Posted: Apr 16 2007 at 1:11pm | IP Logged

I'm having a shifting issue(s) with my 2003 Frontier, 4cyl, rwd, automatic transmission.

The tranny seems to shift rather harshly around town, and when passing on the highway (pedal to the floor) it upshifts at only 4500rpm.  Also when the O/D is turned off the torque converter does not lock up.  Is this normal for Nissan trannys?  All of my past Nissan's have been manuals.  The dealer has been useless, and my indy thinks the tranny computer is in "transport mode" what ever that is, and dosen't want to touch it since it is still under the powertrain warranty.  Truck has 30,000 miles, the fluid is pink and full, smells normal.

Any info would be greatly appreciated,

Justin

Posted: Apr 16 2007 at 2:50pm | IP Logged

..

wolfc70;

Welcome to the group!

... I would recommend +doing the 30,000 mile service and changing the transmission fluid. My V-6 4x4 automatic transmission only had a window screen style filter and a simple clean-out of it would be sufficient. The simple drain and re fill only changes about 5 quarts so some people change it a second time after a 1,000 more miles.

Remember the additives in the oil wear out even if the tranny has not been over heated or abused.

If something I’ve posted on the Internet offends you please ignore it. If you don’t know how to ignore something on the Internet e-mail me … and I’ll demonstrate.

Posted: Apr 19 2007 at 7:09am | IP Logged

Ok, I got the tranny serviced, no difference.  I think it has more to do with the mapping of the tcu (transmission control unit).  Going through a parking lot at 15mph, it is in 4th gear, so you get a three gear kickdown in a parking lot, not too smooth either.  Is there a way to scan the computer(s) to see if the mapping can be changed?

On my VW, I could VAG-COM the computer and change the shift points and shift speed through the software.  I can also log fuel trims and injector timing too.  Does Nissan offer something like this?

I'm not that familiar with Nissan auto gearboxes but something does not seem right.  Upshifts are rather harsh, downshifts, when you can get one, sends shudders though the body of the truck.  Also once above 70mph I can not get the truck to downshift going up hill, even with my foot to the floor, once it drops to 60mph, then it will kick down to third, is this normal?

Any help is appreciated,

Justin

Posted: Apr 21 2007 at 9:05am | IP Logged

Could be the TCU...

but to me, it sounds more like you have a pressure issue within the transmission.  That would give you both the harsh up shifts, and lagging downshifts.

If it's still under warranty, and the one dealership doesn't want to check it out.  Call the regional rep, and let him know of the situation.  That will put a fire under the service manager to get it looked at completely.