Transmission not shifting properly

TOMBOYWV

MEMBER
1984 CHEVROLET TRUCK
V8
2WD
AUTOMATIC
150,000 MILES

After pulling out and getting my truck to shift through all the gears as soon as I let off the gas it shifts down. When I put it into neutral and back in drive it works until I let off of the gas again then it shifts down into second again and will not shift back up until I put it into neutral again.

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Hello,

It sounds like you have a vacuum leak to the modulator. There is a vacuum line that runs from the engine intake manifold to the valve. Here is a diagram that will show you the location. Check the hose for leaks and sometimes it just falls off #22.

Check out the diagrams (below).

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

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Saturday, December 16th, 2017 AT 11:30 AM

TOMBOYWV

MEMBER
3 POSTS

I have changed the vacuum modulator, and the tv cable. Checked the vacuum line that runs all the way up to the intake manifold. Nothing has helped. Do you have any more suggestions

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Monday, December 18th, 2017 AT 6:39 PM

TOMBOYWV

MEMBER
3 POSTS

Now when I let off of the gas it acts like it goes into neutral instead of shifting down into 2nd

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Monday, December 18th, 2017 AT 6:42 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

It sounds like you have an internal issue such as a broken sprag or planetary gear. It might be time for a rebuild.

Please let us know what happens.

Cheers, Ken

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Tuesday, December 19th, 2017 AT 12:57 PM