TH 400 problems
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TECH Enthusiast
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Joined: Aug 2005
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From: Knoxville, TN - Cedar Bluff
TH 400 problems I have a Hummer H1 that I'm working on that has the 6.2L diesel and the TH 400 transmission. The tranny won't shift unless you wind out the motor then it'll bang into gear. I took the transmission to a shop to have it looked at but it checked out fine, they told me to replace the modulator valve and cable that runs to the injection pump. I installed a new valve and cable but it still does this, I've tried adjusting the slack to get line pressure but still have no luck. Could this be a faulty transmission pump or torque converter? Any help would be greatly appreciated, thanks
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Joined: Feb 2004
Posts: 439
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From: burbank ca
vaccuum there is a little, looks like a hat, where the vaccuum hoses connect. one goes to the vac mod and the other comes from the vac pump. it's on the ruel reg by the top rad hose. check the vac on the one going to the trans. if it is very low about 8" you will need to adjust it by turning the ring that has 4 little feet that hold the hat. you may have to use a small pick and break the feet loose from the hat. you turn the feet to change the vac. to the mod. you need 15-18" to have the trans work correctly. l hope you can understand that if not call me. my number is on my site kilgoretrans.com ps by the way you will need a vac guage
