Adjustable Modulator 4T60E

[3400-95-Modified]

yes further in equals hard shifts, so yeah righty tighty harder...

[karateguy62]

I turned mine all the way in (turning clockwise) then unscrewed it 3 full turns of the screwdriver counter-clockwise. I dont seem to here the pump or it is real faint...should I unscrew it some more or is this adequate???

[Azrael]

Only way to find out is a test drive and keep adjusting it from there.

Would one from a TH350/TH400 work? Summit has a few options there that look the same.

[Azrael]

Found another part# for an adj. mod at NAPA. ATP17783 A little more expensive than 37888 but cheaper in the long run than ordering it from the US for us Canadian folk.

So to recap, all known part #'s for adj. modulators are:
Pioneer - 747017
transmissionpartsusa.com - 37888
NAPA - ATP17783

[IsaacHayes]

I got the Pioneer one on, it just came with the rubber elbow and an instruction sheet for TH350/400/powerglides on how to adjust it for V6 or V8's. It said don't go more than 4 turns in that how it comes or that can damage the trans. But maybe they are referring to TH350/etc and that doesn't apply to our trans? 2 Turns in and it wasn't sticking out farther than the original one... I put it up to 3 turns from out of the box and might go for 4 today. (loosen the bracket that holds it in before turning the screw to relieve pressure on the modulator).

Does anyone know if this just firms up the line pressure at vacuum shifts, or if when at WOT it is firmer as well? As WOT is the increase I'm looking for. I keep bouncing off the rev limiter on occasion on the 1-2 shift since it's gotten cold and I'm making more power. It still shifts fine but just not soon enough.

[PCGUY112887]

I am not sure how it works really. In theory, when at WOT there should be more manifold vac so it would make it shift harder, however we are actually limiting how much vac it gets by screwing it in, and it also makes it harder.

I must not understand something?

All I know is that mine needs to be turned in more

[IsaacHayes]

Wrong. When at WOT, your manifold vacuum drops to 0 (unless your TB or air filter is a huge restriction) When idling or partial cruise your vacuum is high because the motor wants air, but you are limiting it because the throttle plate is closed, so it tries to pull air from anywhere it can, such as the vacuum ports on the plenum. When the throttle plate opens, it can flow as much air as it wants through the TB, so it stops pulling air from the other ports on the plenum because enough is coming through the TB.

A vacuum gauge will show you how much vacuum your car has. The higher the vacuum while cruising, the less air you are sucking and less fuel used, so more mileage. A hot cam will reduce your vacuum at low RPMs. And when engine braking (down shifting and letting off the gas) the vacuum will jump up to full 32inches. They are quite fun to watch even if you don't have boost, and lets you know how good your engine is running and you can strive for more MPG by keeping the gauge pointing towards high vacuum while driving.

The modulator when it has a vacuum on it pulls the plunger on the back inwards. This reduces the push on the thing inside the trans which lowers line pressure. This is so when cruising you'll get a soft nice shift. When WOT, there is no vacuum on the modulator, so it pushes forward, raising pressure so it shifts faster and firmer, so it slips less and shifts quicker, where you won't notice a hard shift as bad as when cruising.

I'm not sure what the screw does, if it moves the plunger out more overall or if it just limits how much it gets pulled back under vacuum which would mean it doesn't affect WOT shifts. You could increase pressure for WOT shifts by getting the modulator to press further inwards, by putting a shim between the modulator and hold down bracket, to force it inward more. Or bend the bracket some. I am not sure what the safe limit is though.

I do know I can not hear the trans pump with the modulator. Only when going into L gear but that's normal.

Another idea is to possibly remove the filter/restrictor that is right before the modulator. I took mine off and noticed it has a screen inside. I'm not sure if it's there to keep oil and sludge out or if it's to buffer air so it responds slower. If you got the manifold pressure changes quicker to the modulator it could help with quicker downshifts in theory.... The metal line though has a small hole in the top where it goes to the plenum though so that limits the amount of air going through it even though the rest of the line is bigger inside. I may try removing that restrictor and see if that makes a difference. It should even with the small hole on the top of the metal line. It's not a check valve though, I know that for sure. That would make no sense to have one there anyways.

[Azrael]

I've done this awhile ago. I screwed it in as far as it would go and backed off 2-3 turns. 1-2 shifts under part-throttle are much more aggressive. Not so much on 2-3. No perceivable difference under WOT. So this seems to just affect your day to day drivability. Still...having a 1-2 shift on an automatic that's twice as fast as most on a manual is a good feeling.

[IsaacHayes]

Yes did some thinking and it's only adjusting the vacuum part of the shifts. I have it at 4 and downshifts seem to be better and quicker since the pressure is already up a bit higher from the get go. When pulling the shifter into L it goes right into it a lot faster with less of a jar and less need for rev matching. Feels really nice. And yes the 1-2 shifts seem much more authoritative but not jarring.

For the WOT one could put an o-ring around the modulator between the hold down bracket to push it a bit more forward. But I'm not sure if that would damage the trans part inside, or if the modulator is already bottoming out the trans part and it would be futile....

[Spankdamonkey]

I get mine tomorrow via UPS, so I'll have to see what all the fuss is about mmmmmm....firm shifting goodness

On a side note, I was thinking of changing out my trans fluid at the same time with Dexron VI......anybody use it yet?

Just checking though, if any further adjustment is wanted after installation, you need to take it back out because the adjustment screw is inside the vacuum connection right?

[PCGUY112887]

Can you even get VI anywhere aside from the dealer?

Even then, it's probably $10+/quart.

[Spankdamonkey]

Actually you can! The ONLY place I have seen it available outside a dealership is zzperformance.com

Here's the link: http://www.zzperformance.com/grand_p...=607&catid=105

$59.99 for 12 quarts....so $5 a quart (less shipping of course)

[IsaacHayes]

I can adjust mine without taking it out. However it says in the instructions to loosen the hold down bracket to relieve tension on it before you adjust the screw. So I've been doing that. It still stays in the trans just moves out, then screw it, then turn the bracket bolt back tight.

[Spankdamonkey]

I just got around to installing the thing NOW at 3:40am (me and my girlfriend of 2 years broke up and I was a little suicidal for the better part of the night so I didn't do it earlier, big whoop wanna fight about it)

At any rate, I set the damn thing all but 2 turns fully in. For the life of me, my trans pump isn't working that hard even at that level or the engine is just too damn loud for me to pick up on it (I could be losing my hearing at the ripe old age of 19 too Damn kids and our loud music)

From the short drive around my street, the light throttle shifts did seem quicker/harder. Not to a great degree mind you, but better. I was under the assumption it would kick like a damn horse (similar to the 2-1 downshift in L when under 20mph, but I always felt like I was DAMAGING it when that happened lol) But I must say overall I am quite pleased with the purchase. Aside from my trans cooler, best bang for the buck longevity wise

[IsaacHayes]

Yeah some shifts it's not so hard others you feel it more. You have to have some decent throttle on it as it's shifting or you won't feel it because there is no force behind it. (like if you let off the throttle completely, and it shifts then)

I do notice down shifts seem to be quicker and when pulling it into L like I said above you don't have to rpm match it as much (or as long before it finally down shifts). The higher pressure seems like the torque converter doesn't slip as much before it grabs too on take off. Seems to feel more connected.