I've done a vast search on this on both forums and I got an idea of what it is but not what causes it, what it effects, and whether it's a problem.

Recently installed a new clutch and had the restrictor pill removed; car has Cobb Stage 1, intake and UICP. It's been over 500 miles now for the break-in and I'm starting to get on it a bit more. I've noticed that during hard shifting/acceleration, upon clutch release, I hear/feel a thud come from the rear of the car. My search has led me to believe it's coming from the rear diff and is quite common but further details are varied.

Now what I'd like to know is:

1) Why is it making the thud/thump?
2) How do I prevent it from happening?
3) Is it causing premature wear and tear to vital parts?

Thanks in advance.

 

You rear diff is just moving around which is fairly normal, especially with an aftermarket clutch and removed restrictor pill. Lucky for you, the solution is quite simple and cheap.

You need some Beatrush urethane rear diff bushing inserts and maybe some Torque Solution driveshaft bushings too. Both of these are very easy to install with basic tools and limited mechanical experience.

http://www.maperformance.com/beatrus...051mtdfsr.html

http://www.maperformance.com/torque-...ts-ev-dsb.html

 

Thanks for the reply Kracka. I've looked into those bushings and apparently they increase noise level in the cabin because of the direct, more solid contact. Do you have these intalled? If so can you comment on them? Also, other than being kind of annoying, is this thump damaging any components? That's my main concern.

 

Kracka is right. I have done research and a few of the EVO guys here in killeen are having the same problems. they solved the problems by replacing the bushings and like Kracka said they are very easy to install.

You are not doing damage, but eventually the oem bushings will go boo boo on you and then you will have problems.. A high performance motor is no good unless its secured properly in the engine bay, hence poly bushings and billet motor mounts and other types of metal and solid mounts

 

I do have them installed on my X, they're one of the first mods I did. I also had them on my IX. The increase in noise is very minor, especially if you have an aftermarket exhaust, this is why I recommend the rear diff urethane bushings rather than solid aluminum ones. I've recommended them to numerous people and have yet to get negative feedback from anyone.

 

Sweet, good info. So will these bushings totally eliminate this thump or at least minimize it to a point of negligibility?

 

Minimize it to the point of not having anything to worry about.