Hey, just wondering is a diff brace absolutely necessary for drag racing? If so I ordered one but it will not be on the car the first time I take it to the track, so what rpm should I launch at? Thanks Ryan

street port motor
99 twins 12.5psi
et streets 10.5
bla bla bla

 

a diff brace is not necessary
do you have an upgraded diff? i blew mine out on the stock twins the second time i went to the track

 

No its just the stocker, crap!

 

A diff brace IS a necessity when drag racing an FD! Once you install a stronger differential in the FD casing, the casing itself becomes the weak point. Differential housings break ue to the diff case moving and flexing causing it to crack open.
The only way to stop it from moving/flexing is by installing a brace to hold it in place.

 

i would save for the diff then buy the brace i can assure you the diff will go first and ive never seen a case crack with the diff still intact.

 

Well the ring and pinion won't make it, but the differential limited slip unit will, I'll get the pics I have to show you, gimme a few hours to post it.

 

Witness the carnage of launching hard at the dragstrip(As you can see the differential is still in place and not broken but the casing is broken!, NOTE this car also had a brace and it still broke the casing!) This is all too common a scene with FD's that hit the dragstrip and are making power when launched hard.

 

 

What kind of power do you put down RX794? And at what rpm lanch did all this take place? Thanks Ryan

 

wow like ive said i never saw that happen!(until now) when i blew mine the center limited slip shatered which caused the housing to crack i blew all those little gears in the limited slip apart the ring and pinion were fine!

I also just noticed you have a clutch type diff in there not the stock lsd which is probably why it stayed together

 

That's not my car, it's a friend of mine who was making about 450-475RWHP at the time of the incident, BUT I will tell you that this has happened to me personally a few years ago at only 330RWHP with no brace and no upgraded diff. There are alot of forum members here that can vouch for this happening to them as well, I'll see if they can chime in confirming broken casings.

 

I had this happen to me at arround 400whp, almost identical to the pics posted above. i have since installed a brace and have had no more issues with diff casings even tho im making more power now.
i wouldnt recomend drag racing an fd without a brace unless you dont mind towing the car from the strip.
im just glad that mine broke on the first to second gear shift and i wasnt going very fast. when the casing broke, the rear end locked up and started fish tailing. luckilly i was able to keep the car out of the wall.

on a side note there was a forum member in australia about a year or so ago that lost his life when the diff casing on his fd broke and locked up on the top end of the track, sending his car into a wall. he was in a coma for about 2 weeks before he passed away. theres a thread somewhere here about the incident with comments from his wife.

in short, BUY A BRACE. you can never be too carefull

 

Mine exploded when I only had 350 whp.

 

i also snapped my diff casing in half before i got trans and diff braces. all i did was try and do a burnout on street tires and it exploded.... upgrade your diff and while you are under buy the braces they are worth the money!

 

who sells a diff brace, and how much , or can I make one? is it just one brace, or two parts????

 

Make a (WTB) thread in the for sale section or check gothamracing.com or rx7store.com/net

Jay7..

 

Thanks Guys, did not go to the strip tonight, going to wait for the brace!! Ryan

 

KG parts makes a nice one also.

I have the brace on now but had to replace my motor and diff mounts due to flex in the drivetrain. When will it end....

 

I am sorry, but that brace dose pretty much nothing.

Andrew

 

He's right, the brace does nothing. I haven't been on the forum much lately due to the fact that I have been non stop on the car ever since Moroso. I have been breaking the differential just the same as posted earlier in this thread. Unfortunately, I have gone through 4 diffs in the past month and a half, 2 axles, and 3 mainshafts since Denver in June. There has been much debate on exactly why the diffs are breaking, and it seems to be all to common lately. I have been talking with Josi, Ari, Greg, Ken, Jesus, and many others trying to find a cure for this problem. It seems that the pinion wants to drive forward and up (due to the cut of the gear) and splits the case in half right at the pinion head. I have tried a few cradles and braces, changing suspension, setting ride height, different clutches, tire pressure, and many other trials to cure this problem, but so far have had no luck. The one thing I found that may help is that I just recently noticed that my PPF is slightly bent. I made a brace that goes from the case snout to the subframe to keep the pinion down, but it just "sucked" the bolts right out of the housing on the first launch and stripped out the case threads! I am now currently making a thicker, stronger cradle to try to encase the diff and keep it together. I leave for NHRA finals in Pomona in 4 days, so I hope it works! Attached are a few pics of:
1. Brace to hold the pinion
2. Broken diff with a secondary brace on top bent like the Terminator got it
3. The new cradle in the making.

 

More Pics.....

 

Hey Dan, the last two pics of the craddle should be your best bet, since it encases the whole diff and transfers the load all the way to the back, and will want to raise the whole diff instead of breaking it in the middle or near the front of the pinion.

 

I certainly hope so. Cause right now I'm .... (Haha, I love these smileys).

 

As with many I learned the hard way. Last Friday I blew the rear diff at the drag strip. With street tires, diff. brace and solid mounts the LSD became the weakest link along with the case.


_________________
'93 R1 177k miles
Ported motor
Power FC
Greddy SMIC
'99 non-seq twins

 

Stating that the brace doesn't work at all isn't true. Maybe at the level that Dan is at it doesn't work anymore which I can understand because he's reaching the limits of the entire powertrain in the FD, BUT for people making less power it's proved itself beneficial in preventing breakage. Me as well as alot of my friends have seen this benefit firsthand after breaking so many diffs w/o any brace.