86.5 auto tranny shift "firmness"
12-25-2005, 01:33 AM
#31
Drifting
I'm currently overhauling the automatic on my S4.
You should have a "green" modulator actuator installed. You can find some modulator actuator info in this over haul spec:
http://www.transtec.com/tech_insert/94642.pdf
Our's (4-spd) are based on the Mercedes 722.3 model transmission.
The modulator pressure is supposed to be set at the vacuum control unit with the vacuum line disconnected, while driving at a prescribed speed, on a road or dynamometer, and using a pressure gage connected to the modulating pressure port. Also, see WSM Vol 3, p. 38-110a.
As for rebuilding a transmission, most rebuilts don't last long. The cost of replacement parts (Porsche or Mercedes Benz) makes it difficult to overhaul at a reasonable price, even with less expensive aftermarket parts. It's easy to cut corners.
borland
90' S4, Slate Metallic
You should have a "green" modulator actuator installed. You can find some modulator actuator info in this over haul spec:
http://www.transtec.com/tech_insert/94642.pdf
Our's (4-spd) are based on the Mercedes 722.3 model transmission.
The modulator pressure is supposed to be set at the vacuum control unit with the vacuum line disconnected, while driving at a prescribed speed, on a road or dynamometer, and using a pressure gage connected to the modulating pressure port. Also, see WSM Vol 3, p. 38-110a.
As for rebuilding a transmission, most rebuilts don't last long. The cost of replacement parts (Porsche or Mercedes Benz) makes it difficult to overhaul at a reasonable price, even with less expensive aftermarket parts. It's easy to cut corners.
borland
90' S4, Slate Metallic
Last edited by borland; 12-25-2005 at 01:13 PM.
12-25-2005, 04:16 PM
#32
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Install a vacuum gauge directly into the modulator vacuum hose at the transmission, with the engine running on a healthy engine there should be a steady reading of manifold vacuum present, ”18 to 15 ”HG.
A quick opening and closing of the throttle should drop the vacuum to below 5”. The needle on the gauge should act as an extension of your foot, foot down needle drops foot off needle comes up. The needle MUST RESPONE Quickly, with no lag. Any delay means a restriction in the line.
This is very important; a slow vacuum repose drop in the needle will cause no line/ working pressure rise, a sure way the brunt the transmission; too much vacuum under throttle will also cause no line rise, low working pressure, soft slipping shifts.
To optimize the shifts you must check and adjust if necessary, working pressure. Install a pressure gauge to the working pressure port, with the modulator line disconnected, in drive at 1400rpm stall; pressure must be 16.0 or 15.8BAR depending on your transmission. WSM 38-110a. Adjusting working pressure instead of modulating pressure will compensate for any internal leaks.
To start we need the proper volume of vacuum source, preferably intake manifold vacuum. Install a one-way check valve into the modulator line, close to the manifold with the ARROW facing the intake; we want vacuum flow into the manifold and positive pressure away from the modulator.
With a vacuum gauge do the aforementioned vacuum responses test. If you find vacuum above 20 inches make and install an orifice restrictor into the vacuum line in between the modulator and the check valve to reduce vacuum, you may need to buy a rubber vacuum hose.
Break the steel end off of an automotive glass tube fuse, drill a .020 hole into its center then insert it into the vacuum rubber hose, a home made orifice. Check vacuum response; increase the hole by .005 until you have the proper volume of vacuum source. 18 to 15”HG
As added protection buy and install a vacuum bleed of valve for the modulator. Plug it into the modulator and connect the other end to the vacuum line, the bigger opening is left open, allowing excess vacuum to bleed off. This may create to much bleed off, you can use this first. GM uses it on there turbo grand prix. Part GM # 12397852. You can buy the check valve and hose here. http://catalog.autopartsgo.com/?make...1989&x=41&y=16
I have never done this before so I don’t know if it will work.
A quick opening and closing of the throttle should drop the vacuum to below 5”. The needle on the gauge should act as an extension of your foot, foot down needle drops foot off needle comes up. The needle MUST RESPONE Quickly, with no lag. Any delay means a restriction in the line.
This is very important; a slow vacuum repose drop in the needle will cause no line/ working pressure rise, a sure way the brunt the transmission; too much vacuum under throttle will also cause no line rise, low working pressure, soft slipping shifts.
To optimize the shifts you must check and adjust if necessary, working pressure. Install a pressure gauge to the working pressure port, with the modulator line disconnected, in drive at 1400rpm stall; pressure must be 16.0 or 15.8BAR depending on your transmission. WSM 38-110a. Adjusting working pressure instead of modulating pressure will compensate for any internal leaks.
To start we need the proper volume of vacuum source, preferably intake manifold vacuum. Install a one-way check valve into the modulator line, close to the manifold with the ARROW facing the intake; we want vacuum flow into the manifold and positive pressure away from the modulator.
With a vacuum gauge do the aforementioned vacuum responses test. If you find vacuum above 20 inches make and install an orifice restrictor into the vacuum line in between the modulator and the check valve to reduce vacuum, you may need to buy a rubber vacuum hose.
Break the steel end off of an automotive glass tube fuse, drill a .020 hole into its center then insert it into the vacuum rubber hose, a home made orifice. Check vacuum response; increase the hole by .005 until you have the proper volume of vacuum source. 18 to 15”HG
As added protection buy and install a vacuum bleed of valve for the modulator. Plug it into the modulator and connect the other end to the vacuum line, the bigger opening is left open, allowing excess vacuum to bleed off. This may create to much bleed off, you can use this first. GM uses it on there turbo grand prix. Part GM # 12397852. You can buy the check valve and hose here. http://catalog.autopartsgo.com/?make...1989&x=41&y=16
I have never done this before so I don’t know if it will work.
12-25-2005, 05:10 PM
#33
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Glen,
Turn clock wise too increase pressure; it’s much easier to adjust the rubber cup style modulator. The other one has no performance benefit. You can make the shifts later by adjusting the Bowden / control pressure cable on the throttle linkage, before adjusting the cable make sure you get full throttle on the gas pedal cable first. No slack in the cable. By a lazy 2-3 do you mean a flare up if so it’s usually cause by a leak in the valve body, increasing the pressure my fix it but you are only masking the true cause, a leak. Stop by on your way to Albany.
Turn clock wise too increase pressure; it’s much easier to adjust the rubber cup style modulator. The other one has no performance benefit. You can make the shifts later by adjusting the Bowden / control pressure cable on the throttle linkage, before adjusting the cable make sure you get full throttle on the gas pedal cable first. No slack in the cable. By a lazy 2-3 do you mean a flare up if so it’s usually cause by a leak in the valve body, increasing the pressure my fix it but you are only masking the true cause, a leak. Stop by on your way to Albany.
12-25-2005, 05:53 PM
#34
Burning Brakes
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A quick opening and closing of the throttle should drop the vacuum to below 5”. The needle on the gauge should act as an extension of your foot, foot down needle drops foot off needle comes up. The needle MUST RESPONE Quickly, with no lag. Any delay means a restriction in the line.
This is very important; a slow vacuum repose drop in the needle will cause no line/ working pressure rise, a sure way the brunt the transmission; too much vacuum under throttle will also cause no line rise, low working pressure, soft slipping shifts....
Steve...what would cause "too much vacuum under throttle"... ??? there are no check valves between the 7 way vacuum connector under the engines air filter box, and the vacuum modulator on the valve body of the trans. The 7 way connector feeds direct from the base of the throttle body.
How could too much vacuum be present at the modulator under throttle ?
This is very important; a slow vacuum repose drop in the needle will cause no line/ working pressure rise, a sure way the brunt the transmission; too much vacuum under throttle will also cause no line rise, low working pressure, soft slipping shifts....
Steve...what would cause "too much vacuum under throttle"... ??? there are no check valves between the 7 way vacuum connector under the engines air filter box, and the vacuum modulator on the valve body of the trans. The 7 way connector feeds direct from the base of the throttle body.
How could too much vacuum be present at the modulator under throttle ?
12-25-2005, 06:07 PM
#35
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Darien,
It’s a lot of work to remove, correctly rebuilt the transmission, check the ring and pinion adjust and reinstall, for $3400 that should have included the torque tube. Tran’s mounts and axle boots. The 722.316 number is the right transmission for your ca, USA 1986 model.
Five turns is a lot of adjustment. You can’t just adjust the modulator blindly, without knowing what the pressures or vacuum response numbers are. You have too adjust from the inside out, with a gauge. You would never know if you have an internal problem. You could have too much or no vacuum drop to the modulator. Good luck.
It’s a lot of work to remove, correctly rebuilt the transmission, check the ring and pinion adjust and reinstall, for $3400 that should have included the torque tube. Tran’s mounts and axle boots. The 722.316 number is the right transmission for your ca, USA 1986 model.
Five turns is a lot of adjustment. You can’t just adjust the modulator blindly, without knowing what the pressures or vacuum response numbers are. You have too adjust from the inside out, with a gauge. You would never know if you have an internal problem. You could have too much or no vacuum drop to the modulator. Good luck.
12-25-2005, 06:27 PM
#36
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Jeff,
Tony and Darien have superchargers on their cars, the wrong timing, worn valve springs and SC boost pressure can affect manifold vacuum going to the vacuum modulator.
Tony and Darien have superchargers on their cars, the wrong timing, worn valve springs and SC boost pressure can affect manifold vacuum going to the vacuum modulator.
12-25-2005, 06:32 PM
#37
Burning Brakes
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Sorry...thanks for pointing that out...I was thinking that we were all in an NA world here. But ...that DOES make loads o sense form a "boosted perspective".. 
12-25-2005, 09:04 PM
#38
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Tony,
I am partial to synthetic transmission fluids, mainly amsoil, the transmission will benefit with its lower operating temperature and higher boiling point. Transmission fluid is the means by which the engine transfers its energy/ torque to the transmission, so a quality oil is very important.
Steve Pappy
Posted a shifting comparison of different oils he used in his car. Greg goodspeed used redline oil and said his transmission was shifting very hard; I flushed the transmission using amsoil, its shifts a lot smoother now.
I am partial to synthetic transmission fluids, mainly amsoil, the transmission will benefit with its lower operating temperature and higher boiling point. Transmission fluid is the means by which the engine transfers its energy/ torque to the transmission, so a quality oil is very important.
Steve Pappy
Posted a shifting comparison of different oils he used in his car. Greg goodspeed used redline oil and said his transmission was shifting very hard; I flushed the transmission using amsoil, its shifts a lot smoother now.
12-26-2005, 10:04 PM
#39
Rennlist Member
Steve, thanks for the great advice 
I thought 5 turns was excessive since the only thing we changed was the source of vacuum. I ran a new vacuum line from the throttle body and adjusted the modulator back to the original setting. I can't find in the WSM where the original vacuum line came from (manifold/t-body)?
I thought 5 turns was excessive since the only thing we changed was the source of vacuum. I ran a new vacuum line from the throttle body and adjusted the modulator back to the original setting. I can't find in the WSM where the original vacuum line came from (manifold/t-body)?
12-26-2005, 10:29 PM
#42
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there I go again....(aka Ronald Reagan Vs. Walter Mondale (i think)...anyhoo, I keep forgetting you fellows are discussing a boosted car scenario...and keep "butting in" with my" NA focused" disinformation...I am sorry. I will read and learn from here on out...and try to remember my father's consistent quotation to me,.... about it "being better to keep quiet and be thought a fool...than to speak up and remove all doubt". 
12-27-2005, 10:04 AM
#43
Rennlist Member
Darien,
The vacuum source for the modulator does come from the back of the manifold at the 7 way splitter like Steve said, I just replaced mine. If I remember correctly, the vacuum is picked up from a port on the throttle body, one of the ports on the rear of the throttle body.
The vacuum source for the modulator does come from the back of the manifold at the 7 way splitter like Steve said, I just replaced mine. If I remember correctly, the vacuum is picked up from a port on the throttle body, one of the ports on the rear of the throttle body.
