Help diagnosing on throttle clunk after rear end refresh

[Nate047]

Here:

https://www.youtube.com/watch?v=oES-2iGIz7E

https://www.youtube.com/watch?v=2tJLnsziQK8

https://www.youtube.com/watch?v=NXLa6lTbPIk&t=233s

Very interesting, that could be it. In the last video where he says how it may have been sitting in the wrong way for a period of time, that definitely happened for me. I was supporting the driveshaft on a jack stand for weeks on end while I chipped away at my RACP job. I did not even think about if the joint was angled in a weird way. The center joint may have also been holding up weight and been under stress where it shouldn’t have been.

Sunday is my day to get under the car and take a look.

[Jarvis]

Did you ever figure this out? Another member posted a very similar sound. But it’s funny you mention this happened after the full CMP kit install. Which happened with me..

[Nate047]

Hey, so yea. Probably good time to update this.

No, I have not yet resolved the issue. I've had almost zero time to put into this car over the last year but now, I am finally starting to slowly get back on it.

The driveshaft is off of the car right now. The guibo appears to be fine, I am replacing the center support bearing, and the CV joint appears to be fine. After I put the driveshaft back on and go for a test drive, if the problem is still there, that means the problem is much more of a pain in the ass.

At that point, I will probably have to drop the rear end back off the car and check the front diff mount. Unless you can install and properly inspect this with everything on the car, in which case PLEASE tell me now so I don't waste a bunch of time LOL.

It's possible but very unlikely that the sound is a crack or other damage on the RACP. My welder and I did a good job on the repair and I am 99.9% sure we didn't miss anything or create any new damage.

I heard someone mention that it could be a RTAB related sound, does that add up to you guys? I have CMP monoball RTABs.

I also heard someone mention that, because I have removed a ton of interior and sound deadening, the sound might be "normal" and I'm just now hearing it for the first time. I feel like that's a stretch because every track guy with a gutted E46 would have the same sound, and they don't.

All other suspension and brake components are solid.

Another thing I thought of was maybe a subframe bolt. But the sound only happens when I go on or off throttle. It does not happen over bumps and dips, cornering, or under braking, etc...

[heinzboehmer]

At that point, I will probably have to drop the rear end back off the car and check the front diff mount. Unless you can install and properly inspect this with everything on the car, in which case PLEASE tell me now so I don't waste a bunch of time LOL.

You can.

If you have CMP subframe bushings, you'll need to remove the v brace, the part that it attaches to and section 2 of the exhaust in order to reach the front diff bolt. But no need to drop the entire subframe.

If your subframe bushings are stock (or stock height), you basically don't need to remove anything. Just slightly bend the plastics out of the way and use a longish extension to reach the bolt.

[Nate047]

You can.

If you have CMP subframe bushings, you'll need to remove the v brace, the part that it attaches to and section 2 of the exhaust in order to reach the front diff bolt. But no need to drop the entire subframe.

If your subframe bushings are stock (or stock height), you basically don't need to remove anything. Just slightly bend the plastics out of the way and use a longish extension to reach the bolt.

Okay awesome, I thought I had read somewhere that it was hard or not doable but I'm glad that’s not the case. I do have the CMP solid aluminum subframe mounts.

I’ll take a look at this now since the exhaust is off anyway. How will I know if something is amiss, aside from obviously loose or ill fitting bolts etc…?

[oceansize]

Okay awesome, I thought I had read somewhere that it was hard or not doable but I'm glad that’s not the case. I do have the CMP solid aluminum subframe mounts.

I’ll take a look at this now since the exhaust is off anyway. How will I know if something is amiss, aside from obviously loose or ill fitting bolts etc…?

You sure heinzboehmer ? I'm pretty sure you have to remove the crossmember too. I had looked at mine a while back and I felt like gizmo had it right.

[heinzboehmer]

How will I know if something is amiss, aside from obviously loose or ill fitting bolts etc…?

I would just put a torque wrench on the bolt. Mark it with something too so that next time you can just check on it visually. Might be worth throwing on a nordlock washer for the peace of mind as well. See this thread for more info: https://nam3forum.com/forums/forum/m...-on-diff-bolts

You sure heinzboehmer ? I'm pretty sure you have to remove the crossmember too. I had looked at mine a while back and I felt like gizmo had it right.

Sorry, yeah that's what I meant by "the part that it attaches to". Should have been more specific.

The crossmember is what actually gets in the way of a socket, all the other stuff needs to be removed to get to it. But just support the subframe with a jack, remove the crossmember, put the two front fasteners back in and remove jack.

[Nate047]

Cool thanks guys, that's not so bad since I already have the car up in the air and a lot of the stuff removed.

[Jarvis]

Any update on the sound? Have been unable to solve the sane exact sound, on and off throttle. Thanks

[Nate047]

Any update on the sound? Have been unable to solve the sane exact sound, on and off throttle. Thanks

I have not fully fixed the issue, but I can say I have tentatively narrowed down what the problem likely was. My front differential mount was pretty loose after all. I did not follow the installation steps properly because I was in a rush, so in hindsight I'm not shocked that it was loose. Currently the car is still in pieces so I can’t say for sure if I’ve fixed it, but if you have the same kind of sound and symptoms, and if you have done new differential mounts or removed the diff from the subframe anytime recently, I would check that first.

[maupineda]

I also found my front bolt not tight enough, and my car had developed a knock in the two or so weeks before disassembly. So I am going to follow the below steps based on what I have read online and documented myself on fastener joints

i will use a Nord-Lock washer and keep the 200NM torque spec. Nord Lock has a torque calculator and this is coming at 213NM with oil for a 10.9 bolt. Since I had to repair my diff housing with a timsert, I will keep it at 200NM but lubricate the threads.

i am using an M14 bolt with a non threaded 26mm shank to have a stronger joint

for the diff cover bushings I am using E36 M3 items which are aluminum and rubber, the OE e46 M3 are steel with a PUR core (not rubber) and so the joint will be slightly different and since is a soft metal to avoid the joint loosening over time I am adding nord lock washers there too and tighten to 77NM which is the E36 spec. These will be enough for the washers to bite into the softer aluminum core of the bushings and ensure all is good over time with vibration and dynamic loads.