I have been drag racing my FD for around (10-12) years now. At first it was on street tires, next was nitto drags, then BFG drags and finally et streets. Have run the 10'5's and 11.5's now. I would guess I have 250+ passes on the original diff and axels ( to be honest I have not ever even changed fluids). This weekend I cut a few 1.5's and a couple 1.6's. My best to date was a 1.52 this weekend. Anyways I have always heard along with all the other bad info floating along the inter web on how the first time you try et streets on a high launch you will break parts. So my buddy was making some passes in his FD and trying for a new best. He finally managed a 7.9 in the 1/8th mile w/ a 1.8 or 9 60 foot. I told him if he could get that to 1.6 he would have a mid 7's pass. He tried 7k launch and the diff housing came apart. So the 2 differant things I have to blame is 1. my super still coiolvers alowing my tires to unload and spin saving the diff and 2. I ALWAYS load the driveline whlie staging so no slop left in it.

Now with the stiff struts I see that saving me say on the 2nd gear shift but out of the hole were he broke along with many others I am cutting some pretty good 60's.

I have had this talk with Ari and believe the loading part is saving it.

I also want to note that I know a certain turbo LS1 FD that still runs a stock diff and hasnt broke it yet. I cant not confirm it was in there this weekened while it was doing wheelies but I know on his mid to low 6 second 1/8th passes it was.


So whats your thoughts?

 

I want to also note that this past weekend the track put the place on kill mode! A few cars were going for some 5.9 passes and asked them to put it on axel brake mode. I saw atleast 5 cars brake rears. I tried 6500rpm-8500 launches and the 6500 worked best but then it cuased me to spin 2nd real bad.

 

I agree that the stiff coilovers and pre-loading has literally saved your rear end. I also have a stiff coilover setup and pre-load the drivetrain with my line lock when I launch at 7K. I've been averaging 1.5 to 1.6's 60ft and last friday was able to cut a 1.49. I'm running 10.5 ET Streets with 15psi and I do get a little wheel spin off the line.

 

Are you still on OEM diff? Do you have a diff brace? I dont. BTW... nice times! Last time I saw your sig it was 11's. I need to try the line lock to stage as sometimes I do roll a tad.

From my testing differant rpms to launch on I have found 6500-7400 is best for me as it lets me spin just a tad but whats been hurting me is 2nd gear tire spin. It seems if I launch say 6800rpms then it hooks good, spins just a tad but when I go to second the tires unload then spin bad thru 2nd.

I know there are some proven setups out there but I keep wondering if there is another route we can take using the oem diff and axels. Maybe a stiff coilover spring combo but a double adjustable strut with lower rise??

 

my cuz broke his diff in a 2nd gen couple weeks ago at the track. he made 3 passes the lowest 11.67 @ 121, he was launching the car a 7000 rpm leaving the line with 12psi, tires et streets 8". we had set the struts on the softest settings to try and make the car have better weight transfer, we noticed that the car would bounch. 4th pass of the day he broke it in 2nd gear. im wondering if suspension setting was too soft. still unknown.....we'll see in alabama

 

good info, apparently i launch my FD like a newb.. I am also afraid to break something again.. I have a banzai diff brace installed. Im wondering if my car will die if i launch at 6500-6800 with et streets? What PSI do you run on your tires? I have some RA1's, definitely not good for drag racing.

 

I have run as much as 16psi and as low as 10psi. 12psi seems to usually be were I end up. But since I dont have a 2step on yet my launches are inconsistent with rpms, which changes everything.

 

theres alot of reasons why diff's break.. A good launch put alot of stress on the rear and it try's to push the diff out the back.. This is what happened on my brother's diff..

Also wrong suspension setup with wheel hops, etc. will also break diff's.

Forgiving clutches will help as any type of slippage will save your diff.

Preloading is also a good thing since there's no slop in the drivetrain.
You don't want that slop to suddenly accelerate and snap something..

 

250+ passes ? lol god dammm

 

What's funny is I can remember all the way back to "I just want to run a low 8 in the 8th". I made so many passes on street radials it was crazy. So I would say out of all my passes only the last 50-60 have been 500rwhp+ ones.

I can say I always would slip the clutch on launch's back in the days so maybe thats what saved me all those times. I have the 60 foot thing down well now as 1.5's are pretty regular now with a few 1.6's being bad.

 

I believe that's the main thing that helps you. The stock diff has alot of play when you move the axel back and forward. Most guys will reverse while staging leaving the axle loaded the other way. Then when taking off the axle slams the other ways creating a ton of force breaking the diff. It's like the jack hammer effect. Preloading the diff eliminates the jack hammer effect completely.

 

Enzo, did your bro break on launch or going into 2nd?

Who has broke even tho you preloaded the driveline?

 

Fixed it for ya.

I've never in my life heard of people purposefully reversing into the staging lights... unless you mean that "most guys" over shoot the lights and have to reverse into them. In which case, I highly disagree again - maybe one in 25 people do that and it's only the people who have never drag raced before.

I highly doubt "most" people are leaving driveline slop in at the lights. If you're approaching the second staging lights little by little as everyone does, it will naturally take the slop out of the driveline.

 

I'm still on the OEM diff without any brace. The line lock helps when staging, not only keeps you from rolling but it loads the drivetrain and takes up the slop. My switch for my line lock also activates my 2 step. I don't look at my rpm's when I launch, just activate the 2 step and hold the pedal to the metal

As for my times, I just recently dipped into the 10's. Turned up the boost to see what this 62-1 turbo can do.

 

must be nice..lol

 

I am not quite sure what he meant by being in reverse at the line. I was thinking maybe a transbrake car was what he was talking about. But I have to disagree on the last part of your post about the slack. As soon as you take your foot off the gas you have slack. The only way on a manual car is going to be either staging with the e brake or a line lock.

 

It broke when I shifted 2nd. Heres the vid.

http://www.youtube.com/user/nitrofed...10/QpE23Yl5xkw

 

Over shooting the lights is what I meant. My mistake. Also when I said axle, I meant drive shaft play in the front pinion section. I know when I modified my PPF 3yrs ago, I grabbed my shaft and was able to rotate it back and forward 3/4" of an inch. Another Fd I was rebuilding had the same amount of play. Also not everyone is gonna fully load the driveline while staging. Any NOOB wouldn't think it was neccessary unless they knew. When I found out about my play, I started preloading to take the shock stress away. I think it really helps the diff.

 

Every time i try to preload the driveline, i forget to release the ebrake until like 3rd gear, so i quit doing it. I haven't broken anything in a long time, drive train related. I probably have 100 or so passes this year alone on it. 8100 rpm clutch drop every time. I love it.

 

It was my diff that broke. I would like to find a solution so it won't happen again. I don't have nor want a setup solely for drag racing but would like it to be up for it when the itch arises. I made a total of 4 passes with the final breaking the diff. The first two were pretty smooth, track temps were lower 60's upper 50's, launching about 4k to 5k, ET's at 24 psi, 60' 1.92 and 1.78, resulting in a 8.20 improving to 7.96
The next two were not so good. Lowered pressure to 20 psi, had some wheel hop during burnout, launched at 7k massive wheel hop and tires broke loose on the shift to second and just let off. Temps had dropped to lower 50's and repeated last pull and snap off the line.

 

A few pics of my diff...

 

Looks like it just needs fresh gear lube.

 

Wheel hop is a major diff killer...the instant I feel mine even start to wheel hop,