2015 lml trans limp

[stang_j_99]

Hay guys im looking for some insight here, Just finished up a truck and its having an issue. I have a V2. Tuned ECM with one of PPEI's tunes (eco_tow 30HP). Runs great, but cust. was pulling a 40' float and trans set a P0732- 2nd gear incorrect ratio. Talked to tuner and he wanted me to clear code and complete Fastlearn. Sent Cust. out with trailer and problem hasn't returned. Tuners rep suggested this was internal trans, however I don't feel this is the case (26,00 miles and not doing this until now). No less I was wondering if anyone had seem any issues like this. Hoping it just needs to learn adapts.....

BTW I have ZERO exp writing tunes, Im wet and green behind the ears here. So im likely to ask some stupid questions.

[RDLLC]

I just had with same problem on a 15 LML with 25,000 mi. It keeps limping in 5th gear. Im new to righting lml tunes so wondering if something in the file would cause this or is the trans really week? ive already tried to to trans relearn.

[LMMPerrona]

same problem here. 2 trucks that have been tuned with PPEI and had same P0732 code when towing heavy. I dont know what the problem would be I didnt bother to call PPEI. I just told customer its time for trans upgrade. One truck pulls a 5th wheel and the other pulls a boat. He never had that issue before tuning. wondering if trans just cant hold 30hp added in second gear.

[Road]

Common issue with 15+. These tranny run very low line pressure, you can purchase trans tuning to increase line pressure or purchase a solid plug to install with the pressure control solenoid. Always recommend new filters too.

[Nathan Turner]

I have a 2015.5 lml, started having the same issue with it. Iv done quite a bit of research with Allison and GM.It has a T87 tcm witch Chevrolet decided to take over the electronics side of Allison in 2015. Turns out GM started putting there on valve body on witch has a spacer and gasket between the valve body, it has twice as many holes in it to release the line pressure faster takes away the hard Allison shift, that we who pull know is needed to keep the trans from slipping. My builder is working with GM now to try and come up with a solution for my issue.

[Road]

I have a 2015.5 lml, started having the same issue with it. Iv done quite a bit of research with Allison and GM.It has a T87 tcm witch Chevrolet decided to take over the electronics side of Allison in 2015. Turns out GM started putting there on valve body on witch has a spacer and gasket between the valve body, it has twice as many holes in it to release the line pressure faster takes away the hard Allison shift, that we who pull know is needed to keep the trans from slipping. My builder is working with GM now to try and come up with a solution for my issue.

Might suggest to your builder to start putting a line pressure modifier in on all his builds. Brief description is here:

https://whitehorsetuning.com/#!/2011-2019-LML-L5P-Duramax-Line-Pressure-Modifier/p/128949541/category=29609073

May be more info on Dirty Hooker Diesel website.

[Nathan Turner]

He did, and when he tested the line pressure after the install it was still at factory setting. Almost like the tcm noticed the high pressure and opened the solenoid.

[Road]

He did, and when he tested the line pressure after the install it was still at factory setting. Almost like the tcm noticed the high pressure and opened the solenoid.

Solenoid is bypassed it can't control pressure. We have test them and trans tuning in house and everyone else in the game has too. It works. We were all having issues with this at one time but since the line pressure mods, problems have been fixed.....

[Nathan Turner]

Did the test truck have a t87?

[Road]

Did the test truck have a t87?

Yeap

[Kennedy Diesel]

I've got guys out there running around at 28k+ with stock trans and no issues. I'm probably a bit more conservative with my tuning, but I like to keep things together and not wreck stuff...

[staytuned]

My truck has 30k on it and a non deleted tune by me. Also own a transmission shop. Adding the g-solenoid block plug accomplishes the same results as turning off g-solenoid in trans tuning. Either does not increase idle or full throttle line pressure. It does however eliminate the reducing pressure during shifts. I have had all torque limits turned off, ran the tune for a while G-solenoid off and then installed billet plug. It still shifts almost the same as stock but a bit bumpier down low easy driving. I rarely tow but drive aggressively. I just decided to do some additional work on it and add some power so I pulled the trans. All was perfect except the C3 clutch was tiger striped. So it wasn't enough for my non professional tune in 30k miles. I drove it easy for the first 5k to break it all in. I installed a new pressure kit to bump mainline pressure way up, installed all Ex-Excalibur performance/extra clutch packs and the cooling mod PTO covers for the C-3 clutch. I Removed the G-solenoid block and started with stock trans tune. With a bit more power it shifts full throttle about like stock and light throttle feels way better. All this after re-learn, which banged the shit out of gears after the repairs without the re-learn, I just wanted to see how far it had adjusted for soft shifting. So the re-learn put it to a good acceptable level. Still a bit too soft for me so I will turn the G-solenoid back off to see what that feels like. Oh, the tripple disc converter shifts in to lock up quicker and firmer but very acceptable (Actually perfect) Just need to figure out some hex to get it to lock up in 2nd and to adjust vane settings on turbo.

[rcr1978]

May want to rethink messing with the solenoid with pump pressure mods, they say bad things happen. But if you do post pics when you go back in to fix it :)