No Drive at All Ranges (zero line pressure)

Nov 11, 2005 10 Replies
J

Hi I have a 4L60E of a 94 Chevy with no drive at all ranges.



Before this happened, there seem to be some problem with downshifting, and I had to manually shift it to lower gears in order to get a good acceleration from a stop. This had been going on for about a month or two. Then one day, while accelerating through about 20mph, I heard a little clicking sound, very light but clear, and suddenly there was no drive at any range.



Now, I checked the fluid level which seem to be normal. Oil was not burned, but I changed the fluid and filter anyway. The pan was actually quite clean with no debries.



The next thing I checked is the line pressure, which, not surprisingly, is zero.



I have worked on trannies before, but I'd like to get some more opinions from the experts here before I start to take out the tranny.



Thanks in advance,



Jizhong



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S

Hate to ask but you have checked to make sure the converter is turning with the engine? Possibly the bolts have come out or the flex plate broke.

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P

Sounds like maybe the pressure regulator has jammed shut.

Professor

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J

Yes, I checked and verified the bolts did not come loose on the flex plate.

I did one more check today on the pressure. I wanted to find out if there is any pressure at all. The gage I used before is a 400psi unit.

I took out the gage so the port was open to the air. Guess what, after I started the engine. no fluid came out. So this is absolutely zero pressure.

Now what?

Jizh>Good question Steve, I skipped right over that.

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S

Didn't the front pump disintegrating used to be one of the classic failure modes of the TH700R4 (a direct predecessor of the 4L60E, if I remember right)? I've had a couple of friends to whom that happened, and I think the symptoms were pretty much identical. I *thought* they had most of the really crummy aspects of the 700R4 ironed out before it went electronic, but....??

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J

If it disintegrated, I'd had least see some debris when I opened up the pan.

Anyway, I'm go> snipped-for-privacy@yahoo.com wrote:

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S

not necessarily. When the pump fails two things tend to happen:

1) fluid quits flowing pretty quickly, so the parts don't necessarily go far

2) any parts would promptly get jammed in all the other parts of the tranny (convertor, valve body, actuators, clutch packs) because the pump SUPPLIES pressure to all of those areas and the last place the fluid goes after the pump is back to the pan....

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