odd rat-a-tat chattering sound... transmission area?

[Forrest Nearing]

noticed a strange noise while driving on the highway yesterday...



had the windows down and was passing someone at WOT in 6th... heard a banging/knocking/ticking sound that I thought was coming from the right side, but that might have just been the sound reflecting off the car I was passing...



was able to replicate the sound a few more times... thought maybe exhaust was hitting/banging under the truck? 5" downpipe is kinda tight



pulled over, didn't see anything odd... I had been playing with the wastegate arm earlier in the day thought maybe the wastegate lever was chattering open and closed? or maybe the pop-off valves were bouncing open/shut?



so then I tried to replicate it again with the windows up and it really sounded like it was coming from the transmission area... hmm...



I also noticed that the noise was occuring when I railed on it from 1900 or so and it would rattle around 2000-2100ish and up... and then it would go away...



if I hit it at 2500rpm, it wouldn't do it...



and if I had it happening in the low 2k RPM zone and backed off the throttle a hair, it would go away.



so now I'm thinking it's clutch/driveline related and that it's a torque issue... higher RPM = less torque, no noise... if I'm not at WOT, no noise... less torque...



I'm planning on putting a dual disk in the truck. it currently has an OFE in it... the clutch isn't slipping... wondering if I'm bottoming out the springs in the hub and they're "bouncing" or something?



DDP4's, rips twins w/ a PDR35-12 on top, rack cap is the fuel stop on the 215 pump



already left a message w/ Peter



your thoughts?

 

[SHobbs]

I have the same noise usually around 35-45 mph around 1500-2000 rpm when I get on it hard. I was told that it was the gears in the transmission doing it due to the amount of torque going through it and there is not much you can do about it. I asked if it was causing any damage and was told no. Not sure if thats true or not. Mine is more pronounced if I am towing the 5er than when I am empty.

 

[Forrest Nearing]

I know what you're talking about I think... this isn't your typical lug rattle... maybe it's the same thing on a grander scale, but I've never heard of anyone talking about it