2001 3.5L 2WD chugs/shifts poorly at specific RPM

[barnje07]

Hi All! Any suggestions for my issue would be welcome. My 2001 Pathfinder 3.5L 2WD A/T has two odd behaviors:

In 1st gear, between 1500-2000rpm ONLY, it chugs/shudders - this happens even when it's in D1(first gear).
Additionally, when it shifts from 1st to 2nd or 2nd to 3rd, the engine revs and the shift lockup takes too long (again, this ONLY happens in a 'mild' rpm range, around 1500-2000rpm). If I accelerate somewhat aggressively, there is no chugging and no problem with the automatic shifting, and if I shift manually, there are no problems either.

Background: the truck was perfectly fine before it sat for 2 years with the infamous
TPS/IACV/ECM issue. I finally figured that out and replaced TPS/IACV/sent ECM for repairs. I also replaced plugs, coils, fuel filter,fuel pump, MAF sensor, camshaft pos. sensors, crankshaft pos. sensor front(REF), and I just cleaned/tested the crankshaft pos.sensor rear(POS). I also just dropped the pan and replaced the filter, pan gasket, added an inline magnetic filter, and Royal Purple atf fluid. Whilst I was under there, I believe I verified the operation of the transmission solenoids using procedures from the FSM pdfs I've downloaded (but I don't know for sure).

I've performed the idle learning procedure, it idles perfectly right at 750. I've set the TPS as per the FSM, and I've done the transmission auto-diagnosis(where the O/D OFF light blinks repeatedly) and that's fine. I've driven several hundred miles, mostly highway, in the last two months, and there are no other issues, and it hasn't gotten any worse. I believe the vacuum hoses are all in the right places. The boot/seal on the propeller shaft does not hold it's grease very well, but I have a hard time believing that's related to the issues I'm seeing.

There are no engine codes. It doesn't make any sense to me... if anyone can provide any guidance, it's much appreciated.
thanks!

[302LVR]

You're probably not gonna believe this but i would change that Royal Purple synthetic atf fluid to something regular such as Castrol multi-vehicle atf. While RP is supposed to make good lubricants, i've also heard from a few people they've had issues before with said lubricants. Recently a buddy of mine did an oil change on his Chrysler 300 srt8 using RP synthetic oil and started having low oil pressure readings when he's never had the issue before. Changed back to Mobil 1 and his oil pressure readings went back to normal. Don't ask me why but i'm guessing that maybe the oil is too fine to develop sufficient pressure.

The other thing you can try is adding an additive called Instant Shudder Fixx by Lubegard or Dr. transmission. I had an issue awhile back where my transmission cooler broke inside the radiator on an 01' Explorer and it mixed coolant with ATF. After 3-4 fluid n filter changes the fluid was finally clean but noticed my transmission had a shudder issue as wel and the gears would take a few seconds to engage sometimes. Finally, after adding 2 tubes( 2 fl. oz each), the shuddering and slow shifting went away. Hopefully this will help you out as well. Good luck.

[barnje07]

Update:
I tried the LubeGard Instant Shudder Fix and it had no effect whatsoever. I also added Lubegard Platinum and that had no effect at all.

Clue:
I have noticed that the chugging/shudder does NOT happen immediately following a cold start... once it warms up, however, the chugging returns in first gear.

Someone has to have some idea on here... could the speed sensor or fluid temp sensor lead to this? Transmission control module? I sure hope I don't have to take the transmission apart to figure this out.

[lrwhat]

I'm pretty sure our trucks need lubegaurd "red" , I don't believe platinum would be the right choice , might want to use a trans flush additive and replace your fluid as suggested before with Nissan D or Castrol import or Valvoline , if still having issues after might need tps adjustment possibly also any codes popping up ?

[towncarblue]

i have the same issue, no solution as of yet

[barnje07]

Well, I've been trying to understand how the pressure system in the transmission works by studying the downloadable FSMs.

My suspicion is that the issue is related to the Pilot pressure, since there are no codes to go on and the transmission self-diagnosis also checks out fine, and I know the solenoids and valves are all operational. Possibly a glaze on the pilot filter, and maybe some glazing around the pilot valve... if I'm understanding it properly, that would cause the lock-up issues I'm experiencing. But I still can't explain the chugging in first gear.

I don't want to pull it apart and take the control valve assembly off just yet until I've exhausted my other options. I have ordered Lucas 10009 Transmission Fix 24 oz. I will post an update after i pour that in and drive it for awhile.

[towncarblue]

ill be wAiting for the results

[barnje07]

Well, The various additives have not resolved the issue. I've driven 500 miles and the problem remains. I shall have to remove the control valve assembly from the transmission and take that apart for a full inspection. I have no idea when I'll be able to get to that.

[Rdawg Knox]

Though I am not quite done with my second round of the TPS/IACV issues, I also have this 1-2 shift surge /shudder at light throttle. I have a Auto 4WD, 2002 3.5L.
The ECU was sent out and came back "Clean" no trouble found. Replaced IACV again, and idle started to behave. Shifts were soft and a lot of flair. Then the TPS change, not sure I got the 0% throttle right, but I think so. Anyway, at first the shift was stronger - very clear gear engagement, no flair, but then I did something, and the car stalled again - like it lost it's idle relearn. So - Idle relearn again. Now high idle and the 1-2 shudder/chug is again apparent at low throttle. I also have checked through vacuum lines etc. Though - no guarantee. I have read where possible TPS ground error could cause shift problems. But no sure that I am capable of finding an intermittent ground fault, especially while I have the other issues. look forward to your update on control valve - have you seen the rebuild kit for these. transgo.com
http://www.transgo.com/products.php?prd ... od_start=0
If my shifts don't clean up - after fixing other items. I might look into it - or sell. Not sure your 1-2 chug would be impacted buy the transgo stuff, just figured since you were thinking of taking down the control valve assembly, you were more capable than I was of having a go with it. Good luck - interested to see what you find.