on the transmission to the hard line that connects to the front/top of the motor.

My shifting is harsh (choppy) between all gears, so It seems to fit the profile of a potential "vacuum leak". I don't have a mightyvac but the hose was cheap so I figured I'd just replace it and see if it was the problem. When I followed the hose from the transmission, it goes to the top of the torque tube then I can't see it anymore. I've read a bunch of threads on Rennlist but I don't know if there is a difference between model years.

On my 84, the hard line goes from the top/front of the motor, runs along the passenger side fuel rail and down the back of the motor. Does the same hard line run all the way down the top of torque tube?

Where does the hard line end/hose begin?


Thanks
-Dan

[stepson]

Dan,
On my '89, I had the same symptoms. I found a thread on RL that gave me some really good hints. Basically, the hard line runs the length of the torque tube. I found that on my '89, I could remove the small triangular heat shield at the front on either side (I removed the passenger side)and use a piece of stiff wire with a hook to "hook" the hard line and pull over so I could see it. I then ran my hands from the end of the hard line to the clip that secures it to the torque tube and unclipped it. This gave me enough maneuverability to slide the new vacuum line from the engine on. I re-clipped it back to secure it and replaced the heat shield. I removed the extra vacuum line from up top.
YMMV.
Good Luck.

[MPDano]

Look at post #430, your culprit will be this hose and/or the one near the tranny fluid reservoir.

$900 1983 US 928S The latest LEO928S

[DannyBNH]

just finished doing both vac lines. The one above the Cat and the one in the back that goes from the modulator to the top of the Torque tube.

It still engages a little harsh, but seems a little better. It seems to be smooth when the car is cold. When it warms up it gets a little harsher. I'm starting to think something under the hood ( rubber ) is cause. I ended up buying a vacuum tester to see if I can find it

[DannyBNH]

A week later and I'm pretty sure my shifting hasn't really improved. It's still harse
after replacing the line from the modulator to the metal line on top of the torque tube and the short one above the cat.

Where do I want to vac test from.. The modulator or somewhere under the hood ?
I probably didn't mention this but it also shifts very early.. Like I'm in 4th at 40 mph.


Thanks
-Dan

[Maleficio]

Replace your fluid.