au xr8 diff gears 4.11

XR27 · 14-05-2011, 08:18 PM

Hi Guys,
i am wanting to change the diff gears in my au xr8 220 auto ute.
i use it only on some weekends and do hwy and around town driving.
iam not worried about fuel economy, iam just after performance.
chriss at BPR has recomended 4.11's, can anyone tell me what there like?
i was thinking of 3.9's but maybe 4.11's are the go.
thanks any advice on this would be a great help.

Day-mow · 14-05-2011, 08:43 PM

I know a guy that had 4.11's in an ef fairmont auto. He struggled for traction in 1st. I think you have alot of fun

Cam · 14-05-2011, 09:11 PM

I have 3.9's in my Stroked AU Fairmont, and I love them! In my car its makes traction a big issue in 1st... I also find it works really well for dropping back to 3rd for overtaking..
Cant see a reason to go any shorter with a V8, IMO anyway..

XR27 · 15-05-2011, 06:03 PM

Thanks for the info,

dose anyone know how many revs it would be doing at 100km with 4.11 gears in it,

also what would i have to do to get the speedo reading right.

Thanks Pete

Cam · 15-05-2011, 07:13 PM

As a guide, mine does 2300rpm at 100 with the 3.9's..

For the speedo: http://www.jaycar.com.au/productView.asp?ID=KC5435

MGGT RAA · 15-05-2011, 08:35 PM

Hey mate, i got 4.11s fitted to my sedan (auto also..) i love it!

can be a bit of a pain in the wet at times, with no word of a lie ive taken off at nanna pace and still broke traction haha

Only revs at around 2400rpm, at what i think is around 100, i still havnt got my speedo sorted yet either... And to be brutally honest, i havnt noticed a massive increase in fuel either.

Performance wise the take off is just awesome, although giving it a bit when sitting on 80+ isnt what it used to be but is still more than enough. Also knocked off 0.7 of a second off my quarter mile time!

XR27 · 15-05-2011, 10:54 PM

Thanks again for the advice,

iam still not sure weather i will go for 4.11's or 3.9's,
but i am looking forward to the change either way.

MGGT RAA · 15-05-2011, 11:18 PM

Im sure the breaking of traction under light acceration would easily be fixed with a decent set of tyres.

You might want to take into consideration what sort of events etc, you might wanna do with your car also. Obviously 4.11s arnt well suited for full track racing... However drags, drift, burn-outs, she'll love it!

XR27 · 15-05-2011, 11:53 PM

Hi MGGT RAA,

Breaking of traction under light acceration, is what iam after.

i wont be doing track racing. just around town and hwy driving some times, i want it to have lots of go down low but also be good on the hwy at 100km for passing
Thanks Pete

Rosscco · 18-05-2011, 07:41 PM

The difference between 3.9 and 4.11 is hardly worth worrying about, either will do you well.

dieseltrain79 · 18-05-2011, 10:16 PM

Quote:

Originally Posted by xr 27

Breaking of traction under light acceration, is what iam after.

i wont be doing track racing. just around town and hwy driving some times, i want it to have lots of go down low but also be good on the hwy at 100km for passing
Thanks Pete

Then buy the cheapest crappiest skinniest tyres , and drive round sideways everywhere . Makes me feel safe ... not ! LOL

My old man had 4.1's in his stroked EB windsor . Was awsome to drive , mind you it revved to 6800rpm which the 4.1's benefited . Otherwise 3.9's will do you fine

One of the best bang for buck mods on those cars .

THE CADBURY KID · 18-05-2011, 10:28 PM

I have 3.9 in an auto v8 and my car does 2100rpm at 100kph,improved my economy and made my car feel quite spritely and sometimes it will go a bit sideways when it hits second with newish 225 tyres and a fresh lsd,never did that with 3.23 gears

I cant say it loses traction while you are actually moving though, i hoped it would

blueoval · 19-05-2011, 06:12 PM

Interesting thread. Its certainly giving me ideas.

Anyone know what a set of 3.9s would set one back, and where you would get your hands on a set of gears?

Rosscco · 19-05-2011, 08:07 PM

If I can give you a hint, they say the 3.9s are pretty noisy, and were re-designed as 3.89s for later model cars. (I had a list of crownwheel to pinion teeth count, but I can't find it at the moment.)

They were in Australian R31 Nissan Skylines, are pretty easy to find used, and I believe are still available new. 4.11s were in Australian R31 Nissan Pintaras.

XR27 · 19-05-2011, 08:14 PM

Hi Guys,

Thanks for all the feedback,

iam going to go with the 3.9's. will let you know how it goes.

as for cost i had 2 quotes 1st $1200 2nd $1500-$2000, both are for compleat job.
I dont know how much just for gears.

Rosscco · 19-05-2011, 08:44 PM

Ooops, just found my notes. Seems the 3.89s were noisy and the 3.91s are the replacement / upgrade.

Ross

MGM · 22-05-2011, 10:23 PM

I'm wanting to do 3.9"s in my au xr8 ute auto, but heard some people say it hits limiter a few times before changing gears at wot even with the speedo corrector, second hand gears are about 200 and approx 500 labour with bearings etc

Blown347AU · 12-08-2011, 07:49 PM

heyy, put the gears in yet?? i wanna do mine still, dont know if 3.9 or 4.11

**Stav** · 12-08-2011, 08:12 PM

3.9 are the best compromise for the v8.

Cam · 12-08-2011, 08:17 PM

Agreed that 3.9's are great for a V8, yet even with my NA stroker I have considered going for longer gears.... No need for the 3.9's to get off the line.. Especially if your name and sig is anything to go by Blown347AU.... I would be looking at 3.23's/3.08 and a C4....

DW260 · 13-08-2011, 07:47 AM

I've got the 3.9's in my manual ute, and I wish I spent the money elsewhere. Having said that it does make it a little easier to drive around town, but don't expect a total transformation in performance.

Diff Doctor in the ACT did mine for $1500 which included brand new gears, bearings and LSD cones. The gears he used were new out of the box and weren't recycled Nissan items.