Allison drops out of gear

[coalroller83]

So I'm driving my truck along (just maintaining speed) and it acts like it went into neutral! I left off the throttle, and it immediately 'grabbed' again. It will not do it under power, or accelerating, just when your under maybe 20% throttle. No codes in the ECM or TCM. I have a manual TC lockup box, so I activated it while cruising 60 or so, and it still did the same thing! Like I said it will not act up when your in the throttle, but just when your cruising along it will just fall out of gear! Let off the throttle, and its right back! It's a '02 LB7, PPE Stage VI built trans. Any thoughts????


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[Dirtymaxx03]

Sub. I think my chit did this same thing the other day

 

[coalroller83]

Also, the Neutral Safety Switch, internal wiring harness, pressure switch manifold, solenoids F, D, and E have been changed.


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[Mike L.]

Codes?

 

[coalroller83]

Initially, no. Yesterday I checked again, there was 3 "U" codes. I don't remember the numbers, but I'll get them.


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[Mike L.]

U codes are communication problems between the TCM and ECM.

 

[coalroller83]

You're thinking a broken wire?


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[baddaddition]

Almost garuntee ya it a busted wire. Chase it up the loom. I fought and fought mine for weeks chasing them. Check there by the pinch weld where firewall meets floor pan. Its time consuming but worth every hour.GL!!! Keep us posted on what ya find.

 

[coalroller83]

Thanks guys! I'll keep you posted.


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[coalroller83]

Ok... So I pulled the entire wiring harness out, unwrapped it, and tested each wire in the harness, and they all checked out with a continuity tester. I also physically inspected each wire... no kinks or signs of abrasion anywhere!! TCM is not showing any codes at this time, but it's still acting the same. I have now changed EVERY switch, solenoid, sensor, and internal wiring harness on the trans, including the TCM! I'm not sure what's left to check? The TCM voltage is staying at 13.5v when it's acting up, ruling out the ignition switch.


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[LWATSON]

Same think happened to my buddys LMM yesterday, turns out the transfer case is toast. Initially no codes just seemed to go into neutral, wouldn't move regardless of shifter position. I'm no expert but this may be something to look into?

 

[coalroller83]

Transfer case is freshly rebuilt with a pump rub kit, all new bearings, chain, oil pump, speed sensor, encoder motor, and seals.


LB7 CC SB, Stroker CP3, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFI Live DSP5, Turbonetics Intercooler, 66/74 IHI, to name a few...

 

[coalroller83]

Sorry for the delay in posting! I bought another t-case, and it works fine now. Once I have time, I'm going to tear this one down, and figure out what happened. Thanks for all your input!


LB7 CC SB, 10mm Exergy, 30% nozzles, AirDog II 200, PPE Stage V Trans, EFILIVE DSP5, Turbonetics Intercooler, 66mm IHI, ARP studs, Flex-a-Lite fan, AlliLocker, E-Locker, TrueTrac, to name a few...

 

[LWATSON]

I thought someone mentioned that as a possibility? Glad you got it going, report back when you find out what let go in it.