[disclaimer rant]
Yes, this isn't Single turbo specific and I have stock (based) turbo, but I figured this section would have most useful feedback from high HP applications.

So, since I installed my Toyo RA-1 on my FC I have had the "competition clunk" when the power really came on at 5,000rpm in 1st and when shifting into 2nd and 3rd.

I already had the competition front of differential mount in place. With the help and wonderous tools of ScrapFC I took down the rear subframe to put in the competition rear of differential mounts as the race season starts next weekend!

What we found when we took down the rear subframe was truly fightening. The engine torque had been lifting the entire rear subframe and impacting it against the chassis. It hit at the top of the small links and the large links connecting the trailing arms and I think in at least one other area- can't remember.

The impact had dented the unibody floor pan and cracked it on each side!

I have done exactly one (1) drag launch showing off to another Auto-xer passenger, this is all from 1st gear roll ons and shifts.

I with the comp. rear diff mounts in place it still clunks in 1st, but not on the upshifts...

Pics of damage-







So, any other FC owners have this problem? What was done to correct it?

Thanks ScrapFC for all the help, use of tools and company; thanks FCChan for the delicious meal!

 

Reinforce the mounting area for the camber link, get an adjustable camber link and install a pinion snubber. Thats what I did to fix my problem a few years ago.

 

Ah, pinion snubber sounds like a great idea! Thank you.

Does one typically install it off of the harmonics dampening block off to the side or right up the middle bridging the trans tunnel?

Off the dampning block sounds easiest as it is already acting as a snubber, but is there any concern about transferring the load to one side of the chassis vs evenly to both sides. The car does tend to gently pull to the left as it loses traction currently, though I had previously attrributed that to the .3 deg camber difference the FCs get.

I have the adj camber link as pictured. Do I reinforce its mounting points on both the subframe and the chassis? or is the subframe the weak point as it is not a boxed section.

I may also try to squeeze some polyurethane into the voids of the stock front of rear subframe mounts as well as the new comp. rear end mounts.

Thanks for the reply, Ian.

 

Just recently i noticed this aswell as i was doing exhaust work underneath

Mine is not as bad as yours yet, I have all stock bushings, and a NA lsd back there.... i dont know how i havent snapped that rearend on 1.6x 60fts yet

 

Ive broken 2 rear subframe. Those tabs that hold down the diff alway snap off...Sooo Im going to install the snubber and reinforce the way the diff is held down.

 

OK, for my "low hp" application the Competition rear diff mounts do seem to be working well with the competition front diff mount.

I heard one clunk initially, but not now. I think it was the camber rod sliding to the bottom of its subframe slot as I remember it wasn't bottomed when I installed it.

I seem to have somewhat better traction now, I assume that is because my lateral links are no longer hitting the chassis and preventing suspension movement.

Tried a tire warm up and 4,000rpm drag launch (I lose traction at roll at 5,000rpm so why launch higher?). Clutch can't take it, gets hot from the slip launch and won't hold 2nd on the shift

I currently have ACT fibre disk w/ extreme pressure plate. I guess I will not be drag launching untill I get a sprung copper disk or dual disk set-up.

 

what's a pinion snubber?

 

 

A bumpstop between the front of the differential (pinion gear shaft housing) and the body.

Allows contact of the soft(er) rubber of the pinion snubber to the body after a minimal amount of movement (snubber does not touch body normally to stop transfer of noise/vibration).