Learn me - Auto trans shifting weird

My family and I have relocated for a fixed term contract to my old stomping ground in Perth, Western Australia. Before we left FL, I placed a deposit on an R51 Pathfinder with a 3L V6 turbo diesel and the same (I think) 7-speed auto that the Titan had in the US. They didn't make many of these so I jumped on one with lowish mileage for the year that was listed by a Toyota dealership that had taken it on trade. The dealer was good enough to put it on a hoist and take a bunch of pics and video for me, and it is very clean. Still, I'm placing a fair bit of trust in the dealership and counting on their reputation as a Toyota dealership. Their online reviews were pretty decent. Pic below:

Anyway , it shifts weirdly:

1. Very slow to go into reverse (3-4 seconds); once I didn't think it was going to succeed, it took so long.
2. Shifts into second ok, but then when it shifts into 3rd, 4th and 5th, it seems to do a "double" shift - changes gear, the rpm's drop, and then takes an age for the rpm's to drop to what feels like the proper rpm for the indicated gear. Not sure if it's the torque converter locking up or one of the other clutches being slow to engage. I can tell it doesn't skip gears as when I change gears manually it still does the same thing and remains in the indicated 3, 4 or 5 gear.
3. Sometimes it changes from 3rd to 4th, and when it's halfway through changing, it seems to slip and shift back to 3rd for a brief second, then finally decide to settle on changing into 4th after all.
4. The final symptom is that when cruising at slow suburban speeds (60-80 km/hr) it will remain in the same gear but the revs "hunt" - it will be running at 1500rpm for 4 seconds, then increase to about 1700rpm for a second, then back down to 1500. Again, seems to be related to the double-shift thing above as it's in the same gears.

Once the trans is warm the double-shift symptom is barely noticeable, but it still hunts around when cruising. It is fine in 1st, 2nd, 6th and 7th, just seems limited to 3rd, 4th and 5th.

The stealership did a flush and changed the filter and it briefly seemed better but it is back to what it was before. The stealership says they had a trans shop just down the street from them and "he reckons it shifts fine now". I have the say the selling dealer is a great guy, the service guys seem to put on a dim-witted air as if they might deflect annoyed customer. They are a decently annoying distance from me so I'm inclined to forget about have the dealer fix it and just get a reputable trans shop to look at it for me, even though it is still under the 3-month used car warranty they offered.

Any advice on what the cause would be? What's my chances of it being a cheap fix? I love the vehicle, just a shame about the trans issues.

No one got any suggestions? Figured I'd learn and maybe someone else would too

In reply to edwardh80 :

That's really annoying. I have no experience with that trans, but having just spent a bunch of money at the dealer I'd be pushing them to do anything & everything they can. 

Is there any way to get the service or warranty history for it, either through the dealer or maybe straight from Nissan?

Maybe talk with the trans shop the dealer used directly, especially since the symptoms returned? It wasn't clear from your summary of the dealer actually had the trans shop drive it or if they just called and talked to them.

It may be easier to reach a resolution if you test drive with the trans shop tech so you can show what happens instead of just describing the problem.

Once you have the verdict from the trans shop then you can go back to the dealer and work with them to get it fixed.

No modern trans should do stuff like that. They are all generally tuned to shift positively rather than sloppily.

Slow shifts are a problem, and will burn up the transmission if it really isn't going into gears for that long, or is stuck "between" gears. In the old stuff I'm used to, I'd be looking at line pressures, filter plugging, that kind of thing causing insufficient pressure to complete a shift. If it's that far out of range though, I'd expect a fault code - there is usually one for excessive shift time. Slow forward to reverse, or slow engagement of the first shift of the day, I've seen attributed to failing pumps and accumulators. that transmission is new enough that I don't know how much of that applies. It is probably all solenoid controlled, so maybe there's a solenoid leaking/blowing off? It should have closed loop line pressure control, so could also be a bad line pressure reference sensor that makes the trans think it is working properly when it isn't.

I don't know how those transmissions do their lockup strategies, but many newer transmissions and diesels in particular lock up the converter in most gears. It should feel like a nice firm shift, but if the converter has issues it will do a two-step like you describe.

I think regardless, it would help  to get a good scan tool and see if you can tell what the transmission is doing. In the GM stuff, for example, you can see lockup, torque converter slippage, etc. which would at least point you in the right direction. If you're lucky it may also give you pressure commands and selected gear.

I'm always jealous of the diesel stuff other markets get - if the transmission is sorted, it seems like that will be a really cool rig.

I have no experience with the 7 speed, but are you getting any flares?  RPMs rising/trans slipping once it is in gear?

If not, you may be able to get away with solenoids/valve body.  Also find someone with a good live-data reader and check two things.  Check when the ECM signals for a shift and compare it to when it actually shifts.  Second, read the trans temp sensor data.  When they fail, they often show an open circuit and something like -150C.  Since the ECM varies things based on trans temp, it could be expecting thicker fluid than it has.

Thanks guys. This is very helpful. Definitely doing something like those flares and two step shifts. I'll get it diagnosed by a specialist, then go back to the dealership and take it up with them.