1994 Transmission vacuum shift a4ld

[zkt@meso]

Have to pop the vacuum (let off accelerator) to upshift any gear.
Replaced modulator a few years go.
Modulator and line holds mouth vacuum.
Replaced the vacuum line ends at manifold. No change
Found fuel reg vacuum line laying unpluged. Fixed. No Change
21.5 inches vacuum at idle.


Plan is to connect V-guage and take it for a drive.
Then disconnect and plug each V line and see if anything changes.

My bet is that a V diaphragm is busted somewhere.

Any ideas?
Thanks

 

[zkt@meso]

The tranmission mechanic is leaning toward a throttle body gasket leak or something internal. Did elaborate on what.
I bebuilt a toyota 4speeed a few years ago but it was soleniod operated. I cant think of anything internal that would effect all the shift points pretty much the same like this. But I dont know how the modulator type works. Surely I wouldnt have to past the valve body and have to pull the whole thing.

Does anyone know how a vacuum guage should read during a moderate speed test drive?

 

[something9000]

while driving if the vacuum system is closed it should measure the same driving as it is sitting. it sounds like the modulator is not working correctly. That could change the shift points enough that the pressures that would regularly make the trans shift are no longer doing so which is why your having to let off the throttle.

 

[wood1]

Does the delayed 1-2 shift seem to go away once the transmission warms up?

Should ask when the last time you adjusted the bands and services the transmission was (fluid/filter). Also, did it work well after you replaced the modulator?

 

[zkt@meso]

Replaced the modulator a couple years ago and it woked fine till now. There wasnt any trans oil in the vacuum line at the manifold. Hard to believe its the modulator. Never adjusted anything on the trans. Wasnt aware that there are any external adjustments.
This morning when it was cold outside it shifted 1-2 sort of ok one time. When it warmed up- no shift.
What should the vacuum be at say 1/4 throttle? At what vacuum should it shift?

while driving if the vacuum system is closed it should measure the same driving as it is sitting. it sounds like the modulator is not working correctly. That could change the shift points enough that the pressures that would regularly make the trans shift are no longer doing so which is why your having to let off the throttle.

Does the delayed 1-2 shift seem to go away once the transmission warms up?

Should ask when the last time you adjusted the bands and services the transmission was (fluid/filter). Also, did it work well after you replaced the modulator?

 

[something9000]

do you have to take your foot off the throttle for all the shifts? also how does it act it you go 1-2-d-od?

 

[zkt@meso]

do you have to take your foot off the throttle for all the shifts? also how does it act it you go 1-2-d-od?

Yes. All the shifts are the same. Its not jerky, the shift is smooth and everything is normal except that ya gotta let off the accelerator to shift.

 

[wood1]

I would like to know that too. You should change the fluid and filter and adjust the bands first. Contaminants in the fluid can cause issues with the governor and VB (valve body) sticky valves etc. I would also adjust the kickdown cable. There are threads in the transmission section on how to do these things. Without doing these things it would be hard to figure out what the problem is, it's kind of like trying to pin-point why your engine is running crappy but you have never done a tune-up.

 

[zkt@meso]

It is nothing like that. This is not a degenerative problem; one that gets worse and worse, but one characterised by a sudden change- something broke.
I have presented specific symptoms and asked specific questions that will lead to the resolution of the problem.
How about hooking a vacuum gauge up to your Explorer and giving me some meaninglul info regarding vacuum and normal shift points?

I would like to know that too. You should change the fluid and filter and adjust the bands first. Contaminants in the fluid can cause issues with the governor and VB (valve body) sticky valves etc. I would also adjust the kickdown cable. There are threads in the transmission section on how to do these things. Without doing these things it would be hard to figure out what the problem is, it's kind of like trying to pin-point why your engine is running crappy but you have never done a tune-up.

 

[toomanyfords]

is the new modulator you installed a few years back aftermarket? Something like that I would prefer to have a ford part. If it was replaced with an aftermarket part I would replace that and go from there if that's what fixed it the first time.

 

[zkt@meso]

Post from Mikeman about 8 years ago:
"--------------------------------------------------------------------------------

I think it wouldn't hurt to get your hands on a manual, though. I don't know for sure that your problem is the modulator, I was just going from past experience (that's why I used the weasel words "in some cases"). The manuals used to have some tables giving speeds for the various shift points and vacuum. You would adjust the modulator until you got the shift points at the right conditions. You're right in thinking that the modulator affects shift points. "

Vacuum and speed shiftpoints - anybody have this manual?

 

[edwithers]

Seafoam

I've have a trans in my 94 Exp xlt that always changed gears hard, especially 1st to 2nd. Would go to 3500- 4000 RPMs before banging hard into 2nd, and then slipped quickly to 3rd and 4th immediately. Dealer and trans shop said said they would have to take it apart to investigate. I tested the vacuum hoses for leaks and did a Seafoam (1/2 can in the brake booster line) treatment to the vacuum lines and ever since, it changes gears as easy as my old man's Buick. If I keep the lines clean then it shifts so quietly that I have to watch the tach to know it's changed gears. Ed

 

[zkt@meso]

I've have a trans in my 94 Exp xlt that always changed gears hard, especially 1st to 2nd. Would go to 3500- 4000 RPMs before banging hard into 2nd, and then slipped quickly to 3rd and 4th immediately. Dealer and trans shop said said they would have to take it apart to investigate. I tested the vacuum hoses for leaks and did a Seafoam (1/2 can in the brake booster line) treatment to the vacuum lines and ever since, it changes gears as easy as my old man's Buick. If I keep the lines clean then it shifts so quietly that I have to watch the tach to know it's changed gears. Ed

Interesting! Had never heard of that. Thanks for the knowledge.
Mine is still the same. Its actually become second nature to let off the accelerator to shift now. Its probably increased my gas mileage to keep my foot out of it.