Q45 Transmission Problem

[InfinitiQ45F50Owner]

My transmission has been slipping for a while, but recently it decided to just not shift out of first gear when I’m in drive, so my new top speed is around 30. I was looking into it and thought the q45 might have a CVT transmission and had the solenoid go bad, which would explain the not shifting and the slipping, but 1. Nowhere on earth does it say my car has a CVT transmission, and 2. I cant find a solenoid for it anywhere, but if it’s not a CVT, that would explain why I can’t find one. I would like to find a possible fix that doesn’t include a rebuild or replacement, like replacing a solenoid. I’ve already done a transmission fluid flush and it didn’t help the problem. It is a 2004 q45.

[EdBwoy]

Does it behave any differently if you try to drive the car in manual mode?

How many miles are on your odometer currently, and how many miles had it been slipping for?

You're right, you do not have a CVT. You have a conventional automatic transmission with planetary gears.
If you're looking for solenoids, those will mostly be in the valvebody... which will require some disassembly.
Either way you cut it, this isn't going to be painless.

If you've had any lights pop up on your instrument cluster, it would be good to know which ones they are. Have your car scanned, even if it isn't throwing any check engine light as there might be codes that will help point us in the right direction.

[04pathse]

Well if you look in the FSM on page 67, it lists one of the potential causes could be a faulty speed sensor.

http://www.nicoclub.com/service-manual? ... 004_Q45/at

[InfinitiQ45F50Owner]

Does it behave any differently if you try to drive the car in manual mode?

How many miles are on your odometer currently, and how many miles had it been slipping for?

You're right, you do not have a CVT. You have a conventional automatic transmission with planetary gears.
If you're looking for solenoids, those will mostly be in the valvebody... which will require some disassembly.
Either way you cut it, this isn't going to be painless.

If you've had any lights pop up on your instrument cluster, it would be good to know which ones they are. Have your car scanned, even if it isn't throwing any check engine light as there might be codes that will help point us in the right direction.

Hey thank you for the help! It doesn’t drive any differently when shifting manually, it still won’t shift out of first no matter what I try with it. It’s been doing it for about the past 5 months, but the speed sensor is broken so I can’t tell how many miles I’ve put on. I haven’t had the funds until recently to do anything about it. The car has about 150k on the dash, it throws the AT check light once in a while, it flashes when I turn on the car for a few seconds. It has a check engine light but it seems to be for issues unrelated to anything involving the transmission. They’re things like a misfire and an 02 sensor, high idle rpm, faulty fuel level sensor. It’s also got an abs light and the tcs or whatever Infiniti’s traction control system, I think it’s vdc but I can’t remember, that light is on too, but that would just be a sensor. Ya the car has a lot of problems, but I like to keep my hands full so I’m never bored haha.

[InfinitiQ45F50Owner]

Well if you look in the FSM on page 67, it lists one of the potential causes could be a faulty speed sensor.

http://www.nicoclub.com/service-manual? ... 004_Q45/at

Hey thank you for the help! Yes the speed sensor is broken, the speedometer doesn’t work, and I hooked an obdII up to the car and it didn’t show any speed while I was driving, and also no miles are being added to the odometer, so the speed sensor is broken. Could that really cause slipping and no shifting though? Seems like an extreme problem for such a small thing. But I’ll look into the manual.

[04pathse]

Well if you look in the FSM on page 67, it lists one of the potential causes could be a faulty speed sensor.

http://www.nicoclub.com/service-manual? ... 004_Q45/at

Yes the speed sensor is broken, the speedometer doesn’t work, and I hooked an obdII up to the car and it didn’t show any speed while I was driving, and also no miles are being added to the odometer, so the speed sensor is broken. Could that really cause slipping and no shifting though? Seems like an extreme problem for such a small thing. But I’ll look into the manual.

YES! the FSM says a faulty speed sensor will cause the vehicle to stay in 1st gear so, YES!

It makes perfect sense to me, the speed sensor basically tells the transmission when to shift gears, when the speed sensor isn't working, it can't tell the transmission when to shift gears so therefore it will just stay in 1st gear!!

[InfinitiQ45F50Owner]

Yes the speed sensor is broken, the speedometer doesn’t work, and I hooked an obdII up to the car and it didn’t show any speed while I was driving, and also no miles are being added to the odometer, so the speed sensor is broken. Could that really cause slipping and no shifting though? Seems like an extreme problem for such a small thing. But I’ll look into the manual.

YES! the FSM says a faulty speed sensor will cause the vehicle to stay in 1st gear so, YES!

It makes perfect sense to me, the speed sensor basically tells the transmission when to shift gears, when the speed sensor isn't working, it can't tell the transmission when to shift gears so therefore it will just stay in 1st gear!!

But here’s the thing, it used to shift when the speed sensor wasn’t working, but then one day randomly stopped.

[EdBwoy]

Which particular speed sensor is it and how did you verify - physically broken? Any other codes in the system?

[amc49]

It probably doesn't matter at all now. One either gets that driving a car with a slipping ATX clutch pack destroys the clutch pack or they don't. The clutches can slip totally only a very few minutes before they burn up the steels and frictions to never lock up again and new trans time at that. Rare indeed it would be to have the car now lock up that clutch and go back to working right. You have to fix it right THEN or give it pretty much up, an ATX does not tolerate long term slippage virtually at all. They during their long lives only slip for a fractional second when working right, put all that slip wear into say a month and it's not coming back at all. Why it quit shifting, the clutch pack got too loose to lock up. If so then no solenoids or anything else like sensor will be bringing it back, the drums have depth specs and not having enough clutch thickness from slipping wear then will never lock the clutch up.

I rebuild them. I've fixed one slipping but right then when it began, you cannot wait on money or whatever to do it later. I've used like a thirty cent washer in the correct place to then make one lock back up for another 20 years of use but you MUST do it QUICK.

The cars don't care how much money the owner has and leaving things broken longterm always has a cost.

[amc49]

Download the AT section of the service manual. The output speed sensor can be bad and the instrument cluster ('combination meter') still inputs that signal separately to keep car running. So BOTH are apparently broken. AT-43. Again referenced on AT-67 if you dive in deeper. The speed sensor apparently updates the meter and then ECM uses the meter to set shift strategies.

6 clutchpacks and 7 solenoids and one band that is adjustable and it works 3 and 5. So if one of those gears is slipping or missing then adjust the band. Speed sensor gone looks like failsafes 5th to not work.