Transmission Not changing gears?

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humeysd40

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Ok so after replacing nearly my whole engine bay of parts.

i figured id give this a go, i dont have any power at low gears (2007 d40auto).

and my car never seems like it changes gears, the gauge console says d or 4 all the time. Manually putting it in 1,2,3 also dont fix anything. It revs to like 2,500. Then stops, and stays in that gear. Any ideas? Is my trans fried?
 

Old.Tony

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It really sounds like every single storm cloud in the world has figured out where you live and is sitting over the top of you!

Ok, let's start with indication of gears. Mine - normally - shows P when I first turn the car on, then flickers 'R' and 'N' then 'D' as I drop it into Drive to move off. I don't press the O/D button on the side of the shifter at all, just the large release button so I can put the car in Drive. As I start to move off, there is no indication on the console that I'm in any other gear than Drive. If I stop the vehicle (or if I'm moving slowly, like under 20km/h) and I put the car down into 3rd, 2nd or 1st, the dash will indicate 'D' -> '3' -> '2' -> '1'. It will only register '4' when the shifter is in 'Drive' and I press the O/D button. Is that how yours works? If not, you could have a sensor problem in the gearbox. This sensor is driven directly by the shifter in the cabin but the sensor reports to the TCM inside the valve body of the gearbox which then reports to the instruments. I'd imagine one possible cause for this is TCM harness damage, but it might also just be the TCM hasn't been programmed correctly. It's a job (Nissan say) that only Nissan can do and from my own experience they don't always get it right.

Gear changes occur when the TCM is set to do that, based on inputs like engine load, engine speed, vehicle speed, driveline load - much of this is obtained by the TCM although the ECU does report engine load to the TCM (the TCM can sense engine speed because that's the turbine speed on the gearbox input).

Has the gearbox been serviced?
 

humeysd40

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Hahha yeah, not that i know off. Had this issue for ahwile, yeah it works exactly like you stated.

of course u may be aware of my 9/d light being constantly on at the momment (button does nothing.

ive replaced all tfr case sensors, is there transmission sensors that also go faulty?
Theres no visible damage to any wiring. It just stopped running smoothly one day, i assume a ecu reflash of the tcm will be best bet but also worried the trans is fried haha.
 

humeysd40

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So basically i can send u a video of what i mean if you want.

Full foot down, it revs to about 2,500 rpm thats it wont go higher, then takes like 5 seconds to get to 25km/h.

It literally takes forever and literally cannot go up any hills. Weird, i dont have any black smoke or turbo issues, confident its a trans issue

also do you think this could be the trans in limp mode??
 

humeysd40

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So update, im going to see if the tcm circuit is broken tomorrow.

im fairly confident that my transmission is in limp mode (3rd gear). Ill get back and reply later
 

Old.Tony

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The O/D light issue is probably a TCM fault. That means reprogramming. The only ones I know of that do it are Nissan dealers, and I wouldn't use Maitland Nissan. They kept my car for weeks on bullshit excuses and then didn't do the job properly. I wasn't in a position to take my car elsewhere, because the car was taken there by a nearby auto trans specialist.

Your gearbox (specifically, the torque converter) stall speed is around the 2500rpm. I wonder if that's related to the issue? It really doesn't sound right, no smoke at all, can't rev and won't go any faster ... it could be a cooked gearbox. The Nissan (Jatco) gearbox speaks its own language but most auto trans places can hook up and get data from it. Why not try that? They might even be able to pull a code from it, because if it's in limp mode, it'll have a record of why.
 

humeysd40

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Pulled the circuit and tcm, cleaned connections nothing seemed damaged. Resembled and still the same. No codes were thrown using a snapon diagnostic scanner. Very weird. Still stuck in one gear and only revs to 2,500-3000 rpms with no gear changes. Im going to my nissan dealership monday and getting a tcm reflash see if it helps
 

humeysd40

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No coolant present, car does not go anywhere now, what the hell. Think imma scrap this car really bugging me now
 

Old.Tony

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Dark red trans fluid is ok. Pink isn't.

How does it not have coolant? That's very strange, you'd think it'd be noticed ... no signs of leaks?

This car just seems to go from bad to worse, with all sorts of odd problems!
 

humeysd40

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Yeah well the condition of fluid and solenoids werent stuck, i assume they’re signs of contamination, as well as radiator cap was as normal. Tell me about it
 

humeysd40

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Update: heres the codes the car threw. Any ideas how to fix, hoping its not torque converter is gone
 

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Old.Tony

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The first error indicates that the torque converter clutch (TCC) isn't locking when commanded to by the TCM. This could be debris in the valve, it could be a completely worn clutch too (the torque converter (TC) has a clutch built into it which engages the two 'sides' of the TC when conditions are right). This clutch can wear out.

The second error indicates that the ECU isn't sending the throttle position data to the transmission. That's rather odd. The manual only defines a harness problem that could be causing this. The diagnostics for this (using a scan tool/Consult device) are:

* Turn ignition on but do NOT start the engine
* In the TCM module, select "ECU Input Signals" in Data Monitor Mode
* Press and release the accelerator pedal noting the value of "ACCELE POSI"

With your foot OFF the accelerator it should display 0.0/8
With your foot FULLY ON the accelerator it should display 8.0/8

If this is working normally, the TCM is getting the data. The manual ends the inspection at this point (because it should be working - clear the codes and try again).

For a failed TCC, you could consider one of the following:

* Replace TC with a reconditioned one
* Replace TC with a new one, consider Wholesale Automatics low stall speed
* Replace gearbox with second hand

The last one is possibly the cheapest, but you don't know what you're getting. Reco of a TC should run about $1K or thereabouts. I did this, I had someone fit it for me, they buggered it up and it ended up costing me a motza.

If the TCM is NOT getting the data, check the wiring harness for damage. Check the pins for debris or damage.

I wonder if it's worth going through ALL of the engine bay fuse/relay boxes and just pulling EVERYTHING out one at a time and replacing it (this should cause any oxidisation to be rubbed off). Your car has so many different weird errors in it the damn thing is frightening!
 

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