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Diff ratios for 350 ramjet chevy
Posted: Sun Dec 09, 2007 9:26 pm
by 350 chevy
I have a GU with a 350 Ramjet Chevy and wondering what diff ratios would be best suited.
Posted: Sun Dec 09, 2007 9:30 pm
by mikesmith
hey mate
what tyres are you running?? also what gearbox and transfer??
you will get asked this by everyone so i thought i would do it before u get flamed.
Posted: Sun Dec 09, 2007 9:59 pm
by 350 chevy
Only just purchased car, - tyres are 285/75/16, 2002 3 litr turbo diesel 5 speed manual. Looking at compliance plate differentials are 4.3
The patrol feels like it is revving a bit too high. I know I can go to 3.9 ratios. Would 3.5 be too tall? The ramjet is a talkie motor but not a high revving motor. I want to play with the ratios becuase it is really thirsty. Once I have ratios sorted I would like to possibly upgrade the ECU, has anyone been through this process and could offer advise.
Posted: Sun Dec 09, 2007 10:03 pm
by RN
350 chevy wrote:Only just purchased car, - tyres are 285/75/16, 2002 3 litr turbo diesel 5 speed manual. Looking at compliance plate differentials are 4.3
The patrol feels like it is revving a bit too high. I know I can go to 3.9 ratios. Would 3.5 be too tall? The ramjet is a talkie motor but not a high revving motor. I want to play with the ratios becuase it is really thirsty. Once I have ratios sorted I would like to possibly upgrade the ECU, has anyone been through this process and could offer advise.
torque about , pop music, torque about, pop music
Posted: Sun Dec 09, 2007 10:35 pm
by RoldIT
Find out what RPM your engine peaks and/or begins to flatten out it's torque curve then do some calcs so that your motor lopes along at that RPM at 100klms. Getting yourself a dyno on your motor would be a good start.
Otherwise, select top gear and cruise. Slow your revs down till your at a rpms level you're happy with then check you speed. If you're at 80klm (as an example) and you wanna be at a 100klm, then you need a 25% taller gear set. Even 3.9 are only about 10% taller than what you've got now. So if your running 3500rpm at 100klms, 3.9s will take you down to about 3150rpm.
The first method is better as it will maintain ideal torque will dropping rpm for fuel economy.
Maybe a set of 4.1s with 35" tyres would be a nice fix.
I'd be happy to swap you a set a 4.1 centres for your 4.3s ...