I need some advise. I have a 1995 Mustang GT with approximately 78,000 miles. The transmission consistently exhibits a slight vibration / slippage when the car is driven at a moderate acceleration up a hill or going around a curve. The problem occurs around the 35 - 40 mph speed range when making the transition from first to second gear. The problem is rarely experienced while on a straight level road. However, if I floor the accelerator from a standstill then the transmission moves through all of the gears smoothly with no slippage (burning rubbers and all from 1st - 2nd).
Just some background.....I recently had the transmission completely rebuilt (I utilized an OEM rebuid kit) in the summer of 2004, and installed a B&N Shift Kit . The transmission was fine for a while, but now the problem has resurfaced (8000 miles later). I have already spent nearly $2,000.00 dollars on parts and labour. My mechanic is now advising me to change the drive shaft because he says the harmonic balance at the yoke may be slightly warped. Well as you would imagine I am quite skeptical.
Please I really need some advise and guidance on probable causes and solutions. Thanks.
It's possible your TV(throttle valve) cable could be binding or the
throttle vavle itself could be hanging up...it's also possible some of the
internal shift soleniods could be on their way out.
Does the car downshift sluggishly...if you're going 45-60 and mat the gas, does it downshift instantly or is it delayed, and if so, is it a slighty delay or a second or two? Get back to me and let me know.
I AM SURE NO MATTER WHAT I PUT DOWN HERE WILL BE CORRECTED BY VWHOBO,BUT I WILL SAY ANYHOW.YOU SAY VIBRATION,SLIPPAGE.IS IT A HIGH FREQUENCY VIBRATION,LIKE A CHATTERING CLUTCH OR IS IT A VIBRATION OF LOWER FREQUENCY LIKE A DRIVESHAFT,U JOINT?HAVE YOU THOUGHT OF CHECKING THE DIFFERENTIAL OUT?YOU INSTALLED A SHIFT KIT,WHICH CAN BE HARD ON THE DRIVE SHAFTS,U JOINTS AND THE DIFF.IF IT IS A LIMITED SLIP,CHECK WITH FORD AND SEE IF THEY HAVE AN ADDITIVE FOR THE REAR END.DODGE HAD THIS KIND OF PROBLEM WITH THE 1999 AND 2000 PICK UP TRUCKS,AND WHEN YOU DROVE IT IT FELT LIKE A TORQUE COVERTER KICKING IN AND OUT AT HIGH SPEED.IT IS NOT FELT UNDER HARD ACCELERATION BECAUSE OF THE TORQUE ON THE GEARS.
Hey Don, thanks for providing some insight. As it relates to the downshift
around 45 -60 mph and flooring the accelerator, honestly, I don't recall
having felt the problem at this speed when the accelerator was floored. I
will make it a point to try this out today when I knock off to see how the
Additionally, one very important point I forgot to mention is that from since the tranny was repaired last year the car has developed "morning sickness." When I start the car in the morining and shift it in to gear I have to wait a minute before it actually takes gear. I was doing some reading from the different repair forums and it seems as if this problem is most likely caused by the torque converter emptying at night and it refills in the morning after the car has started....hence the delay in taking gear. My concern however, is that it never did this prior to the transmission being rebuilt.
I will give you an update tomorrow with my findings. Thanks again.
Hey Lobster, thanks for the insight. The vibration is off a lower
frequency. I will follow-up on having the differential checked-out and also
on whether or not it is a limited slip and the rear end additive.
Also, from since the tranny was rebuilt last year the car has developed morning sickness. Once started in the morning and shifted into gear, I have to wait a minute for it to take gear before pressing the accelerator to move. Otherwise, it feels as if the car is still in Park or Neutral. Any thoughts??
IT SOUNDS LIKE THE TORQUE CONVERTER.UNDER LIGHT LOAD IT IS LOCKING AND UNLOCKING AT A CERTAIN RATE.WHAT HAPPENS IF YOU HOLD IT IN 3 RD GEAR?DOES IT BEHAVE DIFFERENT? I WOULD HAVE THE TRANSMISSION FLUID PUMPED OUT AND REFILLED.THE VALVE BODY MIGHT BE DOING IT TOO.IF THERE IS VARNISH BUILD UP INSIDE.WHAT COLOR IS THE TRANSMISSION FLUID?IF IT IS NOT BRIGHT RED,CHANGE IT.ABOUT 120 DOLLARS.THIS MORNING SICKNESS THING PUT A DIFFERENT LIGHT ON THE PROBLEM.THE DIFFERENTIAL WOULD NOT DO THAT.
I was able to test the car yesterday and the problem did not occur. The transmission actually responded very quickly, no hesitation and lots of power. Could it possibly be the harmonic balance on the engine and not the transmission after all that is creating the problem? Let me know what you think.
The interesting thing is that my mechanic replaced the HB last year as well, but he had to use a used one as a brand new HB could not be found on the Island. The challenge though is that I had a lot of work done to my car at the same time and so when the problem went away, it was hard to tell what corrected it. Is there an easy way to determine if the HB is on its way out?
Is it possibly the harmonic balance on the engine?
I will check the colour of the transmission fluid and have it changed if necessary. Do you suggest any additives be added to the fluid? Also, I've never experienced the problem at higher gears it is always around the 30 - 45 mph speed range and during the transition from fist to second gear. Those conditions along with the added strain on the car due to a steep incline or a sharp curve make it happen.
I have not run into the "morning sickness" problem before unless the tranny is going or low on fluid or the fluid contaminated (water or something) try adding one PINT of fluid and checking the level, if it has not changed add another until it does change. That may or may not fix the problem but it is cheaper than a new tranny.
IN FIRST GEAR AT 30 MPH?
the rear end must be a higher gear ratio.take a look at the rpm,and see if you can get the problem in the next gear at the same rpm.there is a company called AMS they make amazing oil and they have a superior quality transmission fluid.if it is the harmonic balancer,look and see if the rubber has any defects.they do separate .i had a 3.0 litre ford v6 and the balancer separated at 146000 km.however,in first gear at 30 mph to 45 mph i am thinking 3000 to 4500 rpm.the balancer would make a very high frequency vibration.because your transmission reduces it ,and it is further reduced by the rear end ,that why i was thinking differential.i have seen a low speed gmc truck problem like that and a dodge in the 5.9 litre.,both were given additives for the problem.jeep had a driveline problem in the 98 to 2000 cherokee.similar thing.but what about the tranny fluid,maybe you have 2 problems.here is the thing that i wonder:since the torque curve on the engine is not a straight line,it might not show in another gear,even though the rpm is the same,because the torque is different.if your car was front drive,then i would say you have a cv joint or axle problem.the parallel to that in your car is the drive shaft as yours is rear drive.the shift kit is very hard on these things,and if you get chirps when you shift,the likelyhood of a driveline problem is likely.these are the order of steps i would take,1 check and correct the fluid situation.2 check the balancer.3 check the u joints and rear end .4 try an additive.5 get the intake manifold checked out .its very common to crack unless you have the ford upgrade which is now 1/3 aluminum. the original is all plastic...if you have a slight vacuum leak,it might show as a stutter or low cycle vibration at a certain rpm...
good luck ...
i am responding late to this but I have fixed hundreds of these problems,
common to any ford AOD transmission, the proper fix is to change the fluid
in the trans along with the fluid in the torque convertor (12 qts total)
also replace the filter while the pan is off.
I had a 1992 Crown Vic where the factory service bulletin called for a tranny flush and refil with Mercon V and an oil cooler retrofit (especilly if the car is operated in the Southern U.S. (both Southeastern and Southwestern)
When I first got my T-bird on the road, the trans would slip like hell
under full throttle between 1st-2nd but the 2-3 shift wasn't as bad...it's
also suffered from morning sickness and would occasionally drop out of gear
all together while going around turns. The fluid was topped off, and the
TV cable was properly adjusted...It was driving me crazy.
I sprung for a B&M trans-pak and that did the trick. There are many reasons for the "morning sickness" in the AOD & AODE transmissions and I believe the valve-body gaskets are one of them. Granted, installing a shift kit in an ailing trans isn't a smart idea, it worked for me...I also installed a large aftermarket trans cooler and that stopped slippage problems after making a couple passes at the track. I've also found that the B&M Trick Shift tranny fluid is a beautiful thing.