new diff gears same times

hi everyone. i just put new diff gears. i went from standard 3.23-3.55. the car feels quicker mainly down low but at the drags, the 660ft mark they are a tenth better but by the 1000ft mark they are slightly slower. the car is doing about 5000rpm in third over the finish. the only thing i can think of is the gear changes
in the auto. has anyone else experienced this or no why it is happening. could it be something to do with the computer? any advice would be great as the gears
are getting changed again because they came out of another car and are noisy.
trying to decide between putting standard gears back in or forking out 500 for a new set

[Racecraft]

did you recalibrate the speedo and ecu shift points?

[OED666]

what model car is it going in... i had 3.89:1 in mine when it was an auto, and it went hard off the line, but shift points were crap...

i no a guy with an EB XR8 with 3.7's and he has no shift problems, as V8's have a separate auto computer, so i am not too sure how they handle the different gear ratios.

you might have to look at getting 3.45's and the correct speedo gear to suit the gears.

or convert your car to a manual, and then you can have any diff gears you want...

[Stav]

Mate I have been thinking about this for a while now..and have come to a conclusion..for the money I did not believe that I could justify the cost .

I once had an xc 250 falcon.It went from 2.92 to 3.5 diff ratio. I did not think it went better .It felt like it was pulling my car back from the change.I hated it. I felt like it made it harder to reach higher speeds.

For the AU everyone says go for 3.7...I think 3.45 will be the best compromise.

At a price of 1400 dollars I can most probably source one from the wreckers for 200 and fit it myself.

Just remember that my experience was in an xc ford.

[jonbays]

Originally Posted by $needmoney$

hi everyone. i just put new diff gears. i went from standard 3.23-3.55. the car feels quicker mainly down low but at the drags, the 660ft mark they are a tenth better but by the 1000ft mark they are slightly slower. the car is doing about 5000rpm in third over the finish. the only thing i can think of is the gear changes
in the auto. has anyone else experienced this or no why it is happening. could it be something to do with the computer? any advice would be great as the gears
are getting changed again because they came out of another car and are noisy.
trying to decide between putting standard gears back in or forking out 500 for a new set

tell us more about the car what model and timeslip info let see more.

What diff did you have and what tyres are you running. going from a 3.23 to 3.55 wouldn't be much of a difference well 8% its not much it shouldn't be much in tenths better you would think.

[Sylox]

If your car is a V8 auto AU and you have changed diff gears forget it the problem is in the ECU and can not be fixed yet. Although if its a factory diff ratio you have changed to eg 3.45 find a xr8 ecu and you will get away with it a bit more cleanly.

Chiptorque and SCT are working on a way to tap into the torque reduction maps in the ecu. Which is the cause of the problem.
An after market computer wont help you because as far as we are aware there isnt one that can control the elec autos in the au's. And the Auto portion of the au computer can request torque reduction as well.

I went from 3.45:1 to 3.9's and with no traction problems had absolutely no gain on the 60ft, or on the et. And it felt no different on road
Datalogging on the dyno shows the ecu is pulling up to 19degrees timing out from the torque maps requesting torque reduction.
I run 97mph on the 1/4 with no traction loss in a AU 2 xr8 ute which is good for a low 14 but can only get a best of 14.89 (approx) (the guys with 2031/2030 cams in the same car with stock gears run a slightly slower mph)
A stall convertor wont get you past the bottom end problem either as it affects the whole rpm range. (Noddy's car still has the issue with a aftermarket stall)

Headsex can vouch for this problem (sct tester)
Noddy's T3 has also been datalogged (auto/stall/3.7's)
I've got slips from willowbank + chiptorque's data logging & AU2xlsv8 will vouch for all of my runs on the 1/4 as for the no traction loss.

---- if none of this apply's to your case just ignore me.

[deankdx]

Originally Posted by jonbays

What diff did you have and what tyres are you running. going from a 3.23 to 3.55 wouldn't be much of a difference well 8% its not much it shouldn't be much in tenths better you would think.

i belive this is most likely,
if you have a cam you'd pick a gear set to mach it, but that will throw out the drivability due to stall and shift points too which will need calibrating to suit.

[OED666]

i can say that i definitley believe i noticed a difference in the performace of my car from the 3.08 ratio to 3.89, but now i have 4.11's and its hard to notice much of a difference between the two.

useless - $1400 is way too much, for diff gears, and i take it at that price they are installed..

i have definitely had troubles getting a good 60ft time at the drags. driver problem obviously, but it will either bog down or get emense amounts of wheelspin.

Rollin has done a 1.94 60ft time which in unbelievable with 3.89's. I would be happy with 2.05-2.10 60fts. Even though i have 4.11 diff gears Rollins gearing is shorter with 3.89's which is allowing him (the buggar) to get such good 60ft times.

with 3.89's and 4.11's i am around 4800- 4950rpm in forth respectivaly.

new gears installed at mal wood are $520.

[Supa R00]

whats your rpm at 100 in 5th OED666???

[INJECTED_250]

u will only have problems with shift points if u change youre speedo gear to get it right.. if u leave stock spedo gear in youre shift points will be fine and wont change

[Stav]

Originally Posted by OED666

i can say that i definitley believe i noticed a difference in the performace of my car from the 3.08 ratio to 3.89, but now i have 4.11's and its hard to notice much of a difference between the two.

useless - $1400 is way too much, for diff gears, and i take it at that price they are installed..

i have definitely had troubles getting a good 60ft time at the drags. driver problem obviously, but it will either bog down or get emense amounts of wheelspin.

Rollin has done a 1.94 60ft time which in unbelievable with 3.89's. I would be happy with 2.05-2.10 60fts. Even though i have 4.11 diff gears Rollins gearing is shorter with 3.89's which is allowing him (the buggar) to get such good 60ft times.

with 3.89's and 4.11's i am around 4800- 4950rpm in forth respectivaly.

new gears installed at mal wood are $520.

1100 -1400 is the going rate up here and so I am tempted for them to keep their gears on the shelf.This is gears /bearings and lsd.

[jonbays]

New gearsets alone cost $450 so useless Sydney pricing is correct. Here its around $900 for a ratio change and $1500 with LSD fited drive in drive out.

[OED666]

TIKFD6 - i am doing 2050rpm at 100km/h with 4.11's...

thats so damn expensive for a gear ratio change... Rollin paid $520 drive in, drive out... i am getting everything new(gears, bearing etc..., (another LSD Rebuilt) axles and fitted for a nice amount... (cant really say, its a steal)... i cant wait either, as i am getting a lightened xr6t flywheel and clutch fitted... DIE EA FLYWHEEL AND GHEY CLUTCH!!!

[neb]

Originally Posted by OED666

TIKFD6 - i am doing 2050rpm at 100km/h with 4.11's...

thats so damn expensive for a gear ratio change... Rollin paid $520 drive in, drive out... i am getting everything new(gears, bearing etc..., (another LSD Rebuilt) axles and fitted for a nice amount... (cant really say, its a steal)... i cant wait either, as i am getting a lightened xr6t flywheel and clutch fitted... DIE EA FLYWHEEL AND GHEY CLUTCH!!!

are you sure your speedo is right? i thought it would of been closer to 2500rpm? my car does around 2050rpm at 100km/h with 3.27 gears

[EFFalcon]

my car does about 2050rpm @ 100 with an auto and 3.45's..
i know you've got the BA spec T5, but 2050 seems way low.

[EFFalcon]

Originally Posted by $needmoney$

hi everyone. i just put new diff gears. i went from standard 3.23-3.55. the car feels quicker mainly down low but at the drags, the 660ft mark they are a tenth better but by the 1000ft mark they are slightly slower. the car is doing about 5000rpm in third over the finish. the only thing i can think of is the gear changes
in the auto. has anyone else experienced this or no why it is happening. could it be something to do with the computer? any advice would be great as the gears
are getting changed again because they came out of another car and are noisy.
trying to decide between putting standard gears back in or forking out 500 for a new set

what other mods are done to the car?
for a stockish car, diff gears won't make a MASSive difference.
where as for a car with cam/headwork etc, where the power comes on later then it did when stock, the diff gears help the car get to its peak power band, something a stocker may not need *quite* as much.

[Psycho Chicken]

As Injected 250 said, changing the speedo gear will stuff the shift points up. I put 3.45 into my old EB, changed the speedo gear at the same time. It went slower (only just) down the quarter than the 3.28. The ECU let it change up just before the 400 was out.

my car is a series 1 au v8 with full exaust and cold air. i just use my street tyres on 17s
i havnt changed the speedo. the temperatures at the drags were within 1 degrees from my times with the old gears and the new gears.
my car revs at about 2200 at 100km.

[jonbays]

I reckon its because a stock V8 peaks around 4500-4750rpm and the gaerings too low now! A six will peak around 5000rpm and thats the difference. Put a decent cam in it and then you will be in business with those gears.

[Sylox]

Originally Posted by $needmoney$

my car is a series 1 au v8 with full exaust and cold air. i just use my street tyres on 17s
i havnt changed the speedo. the temperatures at the drags were within 1 degrees from my times with the old gears and the new gears.
my car revs at about 2200 at 100km.

Read my first post in this thread. Thats exactly the same as mine and the reason for it is in my above post as well.

60ft nearly the same
Car feels not much different in acceleration
ET is very close to stock gears but mph is higher


Put it on a dyno and get the operator to check how much timing is being pulled in the bottom end (will be though out as well) If its getting timing ripped out its the ecu's torque maps

[Sylox]

Originally Posted by jonbays

I reckon its because a stock V8 peaks around 4500-4750rpm and the gaerings too low now! A six will peak around 5000rpm and thats the difference. Put a decent cam in it and then you will be in business with those gears.

Not the case at all with the Auto AU v8's mate the ecu is the problem. Whilst a bigger cam would help more with over all power the ECU will still stuff with the result
If the cam was the problem then the autos would have a different cam to the manuals because even with 3.9's the gearing in a auto isnt as low as a manual with 3.45's :


The AU I6 is a completely different kettle of fish as it isnt restricted to heavily by the ecu in the form of torque reduction.

[Mechan1k]

Originally Posted by Sylox

The AU I6 is a completely different kettle of fish as it isnt restricted to heavily by the ecu in the form of torque reduction.

That is interesting to know.

[OED666]

Originally Posted by neb

are you sure your speedo is right? i thought it would of been closer to 2500rpm? my car does around 2050rpm at 100km/h with 3.27 gears

yep, it reads 105 when i am actually doing 100... got it checked on the dyno the other day...

i have an extremely tall 5th gear, 0.63. normal t5 ratio is i think 0.68.