Where on the transmission is the vacuum modulator located?

*IF* it has a modulator valve (?) .. It will be on the passenger side of the transmission With the requested information - we can tell you exactly what you need to know!

Thanks "Pushrod" for the very helpful and quick reply. According to the page linked by you, it can only be the GM Turbo 400 TH400 Transmission, since it is not an overdrive transmission, and the other listings are not for that specific year (1990). I wasn't outside yet but going to go check and fix it today before the weather here in Missouri goes freezing again. According to that, and being I haven't checked the production date yet, the TH400 is the only transmission it can be according to the date profiles, and your help is much appreciated. This is a "fix" even I can handle even with my limited mechanical knowledge, as I already have the part, and going to replace it today. Any other tips would be appreciated. Thanks so much, once again.

What kind of problems are you having with the transmission?

Hey there "pushrod": So sorry for the long delay in replying. I had forgotten my password and have just now finally gotten a replacement password so I could even access the forum to even reply. And thanks for all the patience so far. I found a number on the side casing of the transmission but never found the production number or a sticker on the door. This is a specialized conversion Gladiator van so they may have changed stuff like that for painting and such. But according to the link for identifying the transmission, it matches with the number on the side-casing and the chart link for a GM-7004R. And yes, I found out that it does not have a vacuum modulator. I believe this engine and transmission were taken out of a later model vehicle and replaced. SO by checking all that out, and reading up on the 700R4 while I was stuck off the forum with the pswrd problem,I now know that the 700R4 does not have a vacuum modulator, but as I am sure you know it has a TV cable adjustment. After watching several videos on YouTube about the simple fix of adjusting that TV cable, I attempted to do just that. But the TV cable doesn't seem to adjust right, or maybe I am just lacking knowledge, wisdom and experience on this. Pressing the detente "D" button, and making sure that the bare cable between that TV button and the carb connection has no slack, and then releasing the "D" button, I then push the gas pedal all the way down to adjust it, and it does not seem to adjust, or click or ratchet like it does in the videos on YouTube. SO I am open to any suggestions your practiced knowledge has to offer as to what I should check next or try to do. As I wrote before, the transmission shifts fine when cold, but once it warms up, it refuses to go into the next gear unless you accelerate really high while in gear and moving, and then sort of let off the gas at just the right moment and then it will shift into the next gear. This 700R4 has that overdrive to it also and it will shift into that fine also once moving and accelerating into higher rpms in regular drive and then letting it finally shift into the next gear. Thanks again for being patient and sticking with me on this.

Moving the cable HOUSING forward ‘toward’ the throttle linkage will allow earlier shifts @ a lower engine rpm - - Then, of course, moving the cable HOUSING rearward ‘from’ the throttle linkage will delay shifts @ increased engine rpm. The best thing to do is adjust - test drive - adjust again - as needed until it is fine tuned .. This is also best done with engine cover removed - that way you can adjust the detent cable a lot more easily. Often - the normal or the suggested adjustment procedure doesn’t always work properly - this will take a bit of trial and error .. Make adjustments in small increments. Good luck with it!

Hey Pushrod; Thanks for the time and trouble on trying to help me on ths. I know it is probably taxing on nerves to have to put up with trqansmission morons like me at time. LOL laughing here. You also have a vast knowledge worth its weigh tin gold, and so if I may.... When you say "in small increments"? Just how touchy is this, if you might suggest. Having to take the console on this off, each time to adjust it, is a burger for an old fart like me. haha....its a wind tunnel to drive it and test then reset and test again, so I will have to put the console back on each time and removing it again to readjust. It has full adjustment possibilities now, and when it was shifting, it would shift just high rpm to do so. SO what is considered small, a 1/4 inch at a time, or even slighter movements, like 1/32nd to 1/16th of an inch? Thanks even again for the help. It will be a life saver if this cures the problem.

There should be detent notches in the adjustment latch so it can be adjusted in very small increments - furthermore, you can drive the vehicle with the dog house removed .. I’ve done that plenty of times! Replace the cover when finished.

It has been some time since I last replied and I ask your forgiveness for that. Two rounds of pneumonia and hospitalized prevented me from writing more. I was able to enlist some help from my friends here and we replaced the filter and fluid and wallah! Its like a new transmission. With your fantastic help and divinely patience we were able to resurrect this girl into a like new van mechanically and it is performing unbelievably well. Thanks once more for the help. You are good as gold to us here on the forum as this would have been a $900 rebuild at least. For future reference, this model requires one to remove the transmission crossover support as it restricts the area for pan removal between that and the exhaust up front, leaving no room for pan removal! GO FIGURE ON DESIGN FLAWS EH?