Transmission misbehaving.

[MinisterofDOOM]

I've been having some interesting transmission problems, essentially identical to those that subzero car fanatic has posted about recently as well. I thought it might be good to start a thread about what we know to help anyone else who has these issues out. And of course input from you all would be much appreciated. This is going to be long, as there are quite a few details and I'd like to be specific for everyone's benefit.

This is on my 1995 Q45t.

The problem:==The transmission will intermittently slip into third and only third. It COULD be "limp mode" but I'm not entirely sure, due to other symptoms (keep reading).==While stuck in third, a rhythmic clicking comes from the vicinity of the transmission. It is not audible in the engine bay. I've tried to record a clip but none of my recording equipment is high enough quality to sort out the click from the rest of the natural noise the car makes. The sound varies in volume and intensity depending on gear selection (in P, R, or N it is quieter, and in forward gears it is louder and sharper). When the transmission is operating correctly, this noise is not present.==Also while "broken" the transmission will "pulse" brake while OFF the throttle. So if you're coasting, for instance, down hill the car will engage and disengage (I assume between neutral and 3rd), causing the car to engine brake and freely coast cyclically. ANY amount of throttle engages 3rd and stops this. Shifting into Neutral also stops the trans engaging as one would expect.==The issue SEEMS to be heat-related. It took a lot of observing to find a common thread between instances of malfunction, but it does seem like it only happens when the ambient temp is above ~70-72 Fahrenheit.

What I've checked, tested, fixed, and learned so far:==First move was to run trans self-diagnosis. This came up multiple times (multiple occurrances of the issue) with codes for bad Revolution Sensor (NOT turbine rev sensor) and bad Vehicle Speed Sensor. Occasionally, though, it will show as fine.==I ran FSM-described diagnoses for both, and both checked out fine. Of course, as tends to happen, the car was operating FINE when running the tests. I haven't been able to test voltages while the car is misbehaving (it never ever happens at a convenient time...I need to just keep my DMM in the car).==I then took the car to the dealer, since I figured they'd be able to do more with a Consult than I could with a DMM. I took it to my regular Nissan dealer that has serviced both my and my father's Maximas for years...I know the head tech there and have always been happy with the place. They advised that TPS needed replacing, I had them do so. Wes had mentioned the first time I called him about this that he thought that may be the issue, so I felt relieved the problem was solved. Later, though, I started wondering since I didn't see the TPS causing the clicking noise. My doubts were proven warranted, as the problem occurred once again shortly after retrieving the car after the TPS replacement.==The Nissan dealer told me (when I picked up the car with new TPS) that, even with my "bible-sized" FSM on hand, they were unable to test accurately enough to diagnose the problem. They mentioned something about color codes being different and Infiniti being unhelpful about that. They advised that I take the car to an Infiniti dealer (which I'd probably have done to begin with if the nearest one weren't so far away). I will be doing that tomorrow or as soon as they'll take it.But they also added that their further testing indicated a communication issue between the TCU and ECU. Just FYI, I have the robert 8-way ECU and a stock TCU. I have tried the ECU on multiple programs including stock and the problem occurs regardless of setting.

So, all that out of the way, here's what I wonder now:Could this be caused by a bad (heat-sensitive) TCU? I had the idea today to try putting some ice (in a well-sealed bag) next to the TCU to see if it'd make a difference but didn't have ice on hand in time to try this.Or do you think it's more likely the two suspect sensors (rev and vehicle speed) that are susceptible to heat?Or something else entirely?

As I said, I'll be leaving the car with Infiniti tomorrow, so whatever new info I find out I'll add.

[Q45tech]

Check all the connections and clean contacts on transmission sensors and connectors and TCU/ecu.

How many miles on transmission? Is it orginal? I've never seen many trannies last more than 10 years unless annual miles were very low.

[MinisterofDOOM]

No, trans isn't original. It's new OEM rebuild from Joe installed last January (2007). It shifts and operates beautifully when it's not having it's problem. In fact, when it occurs on the freeway, even at 80-85mph, the shift into third is SILK.

I'll try cleaning all the connections. I'm not sure if I can get to the revolution sensor to clean the sensor itself (if there's anything to clean) without a lift, though.

[maxnix]

Connections are good, low mile transmission may not be.

No mention of fluid appearnce or smell. I think eventually you will be calling Joe.

[Rex]

Connections are good, low mile transmission may not be.

No mention of fluid appearnce or smell. I think eventually you will be calling Joe.

It was an OEM replacement from Joe

[qship96]

It was an OEM replacement from Joe

How do you know that? I didnt see any refrence to that in his posts?

[Rex]

How do you know that? I didnt see any refrence to that in his posts?

Because I know

Do I have a reputation of lying or making things up?

=============================================Let's stay on topic. Trans and TC replaced with OEM units from Joe, Jan of 07.

It is an OEM Transmission for a 1992 Q45, as was the unit it replaced.

Cooler was completely flushed before install new trans and Nissan recommended ATF.

No issues experienced for ~10 months 10k miles on either long or short trips. Then after (mostly) sitting for 45 days (started and driven once every week or 2) this issue has popped up.

I still wonder if the battery isn't an issue and after the alternator has been "loaded" for a good days worth of driving, the voltage drops, the amps spike and then things start acting up.

[qship96]

Rsiwickis old car........no wonder trans. has problems as motor was highly modified and put out more horsepower and torque than the stock transmission was designed to handle, and the car had the balls driven off it frequently according to his old posts....ragged out like an old prostitute

[Rex]

Rsiwickis old car........no wonder trans. has problems as motor was highly modified and put out more horsepower and torque than the stock transmission was designed to handle, and the car had the balls driven off it frequently according to his old posts....ragged out like an old prostitute

Nope, that (Level 10 modified) Transmission was replaced (01/07) due to an ATF cooler line getting nicked back when he had the car. The Level 10 trans a still lasted another 20k/1.5 years, but the few seconds of leaking did their damage.

The Trans in the car now has not seen any where near that abuse. Never "brake launched", rarely ever saw >6k, and was run on the JWT, never NICO Mad Max setting.

[maxnix]

No, trans isn't original. It's actually pretty new...low-mile replacement swapped in last January (2007).

If it was from Joe, then it wasn't a low-mile replacement but a zero-mile factory remanufactured one.

How does one nick an ATF line? Hanging too low?

Regardless of it's pedigree, it's fate may be the same ultimately.

Mine sees 6Krpm at least once a week with no problems. Necessary to keep 6 heat range plugs clean.

So next question, who installed it?

[MinisterofDOOM]

Yeah, Keith's right (of course). That's my absent-minded dead-tired posting for you. I fixed my previous post.

I did ask the Nissan dealer to load-test both the battery and alternator. They didn't ever say anything about the results which either means they didn't do it (would seem odd after the discussion I had with the tech about their new testing equipment for just that) or they didn't find anything wrong.I'll make sure the Infiniti guys load test them both and let me know that they find.

and the car had the balls driven off it frequently according to his old posts....ragged out like an old prostitute

Still does when it feels like running right. In fact, if I can get her running right, I'm taking it on the West Track at Miller at the end of the month.

[AZhitman]

Hey Chris - Get on AIM

[MinisterofDOOM]

Answers at last!

I was finally fortunate to have the car misbehave AND be able to take it to a dealer at the same time. Quick check with a Consult shows that the TCU is on vacation. Everything else "checked in" with the Consult, TCU did not. The tech did a quick check to make sure the TCU was getting power, and it was.

So, it looks like the TCU is the cause.Anyone have a spare 1st gear start TCU?

Does this sound right to everyone?

[maxnix]

TCU needs to be matched to TCS or not, can't remember if Fed or CA applies.

Make sure it is a 1994 - 1995.

[MinisterofDOOM]

Thanks, Maxnix. I knew I need 94/95 but didn't know TCS mattered.

[maxnix]

If you have it, it matters. If you don't, I don't think it does.

[MinisterofDOOM]

Yeah, my car does have TCS, so I definitely need to get the right one. I don't think winters here will be too fun with a TCS-less Q.

[maxnix]

You know, I couldn't find my notes on that. Surely the ECU is different, but I haven't been able to confirm the TCU is. Let me research some more and post back.

Sorry, I can not find documentation to confirm if TCS changes TCU specification. I'll keep looking toomorrow.
Modified by maxnix at 5:07 PM 6/11/2008

[SUBZERO]

Answers at last!

I was finally fortunate to have the car misbehave AND be able to take it to a dealer at the same time. Quick check with a Consult shows that the TCU is on vacation. Everything else "checked in" with the Consult, TCU did not. The tech did a quick check to make sure the TCU was getting power, and it was.

So, it looks like the TCU is the cause.Anyone have a spare 1st gear start TCU?

Does this sound right to everyone?

Hopefully this is my problem too!!

[maxnix]

Hopefully MOD will post his resolution.

[MinisterofDOOM]

TCU replacement did indeed solve my problem. Since I replaced the unit, the car hasn't had any further transmission issues.