What is the cause of vibration? 04 Mustang V6 Auto

Hi All,
I’m looking for advice on this issue. I recently bought a 2004 Mustang convertible V6 auto with 180K miles to be my daughter’s first car. The car has a driveability issue. It has a “rumble-strip” like vibration at speeds between 35-55 mph. This is when accelerating or decelerating. If I slip the car in neutral when driving the vibration is gone. Here is what I have done: new plugs, wires, coil. New u-joints. Front end needed a new tie rod end on right side, new transmission filter and fluid (only replacing lost pan fluid). Another thing wrong with the car (possibly related?) is that the ABS & traction control lights are stuck on indicating a system failure with the ABS.

Note that when replacing the ujoints I noted a couple of things:
1- there is SOME amount of play at the transmission tailshaft bushing. It seemed excessive to me, but a local transmission shop told me that if it is not leaking fluid that it is not a problem. I did not gage the movement, but it was close to 1/16".
2 - The other thing I noticed is that the universal joint for the rear yoke was a little bit stiff, meaning that it did not move as easily as I would have thought that it should. This was the case with both the old rear u-joint and the new, This indicates to me that the pinion trunnion ears are not perfectly aligned, but not sure what I should expect.

Anyone have a similar problem solved or recommendations?

I am fairly confident in saying that the symptoms are the result of a problem with the torque converter lock-up mechanism.

If you can find the electrical connection for this solenoid on the outside of the transmission case, try unplugging it, and seeing if the problem goes away when you drive the car. If it goes away, then you need to replace that solenoid.

Thanks VDCdriver. I will definitely attempt to find that solenoid connector, fuse, or something to take it out of the loop and give it a try! I thought it might be torque converter related also, so I tried a simple test of holding the brake and applying throttle, but there was no vibration. The car is probably sophisticated enought to recognize the I was not moving and handlle torque converter lock-up differently. I read somewhere that Ford designed this tranny to be a constant-slip, so I have been considering ways to figure out if it is a torque converter problem.

Does the car have to moving for the vibration to occur? Or can you make it happen at a standstill by manipulating the engine RPM?

Does the driveshaft spin true with no wobble or run-out? Have you checked the rear wheel bearings? There should be NO up and down movement of the rear axles in their bearings…


Yes the car has to be moving - 35 mphto 55 mph and vibration seems worse in the middle of that range. I will have to check for driveshaft runout - probably can loan a dial indicator from work. I will check the rear wheel bearings, but have not noticed rear wheel play.


Disconnecting the TCC solenoid had interesting result, but did not prove conclusive for me. I still noted vibration at the speed of concern, but the engine was running much higher RPM as it would not shift into OD. At 50 mph the torque converter would only lock when engine RPM reached about 3200 RPM. Otherwise disengaged like the car was in neutral. Not sure if that is normal to be expected or not?

In looking at the electronic control for your transmission, I noticed that all of the wiring goes through one plug into the transmission. So unless you pulled out only the wire for the TCC, you disconnected the entire plug. The transmission would stay in 2nd gear with the TCC unlocked. Off the top of my head, I don’t know if 2nd is a freewheeling gear.

Another way to test for TCC shudder is to lightly press the brake pedal while holding the throttle pedal steady to the point where the brake lights come ‘on’ but the frictions have not engaged. That will unlock the TCC. See if the shudder goes away when you use your left foor to lightly press the brake pedal. Do this safely when no one is following you closely as this might anger the follower into thinking you are goofing with him/her.


Thanks for the response on this. Checked the codes last night and had P0743, P0750, & P0755. I believe that all of these were most likely related to my short drive with the TCC plug disconnected. Your description of being stuck in 2nd gear is dead on. I read elsewhere online that a lot of cars have high stall torque converters and the TCC is what causes lock at lower RPM. That seems to be an accurate description of how it drove with the TCC solenoid disconnected. The TC was disengaged except for over about 3K RPM. Next drive will be with one foot on the brake and one on the gas (ref Sammy Hagar). From now on when I see people riding their brakes I may assume that they are correcting a TC shudder instead of thinking bad thoughts about them!

Here is a low tech suggestion. You may have a broken belt in one of your tires that do not cause issues until a specific speed. Check this out by rotating your tires and seeing if the vibration is suddenly in the rear of your vehicle.

Tested the TCC solenoid by gently touching the brake pedal when driving and noted that the RPMs rose by about 10%, but no change at all in the vibration. I guess that means that it is not a torque converter slip issue. I am becoming more convinced that I have a driveshaft or something else out of balance or bent. I noticed last night that the driveshaft has yellow paint pen letters and numbers written on it. Makes me think that a previous owner may have replaced it for some reason. Also makes me think that the factory yellow marks on the ends that should be aligned with the pinion and slip trunnions are not correct for that car. I guess that I will have to start playing with driveshaft indexing to see if that makes it better or worse.

Hey All,

Accepting any and all ideas on what might be the cause that I need to look into closer:

I have been struggling to find and repair this issue using hit or miss approach without success yet. Here’s what I have done to date:

  • New Trans filter and some fluid (replaced amount from pan only)
  • TC Shudder Fix Additive
  • replaced universal joints
  • replaced tail shaft bushing & seal
  • balanced drive shaft
  • replaced right side axle shaft & wheel bearing
  • new rear end fluid
  • had all 4 tires rebalanced and rims checked

The symptoms remain unchanged:
high frequency vibration (aka “rumble-strip”), not a thump-thump. This occurs between 40-60 mph with it worst at 50mph. Most noticeable during acceleration, less noticeable during deceleration or maintaining speed, disappears in neutral. This is definitely NOT engine RPM or gear dependent.

The tail-shaft yoke still had more play after replacement than I would like to see, but everyone seems to indicate that some play is normal and I have yet to find a spec for it. I replaced the right axle after running the car up to speed with a jack under the rear and noticed that there was some runout wobble of the hub that wheel. That same wheel brake was rubbing intermittently as the wheel would come around also. The new axle corrected those issues, but the vibration has persisted!

The yellow paint numbers and letters tells me that the drive shaft was replaced, with one from a junkyard. I also will guess that your driveshaft is aluminum and Ford has had a lot of trouble with these. Only the V6 engines came with the aluminum driveshafts, the V8 models have steel driveshafts, at least the later V8’s do.

Try googling for Mustang driveshafts, there are companies that specialize in steel replacement driveshafts for Mustangs.

Nope. The driveshaft is steel and was just balanced/corrected by a local reputable shop. They cut off both ends and realigned and welded them. They said that the tube was .04 off concentric and their spec is .01. After reintalling there was no noticeable improvement.

Great discussion (NHM2S)! I too recently bought a 1994 Mustang convertible 73K V8 GT. Noticed the same vibration in my car. The rumble-strip vibration are at speeds between 35-55mph. I have not done anything to this car. The history I was told by previous owner was it was an Arizona car. This car is in Anchorage Alaska now. It drove the Alcan that’s not a great road. Tires need to be replace for sure. The right side looks like it may have seen a smokey burn out ,ok maybe 2 alright maybe 3…LOL. Anyways tires are shot

What’s the cause of the vibration? I bet the answer is “HEAT”. As I said earlier post my car is from Arizona. It’s hot in Arizona. I’m not sure where your car is located. I’m guessing during the 180K miles your torque convertor got to hot. Also the transfluid may not have been changed by previous owner.I’m not a mechanic and know very little about transmissions. There are two types of transmission fluid changes. One being the pan fluid replaced. The other being the entire transmission fluid getting replaced. I’m going to get the all transmission fluid removed from my transmission.I’m not ruling out I just might need a new transmission. Part of the problem for us on these two cars we don’t have the full history of the cars. I’ve left off some information. This is my second Mustang. Look for my next post.

Alright,So why Heat! Maybe you live in Alaska not Arizona. Maybe your in a cold climate and over heating the transmisson is not as likely. Well here’s the full car history on my 1995 ford Mustang GT Convertable at 60K. Grandma drove it off the lot in 1995. She owned it till 2002 when she passed away 17K. I recieved the car ( thank you Grandma). Grandma had a problem she didn’t remember some details. What’s the second step in dropping the top on a ford Mustang? Well which ever step it is. The emergency brake must be applied. The top will not drop with out brake set. Long story short Grandma drove 17K miles with emergency brake set. This builds alot of heat in your transmission. Around 35K miles I realized something was wrong in the transmission. On the free way the car drops 4th down to 3 gear at random. Some sort of pressure problem in the torque convertor my guess. Anyways the pan fluid was removed. It didn’t look like transfluid at all. More like very old oil, bad burn smell. This is an example of history of another mustang. Who knows what happens in a 180K period. P.S. I’m thinking of running a cooler thermostat becasue both 302 motors run hot. To reduce heat transfer from engine to transmission.

So, 1KID - did your complete fluid change resolve the vibration issue? I’ve been off working on some house project and not been on this case for a little while, but I am about to get back into it. The fluid change that I did was the pan drain only, so majority of the fluid resides in the converter did not get replaced. You are correct about the parking brake, in fact my wife and daughter put the top down to drive it one time and she called me from the school which is a few miles away and said that the car has shaking very badly and smelled really hot. Ugh. I might have to bypass that safety feature and rely on good old common sense not to mess with the top when moving.

Still seeking a solution! So, based on observation of problems with the rear end of the car I went and got a used rear end from a salvage yard. Had a trusted shop install it. Even though they agreed that the original rear end had “significant problems”, that did not improve the vibration issue. The shop said that I had a driveshaft problem, even though I had changed the u-joints and had the p driveshaft balanced, so I found a used driveshaft and installed it. Still the same problem. The shop then said “We have seen this before, there is a problem in the transmission”. So there is a salvage yard local that has a under 100K mile transmission that I could pick up for $200. I’m not convinced that it will fix the problem.

Note: vibration seems to be worse with outside temperature. It had seemed improved, but then temps have gotten colder recently and now it is back to doing it as bad as ever, starting at 35 mph and smoothing out by 70 mph. The only thing that smooths it out is taking foot completely off the gas or putting the car in neutral.

I’m determined to beat this problem, but man just throwing expensive major parts at it is really beginning to irritate me.


To anyone following this thread or searching it in the future, the problem turned out to be the transmission or torque converter. I did not dissect them to determine the exact cause, but replacing fixed the vibration issue. Mustang rides nice now.

Thanks @NH2MS. It’s always nice to know the fix.