Currently have 3.73 single spinner diff, auto and 2500rpm stall.

at the moment i can jump on the throttle from a standstill and the tyres hook up fairly well, stall flashes to its max rpm and eveyrthing is happy until i realize how long 1st gear still is

now im thinking about 3.9 or 4.11's, but i'd say i wont be able to make use of the stall with these gears as i'd always be feathering the throttle off the mark, so if i fit LSD as well with these shorter gears, will that still allow me to stomp on the pedal off the line...or is LSD over-rated.??

LSD, KAAZ, locka's or anything that allow you to maximise your available traction are awesome... except in the wet.

Just as an example, with an SS you can only put down the power to a single wheel when you at the limit, so you are limited to say a single 205 tyre. with LSD you can slap down power to twice the rubber.
In the wet though it really doesnt make 2/10ths of f**k of a difference as the good ol falcs like to break traction easily enough in SS form.

I <3 my LSD, I think I would die if I had a KAAZ tho going from reports.

also being able to pop the clutch and smoke 2 wheels instead of one is a massive bonus

im basically worried that if i went from 3.73's to 4.11's that i wont be able to stomp on the pedal and make use of the high stall without frying the rears, and that LSD is only limited to how much it can do.

also, with the single spinner diff, i can hear both rear wheels chirp, sometimes one at a time swapping back and forth which i thought was strange, cause i defintely know its not LSD

i find an LSD more reliable than anything else.
-nothing like doing a ss burnout at the track only for the other non warmed wheel to spin on launch
-if it lets go, you know what its going to do, ss's are a bit of a guessing game esp after they have gone sideways they snap back soo much harder.
-nothing looks more gay than a ss burnout, at heathcote youll get laughed at by the officials

but when i fitted my lsd i found my launch rpm raised a lil bit, considering there was a large change in ratio so idd say grip increased.

yep i appreciate the info so far, although im not sure if im asking the question the right way..

basically, my s/s 3.73's are not enough to shorten the s**t BTR ratios, so i want to go 4.11's,

BUT, i dont want to go 4.11 & LSD if i cant launch the car with full throttle without s**t of wheelspin. Because it seems pointless of having a high stall, if you cant launch full throttle, as it will only flash like a stock stall if i have to feather the car off the line.

I guess im asking a question that can only be tested once is done, but maybe others with 4.11 LSD could clarify if they can get decent grip off the mark, or if 4.11's are only good for burnouts?

You can launch much harder with an LSD, though I'm not sure about with 4.11s. I know an auto XR with 3.45s cant spin em off the mark.

lsd = awesome!

I would get LSD for sure, i had major problems with my 3.08 single spinner getting off the line proply and i still do now its lsd aswell (but its alot better). You must have some pretty nice tires to get off the line good with your setup. If i gun mine at the lights it will step out to the side spinning to about 40k's then grab then shoot off.

yeah it does launch good, but then 1st gear is so long the smile is gone off my face Im running 245's on the rear

according to this useful calculator....
http://www.angelfire.com/fl/procrastination/rear.html

..... with 4.11's i should be crossing the line over the 1/4 mile in 3rd gear @ roughly 5100rpm, which sounds alot better than 4700rpm with 3.73's or 4900rpm with 3.89's.

so looks like i will be getting 4.11's, and worry about traction issues later

i would go the lsd for sure...
you could say that with the lsd you will have twice as much traction as you did with the s/s..

yeah you will get better launch, but sideays action on a LSD i find a lot hairier than the SS. I cant put even partial power down in the wet if ive got the steering in any other posi than straight ahead. This LSD though had been tightened up a lot according to its previous owner, im not sure how a forctory lsd setting would go. Mine is seriously schizophrenic in the wet. theres just nothing holding the back end in line once traction goes. at least with an SS theres still one tyre providing lateral grip.

you should have the lsd even with 3.7's. you would be swapping your rear tyres every 5k klms with a 4.11 ss to keep tyre wear even :p

I dont know about you with 3.7s but i find my 3.89s are about as short as id ever go, 2500 rpm at 110, 60ks from first, 100ks from 2nd, 140 from 3rd... let us know how the 4.11's shape up

edit: oh and when taking off from the line with the foot flat, it does not dip below 4k rpm on the changes. Id imagine 4.11s wouldnt dip below 4.5K? this neccesitates a cam change if you havnt already got one. factory i6 cam gives up the power game at 4k.

yeah been meaning to get LSD for the last year, but finally decided it might be worth the money. Just waiting for the 4.11's in the mail, then will get it fitted along with a reco LSD ive got lined up



You should be getting more than 60km's from 1st? I worked out i would get 72kph out of 1st gear with 3.89 diff shifting at 5500rpm, and 68kph with 4.11's. And yeah the downside is the highway rpm's, but after having 3.7's behind an EA manual box, im used to it lol





am running a 977b which starts making peak torque at 3300rpm, and torque drops off sharply at 5000rpm. At the moment it drops to 4200rpm between 1st to 2nd gear shift. However the box likes to shift at 5700rpm in "normal/power" mode which is a bit strange as ive done all the right things to correct shift points.

another thing i might mention, every drag racing calc has said 4.50 diff ratio would be perfect for 1/4 mile with the BTR auto ratios, which according to the above calc i posted, would have me crossing the line in 3rd just as it hits redline. Would be great if i didnt care about 3000+rpms at highway speeds

im pretty sure its around 60 could be a smidge more, next time i get the gps out ill find out exactly how much.

you would be in 4th i reckon at the line with 4.5's lol, but im no expert.

i was at the very top of 2nd with a 3.08, at 143 kmh when stock, and with the 3.89's im limited to 135 (due to speedo correction not yet carried out), but im sitting on about 4700 rpm+ at 135 in third. Id imagine with the 3.89s ill be shifting to fourth just before the line... just a guess, but all ive got untill I get it out there.

I know the lsd sounds the better option but with a SS you could wear a shirt saying " I went with 4.11's and Single Spin diff and lived" and get respect lol.

lol "i survived the 4.11 Single Spinner"

update on in gear maximums- ive checked against the gps unit and the max i got out of first gear was 67kmh and that was bouncing the limiter. the most reasonable speed you could expect me to do out of 1st with 3.89's is therefore 65 kmh. 2nd was 103 kmh, keeping it a few mm off the redline.

i would expect therefore maybe 55-58 in first - 4.11 with btr 4 speed. 2nd maybe 95 kmh. 3rd somewhere around 130. you will be more than halfway thru fourth on the line is my bet.


edit: your chart says i should be doing 72 kmh in first. either the chart doesnt account for real world data like wind resistance car weight etc, or my gearbox is slipping 10% constantly! (which would not suprise me)