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4L80E - No reverse

This is a discussion on 4L80E - No reverse within the Technical / Maintenance forums, part of the General Discussion category; I know these threads come up a lot, but I haven't been able to find anything as peculiar as mine. ...

  1. #1
    Registered User bayko's Avatar
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    4L80E - No reverse


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    I know these threads come up a lot, but I haven't been able to find anything as peculiar as mine. The truck is a 1991 K2500 4x4 with a 6.2 diesel/4L80E

    The other night I parked my truck in a parking lot and when I went to leave I found myself stuck. When in reverse the truck just revs up like in neutral, but all other gears work fine and the truck shifts just fine while driving. The truck never made any noise when it happened, nothing. I checked the fluid and it was a little overfilled and smelt burnt, but it looked good and red.

    I talked to a transmission shop and he told me I was basically screwed and to not bother bringing it in because it wouldn't be anything to find without removing the transmission. I've been researching and have found otherwise though. Something about a solenoid possibly? Or some sort of screen that could be clogged up?

    I know I probably am going to need a new tranny(can't afford a rebuild) but I'm just looking for anything to throw at it before I suck it up and spend too much money.

    Thanks

    Also- I'm keeping my eye out for a new transmission, but what do I need to look for? I'm sure I'm not going to find the identical combination. Any year specific things I need etc?

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    ASE Certified Trans Tech transbuilderguy's Avatar
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    Re: 4L80E - No reverse

    you may not need a new tranny the reverse servo piston is bad about cracking in those ans its easy to check drop the pan and there is a cover in ther that has 6 bolts remove that and inspect the servo

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    Re: 4L80E - No reverse

    to shed some more light on this the 80e uses the direct drum o turn reverse so if you have third gear this means that the direct clutches are good and should be able to hold...the only difference is in reverse the reverse band gets applied by the reverse servo which is in the pan those servo pistons are bad about cracking which wil cause a hydraulic leak and not apply the band. OF course the band could be bad but not likley those bands are pretty robust. its the same band used in the th400s and i have taken those apart original from the 70s and the reverse bands are still good lol. Its kinda hard to damage the reverse band.....

  4. #4
    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Do they make replacement servo pistons? That definitely sounds like my problem. Hopefully tomorrow I can get my truck on the hoist and inspect mine.

    Also, when I'm looking for a new tranny, I can use one from a gas truck correct? Is the torque converter different? If so could I use the torque converter I already have?

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    Re: 4L80E - No reverse

    yes the converter will be differnt. I will bet you dont need a new trans I will almost guarantee that the servo is cracked or the seals are blown out. yes they do make a billet servo but its pricey a stock servo is around 15 bucks

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    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Anyone have a part #? I can't seem to find one online anywhere.

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

  7. #7
    bikes cars trucks women vic_V8's Avatar
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    Re: 4L80E - No reverse

    http://www.transmissionpartsusa.com/...-00046956a.htm

    I think this is right, I've only messed with the 4L60e
    Selling a front Chevy Dana 60, 5.38s welded, $1000 never run, PM for more
    1992 K2500 6.5 Turbo Diesel/4L80e/4.10s (sas with Dana 60 just sitting around waiting for a rainy day)
    '84 K10, 6" Tuff Country, now 1 ton frame swap and Cummins swap have begun
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    Re: 4L80E - No reverse

    thats it

  9. #9
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    Re: 4L80E - No reverse

    Should I just buy the part before I drain the fluid and remove the pan? I don't want to have to buy a gasket and fluid twice.

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    Re: 4L80E - No reverse

    the 4l80e gasket is reusable if it has the metal/rubber lined gasket as far as if you buy the part before or after wel lthats up to you.

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    Re: 4L80E - No reverse

    not to hi jack this thread, but transbuilderguy, what would it be if he also lost 3rd?
    Selling a front Chevy Dana 60, 5.38s welded, $1000 never run, PM for more
    1992 K2500 6.5 Turbo Diesel/4L80e/4.10s (sas with Dana 60 just sitting around waiting for a rainy day)
    '84 K10, 6" Tuff Country, now 1 ton frame swap and Cummins swap have begun
    Veteran of Afghanistan (Army SGT)

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    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Quote Originally Posted by transbuilderguy View Post
    the 4l80e gasket is reusable if it has the metal/rubber lined gasket as far as if you buy the part before or after wel lthats up to you.
    Hopefully it still has the original gasket. I'm going to buy the servo piston and get my truck on a hoist hopefully on monday and check it out. How many quarts of ATF do these things take? Everything I've searched says different.

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    Re: 4L80E - No reverse

    the direct clutch pack would be bad..the 4l80e uses the third gear clutches to turn reverse they are applied in third and theyare applied in reverse

  14. #14
    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Turns out my forward clutches are welded together. The guy at the transmission shop told me if I bring the transmission to him, he'll take it apart and tell me what I'll need to do it myself. Should I attempt to do it myself? Or should I wait and pay the $800 of labor?

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Bumping this

    The guy at the trans shop test drove the truck and seemed pretty sure that my forward clutches were welded together because in neutral it rolls forward like in drive and reverse sort of thunks and rolls forward a few inches and park does the same thing. I'm wondering if it could be my linkage or something though, because when I'm in reverse, my reverse lights aren't on, but if I have it a little in between park and reverse, they come on(reverse still doesn't engage though) and if I'm in neutral, its basically drive. I can give it gas and drive normally(I didn't test this over 10mph though).

    I'm just looking for some insight, and I also can't decide whether to rebuild or to NV4500 swap.

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

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    Re: 4L80E - No reverse

    I am interested in this as well. I just had the same thing on an 93 suburban 2500. All forward gears work fine, even low, changed the reverse servo which was a little damaged, put everything back together and still the same. It seems as though it is in forward in all gears. Park, reverse just bog down the engine like it has the brakes applied, but doesnt do anything but shudder. Let me know what you find out. I guess I am going to pull mine and try to rebuild myself. The book is only 30 bucks and it is just basically a hydraulic pump which I am familiar with rebuilding. I am not sure of any special tools besides a spring compressor and lip seal installer. It shouldnt be too hard with some time and patients! Maybe some beer.

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    Re: 4L80E - No reverse

    you didnt say it was lunging forward in N lol then yes if that is happening then there is a problem in the forward drum.

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    Re: 4L80E - No reverse

    I'm sorry about this hijack of the thread, but my granddaughter just was given a '91 C1500 for free. It just had a low-mileage engine installed about a year ago and has an automatic tranny. She got it free because reverse is not working at all. This one does NOT creep in neutral and all other gears are fine. I am guessing that it has a 700R4 tranny in it. Could the reverse problem be the servo piston or is the 700R4 completely different from the 4L80e? I am certainly NO automatic tranny mechanic. I can do everything else on the truck including an engine rebuild. I have just never worked on an automatic. However, I would give it a try for her if it's just something that can be repaired by removing the pan. I have the complete factory manual set for my '90. I'm guessing that the repair procedures would be the same for the '91. Any help would be GREATLY appreciated.

  19. #19
    Registered User bayko's Avatar
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    Re: 4L80E - No reverse

    Quote Originally Posted by transbuilderguy View Post
    you didnt say it was lunging forward in N lol then yes if that is happening then there is a problem in the forward drum.
    Well it was late when it happened, and I was on a forward slope when I tested it and figure that was why I rolled forward. My bad

    2003 GMC 2500HD Duramax
    6" Lift, 35s, 4" straight pipe, PPE stage 3, boost valve, CAT filter adapter

    1991 K2500 6.2L Diesel SM465 swapped(SOLD)

  20. #20
    GMC RULZZ NEUMANNZZ's Avatar
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    Re: 4L80E - No reverse

    Quote Originally Posted by Phantastic View Post
    I'm sorry about this hijack of the thread, but my granddaughter just was given a '91 C1500 for free. It just had a low-mileage engine installed about a year ago and has an automatic tranny. She got it free because reverse is not working at all. This one does NOT creep in neutral and all other gears are fine. I am guessing that it has a 700R4 tranny in it. Could the reverse problem be the servo piston or is the 700R4 completely different from the 4L80e? I am certainly NO automatic tranny mechanic. I can do everything else on the truck including an engine rebuild. I have just never worked on an automatic. However, I would give it a try for her if it's just something that can be repaired by removing the pan. I have the complete factory manual set for my '90. I'm guessing that the repair procedures would be the same for the '91. Any help would be GREATLY appreciated.
    Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


 

 
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