I was wondering what the loud thud sound could have been when I was on the highway this past weekend? I was rolling along at 70 MPH and then needed a burst of acceleration.... I downshifted 5-4 gears and heard a thud....

I think it was coming from the rear diffs....

 

I had this same sound when I first bought my car (with mods already) It sounded like it was a thunk or clunk from teh rear diff. Like some threw a tennis ball against the rear bumper. After some time cruising with my friends I found out it was a backfire during shifting.
It didn't sound right to me at first, but later a friend taped a run of mine, and I heard the sound and the tape showed a back fire. So thats my guess.

 

a backfire? like shooting flames thru the exhaust???

 

thats the car breaking......

 

Sounds like good 'ole rear differential slap to me...

 

Yep play in the rear diff!! My 05' does it in every gear unless I shift very slowly any type of quickness results in a "Thud!"

 

not a backfire

rear diff

 

and my question to all is, is this bad for the car??? and I'm I inflicting damage/stress to the rear diff????

I thought the rear diff was a strong LSD type diff

 

Well, it's not "good."

I know the make stiffer rear diff mounts, maybe that would help.

 

It is bad. My buddy shifts like that when dragging his car and his synchos are out. They have seen been replaced.

 

I hear the "thud" in pretty much 2-5 gears when I'm doing sprints. Scares the crap out of me cause it doesn't sound "safe" and I don't want to spend money on repairs. Speaking of repairs.. does anyone know if the warranty will cover the front and rear diffs on my IX? I know they don't cover wear n' tear items, but are the LSDs considered wear n' tear?

 

That sound is weakness leaving your car
I get the thud sound also , its normal for a evo to make a lil noise when beating on her . I hear she likes it .

 

Ill get that thud as well on a quick 1-2 shift.

 

you said powershifting which can mean a couple different things to people
1) shifting without taking foot off the gas
2) shifting without using the clutch at all

both are really bad.

what you want to do on a 5 -> 4 shift for power is rev-match so that you don't upset the car's balence or put stress on the drivetrain.

 

Why power shift it doesnt save that much time especially on the street. Wouldnt you like to lose .1 of a second and extend your cars life instead of ruining it?