What is causing this noise? I'm at a loss.

Dirtleg

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Good morning hope everyone had a great christmas holiday.

First I'll just go on and say I screwed up the diagnosis of this problem.
And still am screwing it up.

A little background about this issue.

About 3 1/2 years ago I swapped an MT82 into my 07'. From day one it had a pretty loud input shaft gear whine. I drove it that way for a little while because I was working on getting the hall effect speed sensor in the MT82 to work with the 07' instrument cluster/computer. Waited months for a signal adapter that I never did get to work before having what I thought was a major transmission failure. (I will say the gear spread was awesome behind the 4.6. Loved it.)

So at that point I decided to throw my TR3650 back in. Once it was installed the exact same problem was there. Now I didn't think it was the drive shaft as the 2 setups have different driveshafts and what would the chances of that be.

Now I'll go on and admit I blew it at this point in diagnosing the issue.

What I did next was just dumb. I went ahead and ordered a rebuilt transmission as the original TR3650 had been making some unpleasant noises before I threw the MT82 in there and I just figured it had been kicked around and moved when it was out of the car so I may have jacked it up further before re-installing it.

Well I was wrong. The rebuilt transmission did not get rid of the problem in any way. It was exactly the same as before.

So at this point I decided to just go ahead and redo the rear axle. I know throwing parts at a problem is expensive and time consuming but the car has 150K on it and is not my daily at this point. I have decided to make it a track day car and thought rebuilding the rear axle would be good insurance once I start running it hard.

Well one thing led to another and I ended up putting in FRPP 3.55 gears (same as stock), all new bearings and seals, and a carbon traction lok clutch set. I thought I was careful in re-assembling everything. I torqued the pinion flange until I had 25 in-lb of rotating resistance, backlash came in at .008" and carrier caps were properly torqued. Gear pattern was centered on the ring gear although it did seem a little wide. I then proceeded to re-install the axle under the car and finish assembling everything. While I had it apart I put in new BMR lower and upper control arms, relocation brackets and an upper mount. I also changed the upper control arm bushing at the differential.

At this point I took it for a test drive and the problem was still there. So I climbed under the car and checked the driveshaft center bearing. It seemed to me there was excessive play in it so since I'm already so far down the rabbit hole I ordered and installed a driveshaft shop 1 piece aluminum driveshaft. Still has the problem although I'll admit it's improved some. Before the driveshaft it was damn near impossible to get the car moving from a dead stop. Afterwards it's not a problem to get started but the shuddering on off throttle, clashing noises are still there.

So now I'm scratching my head trying to figure out what's wrong. Is my rebuilt transmission screwed up too? Did I fail to set up the rear end properly in the exact same way it was wrong before disassembly?

I'm thinking somehow the pinion preload changed during assembly but not sure how it could have happened.

I've linked a video of the noise. I'm open to hearing any and all ideas at this point.

https://youtu.be/Xx7SMGlFbnM
 
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eighty6gt

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Put a camera under the car so you can see the pinion and diff, also maybe hear something. Knock off go pro or ???

Seems like coast is quiet and drive very bad. Something about the diff mounting?
 

Dirtleg

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In regards to diff mounting every control arm is new. The upper is a Heim joint BMR piece and the bushing at the diff is a Prothane unit also brand new.
With that in mind the car feels planted going down the road not sloppy at all.

I can stick the GoPro under there but it'll be the weekend until I can run it in daylight. Too busy this week. But it's a good idea. I was under there earlier today and everything felt tight by hand, no play in the pinion but under a load it could be a different story.

So the saga continues.
 
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eighty6gt

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Ford has chassis ears and a computer that can determine the speed of the item that is making the noise. If you can get in good with a technician they might be able to help you out for reasonable $ ($100's.) They diagnosed blown bearings in my diff this way back when my car was under warranty.
 

Dirtleg

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Hey haven't been on here in a while. Figured I'd update this thread since I have found the problem.

It was a loose flywheel. Crazy I know. It was not loose enough to detect it being loose by hand but I pulled the transmission again last Sunday just to check. The flywheel has never been removed since new so I just never expected it to work itself loose. Took about 150K to do so.

So while I had it apart I decided to just remove everything and inspect it. I tried checking the flywheel for looseness by hand but it seemed completely tight. Apparently it required the weight of the car imparting force on it in an on/off throttle situation or when under load accelerating to cause the problem to happen.

I reassembled and retorqued Sunday and let the car sit thinking there was no way I had fixed anything. I did not replace any parts as everything was new except the flywheel anyway. The good news is that I've gotten my transmission out and back in, including removing and re-installing the flywheel down to 3 hours. Being on a lift helped immensely.

So today I finally drove the car and the problem is completely gone. Drove it about 20 miles under all kind of load conditions and no sign of it at all. I did not expect it to be any different based on what I saw but that is the only thing it could have been as no parts were changed and everything else is new.
 

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