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Help needed for '84 Chevy Celebrity - where is vacuum modulator?

Hi All,

I have a 2.8L carbureted Celebrity wagon with a 3 speed automatic. I've been having some shifting trouble from 2'd gear to 3rd gear. On level pavement it's fine, but if I go up a slight hill at around 35mph, the transmission acts like it can't decide whether to stay in 2nd gear or shift to 3rd gear. It will shift back and forth. If I gun it, it will shift to 2nd and stay there. But if I just give it a bit of gas to go up the hill normally, it will shift back and forth between gears. This started happening about a month ago.

Anyway I thought I would check the transmission vacuum modulator just to see if the vacuum line had come off or was split or if the diaphram was bad. The factory service manual shows it's supposed to be right at the front of the transmission - but there is nothing there on my car, no port for it, no vacuum lines, no nothing.

Does this car even have one? Does anyone have any other suggestions? The fluid level is correct and color is good.

Ted

Reply to
Ted Mittelstaedt
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No vacuum modulator on the THM-125.

Check the TV cable and the governor.

Reply to
Neil Nelson

Tranny probally getting weak, mine done the same thing just before it started shuddering on take off and shifting, then it started slipping and then it went out

Reply to
Adam

It would probably be a good idea to change the screen and fluid. Has it ever been done?

Reply to
Woody

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No modulater.

Suggestion....... An adjustment on the TV cable may make the symptom go away, if you can adjust it out to a point where it doesn't raise the shift points too high during normal driving.

That's the only thing you can do yerself, the rest is involved to the point of being mute.

~:~ MarshMonster ~wonders if you checked the fluid level~

Reply to
MarshMonster2624

I did that 2 years ago, as well as flushed the trans with the usual detach cooler line and put it in a bucket, then idle the car and pour in trans fluid into the dipstick at the same rate that the trans was pumping it out method.

The prior owner claimed that he had rebuilt the transmission. I am not sure of how many miles had elapsed since that happened. Could have been quite a few. I'm pretty sure the car had 220K on it when I bought it. (the odo shows only

5 digits plus the 10th of the mile)

Ted

Reply to
Ted Mittelstaedt

Well, that wouldn't surprise me, this trans also has that infamous "jet plane whine" under accelleration which indicates the converter wasn't properly shimmed, if I remember correctly.

Ted

Reply to
Ted Mittelstaedt

suggestions? The

Thanks for the suggestion. I have R&R'd transmissions before and I have a transmission jack and cherry picker and all that, but I don't like doing that involved a project during the winter, it's too cold. And if I did R&R it I would probably take it to a shop to be rebuilt or get one from a wrecker.

Ted

Reply to
Ted Mittelstaedt

Just an update on this one,

I adjusted the TV cable per the factory manual and the problem seems to have gone away. The shift points did go up higher espically when going uphill. It was probably just an old stretchy cable.

Reply to
tedm

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