| Message |
I have read a few articles/posts about this issue on different websites/forums and here is what I came up with. On high hp cars, the shifting of power from right to left is the primary reason for broken axles and diffs. To solve this problem, people use a locked rear diff for drag racing only. Here's what Titan Motorsports came up with about a year ago for the MKIV Supra:
[ http://titanmotorsports.com/noname100.html ]Although Titan Motorsports say that the problem occurs mostly in higher gears, there have been people who have broken their axles/diffs while launching. This is an MKIV Supra with a broken axle:
The launch.
 . The car then moved from side to side. As soon as he shifted into 2nd gear, one of the rear axles was destroyed.
 . Both the silver and black Supra (pictured below) belong to Saad Saad, one of the well-known Supra guys. This event was certainly not his best, because after breaking the axle on the silver one, he broke the rear diff on the black one shortly after launch, in 1st gear (this one was a mess because there was oil all over the start line). This took place during qualifying. That same day he bought a used axle outsourced by Joule for the Silver Supra. After installing it, it turned out to be a bad axle and he asked Andrea (from Joule) for a $250 refund. Both of his Supra's supposedly put out 1000+whp (I am sure that the black one does). Here's a picture of the black one:
 . There are many others who have had axle/diff problems associated with the side-to-side shifts while drag racing. With Camaros, the first driveline part to break after launching with slicks is the diff. I have heard from many Camaro/Firebird owners that these cars have very weak diffs, and that it doesn't take a lot of modding to break them.
I have also talked to numerous turbo'd Honda owners who have had broken axles due to hard launches. It seems like a common problem with modified Hondas because most of the people I talked to were in the 300whp range, which isn't monstrous power.
Another example I can think off is my friends Skyline. He broke his driver side axle during a hard launch. He said that the car shifted from side-to-side, which broke the axle. This was also in 1st gear. This car had a 2.7 liter stroker kit and a T-88 turbo. It put out 851whp on high boost, which is a lot of power.
I guess if an aftermarket LSD will solve the side-to-side movement, then it should stop the axles from breaking. I personally don't drag race that often, but I do a lot of spirited mountain driving. I usually drive my NA Z because I wouldn't be too upset if anything happens to it, which lets me drive it harder through the turns. Also when I'm in the NA, I drive through the smaller mountain roads with tighter turns (which means that I don't need all the power from the TT). After driving through a few turns (and heating up the rear end), it becomes obvious that the shifting of power from one side to the other becomes slower. After several mountain driving sessions, when the factory LSD got hot, the car would spin the inner side tire for a couple of seconds during sharp turns. The power then transfers to the other tire, which causes the rear end to slide out. The more I drove the car through the mountains, the longer it took the rear diff to transfer power from one side to the other; until the diff finally gave up. The power transition also wasn't as smooth as the diff was at it's final stages. I changed the diff and now the car drives a lot better than it did before in terms of smoothness, and power transition.
My point is that if the diff looses its effectiveness after a few runs when drag racing, and takes longer to transfer the power from one wheel to another/doesn't evenly distribute the load; then all that load on one axle combined with the grip provided by the slicks could very well be the cause of the broken axle. If an aftermarket LSD would more evenly distribute the power to both tires, then this would reduce the stress on the axles. I noticed that people don't normally break their axle/diff on the very first run. It usually take a few runs which gives the stock LSD time to lose effectiveness. In the case of my NA, the axle didn't break because: 1) I wasn't running slicks, so it just spun the tires, 2) Even if I had slicks, the car doesn't have the power to break the axles. As for the TT, since the diff is known to be strong, the weaker link in this case seems to be the axles.
This is just my theory and it could be waaay off, so I apologize if it is. Let me know what you guys think.
|
 |
Here's my .02 cents - 
