4th gear problem

[oldschool]

I HAVE A 1993 Q45 AUTOMATIC, BUT I HAVE A MAJOR PROBLEM THE CAR RUNS GREAT UNTIL IT SHIFTS INTO 4TH GEAR. THERE IS ZERO POWER IN FOURTH, THE RPM GO DOWN AS IT SHOULD WHEN SHIFTING INTO FOURTH BUT ITS LIKE THE CAR IS IN NUETRAL, AND WHEN I GIVE IT GAS THE RPM’S RISE UNTIL IT DOWN SHIFTS BACK INTO THIRD AND THEN I HAVE POWER AGAIN. The wierd thing is that there is no clunking noise. I NEED HELP, IS MY transmission FINISHED OR COULD IT BE AN ELECTRICAL SIGNAL SHORT?

ANY HELP AND OR ADVICE WOULD BE GREATLY APPRECIATED.



THANKS
Modified by oldschool at 9:06 AM 9/6/2007

[elwesso]

at what speed is this at? If its at like 40-50MPH thats how its supposed to be.

[Q45tech]

Fourth is a 30.6% reduction from 3rd so it should be used only for steady state cruising above 50 mph] mild mild mild acceleration.

With AC on and any road that is not level downshifts are common.

Could be that the engine is not producing rated power. Lockup clutches worn?

What does consult say about codes [knock sensors etc]?

How many miles on current transmission, condition/color/smell of ATF.

Electrical problems will usually show AT codes do FSM diagnosis on/with trip display.

[oldschool]

When the car is above 50mph the car basically coasts even if i am holding the gas to the point where it should maintain its speed (speed continuosly drops until i have to really step on the gas so that she down shifts into 3rd, and then it will have power to increase speed). I will be conducting a code test tonight and will post the results. There is 105k on the transmission, its the original transmission.

[maxnix]

And the transmission maintenence hsitory is?

[oldschool]

I just got the car and have no history of the maintenence

[maxnix]

I just got the car and have no history of the maintenence

Well, Infiniti does for it's dealer performed service.

When not otherwise verified, the first thing a new owner does is exchange all fluids for the correct new ones and install all new filters.

[oldschool]

If anyone has an electronic copy of the 93 Q45 FSM could they send it to me @ [email protected] i would really appreciate it. ThanksZee

[oldschool]

oh yeah i followed the transmission self diagnosis instructions and the "AT check" light came on but thats all that happen, the was no flashing an no chage in the display it just read AT Check. Is there something i'm doing wrong or is there something i'm not doing?

[Q45tech]

The electronic diagnosis only test sensors and cannot evaluate mechanical failures or wear.

ATF color, smell, and a pan drop for debris on magnet is the usually step

10 years is a good life for an automatic transmission behind a powerful V8 getting 15 on a early Q is almost unheard of unless very low stress and annual miles.

Most early Q we see are on at least number 2 or 3rd unit.

I put #3 in mine back in 2002 at 235k.

[infinitinut2]

10 years is a good life for an automatic transmission behind a powerful V8 getting 15 on a early Q is almost unheard of unless very low stress and annual miles.

Most early Q we see are on at least number 2 or 3rd unit.

......uhhhh, Dennis, 92 Q, w/137K on OEM trans. Always heeding your advice, should I carry spare trans in trunk along with that spare MAS?

[Q45tech]

We rarely see weird early low mileage Q45. Real men drive at least 15,000 miles per year in bumper to bumper traffic.

Obviously there are exceptions to every general statement. Using mileage to define something's life where on/off actions occur is confusing, because even transmissions are rated as to the abilty to last thru 100,000 shifts.

I logged a 480 mile trip where there were only ~30 shifts cruise control for 455 miles. Yet my more typical 10 mile trip has 40 gear changes.

Normally a transmission warns you if you are sensitive to the signs giving you a few days/weeks to line up a replacement.

I always keep a spare since buying when you can get the best price vs forced to take any old unit that might work.

You can always get your money back on ebay or a local shop if you junk the car.

I bought enough R12 in the early 90's to last 20 years even with selling 60 pounds. Buying good wrecked Q is a very profitable [or money saving] exercise.

[Fred D.]

transmission is broken in my opinion.Or needs to be rebuilt, in fourth it should maintain and gain speed in less going up a major incline, or hauling five big people.One problem is unkown vehicle history, 104,000 is not enuf to wear out the trans expecialy just the fourth gear.

[Fred D.]

My 1994 Q45 with 150,000 on it with the oem trans, works great in all gears, never rebuilt or replaced just well maintained. It could be abad part, it happens regardless of mileage age even maintance, you just have to be systmatic with determining the problem if it's, electric, mechanical, fuel, air, or fluids.