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1999 k3500 6.5 4l80e issues

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My trucks turning into a night mare 1999 k3500 reg cab long box 6.5 and a 4l80e
The truck kept throwing input sensor codes, changed the sensor fluid and filter now the real issues started, hesitates when shifted into reverse and drive. Atf is clean and full,checked all grounds they are clean. Checked the grey plug in the side of the trans conections clean and its not leaking on the inside of the conector and has a 2-3 shift code P0746 where do i go from here totally lost
 

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THEFERMANATOR

FRANKENBURBAN
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I'm coming up with a pressure control solenoid for a p0746, not a 2-3 shift solenoid. What code was it throwing to begin with? Last thing, was the fluid changed in this trans in the ladt year or so? If so, I hope for your sake dex vi was not used.
 
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Fluid was changed 3000km ago and the code that kept coming up was for the input shaft sensor i changed the sensor and now having the rest of the isssues
 
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#10
I'm coming up with a pressure control solenoid for a p0746, not a 2-3 shift solenoid. What code was it throwing to begin with? Last thing, was the fluid changed in this trans in the ladt year or so? If so, I hope for your sake dex vi was not used.
What is the scoop on NOT using Dexron 6?

I know of 2 trannies that were filled with Dexron 6 just recently
 

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FRANKENBURBAN
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What is the scoop on NOT using Dexron 6?

I know of 2 trannies that were filled with Dexron 6 just recently
I don't care what GM says, but dex vi is NOT compatible with the old seals. I believe the old seals were made from neoprene, and dex vi requires viton rubber to be used. It was such a concern that Allison released a bulletin contradicting GM after they seen transmissions built with the old seals failing roughly 6 months after the fluid was changed to dex vi. These were all older higher milage transmissions so GM said it was age that killed them, but Allison tore them down and traced the problem to failed internal seals. And I believe they finally fixxed it, but early dex vi would wax at temps below -20. It killed many allison's from oil starvation when the fluid turned to wax and plugged the coolers. There was a class action lawsuit brought out because of that problem. Not to mention tbe stuff is thinner than water, hence why I believe it is not approved for use in transfer cases and manual transmissions calling for dex iii(GM still sells dex iii for these, they just call it manual trans lubricant now).
 

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FRANKENBURBAN
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Most of the cases I could find for that code ended up being internal trans issues. You can try new solenoids to see. Another thing to check is make sure no wiring got damaged or pinched when doing the iss. Also check your ignition switch. Many times a flaky trans can be low voltage from the trans fuse inside the cab that supplies power to the transmission. And when the fluid was changed, I hope a dex iii, or dex/merc fluid was used and not dex vi. Dex vi is bad news IMO for transmissions built before 2006.
 

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FRANKENBURBAN
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WOW, and here I was thinking that when it is time for a trans fluid change, I`d go with the XI fluid,glad to have got informed of the possibilities and dangers of using that in My 2000.
Dex vi came out for 2 reasons. The 1st was that the patent on dex iii was running out and GM was getting ready to lose alot of money in royalties. And the 2nd reason was to try and eek out a couple extra tenths of a mile per gallon by going to a thinner synthetic fluid. Not much consideration was given to the base stocks other than it had to work with there new extended drain intervals so they could save a buck by no longer including a trans dipstick, it was a thinner fluid, and they could wheel it out in time to keep the royalties coming in. There was alot of issues with it at 1st, very similiar to say how it was when dex cool came out. I've heard the aftermarket has responded to concerns and the worries of possible legal action for failed transmissions, and formulated there dex vi versions with a seal additive, but why chance it when dex/merc(aka dex iii) is still available.
 

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FRANKENBURBAN
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regarding @THEFERMANATOR

I really enjoy both the knowledge you have to share, and the polite and delicate manner in which you state things like dex6. I just say " it is s**t and they are doing it soley for higher profit only with no regard to the millions and million of current loyal customers.
I was trying to be dignified in conveying this, but your way is a bit easier to understand. It's right up there with all there new engine oil standards, and special oils they make people buy.
 
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Thread starter #19
Fluid is dex 3 i put a new 2-3 solenoid in still get the same code just now t seems to stay in third longer but after a stop it throws the same code again could this be the 1-2 solenoid on its way out as well and the igntion switch is new
 

THEFERMANATOR

FRANKENBURBAN
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Normally shift solenoids work, or they don't. I would be putting a scanner on it and monitoring slippage while in 3rd, and see whats going on if it was mine. I would also go in and command each solenoid electronically, and see if the pressure switches are changing or not. You could also have a pressure switch manifold failing not seeing the shift solenoid change causing this.
 
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