Trans Modulator

[raymire59]

Hi-  Having a hard time finding a replacement modulator. Wanted one of the adjustable aftermaket ones, but having a hard time finding one. Got what was supposed to be one from autozone. Doesn't match the old one- has a built in plunger, unlike the original. Found an old thread about this. The way I read it, he removed the plunger from the new modulator. Tried it. Never got it out- just destroyed it. Anyone familiar with this or have a part# ? Thanks 

[dogginred90]

Go get one for a 1977 Camaro with a 350. It will the right one. Part# for Advance Auto is MD48. And the plunger that is inside the new one should just pull right out. Hope this helps you out and while u r at it get a new check valve aswell. All together you are looking at 15 bucks for both. Smooth tranny shifts PRICELESS!!!

[raymire59]

Thanks for the response. Had already gone to Advance & was given a MD-28 and installed. It also lists TH400 & 350 in application. Not only can you pull the plunger out, but there is also a "spacer" to adjust the length of the part that slides inside the trans. Made sure this part was equal length to original & installed. After removing the original and checking both it & the check valve, I knew this wouldn't solve my problem as both were good, but still liked the idea of fresh parts + adjustability. I guess it's just going to be a trans problem. It "clunks" when going from P to R, R to D, & downshifting. Already replaced all mounts prior to modulator. They all looked good as well. Vehicle has less than 70K. Valve body? ANYBODY????

[dogginred90]

Well the modulator adjusts how hard the tranny shifts. So my guess is try turning the screw a 1/4 turn at a time either way. BUT REMEMBER WHICH WAY YOU WENT AND HOW MANY TURNS, INCASE IT DOESNT HELP THE CLUNKING!!! If the modulator is adjusted right your trans should shift as follows. 1st to 2nd should shift between 12-15mph, 2nd to 3rd 21-24, 3rd to OD 43-50 all at partial throttle. If not adjust the modulator valve and reset your TV cable. And if I am correct the MD28 is different then the MD48 and will shift all wrong. Someone else chime in on this one.

[mfewtrail]

It "clunks" when going from P to R, R to D, & downshifting. Already replaced all mounts prior to modulator. They all looked good as well. Vehicle has less than 70K. Valve body? ANYBODY????

The only thing besides the lower mounts would be the subframe bushings that could possibly cause some clunking on shifts. Even with low miles they could potentially be bad since they're under a lot of stress over the years. If they're in good shape and it still engages harshly, then it's likely an internal issue. A few things including the valve body could cause harsh engagements...

For what it's worth, both my cars engage gears very firmly, but I have no clunking.

[raymire59]

Thanks guys for the responses. I really don't understand why you can't simply purchase the correct modulator per this application unless it's a manufacturing issue of being universal & cutting production cost. I called all around & went to more than 1 parts store and actually purchased 2 modulators. I did all this after much research in "search". Made it sound simple. The first one I purchased I destroyed trying to remove the plunger. Apparently, that one wasn't made to come out. Purchase #2 was from Advance. Couldn't find the brand listed in search locally & needed it back together. I'll probably just put the original back in just to be sure. I'm confident it was good as both it & the check valve would hold a vacuum. Adjustability would be nice though. I'm certain at this point that the "clunking" isn't modulator related but want to be sure what I do have won't hurt.

Concerning the mounts. I had a lot of trouble changing the motor mount, and in the process of trying to find an extra 1-1/2" to slide the new mount in (GM mount that was noticeably taller than what I took out), I finally resorted to removing the mount bolts on the passenger side & greatly loosened the ones on the driver side. Everything looks almost new. By the way, I still had to do some prying for that 1-1/2". Had the jack underneath waiting to control the separation, but only got 1/2". I know it's still connected at the ball joint, but I didn't think I would still have to do some "persuading" to gain enough separation.

At this point I'm thinking something possibly in the valve body. The trans was serviced not long before I purchased the vehicle (fluid + filter). I really wish I knew someone that works on GM FWD transmissions. I seriously don't trust trans shops. Can an "out of adjustment" TV cable possibly cause this? I've dealt with this in a RWD application and it only had an effect on shift points.

Thanks for your time

[Prospeeder]

I find on the mount you have better luck removing the entire horse shoe bracket from the block and take it out with the mount, attach the mount to it, and put it back in. The modulator fixed alot of my harsh issues. Just adjust it untill you like how it shifts. I like my TGP to shift nice and smooth, i cant stand the banging into gear bs.