What diff gearing are people running? Pros and cons

[HDN05LParticipant Canberra ACTVS Olympic Edt 383 stroker Ute View build HERE Member since: March 2, 2015 Posts: 289]

Hi guys,

I am looking at upgrading my diff gearing in my 5L Auto ute currently 3:08 and wanted some honest feedback on what people have/or are using.

The car isn’t an everyday car so economy isn’t my concern, I just didn’t want to go to high e.g. 4:11 if it will affect the car on freeways.

Any feedback is always appreciated.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

Diff selection is a good one for those guys that think power is everything, and torque doesnt matter. A diff is a torque multiplier.  The lower the ratio (higher number) the more torque will be transferred to the road. So with 4.11 you will feel more push in your back as it gets the car moving compared to 3.08. But as you mention the downside is revs at highway speed, or in a drag car rpm as it hits the stripe. Your car 3.9 is my vote.  (Sorry for the long reply)

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

IMO 3.7 is perfect for the 304/4speed.

[HDN05LParticipant Canberra ACTVS Olympic Edt 383 stroker Ute View build HERE Member since: March 2, 2015 Posts: 289]

Interesting info thanks Gary.

Its always a tuff choice because i don’t want to do this twice.

[Anonymous View build HERE Member since: January 1, 1970 Posts: 0]

3,46:1… only because it’s the only ratio available for my front Diffs.. would prefer 4.11:1 for the Track car.

 

[exec24Participant 2004 VY S2 Berlina 1996 VS 5L Sedan View build HERE Member since: April 8, 2015 Posts: 435]

i’ve got 3.9’s in my vs v8 auto, i wouldn’t go 4.11’s as it would probably rev a fair bit when you just want to cruise, mine seems to rev about 2200rpm there abouts, been a while since it was on the road and i cant remember exactly

a mate of mine had 3.45’s and went 3.73’s and said it’s still not quite enough, also a vs v8 auto

• This reply was modified 9 years ago by  exec24.

[HDN05LParticipant Canberra ACTVS Olympic Edt 383 stroker Ute View build HERE Member since: March 2, 2015 Posts: 289]

Thanks for the feedback guys this is why i love the forum, always different thoughts and no bulls$@t.

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

I ran 3.45 gears in my old VN V6/T5.  Very good car to drive (I’m still a big fan of the old cog swappers) and still say to this day that it was more fun to drive than my Senator with 304/4L60e/3.08 gears even though it has more power/torque.

1st gear was very short and badly traction limited even with good tyres and very tight LSD, would happily cruise around town at 55-60km/h in 5th, cruised on the motorway at just over 2000rpm and was no worse on fuel economy, I’d actually go so far and say it improved.

[BLOWNVSParticipant WAVS MALOO VR BT1 project car BF MK II XR6T View build HERE Member since: March 2, 2015 Posts: 47]

I got some 3.7s to suit m78 borgwarner diff for sale if you’re interested. They are surplus to my requirements as they aren’t suited to my new turbo combination.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

I guess you know this, but you currently have 3.08:1, so lets say you went to 4.11:1. So that’s an increase in number of times the wheel rotates for any given engine speed of 4.11/3.08 = 1.33

So rpm wise times whatever revs its doing now by 1.33 and it will tell you what the new revs would be at any given speed. So if it was doing say 2,200 rpm at 100 km/h (a guess), it will now do 2,200 x 1.33 = 2,936rpm.

As I say, gears are a torque multiplier.  So the torque that was previously transmitted to the wheels will now be 1.33 x what it was before, hence the push in the back, and why 4.11’s get the car moving from a standstill quicker.

That’s why in drag racing there is a saying torque gets you out of the hole, power gives you mph.  Yes I know power wins races, but you can’t just ignore torque, in fact its getting the car moving and the push in the back which makes it so important (imo) for a road car.

• This reply was modified 9 years ago by  VRSenator065.

[[TUFFVQ]Participant Melbourne1991 VQ 304 View build HERE Member since: March 2, 2015 Posts: 171]

I’ve had 3.89’s in my VQ for going on 7 years now. Great ratio. sits on 2250rpm on the highway. Don’t get caught into this ‘it’ll rev too hard on the highway/kill economy’. It’s a crock. you might be revving slightly higher but there is less load on the engine so they basically cancel each other out.

Don’t bother with 3.45’s in a stock aspirated engine. 3.89’s at least, maybe 4.11’s.

I wouldn’t worry about running out of revs on the strip either – how often do you actually race? Hits on the street are more 1/8th mile anyway. Gear it up!

[HDN05LParticipant Canberra ACTVS Olympic Edt 383 stroker Ute View build HERE Member since: March 2, 2015 Posts: 289]

Thanks for the feedback guys.

I have just booked the ute in for the diff on monday for 3.7s decided it was the best all round and suits the supercharger a bit better.

[VRSenator065Participant Adelaide SAVR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project) View build HERE Member since: February 17, 2015 Posts: 5 777]

HDN05L wrote:

Thanks for the feedback guys. I have just booked the ute in for the diff on monday for 3.7s decided it was the best all round and suits the supercharger a bit better.

Cool, post up once its done how it feels compared to the old 3.08s

[NickVRParticipant AdelaideVR V8 Exec, VR SS, VF Redline Reserve View build HERE Member since: March 2, 2015 Posts: 264]

Got 3:73s in mine. Its a good ratio compared to the 3:08. Good cruising gears and not bad on the highway either. I think my tacho might be out (I know my speedo is) because it sits on about 3k at 110kph. But my tacho is a bit dodgy but I will leave that for another thread.

[[TUFFVQ]Participant Melbourne1991 VQ 304 View build HERE Member since: March 2, 2015 Posts: 171]

NickVR – Is yours a V8 conversion?

If so the cluster will still think its a 6 and will be receiving 33% more pulses than it expects, so will read higher.

[ImmortalityParticipant 97 HSV Senator 185i 02 VX L67 Calais View build HERE Member since: August 31, 2015 Posts: 535]

[TUFFVQ] wrote:

NickVR – Is yours a V8 conversion? If so the cluster will still think its a 6 and will be receiving 33% more pulses than it expects, so will read higher.

Shouldn’t do, VR V6 and V8’s used the same diffs/transmissions with the same VSS so there is no difference between V6 and V8 in terms of speedo signal as far as I am aware.

[cava454Moderator 93 VR BT1 View build HERE Member since: February 20, 2015 Posts: 2 390]

Immortality wrote:

[TUFFVQ] wrote:

NickVR – Is yours a V8 conversion? If so the cluster will still think its a 6 and will be receiving 33% more pulses than it expects, so will read higher.

Shouldn’t do, VR V6 and V8’s used the same diffs/transmissions with the same VSS so there is no difference between V6 and V8 in terms of speedo signal as far as I am aware.

speedo no. Revs yes

[NickVRParticipant AdelaideVR V8 Exec, VR SS, VF Redline Reserve View build HERE Member since: March 2, 2015 Posts: 264]

[TUFFVQ] wrote:

NickVR – Is yours a V8 conversion? If so the cluster will still think its a 6 and will be receiving 33% more pulses than it expects, so will read higher.

Yes it is a conversion. I put the cluster in from the wreck I got the 5ltr out of. Also tried three other clusters mixing and matching boards and tachos and no luck. Thinking it might be the ignition module, I have been told that it can sometimes be the issue.

Immortality wrote:

Shouldn’t do, VR V6 and V8’s used the same diffs/transmissions with the same VSS so there is no difference between V6 and V8 in terms of speedo signal as far as I am aware.

Yeah, tacho is the only thing different from what I found out.

cava454 wrote:

speedo no. Revs yes

As I thought Cav. Only the tacho is diffferent, and even then it should read incorrectly not erratically.

• This reply was modified 8 years, 11 months ago by  NickVR.

[Slow355Participant Victoriahectic spec 355 vs ss ute View build HERE Member since: March 2, 2015 Posts: 322]

Got 3.7s in my one! Made huge difference from 3.08, go a Harrop center while you at it. Best coin I spent careful tho as one that fits 3.7s doesn’t fit 4.11 so make sure you are 100% first. Think Harrop center was around a grand

munch munch ls1s for lunch
Best 1/4 mile 13.1@105mph 60ft-1.8sec Reaction time .8 sec 0/100-4.8sec

[gtrboyyParticipant gtrboyy1.6 Getz View build HERE Member since: January 20, 2016 Posts: 201]

Put 3.7’s in brother’s vs maloo,daily driver 50/50 motorway driving suited car very well still had good economy & for basic mods on car went wayyyy better than it should have just memcal,full exhaust exhaust & hsv s3 airbox etc,shift kit.

Small stally in it would have made perfect.

 

Getting speedo & shifts corrected was a pain in arse.

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