FAQ: Transmission Shift Modulator

after reading a few posts here and a few on the bonnie forum i went out and picked up a transmission shift modulator to increase the line pressure in the 96's 4t60-e tranny. p# MV303 at autozone. cost me all of $12 and took maybe 8 minutes to install.
the new one is adjustable by a small screw on the outside end. my question is; how do i know where to set it? there are no markings. those of you who have the 4t60-e and have one of the modulators installed, where did you set it? turn it all the way in and back it out 3-4 turns?? do i just need to drive it and adjust accordingly?
also, where are the bad area's to set it? i know too soft is bad for the trans and too hard will tear it up too. and if it drops hard into D i should back it out some right?
thanks for any input.
Matthew

I'm surprised it didn't come with guidelines for initial use. I've read that info somewhere, don't recall though. Have you driven yet at the default setting? I'd set it to shift as firmly as is comfortable on the street. Not TOOO hard of a shift, but you do want to FEEL it. I love the shift settings AA did for me.

yes it has some "instruction" but they are all for settings on other transmissions in old muscle cars. nothing for the 4t60. it does say to adjust 1/2 turns at a time and test drive then readjust. oh well i'll just have to do some driving!

Let me know how it feels and how much you turn it. I'm planning on doing this pretty soon.

I'd carefully take it for a test drive, just moderate acceleration to see how the shifts feel. If pretty mild, start with the 1/2 turns til your satisfied.

just took a quick run around my complex and it feels good. for starters i think the old one just needed replacing! i dont feel the shifts nearly as much right now, but they are much faster. i think i will drive it around tomorrow and see where it sits. of course i cant feel anything but 1-2 shifts in the parking lot, but i'm already liking how it feels.

thanks...now i have to spend more money tomorrow.

i really didnt notice any difference after installing mine.
still shifts too slow for me, I dont notice any difference whether turned all the way "up" or "down".
maybe its just me
the only thing I like is that is half the size of the stock one.

Ok i just bought one and i dont see anywhere to adjust it. I did notice it shifts quicker and smoother( i had some roughness at the 1-2 shift which is now gone) but i think like previously said the stock one was worn out. Its for 15 bucks its kinda worth the extra room and cleaner look in the engine bay.

plus you can shed .2lbs of weight
there is a really small screw on the end that connects to the rubber hose. turn that screw clockwise to firm up the shifts. i still dont have mine set where i want it, and 1/2 turns dont make a decernable difference
you dont realize how worn out the old one was until you replace it, its seems much more responsive to downshifts and i can barely even tell when it upshifts under light throttle.

Still cant find the screw... Any pics?

sure:


clockwise to firm up shifts, though i'm starting to see what drew was saying about no difference between all the way in/out.

the screw is inside that little fitting that the rubber hose connects to.

hmm...that looks different from the one i got.. but i'll check inside anyway. Thanks for the pics.

They aren't all adjustable, are they? Where did you get yours?

I think the adj trans vacuum modulator only affects part-throttle shift points. Unless that is not true for our newer transmissions. I know that is how they work with the older TH350/400 transmissions, where the WOT shifts are governor controlled, not modulator controlled. But I'm no expert, really.

The 4t60 has a modulator the 4T65E (E for electronic) does not have a modulator.

There is only programming and shift kit adjustments for those with a 4T65 aka 97+

ok i finally got it set where i want it. firm but not hard. i can only feel a difference under partial throttle. the shifts are very positive and quick. at WOT they are still smooth and fast but not any harder/softer than the other modulator i had.
one final note: regardless of the difference it made, it's nice to replace the original, and it seems to have made a difference for the better. well worth the $12, and couldn't have been easier to install. i recommended this for any 96 riv!

Looks like I have another $12 to put into my '96.

So when I get it installed should I leave the screw in the default position, test drive moderately, and then readjust? Or is there some adjustment before the install?

you could do that, or turn it in a lot then shift it from park to see if it slams the gear and turn down as needed. you will know on even a short drive if you have it set too hard/soft.

Thanks. I picked it up from Autozone and will install tomorrow.

Well it's in and I like it. My shifts are a little faster and I can definitely tell a difference between it and the old modulator. Some slight adjustments might come over the next few days. I'll just have to drive and see what I like.

i pulled the vac line off my modulator and noticed tranny fluid dripping out of the line and the end of the mod. i also remember the old modulator had fluid inside it.
1.can this be fixed w/out a new tranny?
2.how can i fix this if it can be done easily?
3. is it bad for the vac lines to be sucking up tranny fluid?(i'm sure it is bad, but how bad?)
4. i dont have any driveability issues and i havent lost enough trans fluid to note.

thanks,
Matt

There should not be fluid coming out of that. Indicates a rupture in the diaphragm. Fortunately, the vacuum modulator is replaceable by itself.

the diaphragm of the modulator? or something inside the tranny?