1996 240sx, AT, shifting acting suspicious

[chato de shamrock]

I drive a 96, automatic, all stock under the hood.

Hey guys. Lately I'm noticing my car doing something with its gears and causing the engine to sound revved up more then I think it should. A few weeks ago I was driving on the freeway when I noticed the car seemed to down shift and at the speed i was going (about 70mph) the engine sounded like it was being foced too hard. I let go of the gas pedal for a few seconds and then pressed it and the car seemed fine afterwards.

Some time last week I was driving to work (about 35-40mph) when it did the same thing. The car seemed to down shift 1 gear and the engine seemed it was being forced. All these times it happened it caught me off guard and I wasnt sure what was going on.

This past Tuesday I was entering the freeway on an uphill onramp. The car seemed strong on the 1st gear, 2nd, 3rd gear. By then I was already in the freeway, but it was an uphill road so I kept raising my speed. Everything was fine and the car felt strong but listening to the engine you could hear it reached the point where it had to shift into 4th gear. The engine seemed to be revved up as much as it could on 3rd gear. I let go of the gas and let it cruise then stepped on the gad and sped up some more to see if it would hit 4th gear, but it wouldnt. At this point I knew it was doing this again so I checked my RPMs and noticed they were just over 4000 and I was driving between 61-62MPH. I let go of the gas pedal so it cruise on the speed. Doing this helped in the past but not this time. Once the road started going downhill I cruise and gently pressed the gas pedal again. It still seemed to be revved up high so I exited the freeway and stopped at the offramp red light. Once the green light went on I drove it on the road and everything was fine. I got back on the freeway and drove from around Dodgers Stadium to El Monte and back, everything was fine.

Today I got on the freeway and noticed I was driving 70 at about 2500 RPMs. Big difference from last week's 4000RPMs at 61-62mph. So far this has happened about 5, 6, 7 times within the last month and a half, or so.

The reason why my engine is stock is because I know very little about fixing or upgrading things under the hood, but i'm trying to learn as i go. Can someone point out what may be happening with my car or what I can do to diagnose the problem and go from there?

I thought it might need a tune up but i've driven a car that was well overdue for a tune up and its reaction in comparason to what my 240 is doing are very different. I figure that if it needed a tune up I'd lose power at the start and not while i'm in the middle of driving in 3rd or 4th gear, am I right?

As always, thanks for your help guys. :bigok:

[viperbite]

therse several components in automatic transmissions that go bad. if your car is a 1996 and obd2 you might be able to pull transmission codes from the a/t computer. theres some shops that can pull codes and get a general idea of what is wrong.

to be honest, these cars you might aswell just swap it to 5 speed and be done with it. most mechanics can diagnose exactly whats wrong with a 5 speed transmission just by driving it. down to each gears synchros and each shafts bearings.

[gijoe69]

I have a 95 S14 OBD 1/2 between years but anyways when I use to have a AT i notice my gears be slipping sometimes then one day i only had 1 gear and no reverse so I was like fuck that time for 5spd swap only took me 2 days by myself working only like 8 hrs not so bad... hardest part was removing the freggin pilot bearing lol

[madd ocx]

op check your overdrive button. maybe you pressed it by accident and didn't realize it..

[chato de shamrock]

I checked to see if the overdrive button was pressed. If it was, it's not any longer cause i made sure its not pressed. I daily drive it, mostly short distances that dont exceed 25 miles round trip. So far it hasnt happened since this past Tuesday. I guess this is a wait and see issue. I'm not 100% sure what an OBDi or ii is, but if its the box on the foot area of the passanger side then ya I have it. I'm just not sure which of the I or II it is.

The reason why I'm not planning on an engine swap or tranny swap is cause i dont have the space to work on this type of project or dont have the slightest clue where to start. I can do cosmedic type work on my car but when it comes to hands under the hood, im next to clueless. I also didnt look for a manual transmission when i bought my 240 because I dont know how to drive stick all that good. Last time i tried was back in Jr. High. Those who have access to a stick shift car have a "im not going to let you drive my car" or "im not going to ride shot gun on my car" attitude even though i've been driving for about 9 years now without any accidents.

[roplusbee]

I checked to see if the overdrive button was pressed. If it was, it's not any longer cause i made sure its not pressed. I daily drive it, mostly short distances that dont exceed 25 miles round trip. So far it hasnt happened since this past Tuesday. I guess this is a wait and see issue. I'm not 100% sure what an OBDi or ii is, but if its the box on the foot area of the passanger side then ya I have it. I'm just not sure which of the I or II it is.

The reason why I'm not planning on an engine swap or tranny swap is cause i dont have the space to work on this type of project or dont have the slightest clue where to start. I can do cosmedic type work on my car but when it comes to hands under the hood, im next to clueless. I also didnt look for a manual transmission when i bought my 240 because I dont know how to drive stick all that good. Last time i tried was back in Jr. High. Those who have access to a stick shift car have a "im not going to let you drive my car" or "im not going to ride shot gun on my car" attitude even though i've been driving for about 9 years now without any accidents.

Can you really blame someone for acting that way? I mean if my brother or close friend asked me to teach them to drive a manual, I would go thru the motions with them. And I have issues with letting other people drive my car.

If you are thinking of having a shop look at your AT, be prepared to pay for the diag and work. Guys, correct me if I am wrong, but an MT swap may be cost effective even if you had to have it serviced/rebuilt as opposed to the AT.

[S14DB]

When was the fluid changed?

[BlackTopS13]

Good question. When was the fluid changed last? It sounds like you may have a leak in one of your clutch packs. The way an automatic transmission works is with hydraulic pressure. basically if your fourth gear clutch pack has a leak it will never build up enough pressure to engage the clutches to engage the next gear. It can also be an issue with your valve body which is attached to your transmission and covered by your transmission pan. The valve body takes hydraulic pressure and engages different solenoids to send the pressure to different clutch packs. If the fluid hasn't been changed the solenoids could be sticking or the passage ways could be clogged. Is the engine at operating temperature when it occurs?

[chato de shamrock]

Good question. When was the fluid changed last? It sounds like you may have a leak in one of your clutch packs. The way an automatic transmission works is with hydraulic pressure. basically if your fourth gear clutch pack has a leak it will never build up enough pressure to engage the clutches to engage the next gear. It can also be an issue with your valve body which is attached to your transmission and covered by your transmission pan. The valve body takes hydraulic pressure and engages different solenoids to send the pressure to different clutch packs. If the fluid hasn't been changed the solenoids could be sticking or the passage ways could be clogged. Is the engine at operating temperature when it occurs?

Im not sure what fluids your talking about but no, ive only topped off the power steering and once the oil. I dont drive it very much cause of gas prices right now, just work and home and sometimes to visit family.

Since I last posted the car hasnt done this anymore until this past Monday while coming home from work and today, Friday. As I was going to work i noticed the check engine light turn on while it was doing this (A while back I made sure the overdrive was not on so thats not it). Again I was on the freeway when it happened. I pulled over and drove on the street and it seemed fine except i noticed one thing, the car was hitting 2nd and 3rd gear at 3K RPMs. Since there was traffic I couldn't get it to hit 4th gear. I pulled over at a parking lot and turned off the engine, restarted it and drove off. This time I noticed it hit 2rd and 3rd gear at 2500 RPMs and 4th gear would kick in at 2k RPMs.

[projectRDM]

Im not sure what fluids your talking about but no, ive only topped off the power steering and once the oil. I dont drive it very much cause of gas prices right now, just work and home and sometimes to visit family.

Since I last posted the car hasnt done this anymore until this past Monday while coming home from work and today, Friday. As I was going to work i noticed the check engine light turn on while it was doing this (A while back I made sure the overdrive was not on so thats not it). Again I was on the freeway when it happened. I pulled over and drove on the street and it seemed fine except i noticed one thing, the car was hitting 2nd and 3rd gear at 3K RPMs. Since there was traffic I couldn't get it to hit 4th gear. I pulled over at a parking lot and turned off the engine, restarted it and drove off. This time I noticed it hit 2rd and 3rd gear at 2500 RPMs and 4th gear would kick in at 2k RPMs.

Alright, it's readily apparent you don't know a thing about cars. Period. So let's start with the basics.

Your automatic transmission has fluid in it. It's called automatic transmission fluid. There's even different types. Welcome to Earth.

Autos are susceptible to wear from old, heated fluid. It's common practice to change the fluid and filter every 60k miles, not doing that ensures the fluid will overheat and breakdown. The filter also should be replaced as like any filter, it builds up debris and grit, which eventually will damage the filter. That's the first place to start.

You might also try going to google and learning a little about automatics.

[Nismology]

I agree with you on the manual thing. I was never allowed to drive my friends. I grew up driving an Autoshatic shitvic. I got my car a few days ago and once I get the car insured and plated im gonna practice. I got a new clutch making it difficult to drive already but I know the boat your in and if you lived close i'd do you one solid.

[chato de shamrock]

Hey guys, I had it diagnosed and it came back with code 750. I found this website a few hours ago:

www.tuiz.com - Nissan 240SX OBDII 2 Codes 1995 1996 1997 1998 Car Check Engine Light (http://www.tuiz.com/nissan-240sx-obdii-2-codes-1995-1996-1997-1998-car-check-engine-light-p23.html)

750 - Shift Solenoid Valve ‘‘A’’

Part of the diagnosis paper reads, "computer scan revealed the following codes: 750 - shift solenoid. the following service(s) is recommended: safeguard service/power purge,. with solenoids"

The guys at Aamco Pasadena hooked me up with a free diagnosis, said the solenoids needed replacing and gave me a quote of $350

I went to Kragens to get some stuff and since i was there asked if they sell the solenoids but they said they didnt. Is this going to be a part you either get at the pick your parts or dealership or can it be purchased at some autoshops? Was that quote of $350 in the ballpark of what this type of service costs?

[BigVinnie]

If you keep your AT fluid clean, you wouldn't have that issue.
I remember buying a 240sx auto the fluid seemed to have never been changed, it smelled horrible and the fluid was a nasty poopoo brown. Tranny flushed that shit, and ended up plugging up a valve in the process. Eventually new fluid ran through the tranny long enough it started to run fine again.

You should tranny flush if you haven't done so. Add new fluid and drive around for about 150miles and see if it resolves your situation. AAMCO loves making money off of teh ignorant. Also check to see how much the fluid level in the tranny raises when it operates at operating temprature.

[daisy_is_sweet]

Just change to 5 speed and get it over wit it... Wayy better..mines also a 96 i love it..awsome!! Lmao