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06 4.0 auto hard shift on start up

4K views 4 replies 3 participants last post by  SolarColumbia 
#1 ·
2006 4.0 auto when I first start it after it's been sitting for a couple hours it shifts hard between 1st to 2nd just one time then it's ok until you let it sit a couple hours it doesn't do it all the time but a lot here lately. I can disconnect the battery for about 5 min and after that it shifts fine maybe for a couple months or a couple days. With that happening I don't think it's the tranny seems more like the computer. Anyone had this problem or have any ideas. I am still under extended warranty so when we get back from Colorado I may take it in.
 
#3 ·
Have you checked the fluid level? Hard shifts between 1st-2nd (especially when cold) will result from there not being enough fluid in the trans. Depending on how many miles you've got, I'd dump a bottle of Lucas Trans Fix in there which will condition all the seals and help the clutch bands out. I just dumped a bottle into my 2003 Rubicon (123k) and it shifts a little smoother now when it's cold (it shifted perfectly fine to begin with, but I'm the kind of person that fixes it before it's broken haha. I replaced a LOT of stuff on my 2000 TJ that was perfectly fine just because I didn't want to wait for it to go wrong).
 
#4 ·
I don't think it's a tranny prob otherwise unhooking the battery wouldn't temporarily fix it , it's been serviced and I also keep up on maintance. I think it has to be in the PCM and I have read about them being replaced or re flashed to fix it. I would just like to know for sure before I go fight with the dealer to get it replaced.
 
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