Need help with clunk in the rear.

DJ

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Let me start with the background and everything I have done to this point. I bought the car from a down to earth and nice guy that is actually on the forum. When I purchased it he told me that I need to replace the upper control arm bolts because it has an light clunk. He was right I pulled the uca bolts and they had large grooves in them and the stock ucas were trashed. Hole was double the normal size. I think no big deal I bought a set of UPR adjustable ucas and a set of hardened bolts for the whole rear end. At the same time as replacing the bolts I threw on some cut mach 1 springs, shocks, and struts. I drive it and the noise goes away for about a day. Then it comes back and now getting louder, to the point where I feel uncomfortable driving it. I remove the lca and those bushings are also beyond shot. Find out that the car has Lakewood lcas so I order a replacement set last week and put them on Saturday. I new the pinion angle was off so I set it at the exact same time as I put the new bushings on the lcas. (set it to 3 degree)

Today I take it to work which is a 35 min. drive down some back roads to Morris. I was easy on it for a while and everything was good. Never heard the rear end so quit. I get some confidence and start getting on her a bit, all is good. I leave work drive home taking my time and about 5 miles from the house I hear a f&%#ing Clunk. Not just once, it came back just like it was last week.

Not sure where to go from here. I will take any suggestions at this point. All this is on a 94 GT.
 

ajdereicup

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There's something about dropping some grease on the fittings or something if they're not sliding like they should or whatever I was advised it when my rear end was clunking randomly but it has gone away just randomly looked and it all looks good. Does it have a rear sway bar those can potentially make noise too
 

greasy

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If the mounting hole is double the size I bet you are getting some movement in the UCA no matter how tight you make them. Also what type of bushings are in the UCA's and LCA's? If you are using solid bushings they will be noisy as well.
 

DJ

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Does have the rear sway bar and I removed it to see if it made a difference and it did not. I am using all poly bushings and the mount holes were not elongated it was just the bushings.
 

ajdereicup

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Can you get it to clunk while hopping on the ass end of the car parked?

Might be a stupid question but you did use poly lube when assembling correct?
 

ajdereicup

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Usually used to keep it from squeeking but maybe if its got a lot of resistance somehow its getting caught up then the load is being released making a clunk?
 

DJ

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I can not duplicate the noise by jumping on the back or trying to push and pull the car. Yes they are lubed and this is not a little clunk. You can definitely tell it is metal to metal type of noise. I looked at the torque boxed again tonight and do not look bad from what I can see.
 

ajdereicup

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Can you see where it's hitting at in there? The bushings are 1 piece that you replaced them with right?
 

DJ

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No the Lakewood arms are two piece to allow a valley for grease. I can not see where anything is hitting. Not to sound like a dick but if I did my problem would be solved.

Has anyone seen a bad torque box? If so is it usually obvious to see its bad?

Thanks for all the input I have been tracking this for so long I am probably missing something stupid.
 

ajdereicup

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I know but sometimes people leave out the obvious if they freak out about something happening so better to be safe and ask instead of keep running through possibilities when its something simple

If a torque box is messed up you'll either see cracks in it or it might look deformed. I've never seen the torque boxes on those year mustangs though so I'm not sure the shape they're supposed to be. Do the control arms look like they're going into the torque boxes straight or kind of at an angle? Like not up and down angle but like angle with the side of the control arm in relation to the torque box? You MIGHT be able to jack up the rear of the car and attempt to wiggle the rear end to see if there's play in the control arm side that goes into the torque box but that may be more difficult then its worth. It's easy to see if it has cracks in it somewhere. Its harder if its just bent outta shape to see unless really extreme
 

DJ

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Well now I have an added attribute. Yesterday I lifted the car to look at the torque boxes and couldn't see anything. Pulled and yanked on some components all felt good. Lowered the car down and the noise disappeared for about 20 miles. All of a sudden came back like it never went away.
 

ajdereicup

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So by unloading the suspension it got the parts back lined up in the right spots then driving it letting the suspension reload it got back to being in the wrong spot.

Maybe the springs or shocks are shot and by having it in the air hanging it let them spread open a little then after sitting down and having the weight back on them they went back to sagging? Are they older springs/shocks? Are there bumpstops on the car you can check to see if they're all messed up from hitting due to shit springs/shocks? I'm thinking the other suspension parts should be loaded once you set it back down or fairly soon afterwards not take 20 miles hence why I'm thinking springs/shocks because they can take a little bit of time to settle back to their position of being shit
 

DJ

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I do see what you are saying but the metal noise comes more from a torque movement of the engine. Not necessarily from the suspension loading and unloading. I can barely let go of the clutch to the point where the car doesn't move much and the clunk will be loud. It seems like soon as the rear end receives the torque of the engine it clunks.
 

ajdereicup

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Ohhhh did you check the rear end fluid and gears themselves. Sadly that's what it sounds like it might be if its clunking when your just barely letting off the clutch and hearing it. Does it have main cap supports on the cover? Did the previous owner launch it hard do you know or use slicks on it?

Maybe do a quick check to make sure nothings too close to the driveshaft that when the engine twists and make sure its bolted in good because it its when letting off the clutch it should have to do with the driveline most likely not the suspension

You can also check the motormounts because IIRC they can lead to clunking when letting off a clutch and all but I think the clunking when they're bad is more localized to the front of the car but not 100% sure on it
 

Turk

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What about the exhaust hitting up against something? Used to happen in my M3. Or it was more the rear end hitting the exhaust.
 

ajdereicup

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The exhaust is usually more then just one clunk though I thought? That's how my cats used to be the shield would get against the tranny crossmember and make a hell of a racket. But only do it sometimes and then going over some bumps. Drove me crazy trying to figure it out
 

DJ

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Don't want to jinx it but I haven't heard a knock in two days. I looked underneath to see if anything changed any all looked fine. Not sure wtf is going on but I am going to do the number one rule that you shouldn't do and that is ignore it and hope it goes away. Hoping to make the Starve Rock cruise.
 

DJ

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No I am not 100% sure what it was but it seems to be gone. Took it on the Starve Rock cruise with a few twisty roads and some bumpy ones and hasn't made the noise yet. Just keeping my fingers crossed.
 

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