Cobra Clunk - Any new proven fixes?

IA Shelby

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So I have found the perfect terminator with one small caveat. It has the cobra clunk.

Can this be fixed or is this something will cost thousands to diagnose and with no guarantee of success.

How many of you have been able to fix it and how many have not had success?

FWIW my current terminator is clunk free.
 

Sagittaria

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Solid diff mounts and tightened rear end backlash. The "clunk" is just the tranny/DS/rearend/CV axles bouncing back and forth from all the slack. The tranny and CV axles have inherent slack that you can't do anything about but you can tighten up the gears and hopefully remove enough of the slack to take care of it. Should be shooting for .008-.010. Ford calls for .008-.015.

Go underneath the car and try moving the DS with your hand with the car in gear. You'll see exactly what I'm talking about.

http://www.svtperformance.com/forum...really-figured-out-clunk-sound-issue-yet.html
 

IA Shelby

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Solid diff mounts and tightened rear end backlash. The "clunk" is just the tranny/DS/rearend/CV axles bouncing back and forth from all the slack. The tranny and CV axles have inherent slack that you can't do anything about but you can tighten up the gears and hopefully remove enough of the slack to take care of it. Should be shooting for .008-.010. Ford calls for .008-.015.

Go underneath the car and try moving the DS with your hand with the car in gear. You'll see exactly what I'm talking about.

http://www.svtperformance.com/forum...really-figured-out-clunk-sound-issue-yet.html

Thank you for the help. Any specific recommended brand of solid differential mounts?
 

Sagittaria

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Blueline

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It could be something very simple: loose differential bolts, need to upgrade the sub frame bolts to 14mm or 9/16", and just look over the rear irs for anything loose. Depending on the "clunk" it can be anything from mounting hardware to rear differential backlash. You really need to get it in a lift and inspect it. GL!

Edit: when I bought my first 04 Cobra the first day I took it out for a drive I was stopped at a light, put the car in first and as I let off the clutch I had a huge clunk! Scared the crap out of me. Lucking I was 1 block from my buddies shop. Put her on the lift and found the two rear differential bolts which go through the cover were about to fall out! Needless to say I had other issues with the rear but tightened the bolts and no more clunk.
 
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03cobra#694

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It could be /something very simple: loose :differential bolts, need to upgrade the sub frame bolts to 14mm or 9/16", and just look over the rear irs for anything loose. Depending on the "clunk" it can be anything from mounting hardware to rear differential backlash. You really need to get it in a lift and inspect it. GL!

Edit: when I bought my first 04 Cobra the first day I took it out for a drive I was stopped at a light, put the car in first and as I let off the clutch I had a huge clunk! Scared the crap out of me. Lucking I was 1 block from my buddies shop. Put her on the lift and found the two rear differential bolts which go through the cover were about to fall out! Needless to say I had other issues with the rear but tightened the bolts and no more clunk.

This is what fixed most of mine, I used 9/16".
 

UncleSAm

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I did the front and rear diff bushings from FTBR. Just replaced those 3 rubber parts and went away. Can't see it being much cheaper fix then that
 

mrose75

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I've always thought the "Cobra Clunk" was just drivetrain slack. My brand new Cobra did this in 04. Called the dealer and they explained it as such. Haven't given it a second thought since then. :shrug:
 

nxs450

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The biggest player is the 3 differential bushings. Even a car with 10k will exhibit some degree of fatigue in the bushings. Most of the cars with higher miles will see severe breakdown of the bushings, and a few with complete failure. Another wards the front bushings will be totally worn out and the center bolt will be thumping against the bushing housing. I have seen it on several cars.
 

cj428mach

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The biggest player is the 3 differential bushings. Even a car with 10k will exhibit some degree of fatigue in the bushings. Most of the cars with higher miles will see severe breakdown of the bushings, and a few with complete failure. Another wards the front bushings will be totally worn out and the center bolt will be thumping against the bushing housing. I have seen it on several cars.

Alan, do you know did the FTBR bushings fix the clunk on Danny's car?
 

cj428mach

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Glad to hear that fixed it.

OP nxs450's nephew bought my old 03 with 80k miles on it. The car had a pretty noticeable cobra clunk, so if FTBR bushings fixed it then that's where I would start.
 

Bdubbs

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I have the 9/16 subframe bolts and ftbr diff bushings. I still get the "clunk" normally only when shifting into 2nd gear. Neither of the mods I listed made any difference in less "clunk" sound.
 

IA Shelby

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I have the 9/16 subframe bolts and ftbr diff bushings. I still get the "clunk" normally only when shifting into 2nd gear. Neither of the mods I listed made any difference in less "clunk" sound.

Your experience is what concern's me the most. Every car is different. While the bushing change and subframe bolts seem to fix most they don't fix all. Hate to spend big dollars on a car to find out it is one of the tough ones.

Decision time.
 

Midnight_Cobra

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Your experience is what concern's me the most. Every car is different. While the bushing change and subframe bolts seem to fix most they don't fix all. Hate to spend big dollars on a car to find out it is one of the tough ones.

Decision time.

New bushings, bolts, and mounts get rid of the 'IRS Clunk'. The clunk in the drivetrain varies from car to car, backlash, play, etc. To be honest, you probably won't know until you do one or the other. I personally have stock gears, stock drivetrain for that matter. I have no clunk what so ever. Like you said, one way to find out.
 

nxs450

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Most vehicles with standard transmissions are going to have a little drive train clunk. The main reason you notice it over a automatic, is the torque convertor acts like a cushion. Standard transmissions are directly connected to the fly wheel. Once you get a feel for the car you can avoid a lot of it. Clutching, shifting etc. Basically keeping the drive train preloaded is what keeps it from clunking.
 

CobraBob

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New bushings, bolts, and mounts get rid of the 'IRS Clunk'. The clunk in the drivetrain varies from car to car, backlash, play, etc. To be honest, you probably won't know until you do one or the other. I personally have stock gears, stock drivetrain for that matter. I have no clunk what so ever. Like you said, one way to find out.

This is true. I think most accept it. I remember back in the late '90s my Camaro was at Callaway Cars for a new motor and some suspension modifications. While I was chatting with their chief engineer, I asked him if the drivetrain clunk (I had a T-56) was normal. His reply was that since it was a Camaro, yes, it's normal play in the drivetrain, and that the higher cost Corvette with a T-56 has less slop in the drivetrain. I don't know if that is entirely true, but it made sense at the time. Do the GT-500s have the same drivetrain clunk issue?
 

zeus201

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Your experience is what concern's me the most. Every car is different. While the bushing change and subframe bolts seem to fix most they don't fix all. Hate to spend big dollars on a car to find out it is one of the tough ones.

Decision time.

If you are hesitant then don't do it, but if you do pull the trigger, I'm pretty positive a few of us could help you out. I still have the FTBR installation tools....
 

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