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Old 10-09-2004, 09:46 AM   #1
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Default vacuum modulator

If you have read my thread in the '87-'91 forum, you know I have slow engagement from 2-1 manually. I was reading around in my FSM, and some of the symptoms of a bad vacuum modulator are:

1. Harsh upshifts, and downshifts
2. Harsh Park to Reverse engagement
3. Harsh Neutral to Drive engagement
4. Slow upshifts and downshifts
5. Harsh or firm light throttle upshifts
6. Second gear starts
7. Slips in LOW, DRIVE, and REVERSE
8. Harsh 3-2 coastdown shifts
9. Rough 4-3 and 3-2 manual downshifts
10. Slipping in Drive or Reverse
11. Pressure regulator valve hydraulic buzz
12. Engine burning transmission fluid

I am experiencing, 1, 2, 4, 5, [sometimes 6], [sometimes 7], 8, and 9.

Dr. Jay had posted some links for good Transmission Articles, and one was for a fiero switch, and had a regular vacuum modulator, and an adjustable vacuum modulator. I have not found any documentation in my FSM about an adjustable vacuum modulator, or anywhere else for that matter [for my transmission, I found one from B&M for a turbo 350+400]. Can I just buy any adjustable vacuum modulator? I am going to make it electronically adjustable, and devise some sort of something.. to adjust it from the driver'* seat. Also, I would like to replace all the vacuum lines while I am at it, just because all rubber and plastic on the car is broken.. so I am sure this is true for the lines to the transmission. The FSM lists about 60kPa pressure, I can just use regular rubber lines.. this isn't big pressure, is it? I don't know the line thickness, I still have no clue where the hell this magical line is, but I haven't spent a whole lot of time searching.


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Old 10-10-2004, 07:26 PM   #2
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anyone?

-justin
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Old 10-19-2004, 10:19 AM   #3
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Next order I make from summit, I want to get the B&M one, but its for TH400, this going to work for mine? I don't have a single clue where mine is, so I can't look at it to see if it'll work, i'm guessing it'* just a generic vacuum modulator



I saw this on eBay, and it stirred up my curiousity again. Somebody please tell me if this will fit in mine!


-justin
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Old 10-24-2004, 08:08 PM   #4
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Since nobody is responding to the questions I have asked. I have recently figured out, that my modulator, plus the vacuum line going to it, is shot. This means, I am going to replace it. However, I have a little more information on these questions. The 4T60, has a non adjustable, monster modulator. The 4T60-E, has a smaller, adjustable modulator [i want adjustability]. Now, the picture below, is of two modulators, the one on the left, is the 4T60'* modulator, the one on the right, is the 4T60-E'* modulator. The modulator mounts on the goldish bottom part, and it has the correct lip for the mounting bracket to hold it in place, the only thing i'm questioning, is the little button on the bottom, seems smaller on the E, would that have any effect whatsoever? The vacuum line will need a little modifying, but that'* no biggie.


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