Author Topic: Truck jerks BAD when shifting into reverse/drive  (Read 4236 times)

Offline tyler5726

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Truck jerks BAD when shifting into reverse/drive
« on: September 15, 2017, 05:44:49 PM »
I have an 80 Chevy 1 ton pickup (automatic tran) that jerks BAD when shifting into reverse or drive. A friend told my it could possibly be the u joints so I checked them and there is no play. There is maybe 1/4" play in center carrier bearing rubber, which I think is normal? Also, when I'm driving and step on the gas pedal pretty good it will shift really hard into gears and the tires rear will skid for a second. I noticed a week ago that red fluid was leaking under the truck and the fluid was slung on the driveshaft and all under my truck from driving it.  Anyone have any idea of what could be causing this? Thanks in advance!!

Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #1 on: September 15, 2017, 05:47:48 PM »
Also it's a 2wd

Online VileZambonie

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #2 on: September 15, 2017, 06:17:58 PM »
Check your transmission mount. Maybe bring it to a shop for a diagnosis.
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Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #3 on: September 15, 2017, 06:32:42 PM »
Didn't even think about the mounts , I'll check those and see. Thanks

Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #4 on: September 16, 2017, 06:56:11 PM »
I checked the mounts and they look good. Any other suggestions? I've searched all over the internet and asked some buddies but still can't figure out what it could be.

Offline Irish_Alley

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #5 on: September 17, 2017, 04:26:22 PM »
how did you check them? is there any oil on them?
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Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #6 on: September 17, 2017, 04:43:35 PM »
I took video of the engine and transmission while I revved the engine and shifted gears and saw no movement out of the ordinary. A mechanic friend told me it may have something to do with the ring/pinion. I did notice today I have a leak in the transmission pan and low on oil. I'll replace that. Not sure if low trans oil could cause it.

Offline arby87

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #7 on: September 18, 2017, 08:58:30 AM »
Low tranny fluid can cause hard shifting- do you know which transmission you have?

Seems the general opinion is 2 of the 3 model of transmissions these trucks came with do not handle low fluid levels very well (TH350, 700R4) while the third model (TH400) handles low levels a little more gracefully. But this is coming from a newb, take with a grain of salt.

Leaking fluids is normal, but enough to splatter the underside of your truck might be a bit more serious.

Also, search the forum for clunking into reverse- you might have a driveshaft greasing issue (regular maintenance).

Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #8 on: September 19, 2017, 07:43:49 PM »
I have a TH400 transmission. I just got finished changing the trans filter, oil and oil pan gasket and it still jerks. it sounds like a loud banging/clunking noise coming from the rear end area and jerks the truck forward and back pretty hard.

Online bd

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #9 on: September 19, 2017, 08:20:01 PM »
Are the symptoms new, meaning that it just recently began its harsh engagement?  What is the idle RPM of the engine?  Might the transmission have a shift kit in it?

With the park brake firmly set, engine off and the transmission in neutral, rotate the driveshaft in either direction until it stops.  Next, rotate the driveshaft in the opposite direction until it stops.  Roughly, how many degrees did the driveshaft rotate stop-to-stop? 
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Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #10 on: September 20, 2017, 07:04:05 PM »
I removed the diff cover today and did not see any metal shavings or chunks of metal. Gears looked good. I'm starting to think maybe the u joints. The symptoms I'm having keeps pointing to the u joints (what I keep seeing on google). My u joints have no play when trying to move them, could they still be bad?

Offline tyler5726

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Re: Truck jerks BAD when shifting into reverse/drive
« Reply #11 on: September 20, 2017, 09:33:48 PM »
Another thing I should add is (this has only happened a hand full of times) but every now and then while I'm driving down the road my whole truck will start shaking a vibrating, almost to the point where it could give me a headache! The steering wheel doesn't shake but the whole truck will.