Ok, this issue is driving me nuts.

2001 I30, 139K miles.

Transmission was flaring on the 1-2 shift at slow speeds. I got another TCM from a junkyard, problem did not go away.

So I bought a used transmission with 70K miles and yanked the entire valve body out of it with solenoids, it improved shifting and I thought it fixed the problem, but a day later flaring was back.

So, only thing I could think of was the entire transmission was just bad and worn out. So i bought another used transmission with low miles (the one I got the valve body out of had a damaged gear selector and could not be used)

So after a weekend of cursing I have the new transmission installed. Now it's almost perfect, it doesn't flare during normal driving, but it still does it when i am going downhill with barely any load on the engine. When i am going uphill or give it more throttle, it shifts perfectly, even on level ground it usually works fine. There is a downhill slope by my house and I can make it flare 100% of the time at 10-15mph though.

My next idea was maybe i had a old revision of the TCM. So i searched for a 4Y901 revision TCM that supposedly was the the revised version that the nissan TSB mentioned. I installed that one and it made exactly zero difference.

I also swapped the revolution sensor, but that made no difference either.

So now i am almost ready to set the car on fire. I can't believe that between all the changes i have made the problem always follows, are all the nissan transmissions like that after 50K miles??

Is there something else that the TCM relies on to make decisions during part throttle condition?

I am stumped

 

Did you wipe the ECM contents off by disconnecting the battery overnight.? Any electronic item change or changing tranny fluids needs a wipeout of the old tables in the ECM.

Next step will be dropping pan and cleaning gunk and replacing magnets and new gasket (pl. take pics of VB and pan).

 

I swapped a TCM that was sitting on a shelf for months, so i am pretty sure it was wiped. When i swapped the transmission the battery was disconnected for 2 days as well. I flushed all the fluid when I swapped the transmission. When i swapped the first valve body, I cleaned it for a long time and cleaned the pan and magnets, it made no difference.

 

1. Fluid level AT-63
2. Accelerator pedal position sensor
(throttle position sensor) adjustment
EC-304
3. Line pressure test AT-67
4. Accumulator servo release AT-277
5. Control valve assembly AT-277
6. Brake band

Since you've replaced the transmission more than once, I'd look into the throttle position sensor.

 

You might be on to something, I've had idle issues before and I replaced the TPS sensor, maybe it is not adjusted.

 

If the throttle and transmission aren't synced, it can cause shifting problems. I know when the throttle cable to my transmission in my old Accord had some slack in it, my lock-up torque converter wouldn't lock up. Once I took out the slack, it worked perfectly again.

 

I think my sensor is off in the negative position so in a part throttle condition the TCM still sees the TPS at 0 so it doesnt shift gears.

 

I know this has been over stated, but I've seen a bad MAF give all sort of tranny problems. Friend of mine was ready to replace his tranny and a new MAF cleared up all the shifting symptoms!

Are you still on the original MAF?

 

nope, new maf 6 months ago.

 

going to go mess with the TPS sensor in an hour.

 

I adjusted the TPS sensor using the FSM, made no difference, still flares going downhill.

Any other ideas?

 

Sounds like a line pressure issue. Probably not the clutch packs because slippage would be worse the more throttle pressure you give it.

Just go down that list I posted, ought to be one of those issues.

 

Maybe try using a modded VB to see if that helps.

 

Not sure about the correlation, if any, but I've had issues in the past in which ocassionally the transmission would slip on the 1-2 shift, on a slight downhill slope at low speed, with barely no engine load, in my neighborhood. I also used to hear and feel some kind of a pull while accelerating on a level surface, more so when the tranny shifted from 1-2, as if something was not fully tight around the engine. For some reason, after replacing the passenger side engine mount, I have not felt none of those issues again so far. The intention of the replacement was to get rid of a right front end clunk that I had, even after replacing most of the suspension components, and some annoying vibration I was feeling a low idle. Those 2 issues are also gone and I don't even hear an engine whine that I used to hear inside the cabin any more. Car feels quiet and solid.

 

I understand you adjusted according to the fsm. However, when I had a similar problem I adjusted mine to about 1100 rpm on idle (car being on) and when I restarted the car it was back down to 725 rpm. The tps adjustment worked for me as the transmission shifts good and my idle is still good.

What I am trying to say is increase the idle with the tps, restart the car (shut down and start up) and go for a drive. If its helps then you know the problem and if not, you can just set your tps back.

 

Somebody's been around computers far too much...

 

I didnt want it to show. I am at work right now lol (Work in IT)

 

Lol, I can relate to that!!!... sometimes I catch myself looking for an "undo" button in real life!!!...

 

Hey Kaane, did you figure out what the problem was in your car? Looks like I have the same problem on my 2000 SE.

 

i had a bad 1-2 shift on my car once...but it was because i didnt push the clutch in all the way

 

Cool story bro

 

no, it is for Auto tranny.

 

 

thanks