Possible axles not in all the way causing a thunk?

[2017RoushStage3]

Car has FP axles, CF driveshaft, BC stage 3 MT-82. PP1 with torsen 3.73
Noticable thunk when engaging the clutch in gear, forward or reverse. Even when power shifting it thunks.
I have tried everything and out of ideas to fix. I can't stand the thunking...
Replaced, clutch, transmission, driveshaft, differential, IRS lock outs, bracing etc
When I turn the driveshaft by hand it turn about an inch before the axles engage.
I did try swapping axles with a set of gt350 axles and the thunk was noticably less. I really want to keep the FP axles since they are designed for higher HP, I am currently at 700+ rwhp.
I am just wondering if the axles are not in all the way? Does anyone have a picture of what the gap is supposed to be between the differential and inner CV joint? Driverside and passengerside gap different?
I have tried knocking the axles in further but they seem to be seated and won't go in further.
this can't be normal. I have driven many other S550's and they do not make this sound.

Sponsored

 

[tdstuart]

The is a ring on the half shaft that "locks" into the differential. Once it is seated then the half shaft is in. You can tell it is seated because you can give a good tug on the halfshaft and it won't pop out. You may even be able to tell when pushing it in when the ring goes into place.

Did you inspect the splines and make sure the halfshafts are on the right side?

 

[2017RoushStage3]

The is a ring on the half shaft that "locks" into the differential. Once it is seated then the half shaft is in. You can tell it is seated because you can give a good tug on the halfshaft and it won't pop out. You may even be able to tell when pushing it in when the ring goes into place.

Did you inspect the splines and make sure the halfshafts are on the right side?

Oh my gosh. The axles have a specific side???? How do you know the difference?

 

[tdstuart]

Oh my gosh. The axles have a specific side???? How do you know the difference?

If I remember right I had to search up the part numbers to determine which was which for my FP ones. I think there is a letter at the end of the part number and I matched it to the letter of the stock ones.

If you post the part numbers and can't find any info I will search for you and see if I can pull anything up.

Worst case you could probably call FP and they can give you more info.

 

[WildHorse]

Replaced, clutch, transmission, driveshaft, differential, IRS lock outs, bracing etc

That's a lot of money to blindly throw at a problem.
Diagnosis procedures exist for a reason.

 

[2017RoushStage3]

That's a lot of money to blindly throw at a problem.
Diagnosis procedures exist for a reason.

Not blindly thrown at a problem, sir.
I had a mantic clutch that broke, so that was a good excuse to upgrade the transmission since the car was at the top end of a Mt82 power level. CF driveshaft was installed by previous owner.
That didn't solve the cluncking so the differential was pulled out and had another installed while the stock one was inspected and came back perfect.
Lots of time researching forums and such.
Not sure what other logical diagnosis steps I missed?

 

[2017RoushStage3]

If I remember right I had to search up the part numbers to determine which was which for my FP ones. I think there is a letter at the end of the part number and I matched it to the letter of the stock ones.

If you post the part numbers and can't find any info I will search for you and see if I can pull anything up.

Worst case you could probably call FP and they can give you more info.

I found the install instructions and they have the part numbers. Will get under the car this next week and see if I got them on the wrong side. I really hope that is the case...I am ready to get rid of the car because of this cluncking....thanks for your help

 

[17MagMetal]

That's a lot of money to blindly throw at a problem.
Diagnosis procedures exist for a reason.

Maybe it’s thrust washers LOL.

Thrust washers are $15!

 

[17MagMetal]

Perhaps brake pads + hardware???

Are the rear brake caliper brackets properly tightened?

Do you hear the clunk during every shift? Only during direction changes?

You’ve changed a lot of the rotating assembly, I’ve bet it’s somewhere on the wheel hub somewhere

 

[WildHorse]

Maybe it’s thrust washers LOL.

Thrust washers are $15!

Delete the sucker's..

 

[Cobra Jet]

I found the install instructions and they have the part numbers. Will get under the car this next week and see if I got them on the wrong side. I really hope that is the case...I am ready to get rid of the car because of this cluncking....thanks for your help

What was the result of your findings ?

 

[2017RoushStage3]

Axles can only go one way. Tried switching them but the driverside axle spindle is longer and does not go far enough into the differential on the passengerside. Frustrating....

 

[2017RoushStage3]

Delete the sucker's..

no thrust washers on the FP axles that I know of...

Sponsored