928 U.K.

Steve i read in an earlier post that you have a copy of checking the gouvernor pressures on the auto trans and i was wondering if you could possibly forward them to me of post them on the board

many thanks

Tim

euro
1984
s2
auto

Steve Cattaneo

Tim,
What makes you think you transmission pressures are out of range?

What symptoms does the transmission have? What have you done?

Post them and I will try to help you.


Steve C
The Great White
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

928 U.K.

long story
the gears started selecting incorrectly(not going into gear at the correct speed.)
i changed the fluid and filter and noticed a bit of sludge in the bottom of the pan and a few very small bits of brown plastic
after i changed the oil the car drove well with positive shift changes apart from top gear which would only select when let my foot off the gas slightly
a week later i took the car out(last night)and it was behaving badly jumping gears again and then it felt like a slipping clutch on a manual car
when i got home it would not bite in any gear just rev up
this morning it will go into gear when selecting and i am going to put it up on ramps to have a look under it
also the bottom cable on the throttle linkage is fairly loose and i notice that the intake where its attached to moves when pulled about(is this normal)

any thoughts
cheers
tim
euro
84
s2
auto

928 U.K.

went to go for a small drive in the 928 and it stopped seleting after about 2 mins checked trans oil and about 250 ml poured out of it.
its on the ramp now any ideas what i should be looking for?

cheers

Tim

Steve Cattaneo

First you need to check the transmission fluid. Check it hot, the car should be running in park. The correct level should between zero max and zero min on the plastic fill tank. Did you install the correct transmission filter? Was it exactly the same as the one you remove (in appearance)? Some Mercedes Benz filters have a longer oil pick up tube, if you install the wrong one it could be hitting the oil pan and restricting the flow. The throttle cable should have no play in it at all.

The TV cable (Bowden cable) controls shift TIMING, EARLY OR LATE SHIFTS; the vacuum modulator controls shift FEEL HARD OR SOFT SHIFTS. It does this by controlling the line pressure (working pressure) in the transmission by way of a load input, vacuum. To make the trans shift later, make the TV cable tighter, no slack in the cable. A loose cable will yield a soft and early shift. This cable is very sensitive to adjustments,

. Use a pair of long needle nose pliers they work well. I’m taking my car to the shop tomorrow (Saturday). I will connect a pressure gage so you can see how it’s done. I’ll try to post the procedure tomorrow. Do not drive the car until you verify line pressure (working)

Steve C
The Great White

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

928 U.K.

Steve is the tv cable the lowest one on the inlet linkage? mine has a lot of play on it can i adjust it at the engine end. should i tighten the throttle cable? any ideas why it did not select any gear and just rev up when selected?any ideas why some fluid poured out when i took the trans bottle cap off

cheers

Tim
84 s2 euro auto

Steve Cattaneo

Tim,
Did you change the filter; was it exactly like the one you removed?
Does the trans. slip when shifting through all the gears 1st to 2nd to 3rd to4th?


Yes, the TV cable is the one on the bottom, spray the cable with WD40, loosen the jam nut, and turn the ball to tighten the cable, adjust it until the ball will fit on the pin, with no slack in the cable.

You over filled the trans. you must drain it. Read above.

Remove the rubber cap from the modulator, check for cracks. Reinstall if its not cracked .if it is buy a new one. MB # 1262770081 If the trans. does not slip on take off, drive it easy see how it feels
the cap is 9264

Steve C
The Great White

928 U.K.

Steve
The shift was occasionally slipping through all the gears however it then would not pick up in any gear and just rev up.
when i filled up the trans when i did the oil filter change i put 6 litres in
the filter looked the same as the one i took out
i will next tighten up the cable as it has a lot of play looking at it there will not be enough adjustment to make it tight where does it connect to the trans?
where is the modulator?and what does it look like?

thanks Steve i am learning a lot about my porsche from you and the rest of the board

Tim

84 s2 euro auto

Steve Cattaneo

Tim,

I read from your post that the trans was slipping when shifting through the gears. Do not drive the car since; the transmission is ALSO slipping on take off. We don’t want to do any more damage. My mistake. You are going to need a pressure gage. I don’t know where you live, but NAPA has a gage with the right fittings for the case. It must be able to read at least 500 PSI. If it reads higher that’s Ok.

First you need to check the transmission fluid. Check it hot, the car should be running in park. The correct level should between zero max and zero min on the plastic fill tank

You need to verify the CORRECT TRANSMISSION FLUID LEVEL. If it’s not right we will get an erratic pressure reading on the gage. Forget about the , throttle cable and the modulator for now, we will look at that later.

Steve C
The Great White
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

michael

Tim wrote: "i changed the fluid and filter and noticed a bit of sludge in the bottom of the pan and a few very small bits of brown plastic"

Tim - is this the same tranny that you reported had no sludge and no bits or pieces in the fluid? I'm confused. If you found bits of plastic, they obviously came from somehwere in the transmission. Continuing to work the tranny knowing that there is something falling apart is not a good idea. You're gong to have to tear in to it to see where those bits and pieces came from.

928 U.K.

Michael

sorry if i confused you.it is the same car and it did have a small amount of sludge in the tranny pan which contined a very few small pieces of brown plastic stuff(about 5 which were approx .5mm by 1mm by 2mm in size) however the oil was clean(red not as red as the new stuff but pretty red) and it did not smell any different

thanks for your input

Tim

Steve Cattaneo

Tim,

To check line pressure your going to have to disconnect the vacuum line from the modulator. The modulator is located on the driver’s side, in the center of the transmission. It has a plastic housing on it. It’s either green or red. You may have to move your heat shield out of the way. The modulator is between A and B

Cold Test

Check the line pressure with the engine cold first. This will aid me in my diagnosis. Start the engine, let it idle then put the shifter in drive. With your foot on the brake make a note of the pressure reading on the gauge. It should read 220 PSI. (15.3 BAR) THE LINE PRESSURE TAP IS - C

Hot Test

The car should be up in the air, safely on jacks. With the transmission in gear, let the wheels turn. Let the car reach operating temperature (above 160 degrees on the temp gauge). When the car reaches operating temperature, step on the brake and read the pressure gauge, make a note of it.

Vacuum modulator response test

Turn the car off; reconnect the vacuum line to the modulator. Start the car and put it in drive. With one foot on the brake and the other on the gas pedal, do a quick opening and closing of the throttle by stepping on the gas pedal then quickly releasing it. While observing the pressure gauge, the needle of the gauge should respond to the movement of your foot on the gas pedal. The gauge should increase in pressure when you step on the gas pedal with no lag (delay) and should decrease in pressure when you release the gas pedal with no lag (delay).

Good luck
Steve C
The Great White

928 U.K.

Good morning Steve(or probally good nignt in New York)
Its 9.00 am here and i am going under to check where the modulator is. i have not been able to locate a vacuum monitor over the weekend but i will try this coming week. the car is up in the air level so i will also concentrate on getting the tranny level spot on the correct levels

many thanks for taking time to help me

Tim

84 s2 euro auto

928 U.K.

mon 12.30

Steve

i have put the correct amount of fluid in the box i drove the car off the ramps and took the car up and down the road went great for a while then it started slipping and then it would not select at all and just revved up when any gear was selected. stopped for a while car went for about 30 seconds just enough time to get home then no movement again.
looked under trans while it was on the ramps and found modulator checked little round cap which was fine but i still can not see where i should connect the vaccum lines.there is a smallpipe above the modulator is that it? and there are a couple of 13 mm bolts on the side on the other side of the tranny where there is a white plastic part with a clip on the bottom with a wire or pipe coming from it.
from the pictures it seems straight forward to check the vaccum lines but i cant see where or what i should attach them to

thanks for your time and effort on this one Steve

(still searching)

Tim

84 s2 euro auto

928 U.K.

Steve

i left the car for 2 hours started it up and the car picked up all the shift gears as it previously had not when warm. checked oil level and it as about 1/2 inch from bottom of checking bottle? thoght this may help in the analysis

cheers

Tim

84 s2 euro auto