2021 Mach 1 - 1200 miles - clunk when taking off (Sometimes......)

[wiedemab]

Well - dealer figured out the issue, but we are working to figure out the best way to solve it. As I mentioned, I put the car up on my lift and check all of the bolts I could find and nothing seemed loose.

They were able to identify that the PS front differential mount bolt was "loose" - more like seized up, but not tight against the mount. I checked it and it wouldn't turn, but apparently it got tight before pulling up against the mount. They can't get it to tighten or loosen/back out. I'm not sure if it cross-threaded at the factory and they just torqued it until it hit their spec and didn't realize it or what.

Worst case, I'm thinking I can center punch the bolt from the back-side and drill into it to relieve some of the pressure and see if it'll come out. If the bushing is messed up, that's a bit more of a PITA to deal with from what I gather. One option I would consider is to drill it out and "Thru-bolt" it, but I'm guessing the dealer won't do that under warranty.

I'll keep you all posted........ :(

Sponsored

 

[wiedemab]

I think I'm going to just have them replace the entire cradle......

 

[Cobrajet70]

Those bolts are not fun, they use a serious amount of red Loctite on them and take alot of effort to take in or out. I always drop the K member when I'm dealing with the PS rack on Mustangs.
We just had a new guy replacing one a week ago and we told him 100 times make sure its tight, use heat, just drop the whole thing. Same deal, he thought he hit torque and the bolt still wasn't fully threaded yet.

 

[wiedemab]

Those bolts are not fun, they use a serious amount of red Loctite on them and take alot of effort to take in or out. I always drop the K member when I'm dealing with the PS rack on Mustangs.
We just had a new guy replacing one a week ago and we told him 100 times make sure its tight, use heat, just drop the whole thing. Same deal, he thought he hit torque and the bolt still wasn't fully threaded yet.

I thought about heating it, but was afraid it would damage the bushing. Are you saying they use red Loctite on them from the factory and that it requires heat to remove it?

 

[Cobrajet70]

The bolts, if I'm thinking about the same ones, have a heavy amount of Red locktite from the factory, every bolt that attaches the rack is a one time use, They bind, pop, and are extremely stubborn to remove while the K member in installed. I think the bolts are torqued to just under 150 Lbs, I've seen them hit that while still trying to seat them.

 

[wiedemab]

The bolts, if I'm thinking about the same ones, have a heavy amount of Red locktite from the factory, every bolt that attaches the rack is a one time use, They bind, pop, and are extremely stubborn to remove while the K member in installed. I think the bolts are torqued to just under 150 Lbs, I've seen them hit that while still trying to seat them.

These are front diff to cradle mount bolts - we may be talking about different bolts.

 

[Cobrajet70]

I think so too, I miss read it as a PS rack mounting bolts which are a common culprit for a clunk.
Those rear Diff bots have factory Locktite also...blue I believe, and are also a one time use but not nearly as aggressive.
Without seeing what's going on I really can't upstand what would cause the bolts not to seat but I do believe that's a weld nut on the front side.
Last Mustang I had with a Issue with rear end noise was from those bushings being worn, I used Steedas Threaded Differential Through Bolt Upgrade Kit but I also used their bushing inserts to repair the customers torn ones without replacing the whole rear cradle, the Through bolts I think are a better set up. But being under warranty its really up to ford to make the call for the repair. A full replacement can be possible once all other repairs are attempted.

 

[wiedemab]

I think so too, I miss read it as a PS rack mounting bolts which are a common culprit for a clunk.
Those rear Diff bots have factory Locktite also...blue I believe, and are also a one time use but not nearly as aggressive.
Without seeing what's going on I really can't upstand what would cause the bolts not to seat but I do believe that's a weld nut on the front side.
Last Mustang I had with a Issue with rear end noise was from those bushings being worn, I used Steedas Threaded Differential Through Bolt Upgrade Kit but I also used their bushing inserts to repair the customers torn ones without replacing the whole rear cradle, the Through bolts I think are a better set up. But being under warranty its really up to ford to make the call for the repair. A full replacement can be possible once all other repairs are attempted.

They've already ordered the new cradle. I think I'll go that route and then once I get it back I'm going to put the Steeda bushing supports and thru-bolt kit.

 

[wiedemab]

Quick update - got the car back. Dealership was awesome to work with - Service Mgr. and the mechanic kept me up to date, took pictures etc.. I have the car back, have only put a few miles on it. No clunking!

It now has the Steeda toe links and camber arms, bushing support kit, subframe alignment kit and rear braces. I'm getting a little bit more NVH through the chassis, but will see how that trends over time.

Sponsored