92 Q45 Trans Shifting issues...need help

[pbedrosi]

I've had numerous little issues with my 94 used replacement transmission.

My first issues right after trans swap was trans malfunction error in the lcd display. Secondly, it shifted very harsh until the trans warmed up. I decided to replace the TCU to a 94 to match the trans and to get rid of 2nd gear starts. I also decided to use BG cleaner and change the fluid/filter. After I changed the TCU, fluid, filter, and BG trans supplement, the transmission has been misbehaving worse.

First, with no trans malfunction error, the transmission will not shift into 4th gear. While all other shifts 1-2-3 happens smoothly.

Secondly, if I have the malfunction error, the transmission does not shift into 2nd or 3rd gear until 3,000 rpm when cold, but I get 4th gear (is it in fail safe mode?)

Since driving the car for longer, I lost 4th gear regardless of error message. Shift harshness is still there. This gets expensive when you’re spinning 3,000+ rpm on the highway in 3rd gear burning up $3+ premium.

I knew the fluid level was bit high so during my coolant flush service I had the guys drain the fluid. I was 1qt too full. I notice the transmission shifting better leaving the shop, but still no 4th gear.

Next morning still the same cold shift harness, you basically stuck in 1st gear unless you hit 3,000 rpm then it shifts into 2nd, then again you need to reach 3,000 rpm before it shifts into 3rd. It’s known to chirp the tires like a really aggressive shift kit I used to love in High School.

On the highway I can get the trans to upshift to 4th if I hit the accelerator 1/2 down or more basically load up the engine/trans during hard acceleration. Soon as I lift my foot the trans downshifts back to 3rd. Rarely, I can have the trans hold 4th gear, but this happened 3-4 times in the last couple of weeks.

What could it be?

Couple of things to know:- Group of connectors located near the tailshaft has trans fluid inside. But, no visible external leaks. Local mechanic told me that the fluid is coming from the trans speed sensor (travels inside the harness down to pack of connectors). I use contact cleaner to clean out the trans fluid and applied dielectric grease, etc... but no change.

- Ran TCU pin check for the shift lever, I get the correct Voltage reading in all shifter positions except "D". I do the similar check at the trans harness, again, no Voltage in D-mode. Suggests the electronic PRNDL switch on side of trans bad.

- When cold the trans does not shift up until 3,000 rpm, and when it does it hits hard, almost chirps the tires. Leaving work in the afternoon, it seems to shift okay (no 3rd though).

- I experience these issues with 92 TCU and 94 TCU from PopPop.

- When I had the trans R&R'd and went back to pick up my old trans the converter was missing, the tech was not around so I never asked why. Talking to another Nissan tech, he suggested most likely failure was converter. Now considering my original trans issues may have been a simple converter failure. I'm inclined to re-swap with reman converter.

- I had my MAF connector replaced by local Nissan/Infiniti shop for bucking issue. These guys told me the ECU has Throttle Position Sensor error they can’t erase. Could this affect trans?

Do I have a mess of problems or a known issue? I still have my 92 trans sitting in the garage, should I swap harnesses? I'm going to sell this car (77k miles) but I want to fix this issue first.

[maxnix]

Sounds like you have a mess.

Did you not replace the turbine sensor before installing the transmission? Is this a Nissan rebuilt or somebody else's with unknown issues? Oh, I see it is a local rebuild. Too bad they didn't do a complete job. You realize you are in the same state that Nissan does their factory remanufacturing? Hope they have a lifetime guarantee. If you drop the transmision again, be sure to replace the rear main engine seal if you didn't before.

The TPS is also a necessary repair, so read the posts and the FSM diagnostic so you will know how to proceed.
Modified by maxnix at 10:51 PM 5/24/2007

[Amesdude25]

Ok so I had the same problem when I had my transmission rebuilt. It sounds like your transmission is in safe mode. I changed the top sensor and found I had a wire that I forgot to hood up (I think it was on the driver side). After that it shifted normally. Also check that the TCU is properly conected as I repeaded this symptom when swaping CU's and didn't have the connecter in all the way.

[pbedrosi]

The trans I have is not a newly remanufactured trans. Used salvage. But....it used to shift into 4th in the begining.

I'm going to try and swap the turbine sensor or buy a new one if not too expensive. I'm waiting for my buddies trans jack and 6-ton jack stands.

TCU seems to be in all the day but I'll re-install for prosperity.

[elwesso]

you did the self diagnosis, right?