4l80e swapped in, overdrive not working
4l80e swapped in, overdrive not working I have a 2005 5.3 (dbw) swapped in a 66 El Camino that I've been driving around for a little over 4 years now with a TH400. Last week I got a 2003 4l80e swapped in which is a fresh rebuild by a local shop and it mostly works except for overdrive. I have HP Tuners, did the segment swap twice now using the full write option, transmission wiring I double checked last night and as far as I can tell is correct. In the scanner software while driving, if I command 4th gear it'll work. Cruise control also works which is going to be nice for the longer trips but without overdrive, kinda sucks.
There is the PRNDL switch (2 socket style) on the side that has just the 4 range wires hooked up plus the ground wire. In HP Tuners it's set to "none" right now. I've tried the other options with no change in 4th gear. Another thing is, it freewheels with the shifter in 4th while coasting downhill. RPMs drop right to idle when I'm doing 60 down the road. Under load (driving back up the hill), moving the shifter from 4th to 3rd doesn't change RPM, also in 3rd it doesn't freewheel when coasting. TCC seems to be working in 3rd plus when I command 4th through the scanner. Showed about 1700 rpm in 4th locked up doing 60 mph.
Spent 3 days so far trying to figure this out and it's time for some fresh brain power lol. Thanks for any suggestions.
There is the PRNDL switch (2 socket style) on the side that has just the 4 range wires hooked up plus the ground wire. In HP Tuners it's set to "none" right now. I've tried the other options with no change in 4th gear. Another thing is, it freewheels with the shifter in 4th while coasting downhill. RPMs drop right to idle when I'm doing 60 down the road. Under load (driving back up the hill), moving the shifter from 4th to 3rd doesn't change RPM, also in 3rd it doesn't freewheel when coasting. TCC seems to be working in 3rd plus when I command 4th through the scanner. Showed about 1700 rpm in 4th locked up doing 60 mph.
Spent 3 days so far trying to figure this out and it's time for some fresh brain power lol. Thanks for any suggestions.
first thing that comes to mind is the shifter linkage, misadjustment.
Maybe put it into 4th manually with no cable and drive it.
You want that P/N switch working also. check the wiring and set it in the computer to PRNDL so it knows what gear you are in: this way you can tell if the computer is recognizing the trans is in 4th or not.
Maybe put it into 4th manually with no cable and drive it.
You want that P/N switch working also. check the wiring and set it in the computer to PRNDL so it knows what gear you are in: this way you can tell if the computer is recognizing the trans is in 4th or not.
Cable slips in and out of the arm no problem, should be adjusted correctly. Im using a B&M Pro stick shifter, really similar to the hurst quarter stick. Does every single wire need to be hooked up on the prndl switch? From the reading I've done so far, seems only the range wires are really needed and that's only for a crank re-learn. The reverse light, NSS parts people recommend just because it's a better switch than what you bolt onto the shifter.
I left the PRNDL wires in the harness as per the instructions on LTswap.com. It allows the computer to show each gear. I am not sure I would like being ignorant of what gear the trans selector "thought" it was in.
I can't even get the HP Tuners scanner to show what gear the transmission is in, not even in my stock Silverado. At any rate, I don't believe it's a switch problem but of course could be totally wrong. Came across a post with my exact problems but the person just faded away and never said if they got it working right. Some suggested it was a tune problem and I've seen mentions of segment swaps going bad or other incompatibilities. I have a couple ideas to try out so maybe something will pan out before throwing in the towel and heading to a shop.
Teching In
Joined: May 2007
Posts: 36
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From: Monroe Township, NJ
I had the same issue with my 4l80e but I never trusted the trans because I bought it for $150. I recently changed out both shift solenoids but I never got a chance to try it out since I ended up breaking piece of the bell housing while bolting it to the engine.
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Restricted User
Joined: Mar 2014
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From: Ohio
1,2,3,4 are all commanded by the PCM and the PRNDL switch doesn't relay any of that info back to the PCM. Meaning for forward gears, its completely useless.
I can't even get the HP Tuners scanner to show what gear the transmission is in, not even in my stock Silverado. At any rate, I don't believe it's a switch problem but of course could be totally wrong. Came across a post with my exact problems but the person just faded away and never said if they got it working right. Some suggested it was a tune problem and I've seen mentions of segment swaps going bad or other incompatibilities. I have a couple ideas to try out so maybe something will pan out before throwing in the towel and heading to a shop.
T,
Last edited by TomM; Apr 7, 2018 at 05:43 PM.
And for reverse lights I thought it was important but I've heard of other solutions.
Ok, backstory on the 2003 tune file that's in the car right now. This is from the truck the transmission used to be in. 2003 Silverado 4x4 HD 6.0 What I did was keep the transmission info unchanged and segment swapped 5.3 engine info into it. After that, I took the 5.3 info from my original tune file and put it in so it would run the same. Still no 4th gear and 3rd does lock up. PRNDL is set and this is a 12579405 OS
The El Camino tune is a 2005 GMC Sierra 5.3 I think 2wd, bought the computer off ebay 5 years ago. This one had the 4l80e segment swap done using a stock 2005 Silverado HD tune found on HP tuner's site. 3rd gear locks up normal and I can command 4th through HP tuner's scanner and it'll do it. The PRNDL is set to "none" in this file but I've tried all 3 different options in one night with no change. This is a 12592618 OS
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Joined: Mar 2014
Posts: 7,192
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From: Ohio
If you need an electronic device to tell you a shift cable is properly adjusted, you are in desperate need of some mechanical abilities. A scanner should NEVER be used to tell you a shift cable is properly adjusted.
Well, not to leave people hanging that might search this... I changed out the computer for one that was in a 2003 Silverado 2500. It originally was hooked to the transmission and it's working. Needs some tweaks for the speeds it shifts at but it works normally. Strange deal but all seems well now and it wasn't my wiring lol
