Under heavy braking, both of my ISF's experience a repeated "thunking." Brakes are fine, rotors aren't warped, and you don't feel anything through the pedal. Rather, it's felt through the floorboard. I bought upgraded LCA bushings, thinking this would solve it, but it persists.

I've spoken with several other owners that have reported the same thing...what causes it?

 

What LCA bushings did you buy? Mine did it when I installed FIGS. I thought it wasn't tighted enough so I have the dealership torque them to spec. It still does it.

 

Mine did not do this with the OEM bushings and does not do it with the Figs bushing now. What brake pads are you running?

 

May be s stupid question, but are you sure it's not the ABS system kicking in? I ask because just the other day, some idiot pulled out in front of me and I had to quickly slam on the brakes. The ABS kicked in and I could feel a quick thump as you described.

 

I had a noise like that when my JZ exhaust was fist installed until they got it in the right way. Just a thought. It was a thump like beneath my feet and seat .

 

Running the RRRacing USRS "street" bushing.

Whatever OEM supplied pad is.


It's not the ABS system. I've also manhandled the front wheels to see if there was any lateral play. I guess my next step is to put a GoPro in the fender and see what the tape shows me...

 

Just curious if this is in manual, auto or both modes?

Under manual you can usually feel the torque converter unlocking from 2nd to 1st; especially when heavy braking to a crawl.

 

It happens in both modes, though I spend 90% of my time in auto mode

 

I'm going to shoot from the dark here and say it can very well be your Driver's Side Motor Mount.

I just had mind replaced with 117K miles on it.

My thunk or thud noise started not long ago and it would only make noise under certain circumstances.

They found my broken / wiggly motor mount while removing the sub-frame (for some other work)

I still have some more driving to log in, to make sure the noise is all gone.

After driving the NX 200T for two weeks, it left my senses a bit too comfy.

Joe Z