03 Allison problems

Steve_Kibbe

Steve_Kibbe

Well-Known Member
Joined
Oct 26, 2005
Location
Spartanburg, SC
My sister has an 03 chevy with a duramax/allison combo 137K miles.
Lately its been holding a gear longer than normal before it up shifts.
When she gets off the interstate it will some times make the engine rev near 3000+ rpms.

All this is/has been while its not in tow/haul mode and unloaded.

It had a superchip programmer in it but I have since removed it.

It had 2 codes P0700(tran Ctrl Sys Error) and P0842(tran Fluid Pres Sensor/switch A Circut Lo) When she got home from Charleston the other day.

We took it to a local shop and they said it needs to be rebuilt for $3-4K.

Before she spends the money what do y'all think?


FYI the programmer has always been set on "tow safe mode" (the lowest setting) and the truck hasn't been abused.
 
Last time changed fluid?
Or depending on the cost of the solenoids just replace them. Not comparing the alison to the 4l80e but there were similar recommended troubleshooting steps. But when they cost $25 each and there are only a handful of solenoids and the main pressure plate/sensor. I'd consider doing that if possible. (obviously understanding you could be introducing a new problem with new unproven sensors)
 
i agree replacing them is the best thing to do, but replacing them may not fix the issue. if you switch them and the same code returns, it is most likely an issue within the "c" clutch circuit.(an internal problem)
if you switch them around and the code changes, i would then replace all 3.
 
just out of curiosity, when was the fuel filter last changed? Dirty filter on duramaxs cause a lot of stupid stuff to happen that doesn't "say" fuel filter. PO700 is just a generic, "turn the light on" code. it needs to be like a 729, 732,etc to be specific. that would get you a lot closer to a resolution. But i'd try the filter first. Search on duramaxforum.com, they can prolly help alot.
 
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