I have a 2005 Evo 8. When I bought the car, I had a New Tranny installed & then a New Clutch about 8 months later. Tranny has about 35k miles & clutch maybe 15k. English did the work.
Every time I accelerate from a stop or let off the gas then accelerate again I hear a loud knock coming from somewhere close to the firewall maybe?
It's not a deep solid steel sounding knock, but more of an aluminum hollow-ish knock, if that makes any sense?! I feel like I can't explain it accurate enough. It started around the time that English installed my Clutch, and has recently gotten worse. I've tried checking as many bolts & brackets in the tranny/differential tunnel area that I could see, but no luck. I was thinking maybe a CV knock, or maybe a tranny mount? I've also read that the brakes somehow make a knock sound?
Anyone else experience this? I've read a few other threads, but none of them sound like my problem.
I really need to figure this out ASAP tho, so any ideas would be awesome?

 

Check around the center differential hump. There's some piping in that area that could be interfacing with the transmission.

 

Thanx @barneyb I'll look into that.
Another thing I've noticed is that I can sometimes feel it in my pedals.
I don't think this is the issue, but I was told by English that an exhaust w/o a flex joint can cause vibrations & knocks. I don't have any sort of flex joint, just straight piped all the way back.
I'm grasping at straws at this point. It would be so much easier if I could just get it up on a lift!

 

Maybe if I got a list of ALL possible causes for knock/clunk sounds in the "Firewall area" I can't start with some good ol' Process of Elimination

 

check the power steering line - that was mine.

 

I will definitely check that.
What kinda of sound was it making, when did you hear the sound, and how did u fix it?
While searching for the problem, I did find that the tie rod boot was slipped off of the rack. Idk if that would cause the sound I'm hearing tho, u would think if anything, it would cause a sound when steering from side to side.
My noise is happening when I hit the gas. Almost always a single "knock", but occasionally it'll be 2 knocks, almost like it's bouncing off whatever it's hitting.