Clunk In The Rear

kreil45

Member
Mar 18, 2011
36
0
6
Tallahassee, Fl
Ok, I know I have posted this before and I have researched this to no end. Please if some one has the answer help me.

I have an 03 mustang GT automatic and while I am driving around 40-50 if I let off the gas and then on again I get a clunk. Sometimes its louder and hard then others. If I am at that speed and quickly tap on and off it sounds and feels like it the rear end is going to fall off. When this first started I took if to ford and they said the torque converter. So, I wanted a second opion and went to another shop. They said it was the rear upper and lower control arms. Since I wanted to replace them anyway I had them put the UPR rear upper and lowers. I still had the problem. Then they said there was play in the rear and I needed new rear clutchs. So, they replaced them and still same problem. So, they replaced the tranny mount and the u-joints and stiil same problem. They then said that it had to be in the tranny or torque converter. They only charged me $200 for all they did sense the other things they did did not fix it. So, I took it to a friend who is a tranny specialist and he said was the rear end and that I needed a new one. So he replaced the chunk, clutchs and bearings (all ford parts) and still the same problem. So, back to ford and now the say its the rear end but, they don't know for sure.
So, new control arms upper and lower, new tranny mount, new u-joints, and new rear end, and still a loud and hard clunk. Somebody please help!!!!!
It is completely stock except for the rear upper and lower CAs. I have a tune for but, can't use because its 100 times worse.
 
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joshjwc9

Active Member
Jun 12, 2006
1,095
17
39
Palm Harbor, FL
Ok, I know I have posted this before and I have researched this to no end. Please if some one has the answer help me.

I have an 03 mustang GT automatic and while I am driving around 40-50 if I let off the gas and then on again I get a clunk. Sometimes its louder and hard then others. If I am at that speed and quickly tap on and off it sounds and feels like it the rear end is going to fall off. When this first started I took if to ford and they said the torque converter. So, I wanted a second opion and went to another shop. They said it was the rear upper and lower control arms. Since I wanted to replace them anyway I had them put the UPR rear upper and lowers. I still had the problem. Then they said there was play in the rear and I needed new rear clutchs. So, they replaced them and still same problem. So, they replaced the tranny mount and the u-joints and stiil same problem. They then said that it had to be in the tranny or torque converter. They only charged me $200 for all they did sense the other things they did did not fix it. So, I took it to a friend who is a tranny specialist and he said was the rear end and that I needed a new one. So he replaced the chunk, clutchs and bearings (all ford parts) and still the same problem. So, back to ford and now the say its the rear end but, they don't know for sure.
So, new control arms upper and lower, new tranny mount, new u-joints, and new rear end, and still a loud and hard clunk. Somebody please help!!!!!
It is completely stock except for the rear upper and lower CAs. I have a tune for but, can't use because its 100 times worse.
Is it in the driveshaft? Are all of the bolts currently on it and is it aligned properly? Does it only do the clunk at that particular speed? Or every time you let off of the gas? I'd say it is in the driveshaft or Ujoints right now..
 

kreil45

Member
Mar 18, 2011
36
0
6
Tallahassee, Fl
Is it in the driveshaft? Are all of the bolts currently on it and is it aligned properly? Does it only do the clunk at that particular speed? Or every time you let off of the gas? I'd say it is in the driveshaft or Ujoints right now..

the u-joints are brand new. It also does it when I am rolling about 38-55 and i just let on and off the gas real quick its really bad.
 

40oz

Member
Jan 9, 2006
499
2
18
Minneapolis
IMHO you are talking about normal slop in the drivetrain. Everything has a little clearance, and when you let off the gas and then get on it, you are hammering everything with the sum total clearance. IOW, there might be 0.02" clearance between every mechanical connection. If there are five parts, the total slack will be 0.02" x 5 = 0.10" total. When you are on the gas there is no slack - everything is tight against its mate. When you let off the gas and get back on it to make the noise, you are letting everything loose then hammering each part with the total amount of slack in the drivetrain.

Stop doing that. You know your u-joints, rear end, and rear suspension is fine because you've replaced all that. A shop is not going to tell you "it's normal" because you are bringing them business. But the noise you are hearing is normal. It sounds bad because it is. There is nothing wrong with getting on the gas, but intentionally making every part smack every other part repeatedly is not beneficial.
 

trombonedemon

Well-Known Member
Jun 25, 2009
1,963
39
59
U.S.A, U.S.A., U.S.A.!
IMHO you are talking about normal slop in the drivetrain. Everything has a little clearance, and when you let off the gas and then get on it, you are hammering everything with the sum total clearance. IOW, there might be 0.02" clearance between every mechanical connection. If there are five parts, the total slack will be 0.02" x 5 = 0.10" total. When you are on the gas there is no slack - everything is tight against its mate. When you let off the gas and get back on it to make the noise, you are letting everything loose then hammering each part with the total amount of slack in the drivetrain.

Stop doing that. You know your u-joints, rear end, and rear suspension is fine because you've replaced all that. A shop is not going to tell you "it's normal" because you are bringing them business. But the noise you are hearing is normal. It sounds bad because it is. There is nothing wrong with getting on the gas, but intentionally making every part smack every other part repeatedly is not beneficial.
A 99-04 mustang gt w/o some clunks is a world w/0 women or O2.
 
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kreil45

Member
Mar 18, 2011
36
0
6
Tallahassee, Fl
today i lifted up the rear end onto jack stands and put it into drive and it was making a clunking noise while in drive. I know its tipocal for mustangs to clunk but from slowing down because a car in front is turning and accelerating normaly up to speed and it sounding like the bottom is falling out is not normal.
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
80
99
Canada
With the car on stands and the trans in neutral, crawl under and give the driveshaft and U-joints a good inspection. While under there, also inspect the condition of the rear trans mount...
 

flstang65

10 Year Member
Dec 6, 2007
1,487
134
94
SE Georgia
Depending on how you drive your car, some good OEM ones. If you want a little more performance, you can go with urethane ones or solid spherical ones. Have you checked the shock mounts inside the trunk?
 

Foxslider

Active Member
Oct 25, 2019
169
44
38
32
Houston, TX
My foxbody does this also. Only when i let abruptly off gas. Im thinking control arm bushings.(+ giving myself a reason to buy control arms ha) Possibles: loose or bad shocks, axle play, wheel bearing, drive shaft to rear end connection area stuff. I cant feel my clunk. Just hear it. My pinpoint is rear passenger i believe.