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Old 04-13-2019, 10:27 AM   #1
BurbFam
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1991 4l80e no gears

Hey guys, i've got a 1991 v2500 5.7 TBI with the 4l80e. i pulled the original trans do to hardshifting, and the rear main was leaking anyways. found a used trans out of a 93 motorhome with "36k miles" but it was a 2wd so i had to swap the output shafts. i'm pretty confident with how everything went back together.

i dont know how long the trans had been sitting but the truck hadn't been started for a year. finally got evertyhing put back together and started it up yesterday, it took a bit of effort (even with a new battery and starter) just to turn the motor, like something was holding it back, but once it "broke free" it idled and revved fine. but i have no gears, nothing forward and no reverse.

is there any wiring issues that might cause this? my research brought up possibly a bad pump, maybe thats what was holding up the motor from starting? won't have a chance to pull the trans lines off the check for flow till next week, hoping i can get some more info from the minds on this site until then. Thanks.
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Old 04-13-2019, 11:24 AM   #2
sweetk30
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Re: 1991 4l80e no gears

check trans fluid level engine off . then recheck running . if the same level the pump is not working .

if its 4x4 is the t-case in neutral ? seen this a lot .

how much fluid did you fill the trans with ? and how did you fill it ? these 4l80-e units drink a lot of fluid .
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Old 04-13-2019, 02:39 PM   #3
bigdaddy4x4
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Re: 1991 4l80e no gears

Quote:
Originally Posted by BurbFam View Post
Hey guys, i've got a 1991 v2500 5.7 TBI with the 4l80e. i pulled the original trans do to hardshifting, and the rear main was leaking anyways. found a used trans out of a 93 motorhome with "36k miles" but it was a 2wd so i had to swap the output shafts. i'm pretty confident with how everything went back together.

i dont know how long the trans had been sitting but the truck hadn't been started for a year. finally got evertyhing put back together and started it up yesterday, it took a bit of effort (even with a new battery and starter) just to turn the motor, like something was holding it back, but once it "broke free" it idled and revved fine. but i have no gears, nothing forward and no reverse.

is there any wiring issues that might cause this? my research brought up possibly a bad pump, maybe thats what was holding up the motor from starting? won't have a chance to pull the trans lines off the check for flow till next week, hoping i can get some more info from the minds on this site until then. Thanks.
it sounds like you broke the front pump did you make sure the torque converter was all the way in like its suppose to be ?
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Old 04-13-2019, 07:06 PM   #4
BurbFam
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Re: 1991 4l80e no gears

I was told the pan holds about 6 quarts so i added 6 quarts because the converter felt pretty full, so i let it come up to temp today and checked fluid and added 2 more quarts and checked it again, it was within in range on the dipstick. I shift into reverse and gave it some gas and i jolts but doesn’t go anywhere, i think the parking brake might be stuck.
I put a 6” lift on it before i pulled the trans and it did the same thing. The fluid level definitely changed between checking it while off and running and the fluid lines to the radiator were getting warm so looks like my pump is good.
Hopefully it is just a stuck parking brake.
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Old 04-13-2019, 08:03 PM   #5
sweetk30
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Re: 1991 4l80e no gears

a 4l80 can hold over 14 quart when full .
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Old 04-16-2019, 01:05 AM   #6
kwmech
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Re: 1991 4l80e no gears

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Originally Posted by bigdaddy4x4 View Post
it sounds like you broke the front pump did you make sure the torque converter was all the way in like its suppose to be ?
I can almost guarantee this is what happened.
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Old 04-16-2019, 09:32 AM   #7
BurbFam
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Re: 1991 4l80e no gears

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Originally Posted by kwmech View Post
I can almost guarantee this is what happened.
Already ruled out the pump but thatís for the reply
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Old 04-16-2019, 10:46 AM   #8
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Re: 1991 4l80e no gears

I don't understand how it can suddenly "break free" while trying to start it
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Old 04-16-2019, 11:27 AM   #9
Dead Parrot
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Re: 1991 4l80e no gears

Don't overlook the possibility that the reason a '36k vehicle' was parked was the transmission was busted.

Watch the drive shaft while a helper shifts from R to D and back. Even if park brake is stuck, shaft should move a bit due to differential slop.
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