Would appreciate assistance with LSD DIFF MODS. Thanks.

[Ash71]

Hi All,

After a little advice. Currently have a stock LSD diff and wanting to change the gear ratios. Wanting to know if I have to change the whole diff, or just a part of it to get the ratios I want? Apologies, not overly experience in this line of work so looking for some support. Also any ideas on what kind of ratios? Few people suggested 3'5 or 3'4'5 but open to suggestions.

Here are my car specs which might help...

1999 Series 1 VT SS V8 5.0ltr
132,000kms
Stage 3 CAM
roller rockers
Extractors
2'5" exhaust straight through
5 speed manual

The car is basically running sluggish off take off but excellent on the top end. I want more power off take off, and happy to sacrifice a little off the top end. A mechanic was going to charge me $2500 for a brand new diff with 2'5 ratios. I don't see why I have to buy a new diff when it's already LSD.

Any assistance would be greatley appreciated. Thanks.

[VT-565]

A mechanic was going to charge me $2500 for a brand new diff with 2'5 ratios. I don't see why I have to buy a new diff when it's already LSD.

2.5 ratio? are you going to Bonneville? lol

Generally you change the crownwheel and pinion to change diff ratios.
Can't remember if there is a collapsible spacer for pinion bearing pre-load or not, but this will have to be changed too.
If it was me, I would overhaul it all, you should check the gear mesh after installation into the centre as well, ignoring this can lead to diff whining and premature failure.

[GMMAD]

diff gear change and shim the LSD should set you back $1200-1500

[Growler88]

im not too sure on what ratios are available to commodores (only just got one after tinkering with my old kinger) but with a 5speed u could probs aim for a ratio in the high 3's (3.7 -3.9) around that sort of area and still retain "good" cruising revs. especially considering the engine has been cammed it is probably going to need that shorter ratio to get it to where u need it making power. you may even consider going higher but that depends on how hard u want the motor revving while cruising at freeway speeds.

Not knowing on the actual ratio it has tho doesnt help... maybe one day ill learn more about these things. it also depends on what you want to use the car for. if u want it mean go for anything up to 4.11's but it depends on how you want to use your car, talk to a few reputable diff centres and they should be able to lead you somewhat in the right direction.

Never rely on what just one person has said. No matter how knowledgable they seem. i found its the best way to learn.