So here is my dilemma, back in 2012 when I assembled this car I put a 3:45 ratio borg warner 9 bolt in it. Well its 2019 and it blown. I need to weigh my options. I know I can buy parts from 9bolt.com but I have no means of building it myself even though I own my own shop. Rears are just something I dont do. I can get a yard unit but im not going to find another 3:45 ratio 9 bolt. So can swap in a different rear, just got to deal with getting the speedo to read write. I remember when I did this swap i had to mess with some buffer box under the passenger side of the dash or something and change some of the gears on the speedo in the trans. What you guys think? Whats my best option?

 

What part of it is broke?

 

broke some teeth off the pinion.

 

So do you think that the 9 bolt is not strong enough to handle what you are doing with it? Do you think that you need to upgrade to a stronger rear end, or do you think that this is just something that broke due to age or defective parts? I don't know how much power you have or what you are doing with the car, so I can't say which way you should go. The 9 bolt is a little stronger than the 10 bolt, so if you find a junk yard 10 bolt to put in it then you are probably going to break it too.

 

i cant see the car making that much power. Its got stock heads but just about every other possible upgrade. Cant possibly be pushing more than 350 HP. Its gotta be just a freak thing.

 

Rebuilding it might seem like more than you want to take on, but I believe that you can do it. From what I understand the 3.45 is not available new, so you would probably have to set up a used gear. This can be a problem sometimes because it's not easy to read the pattern on used gears. If it was mine I would also want to rebuild the Borg Warner differential or replace it with a Truetrac. It should be a good rear end when you are finished.

 

Yeah just rebuilt it. You can get a Torsen (Truetrac knock off from Australia), and get a new set of 3.70 gears from many online retailers.

GD