[quote="USELESS"]The only issue for me with the 3.7 is the rev limiter.I am going to do my once only 1/4 mile and dont want the car to be dying 1/2 way down the track from the rev limiter.[/quote]

Alot of things will determin if you will run out of revs.

Final drive, tyre diameter, vehicle weight, how much hp, how much torque, traction, rev limit, fuel type, n/a or aspirated etc etc

In a heavy falcon that has a OD gearbox and has a pretty healthy engine I would think you would not hit the rev limiter or get anywhere near it.

My xy ran 4.1's gears rev to 7200-7500 over 1/4 for a best 12.3 @113mph.
Toploader gearbox 1:1 final ratio with 26" dia mickey thompsons.

For better idea just look at other peoples combo's in similar car & set up to your own.

Depending on what cog & ratio you choose when crossing the line you could get quicker ET slower terminal speed(lower ratio) or slower ET higher terminal speed(tall ratio).


You don't want to be using your OD gear when crossing the line.
Also the best time to cross the line is 500rpm past your maximum hp peak.

Give full car specs and I will see if I can work out a good ratio for you.

Down the quarter for me even with a 3.45 still have a almost two gears left. Just changes to third.

yep thats the same with mine.

also with the fuel econ mine stayed about the same when i changed to 3.45

hang on a sec, going off that diff doc that calculates the amount of speedo error:

by running 3.73:1 gears using the black 23 tooth speedo gear and 225/35ZR20 tyres the speedo (at 100km/h) will be showing 100km/h but the actual speed of the car will be an estimated 96km/h?

Thats pretty good isn't it? Datamine was saying that it'll be good for speed cameras....i'd rather that then 106km/h showing as 100km/h on the dashboard...

Im hoping to have 3.73 gearing with the BTR auto in the next few weeks....the new gearing (currently have 3.45LSD) is like re-filling with 95ron and 98ron fuel the difference will be minimal with consumption.

Again like having a modified vehicle u drive it hard u will suffer come top up time....take it easy and give it some stick every once n awhile and you'll have some fun and wont really notice the $$$

easier said that done mate!, but remember we do these mods for performance, not economy. those two words dont go hand in hand....

i didnt notice much of a diff. in fuel economy changing from 3.08 to 3.73, economy went from s**t to s**t

nah they are awsome, i have nothing but praise for em! i noticed a huge improvment all accross the rev range in all gears in terms of acceleration, they go quite well with the cam i have at the moment. good take off, good top end. go for it!

Well actually do it is easy either you know how to drive and can drive casually and responsibly which really with any diff gearing the majority of guys here round town wouldnt see any difference in there fuel bill.....and t yeh and nay on the performance not economy thing...people do these particular mods yes to improve performance yet y do so many ask about how my economy will be like getting a new EMS....improved fuel economy will always popup.

But yeh in the end it is a performance mod that will hinder your fuel economy even if its only marginally.

3.23 + 0.50 = rocketship until you get use to it and want more. Use black speedo gear and 18 to 20 inch rims at 225 to 245 width and the speedo will probably read 4 to 10 kms /h under as opposed to over if you use 15-16inch wheels with 205 tyres etc...

when does the speed limiter kick in with a 3.7 diff?

cheers