fireroasted

iTrader: (3)

I have been reading up on the drive shaft or propeller shaft bushing threads, to see if I could figure out what normal play or non rotational movement should be (up down & side to side deflection). I am chasing down a bunch of little issues since my build and in the tuning forums I am running into something that could be causing audible events, heard as knock. One of the comments has been to do the driveshaft carrier bushings.

Kracka has a nice writeup on his install and most others seem to be along the same positive feedback lines.
https://www.evolutionm.net/forums/ve...trunk-bar.html

MrFred makes a comment in another thread that is along the lines of what I was trying to figure out. His question is directed at how such a bushing upgrade could make any difference when the carrier piece is a super squishy rubber donut thing, that is much softer than the bushings you are replacing.

That keeps leading me to my question when under the car. I can move the driveshaft up and down of the two pieces pretty easily. No much, but some, and I am trying to figure out if that is in spec or normal or degraded to a point that it could be causing some on track clunking. Do the carrier units themselves need to be replaced, and if so how do I know for sure. What is the test for that?

I have several things that this noise could be, but the search of the drivetrain clunk always leads to the drive shaft. In one of my tuning threads someone comments that replacing these bushings addressed drivetrain noise for him, which eliminated false knock.

My clunking seems to come and go on track under hard braking. I guess hard braking could be distorting the diff enough to torque the driveshaft into a position that it would clunk against the body? maybe? Diff mounts are stock, but in good condition.

Any discussion or feedback from guys that are running the bushings, or have experience with how much the driveshaft is engineered to move around, so I could check intelligently, besides just pushing and poking things.

fireroasted

iTrader: (3)

Nobody has any comments on the drive shaft or drive shaft bushing install? bump for a discussion on this. Do I need the advanced forum? Some of my searches on this returned from there.

tscompusa

iTrader: (31)

if carrier bearings are bad they usually visually leak or crack.

if its the carrier bearing, you would feel the shaft spinning as you boost the car
underneath.. clunking is the actual bushings that hold the rear diff not the driveshaft
usually.

personally i would keep OEM style rubber bushings holding the carrier bearing assembly to the vehicle ( the loop)..

it will keep vibrations way more minimal and its better in general.. you can call any reputable driveshaft shop and they will tell you the same thing.. the oem bushings that hold the evo driveshaft up are better then the aftermarket.

thats all i can help you with.. hope it answered some of your questions.

fireroasted

iTrader: (3)

Thanks for the feedback. Does it make logical sense that hard on road course braking could deflect the differential output down, thereby forcing the driveshaft down, which would then force it up on the other side of the carrier housing?

I haven't done any motor mounts for essentially the rationale you posted. I now have a decent amount of gearbox whine due to my trans build, FD, and TC build. I can tolerate quite a bit, but I still daily drive my evo. Its not a commuter, because i work from home, but it does daily duty.

If you did one of the bushings in the rear diff, which ones would you do, and which kind. The inserts, or the full replacement poly urethane ones?

tscompusa

iTrader: (31)

thats not likely to happen no. if that was possible then you would feel major vibration during WOT heavy loads on the driveshaft spinning.

i don't think there is any tolerances for up and down and side to side on the actual driveshaft as a whole unit. do you have the service manual? if there is it would be in there. (aside from the actual driveshaft balancing process in itself rotating)

i cant answer the question regarding the bushings, because i never experienced the clunk before so i just use the oem in there.

poly is gonna stiffen it up a lot vs the oem.. if you're gonna change them then id probably go with them.. this should be asked in the suspension part of the forum that way you get road course guys giving you help and so forth.

theres a bunch of brands to choose from i believe torque solutions, energy suspension, whiteline, and the list goes on.

heres whats causing your clunk probably https://www.evolutionm.net/forums/ev...-bushings.html

fireroasted

iTrader: (3)

Thanks for the input. I have since installed the WL bushings for the diff and mustache bar. it has modified clutch engagement in a positive way, and firmed up the rear. Oddly I now have a more specific 'clunk' than before. It can be repeated every time on quick braking release. I'll have to post something in the suspension forum, but I am not certain if that is a more pronounced version of the same clunk, or something different. The diff isn't moving anywhere now for sure. It may as well be welded to the body.