A4ld shift help

[jd4242]

i know the A4ld is shifted by the solenoid on the side and runs off vac.i have a SC so i need to know how that solenoid works.how does it know when to shift,is it at no vac it shift or a set number of vac it shifts?

this is going to sound alittle crazy but what i really would like to do is remove that solenoid and use an electronic solenoid from a later trans.i then could hook it up to my shift light on my tach so when the light comes on it shifts.anyone know of a electronic solenoid that would fit the bore where the vac controlled one is now?

i dont want to get to crazy with it as the a4 will probably be pulled after summer,but would like to have some control over it till then.ever sense ive done my rebuild on the motor,before sc.it has never shifted on its on at full throttle it just hits rev limiter till you let off or manually shift it.i cant have it bouncing off rev limiter once i put the sc on so need to do something

 

[wood1]

How did Ford handle it with the Turbo Coupe, XR4Ti etc? Seems to me it was a check valve in line with the vacuum modulator? Anyway, my point is it's been done with great success, it has just been too long since I researched home-built forced induction to comment off the top of my head.

The governor handles 1-2 while the VM handles the 2-3 shift I believe. I can check out the Ford manual for more specifics next week if you like. Am away from home right now...

 

[jd4242]

How did Ford handle it with the Turbo Coupe, XR4Ti etc? Seems to me it was a check valve in line with the vacuum modulator? Anyway, my point is it's been done with great success, it has just been too long since I researched home-built forced induction to comment off the top of my head.

The governor handles 1-2 while the VM handles the 2-3 shift I believe. I can check out the Ford manual for more specifics next week if you like. Am away from home right now...

On the a4ld its all done by the vm wile under full throttle,that i do know.i really know nothing about autos,every car and truck ive ever owned has been stick.

 

[wood1]

I will do some reading once I am home again, in the mean time I thought this was mentioned in Maximum Boost (Corky Bell) or some other forced induction how-to book.

 

[Ronin8002]

On the a4ld its all done by the vm wile under full throttle,that i do know.i really know nothing about autos,every car and truck ive ever owned has been stick.

back when I had my vortech kit on my 91 there was a check valve that came with the kit that you installed on the vacuum line for the transmission. Basically it would allow vac but not boost to pass.

 

[wood1]

I see you have never had a full throttle shift after your rebuild, I will have a look to see what the big book says. If you get that issue sorted out the check valve will likely do what you need IIRC that is...

 

[jd4242]

back when I had my vortech kit on my 91 there was a check valve that came with the kit that you installed on the vacuum line for the transmission. Basically it would allow vac but not boost to pass.

Honestly i would just like to replace the vm with a electronic one from like a newer trans like the 4r or 5r then it will shift when i want it to and no dialing in or any of that.

 

[jd4242]

I see you have never had a full throttle shift after your rebuild, I will have a look to see what the big book says. If you get that issue sorted out the check valve will likely do what you need IIRC that is...

Yea never have.it shifts fine under regular throttle but wot it never has shifted,i dont think my motor builds any vac after a certain rpm and pretty sure thats low in the rpm range.but biggest thing is NOONE can explain how a VM works? How and when does it know to shift,at what vac or psi does it shift?

 

[BrooklynBay]

Take a look at this thread: http://www.explorerforum.com/forums/showthread.php?t=239416

 

[jd4242]

Take a look at this thread: http://www.explorerforum.com/forums/showthread.php?t=239416

O wow.its a little confusing though. Does that control the shifts during wot or does it do more than that? And did i see that right,cost over $400 !!???

 

[wood1]

Pretty interesting read. Who woulda thunk it...

 

[BrooklynBay]

They have a special EPC which is designed to replace the vacuum modulator. It's not modulated like the EPC solenoid on the later 4R or 5R. There are switches behind the throttle which vary the pressure. This is in place of the kickdown cable, vacuum modulator, speed governor, etc. The only information that I have is in that thread. I've never seen anything else like it.

 

[jd4242]

They have a special EPC which is designed to replace the vacuum modulator. It's not modulated like the EPC solenoid on the later 4R or 5R. There are switches behind the throttle which vary the pressure. This is in place of the kickdown cable, vacuum modulator, speed governor, etc. The only information that I have is in that thread. I've never seen anything else like it.

Does the vm on the a4 adjust pressure or is a more like a opens or close type of deal?

 

[BrooklynBay]

I think that thread said that it had 2 steps which are controlled by the throttle switches. It should be listed in one of the posts in the thread.

 

[jd4242]

I think that thread said that it had 2 steps which are controlled by the throttle switches. It should be listed in one of the posts in the thread.

No i mean the use version we have,the vacuum type.does that adjust pressure or just a on and off type of deal.like the vacuum controlled fuel pressure regulator of the first gen.

 

[BrooklynBay]

The modulator adjusts the shift pattern by using vacuum from the engine. Engine vacuum varies with load & speed (RPM). Take a look at these links:
http://www.familycar.com/transmission.htm
http://www.ehow.com/facts_6948943_transmission-vacuum-modulator-valve_.html

 

[jd4242]

The modulator adjusts the shift pattern by using vacuum from the engine. Engine vacuum varies with load & speed (RPM).

But how does it work? Does it allow pressure to go by all the time till a set level of vacuum is reached, then closes and stopping pressure from going by?

 

[BrooklynBay]

There is always hydraulic pressure in the transmission. Some gears such as overdrive are controlled by the 3-4 shift solenoid. The part which moves (spool) only acts like a variable valve in one part of the transmission. The kickdown cable lets the transmission know that you need maximum speed to adjust the gears accordingly. The modulator provides feedback for the other gear settings according to the amount of engine vacuum.

 

[jd4242]

Yea i think i wont even worry about hooking it up.i plan on doing a 2.9 5 speed probably after summer