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06 LBZ code P0756 SS "stuck off" HELP NEEDED BADLY!!

2K views 8 replies 4 participants last post by  Allwhitelb7 
#1 ·
05/06 lbz ccsb 4x4 without front driveshaft., dsp5 switch for efi, but its unknown whos tuned it, lift pump, ATS trans, rebuilt clutches, all new solenoids, new TCM, fluid flushed about 4 times, tcm connector re wired. Looked for bad wires, or rubbing issues. Havent ohmed anything yet but figured it couldnt be that difficult or time consuming but its now costing me and my pocket.
The owner is a farmer that is about to throw, what i think is a good tranny away when its not needed, everything stated above and probably more.. has not fixed this exact issue stated below.

limps after reaching 170 degrees, il be going down in gears, coming to a stop sign and once it hits 2nd or 3rd, CEL comes on and its now in limp mode. Reset the codes, drive down the road through all gears, boom does it every time coming to a stop, almost.. im thinking its either

1. Customer keeps giving me "premium ATF, ORIELLYS BRAND"
2. the pressure switch on the valve body.
3. Its not really a shift solenoid stuck off.

I just want this truck out of my shop and good to go for the owner. I own 2 lb7s, one lly, never came across this issue and it seems not a lot of people have. Doesnt throw any other codes. So if i can get pointed in the right direction, im donating a 100$ to whomever directs me in the way of fixing this issue, or to any charity that they choose(other than their own).

Im working with a SNAP ON SOLUS ULTRA on 17.somethen and love for duramaxs.
 
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#2 ·
One quick determination could be made by swapping a known good TCM to the truck you are working on. Otherwise it could be shorted wiring, needs a new harness, needs PSM, stuck or sticky ss2, and of course, the correct trans fluid just might do the trick!
 
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#3 ·
Appreciate the reply! Doing the switch tomorrow so hopefully i can report back with a fix. Any other advice you can give me? Anything of the matter as to what data i can record and look at or what patterns to see, if not all, appreciated greatly!
 
#4 ·
#5 ·
Hey thanks! Yea i understand its the wrong fluid, it literally says on the bucket dont use in gm after 05 or 06 or somthen. I was pretty ticked off about it, then to find out pops(my dad) filled this tranny with the same fluid on previous flushes. Now its in my hands. Do you think it can cause my pressure issues? What happened supposedly is with this being a farm truck, its getting ran around by kids that see a dsp5 switch and go romping it, ate up the trans and TC, its been to Mauls shop, Flynns shop here in illinois, most reputable diesel shops closest to me anyways, so here we are with a trans that we dont know whats been done, said to be done, and ACTUALLY done. Im gonna ohm pins today and maybe rule it out. Or try a trans relearn a few times. I really need an idea of where to begin with this solenoid stuck off. The old man doesnt follow rules as u can tell so hard telling what his color blind seeing eyes did to the VB solenoids....ugh...
 
#8 ·
Have you talked to Mike L at Inglewood Transmission? He is probably the most knowedegable Allison expert in the business. He is a straight, no BS guy.
https://inglewoodtransmission.com/jm1/
 
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