RXT, FTBR bushings, thuds letting clutch out?

[snakeraper11b]

This has been a persistent issue for me since the RXT and FTBR diff mount bushings. If I let the clutch out very gently with few rpms I get what sounds like a clunk, clunk, clunk, clunk, that get quicker as the vehicle begins to move, but never more than 4-5 clunks. This is between zero and maybe 2-3mph, just until the vehicle starts moving with the clutch fully out. It's been like this for 2 years.

This is the 2nd transmission and rear end I've had in that time and it sounds the same. The first diff was an 01 OEM built IRS with 3.31's, the current is an 04 oem built IRS with 3.55's. First trans was a custom t56, current is a Rockland Standard Gear Tranzilla. Anyone have a similar issue or input?

Just so everyone doesn't say cobra clunk, I have all the FTBR bushings, larger grade 8 bolts, FRPP cover, upgraded toe links, full MM coilover, the works. Everything is tight as it's all been in and out several times, with the same results each time. So frustrating. Sounds like someone is tapping on my diff cover with a hammer in parking lots.

 

[P49Y-CY]

could it be the diff itself? what kind of differential is it

sometimes my trutrac makes noise when I first start moving, but it is only a few "pops", not like a banging

 

[BoostedByV]

I have the same problem
It's the three bolts to the rear Mount bushing to the diff cover. I had loss one of the two bolts(12x1.75x 60mm long) that go from the diff cover to the mount .
You should use blue removable loctite on it and torque to 60 ft. lbs.

my guess is that rxt transfers all the power and the irs loosens up

 

[Rich'sTRsvt]

Do you have that spot on the frpp cover ground down so it doesn't hit the bracket when you have ftbr bushings?

 

[snakeraper11b]

could it be the diff itself? what kind of differential is it

sometimes my trutrac makes noise when I first start moving, but it is only a few "pops", not like a banging

It's an oem built 04 cobra diff with low miles. Same symptoms as the stock 01 diff it replaced.

I have the same problem
It's the three bolts to the rear Mount bushing to the diff cover. I had loss one of the two bolts(12x1.75x 60mm long) that go from the diff cover to the mount .
You should use blue removable loctite on it and torque to 60 ft. lbs.

my guess is that rxt transfers all the power and the irs loosens up

It does it fresh out of the driveway after re torquing every fastener.

Do you have that spot on the frpp cover ground down so it doesn't hit the bracket when you have ftbr bushings?

It is the milled cover from FTBR. It did it with the stock ford cover on the 01 diff and 04 diff.

 

[BoostedByV]

It does it fresh out of the driveway after re torquing every fastener.

Even the bolt to the rear mount bushing the one you have to remove the tie rod to get to ?
I have the milled cover from FTBR as well

 

[ac427cobra]

It does it fresh out of the driveway after re torquing every fastener.

Is the car turning at the time this is happening? If so, it could be you need some additional friction modifier in the diff. A diff can make a lot of strange noises if it's a Ford unit and doesn't have enough friction modifier in it.

 

[snakeraper11b]

Is the car turning at the time this is happening? If so, it could be you need some additional friction modifier in the diff. A diff can make a lot of strange noises if it's a Ford unit and doesn't have enough friction modifier in it.

Turning, straight, forwards, reverse, any time the clutch is depressed coming to a stop at low speed. It almost sounds like really lose backlash in the gears, but its an alternating thud, like something shifting left, then right, then left, and right again. I feel like something has to be lose, but there's only so many things it could be, and I've checked them all at least 3 times.

 

[ac427cobra]

Turning, straight, forwards, reverse, any time the clutch is depressed coming to a stop at low speed. It almost sounds like really lose backlash in the gears, but its an alternating thud, like something shifting left, then right, then left, and right again. I feel like something has to be lose, but there's only so many things it could be, and I've checked them all at least 3 times.

Then you may need to get the car up on a drive-on lift and have someone load the drive train in both forward and reverse with the service brake applied and observe what is happening below the car. Maybe you will see something? There is usually an easy solution, however finding it can sometimes be difficult.

Keep us posted.