Rear End Clunk - 2003-04 Mach 1 Registry Owners Club

markthenarc · 09-21-2005, 06:47 PM

OK When I give it gas and then let off (any gear) I hear a clunk or knock
coming from under the car towards the rear. Its more noticable when I tap the brakes and the car slows down and "knock"

If I give it gas it does not make the noise, only when I let off or hit the brakes. Its not LOUD but noticable. It almost seem like something is sliding forward when I brake and hitting something causing the noise.

I did almost total the car last week when I grabbed 2nd instead of 4th getting on the freeway. Went in and out of the ditch and slide sidways across all three lanes and ended up tapping the gaurd rail with the front bumper.

The car felt fine afterwards, just misssing a bit of paint up front. Scarey none the less.

I read somewhere about welds being weak somewhere in the rear end???

Or is this just normal

whitegt46 · 09-22-2005, 10:00 AM

the clunk is drivetrain slop we all have it i installed an aluminum drive shaft and poly motor and trans mounts and the clunk is almost non existant go figure.

markthenarc · 09-24-2005, 01:44 AM

Umm OK, theres like 56 views and only 1 reply. Is this true? This is noise is normal??

goebbelj@hotmai · 09-24-2005, 10:57 AM

Sounds like driveline slop. When your at about 3000 rpms in first and you let off the gas, then tap the gas, then let off the gas do you get that knock? If so, it's probably what whitegt46 suggested. I've changed over to a carbon fiber driveshaft. My shifts are nice and smooth.

MA-MACH1 · 09-24-2005, 11:39 AM

I get a knock from the rear if I'm off throttle at low rpm in 5th then mash the throttle - solution: drive more smoothly, knock is almost non-existant now. It's certainly not unique to this car - I've experienced some sort of transmission slop in about 1/2 the cars I've owned.

markthenarc · 09-24-2005, 02:43 PM

Ok so change the driveshaft and all is good?

How much is a carbon fiber shaft? I've see aluminum for under 200$

I really dont like this sound! But is a Ford right?.....OOOoo my bad. J/K.
I've just never had a rear wheel drive car, or Mustang before so I'm a bit parinoid.
So everything is new to me.

Im a newbie!

goebbelj@hotmai · 09-24-2005, 03:40 PM

Quote:

Originally Posted by markthenarc

Ok so change the driveshaft and all is good?

How much is a carbon fiber shaft? I've see aluminum for under 200$

I really dont like this sound! But is a Ford right?.....OOOoo my bad. J/K.
I've just never had a rear wheel drive car, or Mustang before so I'm a bit parinoid.
So everything is new to me.

Im a newbie!

The carbon fiber will cost in the neighborhood of 900. You just need to make plan's of how much horsepower your going to have so they can build the carbon fiber driveshaft for it. In my case, I had them build the driveshaft to withstand 550 ft/lbs of torque off the initial dig, multiplied by my first gear ratio. I'll probably never make it to that big of a number, but I'm ready for it.

Everyone say's the aluminums work fine too. I dunno.

I have also upgraded my rearend to 31 spline axles and had my spyder gears and backlash tightened down a little more than stock specs.

markthenarc · 09-25-2005, 01:49 AM

UUmm Yeaah....You a bit more serious about it than me thats for sure. I have no plans on any power adder. The car scares me already. So a 900 driveshaft...probably not.

But I'll look into the aluminum one though, if that will stop the clunking....Its either that or I wait to install the new audio sys and just turn it up to drown out the noises..

Thats always worked in the past..

goebbelj@hotmai · 09-25-2005, 02:37 AM

Quote:

Originally Posted by markthenarc

UUmm Yeaah....You a bit more serious about it than me thats for sure. I have no plans on any power adder. The car scares me already. So a 900 driveshaft...probably not.

But I'll look into the aluminum one though, if that will stop the clunking....Its either that or I wait to install the new audio sys and just turn it up to drown out the noises..

Thats always worked in the past..

Go for the sterio option. It's a for sure fix. :LAUGH:

Angus66 · 09-25-2005, 07:03 AM

Quote:

Originally Posted by markthenarc

Ok so change the driveshaft and all is good?

I have an FRPP aluminum d/s & I still have the clunk.

In fact, I have little left back there that Ford installed when the car was new & still have the clunk.

I'm thinking that it's actually forward of the d/s even though it doesn't sound like it from the driver-seat.

MachRan · 09-25-2005, 09:02 AM

I had the clunk. I took it to a different mechanic than the one who set my rear up. He said the backlash was set at 12. Which is within spec (8-12). But he also said that 12 in his opinion is too much for a stick car. He recommended setting it to 7 or 8. So thats what we did and I haven`t had a single clunck since. I highly recommend having your backlash checked and if need be adjusted.

By the way the first thing I did to try to fix it myself was buy an aluminum driveshaft. It helped some, but didn`t fix the problem.

markthenarc · 09-26-2005, 12:23 AM

Is that something under warranty I can have fixed?? If so that'd be great!!
If not I have a friend who is a mechanic who might know what your talking about.

crimsongt · 09-26-2005, 08:08 AM

If you complian they will look at it and try tofix the problem if the ford tech thinks there is aproblem. My 04gt got the rear end guts replaced at 3500 miles cause the backlash was too high and the end play was too high according to the ford tech. but I would hear a clunking when I went to turn at a stop sign

XCELR8 · 09-26-2005, 10:14 AM

it's backlash. Just about any rear wheel drive car will have it.

Blue Baron NC · 09-26-2005, 08:11 PM

I have it! Sometimes it sounds like the front right that clunks to me???? Peace!

Mean04Mustang · 10-09-2005, 11:27 PM

I just installed my FRPP aluminum driveshaft. WOWOWOWOW what a diferance this can make. Its got to be one of the best mods Ive done so far. Everything feels so smooth, the shifting and the CLUNK seems to pretty much disappear. I hope that I wont notice it come back as I get used to the new driveshaft but none the less Its great. I didnt notice much more power or acceration but smoothness Its great and well worth it.

WOODY · 10-10-2005, 10:25 PM

How much does the FRPP aluminum drive shaft run?

E-MACH · 10-18-2005, 05:23 PM

[QUOTE=markthenarc]OK When I give it gas and then let off (any gear) I hear a clunk or knock
coming from under the car towards the rear. Its more noticable when I tap the brakes and the car slows down and "knock"

I had the same problem with my '04. It was bad bushings on the rear control arms. They were bad from day 1... probably pranged at the factory. This was covered under warranty. The Ford mechanic said the rubber was split, thus causing that periodic metallic thud/thunk sound. Also, whenever I drove over an uneven road (twisted) surface, the car would creak and groan out of the rear. This too is gone. It sounded like an old Chevy. Keep us posted.

09-21-2005, 06:47 PM	#1
markthenarc Registered User Join Date: Feb 2005 Location: Brew City Posts: 758	Rear End Clunk OK When I give it gas and then let off (any gear) I hear a clunk or knock coming from under the car towards the rear. Its more noticable when I tap the brakes and the car slows down and "knock" If I give it gas it does not make the noise, only when I let off or hit the brakes. Its not LOUD but noticable. It almost seem like something is sliding forward when I brake and hitting something causing the noise. I did almost total the car last week when I grabbed 2nd instead of 4th getting on the freeway. Went in and out of the ditch and slide sidways across all three lanes and ended up tapping the gaurd rail with the front bumper. The car felt fine afterwards, just misssing a bit of paint up front. Scarey none the less. I read somewhere about welds being weak somewhere in the rear end??? Or is this just normal

09-22-2005, 10:00 AM	#2
whitegt46 Registered User Join Date: Oct 2003 Location: Long Island NY Posts: 104	Re: Rear End Clunk the clunk is drivetrain slop we all have it i installed an aluminum drive shaft and poly motor and trans mounts and the clunk is almost non existant go figure. __________________ Sold my stang........What a mistake

09-24-2005, 01:44 AM	#3
markthenarc Registered User Join Date: Feb 2005 Location: Brew City Posts: 758	Re: Rear End Clunk Umm OK, theres like 56 views and only 1 reply. Is this true? This is noise is normal??

09-24-2005, 10:57 AM	#4
goebbelj@hotmai Mach 1 Driver Join Date: Aug 2003 Location: Prior Lake, MN Posts: 889	Re: Rear End Clunk Sounds like driveline slop. When your at about 3000 rpms in first and you let off the gas, then tap the gas, then let off the gas do you get that knock? If so, it's probably what whitegt46 suggested. I've changed over to a carbon fiber driveshaft. My shifts are nice and smooth.

09-24-2005, 11:39 AM	#5
MA-MACH1 Thread Killer Join Date: Oct 2004 Location: Morrisville, NC Posts: 1,050	Re: Rear End Clunk I get a knock from the rear if I'm off throttle at low rpm in 5th then mash the throttle - solution: drive more smoothly, knock is almost non-existant now. It's certainly not unique to this car - I've experienced some sort of transmission slop in about 1/2 the cars I've owned. __________________ 03 Mach 1 Torch Red 5 sp IUP 98 GT (long gone) Post killing skills - A+

09-24-2005, 02:43 PM	#6
markthenarc Registered User Join Date: Feb 2005 Location: Brew City Posts: 758	Re: Rear End Clunk Ok so change the driveshaft and all is good? How much is a carbon fiber shaft? I've see aluminum for under 200$ I really dont like this sound! But is a Ford right?.....OOOoo my bad. J/K. I've just never had a rear wheel drive car, or Mustang before so I'm a bit parinoid. So everything is new to me. Im a newbie!

09-25-2005, 01:49 AM	#8
markthenarc Registered User Join Date: Feb 2005 Location: Brew City Posts: 758	Re: Rear End Clunk UUmm Yeaah....You a bit more serious about it than me thats for sure. I have no plans on any power adder. The car scares me already. So a 900 driveshaft...probably not. But I'll look into the aluminum one though, if that will stop the clunking....Its either that or I wait to install the new audio sys and just turn it up to drown out the noises.. Thats always worked in the past..

09-25-2005, 09:02 AM	#11
MachRan Registered? Join Date: Oct 2003 Location: Havre de Grace, MD Posts: 1,071	Re: Rear End Clunk I had the clunk. I took it to a different mechanic than the one who set my rear up. He said the backlash was set at 12. Which is within spec (8-12). But he also said that 12 in his opinion is too much for a stick car. He recommended setting it to 7 or 8. So thats what we did and I haven`t had a single clunck since. I highly recommend having your backlash checked and if need be adjusted. By the way the first thing I did to try to fix it myself was buy an aluminum driveshaft. It helped some, but didn`t fix the problem. __________________ 87 Turbo T Limited 10k org miles 87 Turbo T light chestnut (sold) 86 SVO 7B (sold) 95 Cobra 347 (SOLD) 03 Azure blue 5 spd (SOLD) 93 Calypso coupe (SOLD) 90 LX Vert (SOLD) 86 GT (SOLD)

09-26-2005, 12:23 AM	#12
markthenarc Registered User Join Date: Feb 2005 Location: Brew City Posts: 758	Re: Rear End Clunk Is that something under warranty I can have fixed?? If so that'd be great!! If not I have a friend who is a mechanic who might know what your talking about.

09-26-2005, 08:08 AM	#13
crimsongt Trailor Park Pimpin Join Date: Nov 2004 Location: West Georgia Posts: 377	Re: Rear End Clunk If you complian they will look at it and try tofix the problem if the ford tech thinks there is aproblem. My 04gt got the rear end guts replaced at 3500 miles cause the backlash was too high and the end play was too high according to the ford tech. but I would hear a clunking when I went to turn at a stop sign __________________ 2003 Mach 1 Check out WWW.MUSTANGMAFIA.COM

09-26-2005, 10:14 AM	#14
XCELR8 Registered User Join Date: Sep 2004 Location: Virginia Posts: 328	Re: Rear End Clunk it's backlash. Just about any rear wheel drive car will have it.

09-26-2005, 08:11 PM	#15
Blue Baron NC KEEP ON A MACHIN ME BABY Join Date: Aug 2004 Location: southern pines, nc Posts: 1,432	Re: Rear End Clunk I have it! Sometimes it sounds like the front right that clunks to me???? Peace! __________________ Blue Baron NC Bone Stock and still Hot!

10-09-2005, 11:27 PM	#16
Mean04Mustang 2004 mustang Mach 1 Join Date: Jan 2005 Location: Virginia Beach, VA Posts: 352	Re: Rear End Clunk I just installed my FRPP aluminum driveshaft. WOWOWOWOW what a diferance this can make. Its got to be one of the best mods Ive done so far. Everything feels so smooth, the shifting and the CLUNK seems to pretty much disappear. I hope that I wont notice it come back as I get used to the new driveshaft but none the less Its great. I didnt notice much more power or acceration but smoothness Its great and well worth it. __________________ 2004 Mustang Mach 1 Competition orange IUP upgrade MODS: -JLT Ram Air kit -Triple Gauge pod (painted to match) -Colbalt 2 gauges (oil pres. ,water temp, fuel pres.) -MAC Catted Pro-chambers -PHP Intake spacer -SLP Loudmouth II Cat-back -Diablo Predator custom tune -Plasma Booster -NGK Iridium Spark Plugs -MGW Shifter w/ red handle -Kenny Brown Matrix Subframe System -Ford Racing Aluminum Drive Shaft -UPR clutch quadrant extreme w/firewall adjuster Cant fit anymore

10-10-2005, 10:25 PM	#17
WOODY Registered User Join Date: Apr 2005 Location: Houston, TX Posts: 550	Re: Rear End Clunk How much does the FRPP aluminum drive shaft run? __________________ Past: 2004 Azure Blue w/ IUP Short Shifter Kooks Long Tubes & matching o/r X Borla Stinger bowl-ported heads from Lidio @Alternative Auto 01 cobra intake cams Pro5.0 4.10's Superchip K&N Roy Spacer 17X9 Black Bullits w/ 275 BF's Current: 2004 AB Mach 1 w/ IUP O/R Prochamber, Flows, Aluminum D/S, Intake Spacer

10-18-2005, 05:23 PM	#18
E-MACH Registered User Join Date: Apr 2004 Location: St. Louis Posts: 580	Re: Rear End Clunk [QUOTE=markthenarc]OK When I give it gas and then let off (any gear) I hear a clunk or knock coming from under the car towards the rear. Its more noticable when I tap the brakes and the car slows down and "knock" I had the same problem with my '04. It was bad bushings on the rear control arms. They were bad from day 1... probably pranged at the factory. This was covered under warranty. The Ford mechanic said the rubber was split, thus causing that periodic metallic thud/thunk sound. Also, whenever I drove over an uneven road (twisted) surface, the car would creak and groan out of the rear. This too is gone. It sounded like an old Chevy. Keep us posted. __________________ Keep on running

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