05 1500 4.7 just started doing this today. Started off with just 2 small hard downshifts while idling slow through traffic. Got home & looked it up on the computer went to Oreillys to buy a TPS sensor and on the way over it was worse at 1st then. Check engine light came on after it was bucking and skipping out of 1st gear and maybe another skip little bit again in 2nd gear. Left Oreillys and didn't do it even once all the way home. It doesn't feel like the transmission it feels like something electronic interfering w the transmission at low speeds. The codes it is throwing are P0700 & more specifically P0731 &P0734. I've read possible TPS sensor, (i bought one) tran speed sensor and tran solenoid control. Now Im leaning towards downshift solenoid How can I troubleshoot this? as of now I think it may be a sensor or solenoid. Around here I dont trust any mechanic so unless someone knows a specific tool to diagnose I can hold them to. Im in denver mechanics out here in my experince are upselling every job. How can I diy diagnose between TPS & solenoid? those are my 2 best leads, imo.

 

You most likely have a 45 or 545RFE transmission. I would drop the transmission pan and inspect the accumulators on the side of the valve body and check for debris in the pan as well. The 3rd and 4th gear accumulator snap the screw heads and bend the bracket. Causing no 3rd or 4th gears and set a P0731 gear ratio error in 1st.

 

I plan on dropping the transmission pan tomorrow for a visual. I read the filter may be the culprit as well. However, I do not believe this is a mechanical issue just by the way the vehicle is acting. The shifting is very erratic & seems electronic vs a mechanically consistent flaw. Like I said It didn't do any jumping or hard shifting on the way home from Oreilly's. On the way there it jumped about 6 times mostly in 1st or 2 gear. The chk engine & error codes just happened on the way over there as well. they are new. I've read you may not get a shift solenoid error code & can instead get P0731-35 because of the shift solenoid. My fluid is also super clean. I prob won't take it in. I don't have the $ for a mechanic. Instead, I will troubleshoot by swapping out the solenoid & the tps. If that doesn't work, then I will go from there.

 

If the filter is the problem, you wouldn't have any forward or reverse gears.

 

good to know. this morning I drove it to work (only 5 min from here) and back. No hiccups whatsoever. no hard downshifts, no skipping from stop. More indication it's electric. Im prob going to try the solenoid 1st just because bad shift solenoid seems to have the closest related symptoms.

-Dano

 

P0700, P0731 were the two codes my 45rfe threw, Dont waste money on sensors, I dropped over a $1000 after reading so many posts on what would fix it, another $200 at the Tranny Shop to find that my Tranny is now a paper weight.