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d.binding 06-02-2008 01:03 PM

no gear change
i have a chevy g20 van it has decided not to change out of first gear, i havechanged the fluid and filter but no change , any ideas?

richard stewart 3rd 06-02-2008 02:03 PM

First post, Hi I'm so&so from somewhere, I've been
doing this & that,(your project)
Second post, I have a year, Chevy van W/type of trans. that no longer shifts, I've don this & that,
& there is no change, can someone please help,
You will get a response this way.
Welcome to hotrodders, glad to have you with us

jimfulco 06-03-2008 11:22 PM

Any idea what year van or what type of transmission?

d.binding 06-04-2008 03:28 AM

no gear change
hi its a 1981 g20 van six cylinder engine and thm350 auto box with cable kickdown

jimfulco 06-04-2008 04:40 AM

Try the easy/cheap stuff first. First thing I'd check is the linkage, just to make sure it's not actually in low range when you think it's in drive.

Then check the vacuum modulator. It's on the back of the transmission, I believe on the right-hand side. There's a pic below. It should have a vacuum line attached, which runs up to a vacuum source on the intake manifold. If the modulator is defective, or if the vacuum line is leaking, the trans will only shift out of first gear at high rpm, no matter what position the throttle is in. The line should be metal, with rubber connections on both ends, but sometimes they get replaced with a long rubber tube, which might collapse with age and heat.

The straight part of the above modulator will be inside the transmission, and the hose connection may be at a right angle compared to the one pictured.

d.binding 06-04-2008 11:26 AM

no gearchange
hi i have checked the conections on the vacuum pipe they are ok, but it does not go to the intake manfold it goes to a fitting on the sprk plug side of the engine,i have pulled the pipe off when the engine is running and there is vacuum present. there is a single wire going to a plug on the left side of the gearbox above the oil pan what is this for?

C-10 06-04-2008 02:33 PM

Check out the modulator too. Draw a vacuum on it and make sure it doesn't leak off.

Also, check the plastic governor gear. It could be stripped. This is located on the driver rear of the trans. Remove the round cover and pull the gov out.

Check the valve for sticking while you have it out.

d.binding 06-04-2008 11:02 PM

no gear change
thanks i will check the modulator and governor gear

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