auto tranny hitting hard, again

[JPR]

need a bit of help Guys with a auto tranny issue so here goes !!!
second hand ute (08 stx 2.5 D40) from the start this ute had issues with 1st-2nd, 2nd-3rd. would kick real hard..
then the valve body shat the computer so had it replaced with second hand valve body .
still had a very slight kick from 1st-2nd, 2nd-3rd. no where near like it was. oil was bad too.
scanned codes came up with afr issue so i replaced before cat afr.
then came up with throttle body sensor so took it to auto tranny guys and they said same thing, its not the tranny but electrical in the TB sensor.
replaced throttle body,installed catch can and all is great for a week.
then same **** ! reset computer multiple times and goes away for a bit but now its not going away after rest.
tranny works ok till oil heats up it seams.
flushed tranny oil system with castrol multi vehicle oil. was burnt too much for my liking so assumed tranny guy didn't flush system.
two weeks later oil is still great but keeps kicking.
no TB or any codes coming up.

only things I can think of is -
sensor at foot pedal shot ?
clutches in gear box rooted ?

or oil in cooler still stuffing the TB sensor ?
any help guys would be much appreciated .

cheers Jeff

 

[Old.Tony]

Was the torque converter changed when the gearbox was? If it's a little grabby it'll do it and it'll be more noticeable in lower gear where torque and power are amplified by the lower final drive ratios.

 

[JPR]

No mate just the valve body was changed out. I was looking into others issues and some made me think u may b onto something as previously suggested . Just didn't add up after resetting ecu but now it's just always there....Any info on upgrade able options ? think this ute had the same freakin tranny oil from purchase as it was very ordinary. Assume it's caused a bit of damage somewhere.. Oem ones are a tad pricey !

 

[Old.Tony]

ATF oil is not checked at service, it's generally there for the life of the vehicle. So they say. If the oil gets "ordinary" there might be some other issue, among which include the wrong oil used, mixing slightly different types of oil, contamination or component failure.

Torque converters aren't cheap, but if you're looking at changing yours, you could do yourself a little favour here. The stall speed for the torque converter is usually somewhere in the range 2700-3100rpm. This means that to get most of your engine revolutions through to the wheels, you need to be doing AT LEAST those rpms. Reducing the stall speed reduces the revs you need to take off - it'll save you fuel.

Wholesale Automatics in Melbourne produce just such a beasty. Have a look here. No, I don't work for them, but if I had the cash to spare, I'd leap at it. It's especially good since the engine is developing near its peak torque around 2000rpm.

 

[JPR]

Cheers Tony I was just looking at that post earlier to look at pricing. Hard job to replace do u know? What's your thoughts on adding a friction modifier to the oil ? was thinking That would tell me if it's the problem maybe. Tranny guys keep telling me electrical but I'm not convinced....

 

[Old.Tony]

I'm not sure I'd add a friction modifier. If the standard Nissan ATF doesn't provide good results then my mind would turn to finding out what was wrong mechanically with the box.

That said though, it's possible that while the valve body was replaced, there may have been other galleys that were gummed up?

 

[JPR]

Wonder if u can independent line pressure tests like you can on the solinoids ?

 

[JPR]

If i was going on basic mechanical symptoms I would say its the torque converter. only thing I can say for sure is that when I replaced the throttle body it went away for a few days. Im thinking that something is making the torque converter act up. need to go to another auto lecky to get another opinion as last guy was a bit to quick looking at it... what are your thoughts Tony ?

 

[Old.Tony]

I think the first thing I'd do is get a stall test done. Click here for a video of one being done in a Dodge R/T, and click here for a page from "HowStuffWorks" that describes the process nicely (recommended reading, especially the warnings). Yours should stop somewhere between 2700 and 3100 rpm.

If yours doesn't, then that's where I'd be looking. If it seems to stall okay, it might be fine and it could be the oil galleys - and for that I'd take it to a tranny specialist.

 

[JPR]

thanks mate appreciate your help !!! Ill give it a go ..