Drivetrain question

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Dec 20, 2016 | 06:12 AM

Classicdriver

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Drivetrain question

Hello. I have a 70 F-100 with a 390 and a T85 overdrive 3 speed transmission. I have an issue when I let out on the clutch to take off in first gear. When I get about halfway off the clutch, there is a loud thump under the truck, almost like it slips for a second and then drives. It did it several times today for about 5 minutes and then it quit after driving it and getting it warmed up. It was very cold here today, so I don't know if that made it worse but it was worse today than it has been before. I can feel the gas pedal move some too when it happens. It almost reminds me of a broken motor mount but I don't think it is as they are fairly new mounts. Plus the fact that it quit after warming up. Just wanted to see if there was any thoughts on the subject. Thanks

Dan

Dec 20, 2016 | 09:34 AM

Turbo Dog

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From: Laramie, WY

Put a floor jack, or bottle jack, under the engine then transmission. Try jacking them up to see if they move. Even though your mounts are new you should be sure they are tight.

Also have someone operate the clutch pedal, engine off, while you are under the truck. Watch the movement and listen for your thump.

Good luck

Dec 20, 2016 | 12:48 PM

351Cleveland C4

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From: On the Edge of the Desert

Watch the driveshaft and u joints.

Dec 20, 2016 | 01:00 PM

Brian1971f100

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From: Barre Mass

transmission mount?

Dec 20, 2016 | 01:18 PM

Classicdriver

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I have thought of those things. I will make my way out today while it is warmer and jack up the places and check all the mounts, u-joints etc. Will report back. Thanks for the help.

Dan

Dec 21, 2016 | 06:52 AM

Classicdriver

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Checked all the mounts yesterday and everything was good, I also topped off the tranny fluid as well. Since it has the overdrive, I'm wondering if the tranny was just so cold that something in it was just sticking for a minute. It was 3 degrees here the other day. I'm not sure how all that planetary freewheeling deal works. Anyway, drove to town yesterday (at 40 degrees outside) and everything was fine. I don't know. Thanks