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Discussion Starter · #1 · (Edited)
Looking at getting some assistance with a recent issue I've started having. For some background I put on Falken Wildpeak AT3W 285/75R-17 40k miles/3 years ago and adjusted the tire size in the computer using a Superchips programmer at the time. I've towed with it maybe 6 times slow speeds on secondary roads using a tow dolly in tow/haul mode, and took it on the beach also about 6 times in 4-lo with OD off creeping about 5-10 mph. Normally on the highway at 70-75 mph it would cruise around 1800-1900 rpms.

The issue started 2 weeks ago, I was traveling at highway speed (70 mph) and noticed going up a slight incline it was running around 3000 rpms, which if I was putting my foot in it I would expect, but normally I could give it some slight gas before the incline to maintain speed and it would stay in 5th. On the downside it was staying in 3rd, so I cycled through the OD switch from Tow/Haul to OD off to normal and it did then go into 4th gear. I took my foot off of the gas completely and it did shift into 5th but as soon as I gave it any slight amount of gas it would shift down into 4th gear. From a standing start it shifts normally from 1-4 and will downshift like normal with hard acceleration from part throttle.

I didn't want to bring it into the tranny shop with a bucket of parts (been there done that) so I parked it for a couple days until I could get it into the shop. They test drove it with me in the car while running their own Snap-On scan tool that probably cost more than my truck and everything they were seeing looked normal (line pressure, lockup, etc). He called his "tech line" which I'm assuming is Dodge, ahem, Ram, and the only thing they questioned was the tire size, but didn't offer much other help.The one thing he did propose is the plate that mounts to the valve body sometimes the bolts loosen and the plate can bend. He did say it's not definitely the issue and wouldn't know until he cracked it open, he was trying to not just run up the bill. He called it a Shift Kit whic had a thicker plate and longer bolts, I did say go ahead with it since he was going in there anyway. He advised it was not bent or broken, but took it down to inspect the springs which also looked good. The fluid he said was still red like it just came out of the bottle (40k on the fluid) and there was debris in the bottom of the pan and only the slightest of metal on the magnet. I felt better about not putting 14 year old parts back in (my luck the spring would have broken in 2k miles anyway). It is still running the exact same way.

He said everything he is checking in the transmission itself it running as it should, it's downshifting because the computer is telling it to. He was told to check the MAP sensor and the TPS, which he said he is waiting for a general repair shop he deals with to come and check it out. Also I just had this thought, the converter is going into and out of lockup when it should be.

I've read through the forums, and although others have had other problems, nothing specifically like this. I was hoping someone may have come across something similar or can point us in the right direction.
 

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Discussion Starter · #2 ·
Just in case someone comes across a similar issue i was able to find my issue by happenstance. It was due to a vacuum leak in the PCV hose. I have a K&N CAI installed and part of it was to use a longer hose to connect the PCV tube on the front passenger side of the engine to a nipple on the intake tube. While changing my oil i moved the intake tube and when I did the hose fell off the nipple. I put it back with a hose clamp on either end and the problem is gone.
 
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