1996 J30T Gear Shifting / Transmission Problem

[kizodog]

Car Details:I have a 1996, J30T with ~78K miles on it. I bought it in April 2003 from a Virginia dealer who had purchased it in New Jersey. The background on the car is unclear but I believe it was a leased car. I have not performed any services yet on the car (e.g. Transmission flush, etc).

Problem:While cruising down the highway the car will switch gears from cruising (what I assume to be 5th gear) into 4th and into 3rd gear where it will stay for anywhere between 5 seconds to 2 minutes and then correct itself back to 5th/cruising for a minute or two then it will switch again. RPMs are all over the place as a result - going from 2000 to 5000 RPMs even though I'm keeping a constant speed (~60 - 70 MPH) and constant pressure on the gas pedal. There is no reason why the car shouldn't just keep on in cruising gear on a flat highway.

One other issue I noticed is that if I drive the car in 3rd gear (which I did once for a few minutes to check things out), the car bucked a lot. That is, it seemed to be having a very hard time negotiating the gears and there was a lot of jerking.

Plea:I'm concerned about the Transmission going bad but find it hard to believe after 78K miles - not to mention I don't want to spend $3,000 to get a new/remanufactured one put in. Is there any other component that could be going bad within the Transmission? Please help. I love the car but may have to put it on the sale-rack if I cannot get this fixed.

Thanks in advance.

[DAEDALUS]

I would try a fluid replacement and pan drop to see if that'll fix/prolong the transmission. Check your fluid level and color, and give it a sniff to see what condition it's in. After 78k, it can't be in very good shape.

[Mayhem_J30]

With only 78K on her she's hardly lived her life. Get that transmission fixed and hang on to her for another 100K miles. Once you get a new transmission have the ATF changed once a year.

Think about this, you could spend $3000 on a new transmission and go the distance in style with your J. Or you could sale the car with a busted transmission for about $3000 if you're lucky and buy a $3000 POS economy car with 100K miles on it.

[autotech43]

Transmission fluid temperature sensors are known for that, they also will not set a trouble code in either the (ECM) engine control module or the (TCM) transmission control module. Might want to let a dealer consult test the vehicle in the real time mode to catch the sensor when it malfunctions. Consider you may have to leave the vehicle with the dealer for the tech to perform several test drives and scans depending on often the concern occurs. Its not an expensive item to repair if that is your case.

[kizodog]

Thank you to all - and especially autotech43. I had it checked by the Infiniti dealer here in Richmond and they have diagnosed it as the "Transmission Terminal Cord w/ Temp Sensor Failing".

They offered to replace the part and flush the transmission for $576. That seemed like a lot so I inquired some more.

Infiniti Dealer Quote:Temp Sensor Part: $86Labor: $490 (the fluid is included in the job as they will have to flush the system to do the job apparently)

They are quoting 6.5 hours labor to do the job. Upon further inquiry the guy at Infiniti told me that the job would probably only take 2 hours but he's obliged to quote what the book says it will take.

I said no because I want more opinions and I have questions.

Question 1 (Background) : I have read on this forum that when you service the transmission that you want to remove all the fluid (ie. get rid and replace all 10-12 quarts) from the entire assembly. In numerous postings however I have seen that people advocate dropping the pan, cleaning the filter, etc - which I know (believe) is not a full flushing of the system. My understanding of the flush (as prescribed by the Infiniti dealer) is a back-flush that sucks the fluid out like a vacuum cleaner, cleaning the filter, and everything else with some kind of chemical (sounds like Mr. Clean Toilet bowl cleaner). This sounded wonderful until I talked to a local transmission shop that said, "We don't do back-flushes anymore, even though we have the machine, because the back flush seems to move debris and other things into pockets within the transmission where they shouldn't/couldn't be unless the flush is performed ... and then you have to get a new transmission because stuff gets jammed up. We get a lot of cars in here after Dealers have flushed the system because of these problems. Also, some cars - especially those that don't have a plug on the converter - are not/should not get a full draining of the system because that's the way the manufacturer designed the transmission." Bear in mind this is highly respected and specialized Transmission shop (been around for 20+ years) and all they do is transmissions. They advocate just dropping the pan, cleaning the filter, getting out the 4-5 quarts of fluid, and then refilling.

Question 1: What is the definitive answer on the back-flush vs. the pan drop method of changing out the transmission fluid?

Question 2: Can someone recommend a good place to get the "Terminal Cord w/ Temp Sensor"?

Question 3: Is this something that I can replace myself? I am not a mechanic but I'm also not an idiot and work with technology all the time. Is this really rocket-science? If not then would anyone be kind enough to give me some instructions. I have seen those tune-up kits online that seem to have everything one needs to do the fluid replacement/cleaning. Also consider that the temp sensor needs to be replaced and I would need some advice on this too.

Question 4: Is the $570 price tag as quoted by the Infiniti dealer excessive?

Question 5: Can anyone recommend a place in Richmond VA that does reliable Transmission work and/or is the Infiniti Dealer the best bet and the right price?

Thanks again to all who responded to my inquiry.

[autotech43]

Kiszo, you will get many different theories of the pro's and con's of flushing transmissions. Many folks may or may not know that on some Infiniti vehicles, you may or may not can flush the transmission coolers that are located in the radiator, reason being, on some there are a wire screen webbing in between the cooling tubes that go inside the radiator. Depending on the size of metal or debris will determine whether it will allow flushing of the cooler. If a certain size of debris is present, it will get caught in the wire screen and cause a restriction in the cooler. There ia a tech bulletin regarding this procedure. Some of the coolers will require replacing. Back to your vehicle, your J doesn't have that type of A/T cooler, so your ok there. As far as my theory and experience with overhauling Infiniti/Nissan transmissions, I always look at the fluid (reddish color), see if it has a burnt smell, and how much debris is in the pan and on the magnet located at the bottom of the pan. That lets techs know pretty much what condition the overall transmission is in (also depends on the history/recent maintenance). In your case, if everything looks pretty decent, I would drop the pan, replace the filter and refill with fluid. Buy the sensor before you start, so you can get an idea on what your looking at when you get in there, it's not that complicated to change even for the first timer. I think where alot of techs have differences verse the flush and drop method, some will say you still have dirty fluid mixing in with new fluid when you don't do a complete flush(which is true). They do have machines that push out the old fluid and replenish new fluid behind it, i see no problem with that theory. What i would consider a problem, if the trans has alot of debris and the fluid is burnt and dirty, that could cause debris to get lodged in the valve body, which can cause a severe migraine to the trans. Remember, changing just the fluid and flushing the A/T with a chemical are two completely different operations. I think customers need to ask questions about transmission procedures on exactly what is being done, and not just the routine answer of we serviced your transmission, or backflushed the system. Hope this may help!

[Q45tech]

When you flush a transmission you must THINK and meditate on the color and smell [taste?] of the ATF. And decide on a case by case basis what to do. UNFORTUNATELY This is not the option the tech has, as he is instructed to do what's written down.

The question is what would you do if it was your car or your mothers car? The answer is always a pan drop, filter change, chemical flush, flush, and flush, and reflush it till everything is spotless.

Many trannies require more than 1 flush to get them clean as new because they were never flushed EARLY when the fluid change color 30,000 miles ago. THAT IS THE PROBLEM that is not addressed. The screen filter was not changed at 30,000 miles when you could have done some good, instead of letting the tiny metal squeeze through the filter in times of high pressure.

Thats why the later models have inline oil type filters to catch the tiny particles........they wouldn't have added the expense if it didn't have value. This lowers the metal load on the pan magnet and stop the aluminum that it can't attract.

I can easily see how a slam bam flush could cause problems if the technican didn't have the financial leeway to do it again or drop the pan or change the filter.

Service writers have a hard enough time getting $120 out of owners much less $300.

After doing maybe 1,000 flushes on Q/J/G we have never seen a problem but we are selective and won't do the really bad ones without carte blance.

[krewzn_along]

Hi all. Did a search and my problem is a little like this guy's. Read on.

'97 J30, 140k, I've owned since 97K and transmission fluid has been replaced around 105K. Prior had two good owners but can't confirm any prior fluid changes.

I do quite a bit of highway driving, usually from 65 - 75 mph and I've learned this car well. J will shift through the gears into 4th when it's cold but doesn't lock torque converter until it's warmed up - all's fine there.

After this car is warm, sometimes 5 minutes on the highway but more often after 25 or 30 minutes, the torque converter will unlock for no reason. For example driving at 65, rpms @ 2400, sometimes on a slight grade up, sometimes level, sometimes down, anyway with steady throttle and no reason to unlock for more torque I notice by sound the engine speed has increased and sure enough I'm still at 65 and the rpms are at 2600 and if I vary the throttle I can see the rpms vary. And then in 10, 20, or 30 seconds it will re-lock, back to 2400 rpm. And then in a few seconds or a minute it will unlock again. This goes on for 30 seconds to 3-5 mintues and then it locks up and it runs locked as expected for the rest of my 1 hour freeway drive.

This problem is getting worse, as in more frequent and longer spans of unlocking-locking. It has happened with cruise control on and without it. Still, most operation is fine including on a steep grade the transmission unlocks the torque converter as expected based on the decreased speed/increased throttle combination, and as expected with more throttle or less speed it will downshift to 3. I can't narrow the problem down to temperature, load, cruise-control - the only thing that seems mostly consistent is it will drive fine for 20 or more minutes and then behave badly and then work fine.

When this started the fluid level was a little low. I topped it off and that didn't change anything. The fluid has good color and no burnt smell. Now I discovered the fluid is about .5 inch above the full mark and there are some bubbles so maybe it's overfull enough to areate the fluid.

Can any one tell me if the torque converter lock up is controled by the computer (transmission?) or by internal transmission operation (pressure, etc.)? I recall reading once how the fluid is used to control the lock-up. What inputs determine lock up? I'd guess speed, throttle, temp and is the control module external to the transmission?

Any ideas if I could have a bad input or bad control module, or any ideas at all will help? I would really like to keep my J working in top shape.

Thanks in advance, Krewzn~

[maxnix]

Well, going 70 in a car that has not reached operating temperature gives me shivers.

You don't mention any further maintenance nor the addition of an auxiliary ATF cooler. AT 35K past the last "fluid replacement" (Mechanical fluid exchange? Pan drop?) you are due for another.

No matter how good your ATF looks, it is contaminated with microparticles of clutch material and metallic wear items. Read all of Q45tech's posts on transmission fluid exchanges and chemical flushes. Get the parts from http://www.infinitipartsusa.com and find a BG shop at http://www.bgfindashiop.com for the BG services (call first to verify that they will perform the pan drop and filter replacement) or hunt down a SnapOn jobber to see who might have the Sun fluid exchange machine. Don't forget about the ATF cooler nor your PS fluid, nor your brake fluid.

[krewzn_along]

Manix, thanks for the complete reply. I have read through transmission tips for the couple of years I've been a NICO member so I'm also aware of the general transmission discussion. And it's a good point that 35K mi has passed, I'm driving so far that I forget the mileage is racking up twice as fast as many drivers.

Also, the highway it is a few miles away so my J is warmed up before I get there. Plus, I'm in the SF Bay Area and temps are not very extreme here, especially not at the low end.

I am still looking for spedific answers of how the torque converter lockup/unlock works. I recall reading a thread before but cannot find it now, despite multiple searches.

Thanks,