Auto transmission adjustment?
09-18-2013, 02:03 AM
#16
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
No vac to the modulator basically means harsher shifts.
The bowden cable more or less dictates when the shift will occur not really the firmness. Tighter..later.......looser..sooner
As stated, an often missed check is the routing of the source of vacuum on the throttle body. The main line needs to be on the correct port.
I will be checking the operating pressure in mine next week. picked up a simple gauge set for about 30 bucks. This is the pressure you need to start with as far as trouble shooting.
for now I would pull the line off the 4 way that goes to the tranny and put a vac tester on it. DO NOT pull on this line to the tranny in hopes you can get more tubing to work with as you can pull the line off under the car in a place you WILL have major work to do to get it reattached.
Ive been doing a lot of reading/searching lately and its amazing how complex the auto transmission is yet how seamlessly it operates.
The bowden cable more or less dictates when the shift will occur not really the firmness. Tighter..later.......looser..sooner
As stated, an often missed check is the routing of the source of vacuum on the throttle body. The main line needs to be on the correct port.
I will be checking the operating pressure in mine next week. picked up a simple gauge set for about 30 bucks. This is the pressure you need to start with as far as trouble shooting.
for now I would pull the line off the 4 way that goes to the tranny and put a vac tester on it. DO NOT pull on this line to the tranny in hopes you can get more tubing to work with as you can pull the line off under the car in a place you WILL have major work to do to get it reattached.
Ive been doing a lot of reading/searching lately and its amazing how complex the auto transmission is yet how seamlessly it operates.
09-18-2013, 04:18 AM
#17
Nordschleife Master
No vac to the modulator basically means harsher shifts.
The bowden cable more or less dictates when the shift will occur not really the firmness. Tighter..later.......looser..sooner
This is very accurate. If you do not have adequate vacuum to the modulator, or your modulator diaphragm is faulted and won't hold vacuum, your shifting will feel like your in a tank.
Also correct adjustment of the throttle and control pressure control valve (Bowden) cables at the cable quad are crucial to have proper throttling and shifting of the car.
As stated, an often missed check is the routing of the source of vacuum on the throttle body. The main line needs to be on the correct port.
I've attached, and am referring to an S4 vacuum system off the intake. I don't know the MY the OP was referring to. The transmission line comes off the 'T' which attaches to one of two ports in the central portion of the intake, in the area of the ISV electrical connections. The other port here has a single hard line to the valve associated with the charcoal canister. The other port(s) for vacuum are located inferiorly on the belly of the throttle body. One port has a single hard line to the air pump valve. On USA California cars there is a second port here. Mine has this port and it is securely capped.
I will be checking the operating pressure in mine next week. picked up a simple gauge set for about 30 bucks. This is the pressure you need to start with as far as trouble shooting.
for now I would pull the line off the 4 way that goes to the tranny and put a vac tester on it. DO NOT pull on this line to the tranny in hopes you can get more tubing to work with as you can pull the line off under the car in a place you WILL have major work to do to get it reattached.
The line to the transmission from the 'T' is not a one piece line. The rubber line off the 'T' unions with a metal hard line above the torque tube on the right side. About 1.5 feet from its terminus at the pressure modulator it joins with a rubber line again. Because of these unions there is opportunity for disconnections and loose fittings/leaks. I replaced this patchworked line with a single steel braided hard line from Pegasus Racing. The #3 line is the size to fit. It is not a difficult task to change out this line. Get the car up, feed line over the bellhouse up front, detach and fiddle with the heat shields, and run your new line to the modulator. I ran line along right side of torque tube and then ran it over to the left in front of the torque converter and had it follow the ATF line and shifter cable till it slid right into the modulator nipple.
https://www.pegasusautoracing.com/pr...p?Product=3260
Ive been doing a lot of reading/searching lately and its amazing how complex the auto transmission is yet how seamlessly it operates.
I've had a transmission failure last summer. I installed one of Greg Brown's new transmissions that he found in the Deutschland. After a careful install, and meticulously adjusting the 'Bowden' cable to suit my driving style, I only had to make the slightest adjustment at the pressure modulator for PERFECT shifts. One doesn't want to adjust the modulator to excess for the bands can be stressed to excesses. I now have a car that feels like... it is new.
The bowden cable more or less dictates when the shift will occur not really the firmness. Tighter..later.......looser..sooner
This is very accurate. If you do not have adequate vacuum to the modulator, or your modulator diaphragm is faulted and won't hold vacuum, your shifting will feel like your in a tank.
Also correct adjustment of the throttle and control pressure control valve (Bowden) cables at the cable quad are crucial to have proper throttling and shifting of the car.
As stated, an often missed check is the routing of the source of vacuum on the throttle body. The main line needs to be on the correct port.
I've attached, and am referring to an S4 vacuum system off the intake. I don't know the MY the OP was referring to. The transmission line comes off the 'T' which attaches to one of two ports in the central portion of the intake, in the area of the ISV electrical connections. The other port here has a single hard line to the valve associated with the charcoal canister. The other port(s) for vacuum are located inferiorly on the belly of the throttle body. One port has a single hard line to the air pump valve. On USA California cars there is a second port here. Mine has this port and it is securely capped.
I will be checking the operating pressure in mine next week. picked up a simple gauge set for about 30 bucks. This is the pressure you need to start with as far as trouble shooting.
for now I would pull the line off the 4 way that goes to the tranny and put a vac tester on it. DO NOT pull on this line to the tranny in hopes you can get more tubing to work with as you can pull the line off under the car in a place you WILL have major work to do to get it reattached.
The line to the transmission from the 'T' is not a one piece line. The rubber line off the 'T' unions with a metal hard line above the torque tube on the right side. About 1.5 feet from its terminus at the pressure modulator it joins with a rubber line again. Because of these unions there is opportunity for disconnections and loose fittings/leaks. I replaced this patchworked line with a single steel braided hard line from Pegasus Racing. The #3 line is the size to fit. It is not a difficult task to change out this line. Get the car up, feed line over the bellhouse up front, detach and fiddle with the heat shields, and run your new line to the modulator. I ran line along right side of torque tube and then ran it over to the left in front of the torque converter and had it follow the ATF line and shifter cable till it slid right into the modulator nipple.
https://www.pegasusautoracing.com/pr...p?Product=3260
Ive been doing a lot of reading/searching lately and its amazing how complex the auto transmission is yet how seamlessly it operates.
I've had a transmission failure last summer. I installed one of Greg Brown's new transmissions that he found in the Deutschland. After a careful install, and meticulously adjusting the 'Bowden' cable to suit my driving style, I only had to make the slightest adjustment at the pressure modulator for PERFECT shifts. One doesn't want to adjust the modulator to excess for the bands can be stressed to excesses. I now have a car that feels like... it is new.
Last edited by MainePorsche; 09-18-2013 at 04:38 AM.
09-18-2013, 06:08 AM
#18
Instructor
OK its been mentioned a few times here and no report of what you found has been given....,
SO do this remove the aircleaner,
then the feed from the 6 way vacuum fitting that goes to the transmission,
NOTE the 6 way is near the MAF unit.
And attach a mytivac to it ,
See if it will hold a vacuum..
Please post the results of this test.
SO do this remove the aircleaner,
then the feed from the 6 way vacuum fitting that goes to the transmission,
NOTE the 6 way is near the MAF unit.
And attach a mytivac to it ,
See if it will hold a vacuum..
Please post the results of this test.
will report back when i get another Mityvac.
thanks for all the helpful replies, BTW.
i received the K1 spring kit and B2 piston kit from Roger to attempt to fix a pretty bad shift flare, but i seem to have it fixed (crosses fingers) with just a bowden cable adjustment. the next order of business is this harsh shifting .....
09-18-2013, 10:38 AM
#19
Instructor
Join Date: May 2013
Location: Austin, TX!
Posts: 141
Likes: 0
Received 0 Likes
on
0 Posts
Vacuum Nipple locations
Also check that the vacuum line from modulator to intake is sourced to the correct nipple on the throttle body. This is important if the intake was ever worked. There may be closely spaced nipples right near the throttle valve that get different pressures base in valve position. If you swap them by mistake then the modulator will not get much vacuum when you lift off the gas pedal and you will get hard shifts even though there are no actual vacuum leaks. The source line for the 5-way should be from on a nipple downstream of the throttle valve.
I am working with the same situation: sorting vacuum to ensure that trans is getting proper vacuum. Yesterday I removed the air box, crawled on top of the engine and took a mirror so that I could see if there were any vacuum lines that I could see. It was a combination of mirror views and feeling around with my hand. So by my investigation I could see two vacuum lines hooked up at ports that each had brass right angle nipples AND what felt like a non-right angle nipple (a third) that was open...I don't find this item on the diagrams....but whatever it it is I capped it. As well there are two brass nipples coming off of the throttle valve (mine is a California car as Craig mentions, I capped the open/unused one they are side by side. )
From Craig's diagram, which I am familiar with, I don't see the two throttle valve nipples included or hooked up to anything.
Anyone have a picture of an '87 intake underside?
I bought a Mityvac yesterday.
Josh
Last edited by Bonton; 09-18-2013 at 01:28 PM. Reason: detail
09-18-2013, 12:11 PM
#20
Instructor
edit: is it this one ... ?
Last edited by Landshark87; 09-18-2013 at 12:37 PM.
09-18-2013, 01:17 PM
#21
Nordschleife Master
I have an '87 S4 auto:
I am working with the same situation: sorting vacuum to ensure that trans is getting proper vacuum. Yesterday I removed the air box, crawled on top of the engine and took a mirror so that I could see if there were any vacuum lines that I could see. It was a combination of mirror views and feeling around with my hand. So by my investigation I could see two vacuum lines hooked up at ports that each had brass right angle nipples AND what felt like a non-right angle nipple (a third) that was open...I don't find this item on the diagrams....but whatever it it is I capped it. As well there are two brass nipples coming off of the throttle valve, I capped the open/unused one they are side by side.
From Craig's diagram, which I am familiar with, I don't see the two throttle valve nipples included or hooked up to anything.
Anyone have a picture of an '87 intake underside?
I bought a Mityvac yesterday.
Josh
I am working with the same situation: sorting vacuum to ensure that trans is getting proper vacuum. Yesterday I removed the air box, crawled on top of the engine and took a mirror so that I could see if there were any vacuum lines that I could see. It was a combination of mirror views and feeling around with my hand. So by my investigation I could see two vacuum lines hooked up at ports that each had brass right angle nipples AND what felt like a non-right angle nipple (a third) that was open...I don't find this item on the diagrams....but whatever it it is I capped it. As well there are two brass nipples coming off of the throttle valve, I capped the open/unused one they are side by side.
From Craig's diagram, which I am familiar with, I don't see the two throttle valve nipples included or hooked up to anything.
Anyone have a picture of an '87 intake underside?
I bought a Mityvac yesterday.
Josh
The vacuum diagram I posted just shows it from a top view. The valve labeled 'I' has a line which attaches to one of the 'underbelly' ports, and this is intimated in the image. There is at least one metal port there, and two if a USA California car.
09-18-2013, 01:20 PM
#22
Nordschleife Master
Yep, that'll be the one. The others off the 'T' go to FPR/dampeners (front and rear), so a total of 4 off the 'T'.
09-18-2013, 01:36 PM
#23
Instructor
thanks, Maine
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
09-18-2013, 01:43 PM
#24
Nordschleife Master
thanks, Maine
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
Nothing is ever easy on the 928.
I go in with that expectation. When I describe something, I leave out all the PITA stuff like things I can barely reach.
Nothing is ever easy on the 928.
Craig
09-18-2013, 01:52 PM
#25
Instructor
09-18-2013, 02:02 PM
#26
Nordschleife Master
09-18-2013, 02:11 PM
#27
Nordschleife Master
thanks, Maine
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
managed to find some pieces of my Mityvac and tested the line ..... slooooow leak. :sigh:
that was a PITA, BTW. i could barely get the vac line back on, no room to move back there. its scary how "easy" some of you make some of this stuff sound!
i guess my next move is to get the car up on jackstands and test the modulator itself. i'm praying its the modulator and not the line ......
When it's up, would be a good time to put in the Pegasus line for peace of mind with trans vacuum. What I did was fed line down from up top, coursed it along the torque tube, secured it to the modulator, then finally cut it to exact length up top so it fit well with no undue angles. The line is firm so it would be difficult to kink. The #3 line requires a little elbow grease to get on the modulator nipple, but it will stay on forever. I have a look at mine from time to time, and after a year and many miles it is still doing its job.
