It's pretty common on higher mileage JK/JKUs with the 42RLE auto to have the bushing wear & the shifter mechanism to become fully or partially disconnected at the shift arm the shifter cable connects to atop & to the driver side of the bell housing on the transmission. You have to lie beneth and follow the shifter cable up towards the transmission pan & between the cat and the tranny pan & front driveshaft area. Look up in there & see if your cable is just hanging on.

Search Google on this site for " shifter linkage" if it is what it sounds like.

:jeep2:

 

Do you have forward gears? If so time for a trans rebuild.

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i crawled under everything looks connected and fine. im puzzled..

if the trans does need rebuilt i find it odd since there was no signs of slippage or odd noises. just one day it wont go into reverse. it shifts fine when put in drive

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Sometimes there just is no warning shit just breaks.

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Is the fluid level correct at temp? That is very strange to just
up&and lose reverse ; that's why I defaulted-to the shifter linkage.

I can only suggest what I would do in your shoes & once I verified the mechanical shift was occuring ( as you did) I'd probably throw the rear up onto my jackstands & cycle it through or have someone else move thru gears while I listened & observed the transmission & driveline behavior .


If it isn't the shift linkage it sounds as though it could be the shift solenoid ( R is on manual valve body on the 42RLE )or just the reverse clutch pack , maybe it has gone bad?
I'm surprised your not getting any kind of DTC .

:jeep2:

 

thanks for the advice guys, and merry christmas

im going to dive into it more tomorrow. ive been researching the issues with this trans. one thing i found is something about a snag ring failure, but if that was the problem i would not have overdrive. which overdrive works fine, just like every other gear.


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ok, heres where am at now and im clueless. double checked all the linkage it appears fine, put it the rear up on jackstands. put it in reverse and the tires start to spin backwards, but when i hit the gas they dont spin any faster...

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I believe that's normal vibration
and open-differential rear drive behavior. They will begin to spin but not
w any torque being applied it's only one wheel since both are off ground . Someone was watching & touching ( carefully!) both wheels as you pressed the
accelerator?

( edit: I mean , each rear wheel was verified as not being driven & was not seeing any added torque due to your accelerator pressing ? You can't just watch one ...this is two person work ...or a broomstick on skinny pedal which is scary as shit )

:jeep2:

 

yes. also i got my jeep out of the garage by putting it in 4low and reverse. it moved in reverse but will not go up any type of incline

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now im getting two codes.p1790 fault immediately after shift and P0736 reverse incorrect ratio

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yeah, this is now approaching territory that I know no more than you on..I do know/ have heard that 1790 & the other code go hand in hand usually...& Can be electrical or mechanical ( iows= ambiguous). However, iirc, throw too many of the generic " fault" DTCs & it'll go into limp mode. Someone else can verify this ....

I wonder if this might be electrical or as I sggstd , yhe TCM , maybe ?

I suppose the inability to move on anything but flat ground seems like it might be TC based ...I'd probably have to have someone look at that , man...

:jeep2:

 

im have my local tranny shop look at it friday morning to give me a better idea of the repair needed

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update us when you're able to ; glw the diagnosis & I hope it is minor.

:jeep2:

 

i will, im just suprised no one else incountered this issue before. ive searched every forum and found nothing

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turns out the trans is on its way out. im not having it repaired either. Im replacing the the whole entire drivetrain. chevy v8 swap hear i come. probably a ls1 and hopefully a t56 but might settle for auto. so keep an eye out

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hey man i have a question, my father has had his brought into a shop and they said it was that exact problem, we get the jeep back and the reverse will work for about a day or two just for it to go out again. at this point i feel as if it can no longer be the shifter linkage, but maybe a hairline crack or something in the tranny, this is the 4th time we have brought it into the shop for it to keep going out after a few drives, before it went out the first time, we used to do many things with this jeep without a problem. the shop is reputable and i even know the owner through my brother in law, any advice?

 

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