Vz Diff Ratio 3.9 ****** Help ******

[2QIC4U]

hey guys,

Just got my diff done not too long ago.
something deosnt seam right? i got 3.9 but at 100 Km/h it revs at 1500 SPOT ON.?

deos this seam right?

it's a L98 6.0 V8 went from standed 3.46 to 3.91
any1 who's changed there ratio let me no what it sits on? doing a 100?


Cheer's

[V28VX37]

Manual or auto?

[Delft Maloo]

they are either the same gears as std or they are 3.27's.
have you had the speedo recalibrated? it might show your doing 100 but you may be only doing 80-90kph?
either way it doesnt sound like you have 3.9's.

[bush_basha]

as delft said did you get it recalibrated, what did it sit on before to had the diff? im guessing yours is a manual, my clubbie with stock 3.7's sits higher than that, so something doesnt seem right there mate

[snapper5.7L]

Should be around 1800rpm for the manual - dunno for the auto

[2QIC4U]

yeah it's a manual. am not sure what it sat on before i got the diff.
no way deos it sit on 1800 it sits on 1500..?

fuking dum, just wasted my money

[Ahyeah]

You need to calibrate the speedo, your probably only doing 80kmh as delft calais said, 1500rpm sounds like stock gearing ;)

Put it this way, if it goes harder, its money well spend :goodjob:

[2QIC4U]

You need to calibrate the speedo, your probably only doing 80kmh as delft calais said, 1500rpm sounds like stock gearing ;)

Put it this way, if it goes harder, its money well spend :goodjob:


nah the speedo is correct. i got my missis to do a 100KM/h and i matched her car. only way i could think of doing it. speedo is correct. my mate has the same engine as mine L98.. wit the 3.9 gears. his sits on 1750RPM on a hundred? whats the go there?

[Ahyeah]

nah the speedo is correct. i got my missis to do a 100KM/h and i matched her car. only way i could think of doing it. speedo is correct. my mate has the same engine as mine L98.. wit the 3.9 gears. his sits on 1750RPM on a hundred? whats the go there?

Does yours go better than before?

[2QIC4U]

well.. to be honest i cant really notice any diffrence. ?
maybe 10% better? i dono, they sed before i got it done. mate u will feel heaps of torque and all this shit but. i dont feel much at all ?

do you recon the wheel size makes a diffrence?

[Ahyeah]

Mate, take it back, a diff change should give you heaps more off the line, transform the car some say.

Yep, the apprentices must have put your diff in someone elses car :P

Hope you get it sorted soon mate, best of luck :)

btw, wheel size would make a difference, but not a huge difference if we are talking a reasonable size change ;)

[2QIC4U]

Mate, take it back, a diff change should give you heaps more off the line, transform the car some say.

Yep, the apprentices must have put your diff in someone elses car :P

Hope you get it sorted soon mate, best of luck :)

btw, wheel size would make a difference, but not a huge difference if we are talking a reasonable size change ;)


yeah sounds like it ay. just my luck man. F****
lol. thanks anyways

what about the tunning?
or can the taco be out?
i took it back and they checked it with markings and he turned the wheel and shit. he sed. yep it's 3.9 in it. ?

I got no idea what to do ay? i was told from another place only other way is to take the back cover out and have alook

[bush_basha]

if you take it back to who ever to see about it, keep us informed of what happens, if they say its right, take you mates with the 3.9's if roughly the same kw's and see if different or take to a sponsor apparently you can measure the rotation of the wheels, etc etc to see what kind of gears are in it.

[2QIC4U]

if you take it back to who ever to see about it, keep us informed of what happens, if they say its right, take you mates with the 3.9's if roughly the same kw's and see if different or take to a sponsor apparently you can measure the rotation of the wheels, etc etc to see what kind of gears are in it.

yeah.. well my mates one is single turbo puts out 420 kw at wheels?
but he recons that wouldnt make a diffrence to the revs? dont no how true that is. i got a cam, that wouldnt make much diffrence would it?

[Wonky]

I'm guessing these are utes we're talking about if VZ with L98? I'm sure the stock M6 VZ V8s did around 1500rpm at 100kmh, so sounds like you've been dudded. :(


yeah.. well my mates one is single turbo puts out 420 kw at wheels?
but he recons that wouldnt make a diffrence to the revs? dont no how true that is. i got a cam, that wouldnt make much diffrence would it?

Power makes no difference to rpm (assuming you're not spinning the wheels).

[2QIC4U]

sure sounds like it?, wouldnt expect it from sams performance though. well looks like am gona have to hit em up agian


I'm guessing these are utes we're talking about if VZ with L98? I'm sure the stock M6 VZ V8s did around 1500rpm at 100kmh, so sounds like you've been dudded. :(



Power makes no difference to rpm (assuming you're not spinning the wheels).

yeah thats what i thought too..

[Wonky]

Something doesn't sound right and no, certainly wouldn't expect it of Sams from all I've heard. Someone sounds to have messed up somewhere........ It's what happens next that really counts now.

[2QIC4U]

Something doesn't sound right and no, certainly wouldn't expect it of Sams from all I've heard. Someone sounds to have messed up somewhere........

yeah i no. the reson i took my car there is because of there reputation,
well i just wana make sure, dont wana sound like a D*** when they find out it's 3.9 gears in it..

[Wonky]

yeah i no. the reson i took my car there is because of there reputation,
well i just wana make sure, dont wana sound like a D*** when they find out it's 3.9 gears in it..

Yeah, know where you're coming from but from all you've said it doesn't sound right. Don't go in in an accusatory manner (doesn't sound like you would), just ask them what revs they'd expect it to do with 3.9s. Mathematically, if 3.46s do 1500rpm at 100kmh then 3.9s should do 1690.

[2QIC4U]

Yeah, know where you're coming from but from all you've said it doesn't sound right. Don't go in in an accusatory manner (doesn't sound like you would), just ask them what revs they'd expect it to do with 3.9s. Mathematically, if 3.46s do 1500rpm at 100kmh then 3.9s should do 1690.

yeah i will, s** happen i guess.

anyways thanks for ur advice. am gona take it back.


have a good one

[Blown 540]

3.4 to 3.9 is a fair drop ,you should be able to feel the difference aside from the revs. But be cautious as Wonky said , i would be surprised if Sams had made a mistake like this.:)

[2QIC4U]

3.4 to 3.9 is a fair drop ,you should be able to feel the difference aside from the revs. But be cautious as Wonky said , i would be surprised if Sams had made a mistake like this.:)

i no i dont want to beleave that they have, but everything points in that way. i cant really feel a diffrence to make me go man thats torque.. just seams normal. maybe am expecting too much? lol

[Evman]

I can assure you, 3.46 gears sit at pretty much exactly 1500rpm at 100km/h. They probably got it all apart then accidentally put the same centre back in. Damn shame if they threw the 3.9's out!

[Wonky]

I can assure you, 3.46 gears sit at pretty much exactly 1500rpm at 100km/h.
That's what I thought.

I'd go and see Matt Jackson who is now at Sams. I know him from his days at G&D down here and he's a decent guy. He should help you get to the bottom of it.

[2QIC4U]

That's what I thought.

I'd go and see Matt Jackson who is now at Sams. I know him from his days at G&D down here and he's a decent guy. He should help you get to the bottom of it.

yeah. i will do you have a mob number for mat at sams.. i wana tell him al bring the car on monday. rather than just rok up.

CHEER'S

[Rad Kane]

Just to convince youself that you have the 3.91:1 gears, you can do a simple check:

1) Jack-up the back end (so as the wheels are of the ground)
2) Put the gearbox in neutral
3) Strike a short straight chalk line on the tailshaft and partially over the diff housing
4) Rotate the wheel one full revolution and as you are doing this count the number of revolutions the tailshaft makes.

If it turns 3.9 (nearly 4) revolutions than its a 3.91 ratio and obviously if it turns only 3.46 (nearly 3-1/2) revolutions than it is a 3.46:1 ratio.

Hope that this will assist you and put your mind a rest. :)

[VTR8Clubby]

Just to convince youself that you have the 3.91:1 gears, you can do a simple check:

1) Jack-up the back end (so as the wheels are of the ground)
2) Put the gearbox in neutral
3) Strike a short straight chalk line on the tailshaft and partially over the diff housing
4) Rotate the wheel one full revolution and as you are doing this count the number of revolutions the tailshaft makes.

If it turns 3.9 (nearly 4) revolutions than its a 3.91 ratio and obviously if it turns only 3.46 (nearly 3-1/2) revolutions than it is a 3.46:1 ratio.

Hope that this will assist you and put your mind a rest. :)

What he said.. Simple way to check.

[gismo4655]

Hi the best and ezy way to get a true speedo reading which is about 99% spot on is with a nav man sattlelight navagation and put it to the km/h setting. this devices are spot on.

[SS Enforcer]

What tyre size and profile are you running on your car there mate.

cheers

[2QIC4U]

What tyre size and profile are you running on your car there mate.

cheers

it's 245/35 19". when i took it back to sams performance, they did jack the car up and do all that. they recon it's 3.91 but the revs dont seam right. i took it to another place. they recon it's not 3.9 it's more standed when he counted it


Hi the best and ezy way to get a true speedo reading which is about 99% spot on is with a nav man sattlelight navagation and put it to the km/h setting. this devices are spot on.

yeah i already checked my speedo, with another car, it's fine. 100%
but am down 300revs sitting on 100 km/h compared to a 3.9 diff should be?

[Delft Maloo]

100kph with 3.4's is approx 1500-1600rpm
100kph with 3.7's is approx 1650-1750rpm
100kph with 3.9's is approx 1800-1900rpm
all this depends on tyre size ans wear but they should fall between those margins.
there is know way 3.9's will travel at 100kph at 1500rpm if the speedo is correct with any of the std holden gearboxes auto or manual vt-ve.

[SV346]

Maybe you have the opposite of clutch slip... just kidding :p, but this is sounding quite odd... With the 3.9's the engine should be feeling pretty toey and yeah obvously be revving a bit higher about 1700-1800. Your tach couldnt be out by any chance?

[El Narros]

I got 3.9s a few months ago, didn't notice much in the way of performance gain, well none actually. My tacho in 5th definately is a higher rpm but 6th gear sits about 1650rpm. No higher. Would mods/tune make any difference to that?

[Evman]

I got 3.9s a few months ago, didn't notice much in the way of performance gain, well none actually. My tacho in 5th definately is a higher rpm but 6th gear sits about 1650rpm. No higher. Would mods/tune make any difference to that?

If you have a GPS make sure that your speedo is accurate. Other than that, a fixed diff ratio (ie 3.9's) in a fixed gear (ie 6th) will have a fixed RPM for a given speed (with same sized wheels being the only other variable). Sounds like your RPM is way too low for 3.9's...

[bad88u]

hey guys,

Just got my diff done not too long ago.
something deosnt seam right? i got 3.9 but at 100 Km/h it revs at 1500 SPOT ON.?

deos this seam right?

it's a L98 6.0 V8 went from standed 3.46 to 3.91
any1 who's changed there ratio let me no what it sits on? doing a 100?


Cheer's

mine sits on about 2300 in fifth and 1900 in sixth

[ziggycv8z]

This thread in the sticky should help you out.
There is a bit of a differance from M6 to M12.

Australian LS1 and Holden Forums (http://www.ls1.com.au/forum/showthread.php?t=49562)

[Evman]

This thread in the sticky should help you out.
There is a bit of a differance from M6 to M12.

http://www.ls1.com.au/forum/showthread.php?t=49562

Hey good post. I didn't realise there were different gearbox ratios in the VZ manuals :)

[2QIC4U]

100kph with 3.4's is approx 1500-1600rpm
100kph with 3.7's is approx 1650-1750rpm
100kph with 3.9's is approx 1800-1900rpm
all this depends on tyre size ans wear but they should fall between those margins.
there is know way 3.9's will travel at 100kph at 1500rpm if the speedo is correct with any of the std holden gearboxes auto or manual vt-ve.

well. here's a 1 for you boys.. took it to sams perfm. this morn,. they took the diff cover out and guess what. to no suprise it was the 3.9 diff gears.
so all it boils down to is that my gear box is diffrent? checked the speedo all that it's all 100 %

yeah that was a good post with the diffrent gear boxes. anyways. it's 3.9 diff gears in it.. i saw dem for my self. well guess am gona have to live with it reving at 1500/ 100km/h guess ant that bad. but yeah it's not a big performance gain. deosnt make me go wow..

slow thing. need some twin turbo's in there for sure... !!!!!!!!



*************** Thanks boys 4 the infor, *********************


This thread in the sticky should help you out.
There is a bit of a differance from M6 to M12.

http://www.ls1.com.au/forum/showthread.php?t=49562

cheer's bro

[Evman]

:confused:

WTF? So before the diff gears your car would have been doing what, 1200RPM at the most at 100? Wonder what the go is there!?!?

[2QIC4U]

:confused:

WTF? So before the diff gears your car would have been doing what, 1200RPM at the most at 100? Wonder what the go is there!?!?

well yep doing a 100 km/h it would have been idling. lol

[Delft Maloo]

well guess you have to live with it then

[ls1vt209]

Looks like 4.1's for you my friend

[vz300]

There is no physical way your revs will be the same when changing diff gears especially going from 3.46 to 3.89 like you have. Weather you think your speedo is right or not you need the tech 2 from your holden dealer to change the calibrations in the dash and if you have changed your wheel size they will have the code for that as well....... All these little things change alot.........


ps. You werent going down a hill after you got your new gears were you maybe thats why the revs were the same lol........

[toey]

[QUOTE=vz300;1336815]There is no physical way your revs will be the same when changing diff gears especially going from 3.46 to 3.89 like you have. Weather you think your speedo is right or not you need the tech 2 from your holden dealer to change the calibrations in the dash and if you have changed your wheel size they will have the code for that as well....... All these little things change alot.........QUOTE]

while this would be the perfect option it wont happen cause i took my car to holden for service after i got new wheels with same size tyres 245/35/19 and the technition told me they couldnt re calabrate the speedo cause they have no specs on tech2 for this size tyre.
maybe the technition was wrong, i dont no but this was my experiance so i got it fixed up with a custom tune and its now spot on. i would personally get hold of a gps and check speedo for accuracey and not rely on another cars speedo