3.73 Diff Now In

sly · 11-02-2008, 10:51 PM

Got my 3.73 gears on the wagon today, but haven't done many k's yet. It's a near 15% change from the stock 3.23, but the difference doesn't seem as big as I expected, it's pretty subtle. I'm finding that driving around town I'm using less throttle and the box is changing up earlier, maybe fuel consumption will improve???

I had a Gtech arrive a couple of weeks ago. Haven't had time to play with it yet. I would have liked to get before & after figures, but I managed to call for a quote late last Thursday just after a job for today was cancelled, so I got the slot. Had to work Fri Sat & Sun, 12hr shifts, so no time to set up the Gtech. I'll try for figures now when time permits.

EvilChief · 11-02-2008, 11:02 PM

fuel eco will go down, acceleration will go up

i found 3.7s to be magic for my setup, finished the quater at top rpm in 3rd

**Mechan1k** · 11-02-2008, 11:21 PM

Woo hoo ... and I am broke. And will be for a while.
I think i need to save up for this one.

This i like the sounds of ... I am sick of sluggish take offs with load on.

So the difference wasn't overly noticable then?????
So if that's the case ... it really shouldn't rev too much on the highway.
Although around suburbia is where I am wanting shorter gears ... especially in traffic.

I am liking the sounds of this mod more and more.

sly · 12-02-2008, 12:18 AM

It's a 15% difference... 100km/h cruising rpm goes from 1780 to 2050, still pretty easy on the ear and pocket. But 1st gear speed at redline drops from high 80's to mid 70's. It's like 15% extra torque everywhere from idle to redline. That's probably why it feels not much different, the extra shove is everywhere rather than just above or below certain revs.

It does have a sharper take-off from the lights, but the power surge around 3000 is magnified as well. It'd be insane from 3000 to redline with a Raptor or Vortech on it... when the kits are eventually available...

**Mechan1k** · 12-02-2008, 12:20 AM

Hmmm ... I need to start saving.
If it accentuates mid-range punch that much I am interested.

sly · 12-02-2008, 12:25 AM

Quote:

Originally Posted by EvilChief

i found 3.7s to be magic for my setup, finished the quater at top rpm in 3rd

The wagon is speed limited at 180 with a 3.23. This drops to 153 (95mph) with the 3.73. To run it at the Creek with boost I'd need to upgrade the tailshaft as well and "adjust" the speed limiter to prevent it maxing out before the quarter.

GK · 12-02-2008, 08:04 AM

I'm glad you're happy with the outcome sly.

My SR is scheduled for 3:7s tomorrow. I will certainly notice the difference, as I'm going from 3.08 to 3.7!

: I'm expecting mine to rev at about 2,100-2,200 at indicated 100kmph. The speedo will be well out though. How do I correct this? Is it the little plastic gear I need? Easy to install?

The diff is being fully rebuilt too, with the drive train lash removed. It'll certainly be lots of fun with the 5 speed.

I was opting for the 3.45 ratio, but with LPG and the associated weight penalty, I wanted something a little extra to compensate for it.

I'll let you know how mine goes, pick it up Wednesday night!

GK

EvilChief · 12-02-2008, 08:20 AM

Quote:

Originally Posted by sly

The wagon is speed limited at 180 with a 3.23. This drops to 153 (95mph) with the 3.73. To run it at the Creek with boost I'd need to upgrade the tailshaft as well and "adjust" the speed limiter to prevent it maxing out before the quarter.

i ran NA, custom tailshaft with an open speed limiter, crossing the line at 94.33mph

sly · 12-02-2008, 08:39 AM

ATM my speedo hasn't been corrected. You should be able to use a drive gear around -20% (change is -21.1%) without probs on the manual. No idea how to instal it unfortunately, I'm sure someone will help out on this front. I need to get my tune edited to recalc shift points for the new ratio, these all come from the VSS rather than engine revs. AFAIK putting the final drive ratio into the PCM also corrects the speedo. I hope to be making some other mods requiring a retune soon, so I'll get it all done at once. Meantime I'll just do +5km/h in zones up to 50, +10 in zones up to 90 and +15 above that. These are close enough with my -15% change to keep me out of trouble.

I had to have 4 U-bolts replaced on top of the quoted work. They were rusted up and took a lot of getting out, too big a job for the rattle gun. My final bill was $2385.

sly · 12-02-2008, 08:44 AM

Quote:

Originally Posted by EvilChief

i ran NA, custom tailshaft with an open speed limiter, crossing the line at 94.33mph

Not much headroom there LOL. I doubt mine would be that quick NA, but will definitely need the mod with boost.

Eu-GenixX · 12-02-2008, 10:13 AM

$2385 just for the diff? jeebuz

GK · 12-02-2008, 12:24 PM

Quote:

Originally Posted by Eu-GenixX

$2385 just for the diff? jeebuz

My full rebuild and aftermarket gears, with new rear wheel bearings will set me back $1179.

Take into account though, that the borg warner gears would have been over $150 dearer and I'm not getting an LSD. I was quoted around $700 for that alone!

I'm leaving right now to take the car in. Can't wait for tomorrow night!

GK

sly · 12-02-2008, 02:42 PM

Quote:

Originally Posted by Eu-GenixX

$2385 just for the diff? jeebuz

Brand new LSD with 3.73 crown wheel & pinion $1201; New bearings $356; New diff U-bolts (4 off) $185; Diff Oil, assembly lube & enviro levy $54; Labour to remove, strip, rebuild & refit diff $589. Total $2385

The diff U-bolts were additional to the original quote of $2200 as they were U/S.

All brand new parts, I didn't want secondhand. And there isn't a lot of competition in Newcastle unfortunately. No doubt it would be cheaper in a capital city. Then again if you add $850 to GK's price of $1179 you're not too far off that $2200.

GK · 12-02-2008, 04:28 PM

Quote:

Originally Posted by sly

Brand new LSD with 3.73 crown wheel & pinion $1201; New bearings $356; New diff U-bolts (4 off) $185; Diff Oil, assembly lube & enviro levy $54; Labour to remove, strip, rebuild & refit diff $589. Total $2385

The diff U-bolts were additional to the original quote of $2200 as they were U/S.

All brand new parts, I didn't want secondhand. And there isn't a lot of competition in Newcastle unfortunately. No doubt it would be cheaper in a capital city. Then again if you add $850 to GK's price of $1179 you're not too far off that $2200.

Competition does bring the price down. We city folk just take this for granted I guess!

I get mine back tomorrow night. Can hardly wait!

GK

**Stav** · 12-02-2008, 05:03 PM

Sly.You done right mate.All new is the way to go.Ive had my diff done 3 times.2 at the same place and it didnt last(second hand bits) and lastly at Smithfield with the centre done up to new a few months ago..It still is an lsd and not single spinner.I am very happy with it as its done properly.

You won't regret spending the extra.If your car is auto get black speedo cog to bring speedo closer to true speed. Ive got the 4:11's and the gears dissappear faster..maybe this is not a good thing ?

sly · 12-02-2008, 06:41 PM

My gears will disappear faster too, once I can put a Raptor or Vortech under the bonnet LOL. I went the 3.73 to get a bit more down low while not being too short for boost bulking up the power curve over 3000rpm. Hopefully it'll all work as planned.

EvilChief · 12-02-2008, 06:54 PM

my 9" conversion cost me 2g 4 years ago

**Mechan1k** · 12-02-2008, 07:09 PM

Looking forward to the report GK ... If it is as good as you say guys ... I think I'll get more out of this mod than anything else.

Although GK has the manual in his ... it should really get up and go now.

ClassicAU · 12-02-2008, 09:23 PM

Oh it goes! For an auto, 3.7's in the diff are almost perfect! I don't know why they didn't come out of the factory that way!
Pretty exciting in the manual too. Can get a tad annoying in heavy traffic though, but I don't drive during the week so small price to pay. It seriously hauls in 2nd gear! As for the longevity, mine is starting to single spin. Though I have had it on the car for one and a half years. That and I am a lead foot that doesn't know how to drive a manual properly!

:

Evan

**Mechan1k** · 12-02-2008, 09:25 PM

I am tempted to just keep mine a Single Spinner ... I really have no need for an LSD in the work ute ... it never gets raced ... it's just used for pulling decent loads and towing.

ClassicAU · 12-02-2008, 09:31 PM

That's a fair point. The thing is though, I would think with that short a ratio, wouldn't an open diff just wheel spin all over the place? Especially in the wet, I can imagine it to be a bit annoying.

GK · 12-02-2008, 09:57 PM

I'm keeping mine as a single spinner on the advice of a diff place. He said they stuff up pretty easy and aren't built like they used to be. He also said that they're great for pulling boats out of the water and that unless you bag it up off the line, they're fine at the lights.

So I thought, "hey, a $750 saving is good!" LOL!

GK

GK · 12-02-2008, 09:58 PM

Quote:

Originally Posted by ClassicAU

That's a fair point. The thing is though, I would think with that short a ratio, wouldn't an open diff just wheel spin all over the place? Especially in the wet, I can imagine it to be a bit annoying.

It's all about throttle application EV, you lead foot! LOL!

GK

**Mechan1k** · 12-02-2008, 10:04 PM

Quote:

Originally Posted by GK

I'm keeping mine as a single spinner on the advice of a diff place. He said they stuff up pretty easy and aren't built like they used to be. He also said that they're great for pulling boats out of the water and that unless you bag it up off the line, they're fine at the lights.

So I thought, "hey, a $750 saving is good!" LOL!

GK

See ... this is what I like to hear ... as I am not one to bag it up off the line.
I do try to look after the ute as much as possible ... and a $750 saving is a decent amount as well. Seeing as I have had no need for LSD in the ute ... it's not really that much of an issue if i don't get it.

StealthAu · 12-02-2008, 10:10 PM

Thats rubbish, you don't get an LSD to bag it up off the line, you get one to get the power to the ground. Last year I was having troubles with wheel spin, even half throttle off the lights and I would loose traction, so I was planning on getting an LSD, but with the new wheels and tyres seems I don't have this issue. But anyway, this is what an LSD is for, to improve traction not break it.

**Mechan1k** · 12-02-2008, 10:13 PM

I haven't had a problem with getting traction ... I have more issues trying to lose traction ... it just doesn't happen really ... unless the road is wet.

I'd say if the ute was manual ... I'd probably go for an LSD ... as I'd have a heavier right foot for sure ... but being auto ... I really don't give it much anyway.

ClassicAU · 12-02-2008, 10:17 PM

But what about the sideways action.....the SIDEWAYS ACTION! :P

**Mechan1k** · 12-02-2008, 10:19 PM

That can still be achieved with a single spinner ... just takes a little more skill.

StealthAu · 12-02-2008, 10:20 PM

Single spinner or LSD, you can still get it sideways.

ClassicAU · 12-02-2008, 10:55 PM

I must be a worse driver than i thought then, even with an LSD I still rarely get it sideways! :togo: