Hey everyone, i recently got another engine installed with roughly 38k miles on it from Japan. It runs great with zero hiccups and tuner said it’s running great. After taking it easy for a day, I decided to see what it could do and put it in manual mode. Everytime I downshift or get near 5k rpm, it forcefully shifts to the next gear and it never did that before. Any suggestions on what could be up?

Thanks.

 

Anyone?

 

Mine doesn't do that. Maybe you're downshifting so extremely that you're hitting some protection limit that I haven't hit that triggers an upshift to save you? Are you saying if you start in MM in 1st and run it up to 5k it will upshift on its own or does it only happen on downshifts? I know mine doesn't upshift unless on acceleration unless I pull the shifter.

Have you done the mod to reverse the manual shift pattern yet to make it pull to upshift? If not, you could troubleshoot this problem and do that mod at the same time. If I remember correctly, you end up cutting the wires from the two microswitches and soldering them back swapped. To debug your problem, you cut the wire from the upshift microswitch and run the rpm up to 5k or above in MM ( you won't be able to upshift) and see if it upshifts by itself. If the problem goes away, it was your microswitch getting tripped and you'll have to fix it. If it doesn't go away, at least you know it isn't the upshift micro switch. Then you cut the other one and flip them. Now you have the proper MM shift pattern at least and you know one new bit of information to help narrow down your problem. There are several threads to show you how to do this mod if you're interested so you can see which wires to cut.

Good luck and post back if you figure it out.

 

I'm betting it's slightly low on tranny fluid causing a surge in pressure which then bangs the clutch packs. They had the engine off, which means they had the torque converter off, they almost definitely lost a little bit of fluid, your tranny might have been just ever so slightly low to begin with but now you're feeling it more.

There's also a lot of communication that happen between the ECM and TCM and sensors that need to be recalibrated anytime you have a new engine, I would do ALL the recalibration steps listed in the FSM section EC - Engine Controls under "basic service procedures". Accelerator pedal, idle air, throttle position, exhaust cam if it's a rev-up.

 

yea, the mechanic said he doesn’t do any programming of the sort and I will definitely have
the fluid checked.

 

You can just do them all yourself it's really easy, use a stopwatch because the seconds counts need to be exact. For the idle air recalibration there's a bunch of conditions that need to be met, steering wheel pointed perfectly straight, every single electrical load in the car turned OFF, transmission up to temp (go for a 10 minute drive), parking brake set.

You can't screw these things up, it will either recalibrate or it won't, you won't mess up your car by "doing it wrong".

https://www.nicoclub.com/archives/g3...procedure.html

Here's the conditions list from the FSM for the idle air, the other two can be performed on a cold engine.

 

Alternately for the idle air recalibration if you have a bluetooth OBD2 adapter like the BAFX one they sell on Amazon, and an Android smartphone you can use the app Nissan Datascan 2 to just press a button on screen to recalibrate idle air.

 

Went to the dealer and they said it was an issue with my valvebody and not an ECM issue. I called a separate transmission shop and they guy said it was highly uncommon for these to go out on these cars unless coolant seeped into it somehow? Anyway, i'm having him look at it wednesday and go from there. Oh, the code they told me that came up was U1000.

 

U1000 means one of the computers isn't communicated to the ECM properly, I'm guessing it's the TCM which is bolted to the back of the valve body. Might just be a wiring harness issue though, I would get the car up on jackstands and inspect the transmission wiring harness for any damage, might have kicked a rock up and damaged the wires.

 

^^^^

Not all TCM’s are bolted onto the valve body. The earlier models had it located in the passenger’s kick panel.

 

I won’t be able to get under the car myself as i have no lift or jack and the earliest I can get it looked at would be Monday or Wednesday.

also one thing I noticed, when the temps are low, the car shifts like it did before, only after it gets to normal operating temps does it have the issue.

 

Mine is an 05

 

Same as mine. Yup its inside the valve body. Boooo

 

Dude get yourself a jack and stand combo for under $100 bucks!!

 

Did they ever check the fluid level? Cold fluid is more viscous and thus holds higher pressure, hot fluid has lower pressure. There is an internal relief spring that keeps the pressure steady.