I'm looking for advise on transmissions that ate best for the 450-500hp range



Roughly 2400-2500lb EK hatch

24.5 M&H slicks

Currently running a US 4.4 ITR trans and rev limit is at a conservative 8600

I picked up a junk GSR trans with a good 4th and considered swapping the 4th.

My other options are to find a B16 LSD and use a LS 4.2 FD I have or just buying an aftermarket 4.26 or 4.05 final, pretty much the same price.

I have done a 4.7 and LSD in the past so I do understand the work involved.

Looking for something good into mid 130's giving room to grow.

 

ok the fatboyraceworks calculator is down and i forgot the cspeedracing new website so this is just off my personal experience.

i think you will need to change fd or raise your rev limit if you are looking to get mid 130mph on 24.5's. i trap 125-127 at about 8300rpm using a straight gsr trans with mfactory lsd and m&h 24.5's. i think for mid 130's you will be on the limiter at 8600 rpm with 24.5's

 

Ok currently your setup will run about 128mph in 4th gear. Just upping your rpm to 9200 will give you 137mph with everything your currently running.

GSR trans will give you 137mph with your current redline

GSR trans will give you 147mph with 9200rpm redline.

GSR trans with LS final with current redline 142mph

GSR trans with ls final with 9200 redline 152mph

ITR trans with 4.266 final drive will give you 132mph with current redline

ITR trans with 4.266 final with 9200 redline 142mph

ITR trans with mfactory final 4.05 will give you 139mph with current redline

ITR trans with mfactory 4.05 with 9200 redline 149mph

IMO cheapest way to go here is raising your redline
Next would be LS final drive but then you need a new diff (LSD)
GSR complete gearset is the best way to go. will give you more mph with current revs and allow you to maintain your current diff. If you do not have a diff in the trans (LSD) then your options are open to choose either direction.

 

With the parts I have it seems that I'm going with a GSR 4th and LS 5th, should put me around 6k RPM in every gear shifting at 8600. If I can muster up the extra cash I'll pick up a 3.07 first while I am at it.

 

You should be fine with a stock GSR w/lsd.