[Fenderfreak145]

Okay, a few more days driving the car and I've come to some realizations. First I definitely hear the little clunk sound, even with the radio up (it's a mechanic thump, not enough to bother but enough to hear it when you're looking for it).

I've realized that I only hear it when I'm rolling through a stop sign....that is I don't actually come to a complete stop.

Now here's my theory, and this might be wildly off, the car downshifts when slowing down (auto obv) but keeps second gear until a set speed, we'll say 3 mph, then upon stopping the car it goes to first in anticipation of acceleration. Since I only notice the sound after accelerating through a "California roll" or rolling a stop sign I'm thinking the thump is the transmission dropping from second to first as I apply power.

Maybe....maybe I'm wrong but that's just what I'm thinking.

First rear wheel drive and first mustang so I'm probably wrong.

 

[Josephtsai]

Buddy, I don't think that's a transmission problem because there is no shift when my problem happens. The tech also said its more like a drivetrain mechanical problem not a transmission one.

 

[Midnight2012]

So u also notice that sound, right?

Yes but only if I'm watching for it. It's as if the driveshaft has play in it. And it happens most often at a rolling stop like the other poster just said.

---------- Post added at 07:12 AM ---------- Previous post was at 07:10 AM ----------

Okay, a few more days driving the car and I've come to some realizations. First I definitely hear the little clunk sound, even with the radio up (it's a mechanic thump, not enough to bother but enough to hear it when you're looking for it).

I've realized that I only hear it when I'm rolling through a stop sign....that is I don't actually come to a complete stop.

Now here's my theory, and this might be wildly off, the car downshifts when slowing down (auto obv) but keeps second gear until a set speed, we'll say 3 mph, then upon stopping the car it goes to first in anticipation of acceleration. Since I only notice the sound after accelerating through a "California roll" or rolling a stop sign I'm thinking the thump is the transmission dropping from second to first as I apply power.

Maybe....maybe I'm wrong but that's just what I'm thinking.

First rear wheel drive and first mustang so I'm probably wrong.

Try taking off without it down shifting. I bet it stays in second and still does it.

 

[Whitelightning]

No it wasn't my car. Just imagine the feeling on ur car get a lot bigger and noticeable. So it accompanied with a slug and bump feeling. Intuitively, it feels like the brake still slightly trap the car for 0.5 sec when I start to accelerate or so even though there is nothing wrong with the brake. And mine problem happens only when car is warmed up.

---------- Post added at 01:32 PM ---------- Previous post was at 01:30 PM ----------

Maybe I need to have the 3rd dealer to check the car without telling them my experience with the first 2 dealers. I wonder if changing the shock or grease the driveshaft will fix it.

I put some flui in my rear end and fixed my breather valve, it fixed it for a while and now it still does it but is less noticeable.

So, what gears are we all running for this problem? I'm running 2.73 automatic.

 

[Josephtsai]

Mine 2.73. Put some fluid in the rear end can temporarily fix it?

 

[Midnight2012]

I put some flui in my rear end and fixed my breather valve, it fixed it for a while and now it still does it but is less noticeable.

So, what gears are we all running for this problem? I'm running 2.73 automatic.

3:31 but its very slight. Like I said I believe it's normal.

 

[Josephtsai]

Mine is pretty strong, don't know what to do

 

[Midnight2012]

Mine is pretty strong, don't know what to do

Take it to an independant mechanic fora diagnosis. Mine charges like $35.00. Then if they find something wrong make Ford fix it.

 

[Seth7979]

Same problem

Mine is pretty strong, don't know what to do

Joseph,

I just recently purchased the same exact 2013 mustang and have the same issue. It's been almost a year since your last post. Did you find a fix or was this determined to be normal. It seems to be happening only during rolling stops. My car had 700 miles on it when I purchased it.

 

[Whitelightning]

A tune helped my oddly? Because as OP said, it wants to stay in second or something. The tune allows full downshifts and all that. Mine rarely does it now. Still watch the fluid on any 2011/early 12 mustang, breather valve may be gushing it out. No good

 

[Midnight2012]

A tune helped my oddly? Because as OP said, it wants to stay in second or something. The tune allows full downshifts and all that. Mine rarely does it now. Still watch the fluid on any 2011/early 12 mustang, breather valve may be gushing it out. No good

. got any build dates on those 2012's? Where is the breather valve located?

 

[Whitelightning]

. got any build dates on those 2012's? Where is the breather valve located?

It was updated now to say 2011-2013.

 

[Midnight2012]

It was updated now to say 2011-2013.

Thank you

 

[ArtU]

So I do check the shifting, it does start to take off from 1st, I think the sound comes before shifting to 2nd. I haven't try unplug the fuse47. If this is a prob of driveshaft, then why it happens only when I try to accelerate after come to a stop?

The car is designed [factory auto tune]to come to a almost a complete HALT in 2nd gear to save pollution that flies out of engine exhaust during engine breaking. Also coasts better for MPH numbers. Unfortunately, car manufactures have to tune for the Gobermints numbers not customers.

Once you are almost or at complete STOP, the trans will shift to 1st. Backlash all the way from the front to back of your drive train can make that feel like a little bump. In fact if I dot it right, the fron of the car moves forward when that happens. The tiny normal clearance from the flywheel , trans gears, u-joints, drive shaft, differential; all add up to normal backlash. I asked my local Ford Gear specialist about it and he explained it that way to me, I consulted other private shops and they said the same thing.

 

[ronnie948]

ArtU

:thumb:
Ronnie