I'm pretty sure I am gonna buy a set of motive 4.10's for my car, but I'm really worried about breaking them. I don't have the money to buy a 12 bolt now, so if I launch my car from 3K rpms or so will it break my rear? And I also heard a hard shift into 2nd can break the rear also, is this true even with a stock clutch?

Btw I have an M6 and kumho's

Thanks

edit: Racing the car will only be an occasional thing, it will mostly be street driving.

 

4.10's are more brittle than 3.73's or 3.42's. However with street tires your biggest problem will most likely be traction. I'm not saying that you won't break something because whenever you push something to the limit you greatly increase your chances of breaking something but... Without sticky tires, you will probably be very challenged just to hook up. If you do hook up is typically when you should be concerned about breakage. What do I know: I blew up my transmission doing a burnout.

 

Well I've been using 4.56's in my original rear. See's consistant 1.5x 60' times. Trans still has the stock 1st gear set though that will be swapped to a lower set this winter. I run a set of M/T ET Drag 10.5 x 28 slicks. My conv flashes to approx 5k and I generally stage between 3k and 3500 rpm and I shift at 6800. She def hits tires very hard and only part in it that gave me trouble was the Auburn Pro series posi unit which blew the spiders out in turn breaking the ring gear. I have since gone to a mini spool and had no trouble with it since.
I would think you should be fine with your set up and the 4.10's.

 

how are those 4.56's. Why are you changing first gear out, is it to much gear? I thought about going with these gears and a big cam, how are they on the freeway. Do you drive your car much on the street with the spool. I would like to go this route, since I've heard its much stronger(sounds like thy're holding up for you)My only concern is turning corners and such, I never drive fast around them anyway, is there any other disadvantage with the spool? sorry for all the questions, but not to many people have gone this route.

 

Oh I see you have an auto, thats alot of first gear, now I know why you are going to a smaller first

 

With the stick, hiway was just a bit slower at 3k rpm. With the auto and the original 4k stall 10" you couldn't think about due to excess heat buildup in trans.
The 1st swap is not to reduce the effective gear. Stock gear set is 2.48, I'm going to a 2.75. This will help get it off the line better.
I haven't street driven it for a while and would not rec spool on the street. Would do the Pro series posi again if I did start street driving it again. I am going to eventually swap out to the 12 bolt, but so far it hasn't been in the budget.