Auto Trans linkage adjustment
12-12-2004, 05:02 PM
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Auto Trans linkage adjustment
I'm a new owner with a '88 AT. I'd like to take the slack out of the trans linkage and the throttle linkage per the instructions in the archives (for 1st gear starts and/or earlier kickdown). I can get the socket off the ball and I can loosen the locknut, but I'm not sure what to do next. I tried loosening the smaller shaft that the locknut is threaded on but it won't budge even with penetrating oil. I'm not sure I'm doing this correctly. Can someone set me straight or tell me where to look for a picture? I have the shop manuals on CD but don't see the linkages. Thanks.
12-12-2004, 06:41 PM
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Funny, I was trying to do that exact thing today, though with the kickdown cable. Same problem, mainly hard because I can't get my hands/tools down past the spider manifold.
12-12-2004, 07:37 PM
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Dont forget that on the 4 speed the adjuster is on lhs of engine bay, adjustment at the front, but on the 3 speed, the adjustment (on mine anyway) is back at the LHS of the box. Sensitive too!
jp 83 Euro S AT 48k
jp 83 Euro S AT 48k
12-12-2004, 08:22 PM
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Yes, on the '88 (and I suspect other later MY's) the linkages are all easy to get to up top on the driver's side. My problem is once I have detached the cable/socket I don't know how to shorten it so it lines up with the ball (archived instructions). I have a little slack in the trans linkage and maybe an inch on the throttle line. Help, someone? Thanks
12-12-2004, 08:23 PM
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On my 86 it's hanging out front near the fan.. loosen locknut, unsnap ball-cup from pivot, spin ball-cup clockwise to shorten (tighten), c-clockwise to loosen cable, tighten locknut, snap onto pivot, done. Fiddle and fiddle until perfect. Got that puppy hair-trigger now, kicks down nice and easy. Vroom.
GOD I WANT WINTER TO END I CAN'T WAIT 4 MORE MONTHS AIEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
GOD I WANT WINTER TO END I CAN'T WAIT 4 MORE MONTHS AIEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
12-12-2004, 08:44 PM
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Yup, loosen the jamb nut and the ball cup should turn on the threaded cable terminal. Try CCW first and hold the terminal end with something so that the twist isn't imparted to the cable itself. If you are REAL unlucky, you could be at the end of the adjustment range already.
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12-12-2004, 09:47 PM
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Yeah, I think maybe I am at the end of the adjustment range. I can only see a couple screw threads on the firewall sideo of the locknut. The trans linkage seems to have about 1/2 inch of slack; the throttle linkage has a good bit more. Sounds like I might be at a dead end. Any other suggestions are appreciated.
12-12-2004, 10:01 PM
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I've just been through all this on my S4.
On the S4 + ... There are 4 cables on the linkage, all with a ball/socket connection. The cable coming from the accelerator pedal has a pin clip safety catch. The cable going to the cruise control also has this safety catch. On both you unclip the safety catch and then pop the socket off the ball.
The cable going to the automatic transmission, and the cable going to the throttle body, you simply pop the socket off the ball. Inside the ball is a tension wire. I use a pair of needle-nosed pliers to pop the sockets off.
For adjustments work from the inside to the outside -
1. accelerator linkage
2. throttle body linkage
3. auto trans linkage
4. cruise control linkage
1. The accelerator linkage is not as important as you think it might be (or is on *ordinary* cars). There is a spring on the linkage that allows you to go to the floor and ensures the throttle plate is fully open. About the only thing here to do is make sure a floored pedal is tensioning the spring some.
2. The throttle body cable should be exact - no tension and no looseness. This is adjusted by turning the plastic adjustment on the housing. If you undo the cable from the linkage housing make sure it is routed through the pulley on its way to the throttle body (you'll have to pull the air box off to see).
3. The auto trans cable should be exact - no looseness, or maybe a hair of tension. That is the factory recommendation. More tension = later shifts. Less tension = early shifts. Early shifts are not useful at all. Later shifts are okay for a heavy throttle but for regular driving around town it's not that comfortable. Another problem is that when you shift from P R or N into a forward gear you will get a jolt, and higher shifts will tend to be firmer. To adjust the trans cable, first loosen the locknut on the socket. Then pop the socket off the ball. Turn the socket on the cable until it fits perfectly (or add whatever tension you think you need), then snap it back on with some pliers, and tighten the locknut.
4. The cruise control cable should also be exact. Tighten the plastic adjustment on the linkage housing so there is no slack.
Basically it's hard to improve on Porsche, and you'll get the best all-around performance with the factory recommendation for the trans cable.
Once you have the shift points correct you can then adjust the firmness/softness of the shifts at the vacuum modulator. This is the little "T" handle on the left side of the transmission. Pop the black rubber cap off the green modulator and raise the little t-handle from the slots. Turn it clockwise for firmer shifts; counter-clockwise for softer shifts. Shifts that are too soft will allow too much transmission slippage which is a bad thing. Try one full turn of the t-handle at a time. Of course this modulator is dependent on good vacuum which comes from the intake manifold via a 5-way tee under the air box. Make sure there are no crimped connectors, or leaks on the other vacuum components (which include the fuel pressure regulator and fuel pressure dampers).
One thing I discovered during all this is that the throttle linkage is has roller bearings. I pulled the linkage pieces off the pin mounted on the intake manifold and cleaned the bearings. Then I reassembled the linkage using a good amount of black moly grease. My pedal feel is noticeably smoother.
There is no kickdown *cable*. There is however a kickdown *button* beneath the accelerator pedal. The pedal itself is adjustable inside the car. Make sure you have sufficient travel to activate the button, and that the pedal travels freely (it can bind on the side kick panel if that is not properly tightened down).
Many owners have wired in a switch parallel to the kickdown button. The net affect is that the trans will downshift earlier. The switch does not automatically cause the trans to shift to the lowest gear possible. It is possible to drive around all the time with the kickdown activated but no one is sure what bad things may happen due to it being always on. The only time I really use the kickdown switch is for an occasional spirited drive in the mountains. By downshifting earlier than full-throttle you are able to get smoother power and avoid a *full-throttle* downshift and its kick in the rear that will break traction in a curve and take you off the side of a mountain. See http://members.rennlist.com/v1uhoh/ for installation and more info.
Our 4-speed automatic transmission is the Mercedes "722.3" model. There is a fair amount of info available if you google it.
Take your time with it all. These are some of those details that make all the difference in a 928!
John Pirtle
87 a/t 171k
http://members.rennlist.com/pirtle
On the S4 + ... There are 4 cables on the linkage, all with a ball/socket connection. The cable coming from the accelerator pedal has a pin clip safety catch. The cable going to the cruise control also has this safety catch. On both you unclip the safety catch and then pop the socket off the ball.
The cable going to the automatic transmission, and the cable going to the throttle body, you simply pop the socket off the ball. Inside the ball is a tension wire. I use a pair of needle-nosed pliers to pop the sockets off.
For adjustments work from the inside to the outside -
1. accelerator linkage
2. throttle body linkage
3. auto trans linkage
4. cruise control linkage
1. The accelerator linkage is not as important as you think it might be (or is on *ordinary* cars). There is a spring on the linkage that allows you to go to the floor and ensures the throttle plate is fully open. About the only thing here to do is make sure a floored pedal is tensioning the spring some.
2. The throttle body cable should be exact - no tension and no looseness. This is adjusted by turning the plastic adjustment on the housing. If you undo the cable from the linkage housing make sure it is routed through the pulley on its way to the throttle body (you'll have to pull the air box off to see).
3. The auto trans cable should be exact - no looseness, or maybe a hair of tension. That is the factory recommendation. More tension = later shifts. Less tension = early shifts. Early shifts are not useful at all. Later shifts are okay for a heavy throttle but for regular driving around town it's not that comfortable. Another problem is that when you shift from P R or N into a forward gear you will get a jolt, and higher shifts will tend to be firmer. To adjust the trans cable, first loosen the locknut on the socket. Then pop the socket off the ball. Turn the socket on the cable until it fits perfectly (or add whatever tension you think you need), then snap it back on with some pliers, and tighten the locknut.
4. The cruise control cable should also be exact. Tighten the plastic adjustment on the linkage housing so there is no slack.
Basically it's hard to improve on Porsche, and you'll get the best all-around performance with the factory recommendation for the trans cable.
Once you have the shift points correct you can then adjust the firmness/softness of the shifts at the vacuum modulator. This is the little "T" handle on the left side of the transmission. Pop the black rubber cap off the green modulator and raise the little t-handle from the slots. Turn it clockwise for firmer shifts; counter-clockwise for softer shifts. Shifts that are too soft will allow too much transmission slippage which is a bad thing. Try one full turn of the t-handle at a time. Of course this modulator is dependent on good vacuum which comes from the intake manifold via a 5-way tee under the air box. Make sure there are no crimped connectors, or leaks on the other vacuum components (which include the fuel pressure regulator and fuel pressure dampers).
One thing I discovered during all this is that the throttle linkage is has roller bearings. I pulled the linkage pieces off the pin mounted on the intake manifold and cleaned the bearings. Then I reassembled the linkage using a good amount of black moly grease. My pedal feel is noticeably smoother.
There is no kickdown *cable*. There is however a kickdown *button* beneath the accelerator pedal. The pedal itself is adjustable inside the car. Make sure you have sufficient travel to activate the button, and that the pedal travels freely (it can bind on the side kick panel if that is not properly tightened down).
Many owners have wired in a switch parallel to the kickdown button. The net affect is that the trans will downshift earlier. The switch does not automatically cause the trans to shift to the lowest gear possible. It is possible to drive around all the time with the kickdown activated but no one is sure what bad things may happen due to it being always on. The only time I really use the kickdown switch is for an occasional spirited drive in the mountains. By downshifting earlier than full-throttle you are able to get smoother power and avoid a *full-throttle* downshift and its kick in the rear that will break traction in a curve and take you off the side of a mountain. See http://members.rennlist.com/v1uhoh/ for installation and more info.
Our 4-speed automatic transmission is the Mercedes "722.3" model. There is a fair amount of info available if you google it.
Take your time with it all. These are some of those details that make all the difference in a 928!
John Pirtle
87 a/t 171k
http://members.rennlist.com/pirtle
12-13-2004, 11:58 AM
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John, thanks very much for your extremely comprehensive guidance. This is definitely Print-and-Keep material. Too bad I have this Monday morning thing called "a job" or I would be going step-by-step through the procedures right now.
I'll report progress soon. Again, many thanks.
Steve
I'll report progress soon. Again, many thanks.
Steve
