Diff gear brands

[CV8revver]

So following on from my previous post about mod advice, I've started acquiring my first mods! I've got a cube short shifter from a member of one of the facebook pages and to add to this I was thinking of upgrading the diff gears.

I've searched through the forums and found what gears people are running (3.7, 3.9 etc). But not a lot on what brand people get. (might be because there's no real difference?)

The 3 I've found on ebay are MACE, Motive Gear and Spicer. What brand gears are people running/recommend?

Trev

[mfp4073]

Trev,
I had a 390 diff fitted to my 05 CV8 a few years ago and it was the best performance mod I've made. The car has really woken up, 1st gear is a bit low, but all the others are great, you can actually accelerate in 6th.
I'm not sure what make the gears are as they were fitted by Monkfish. Give Roger or Andy a call or e-mail them at Pedders Uk to find out.
Whatever you do don't buy a cheapo set as it will more than likely whine like an old bus. If I rember rightly Roger said I should only hear a low whine at around 45-50 mph, then it will fade away. He was right, I've had no problems with this mod and I recommend it.
You should budget for a full rebuild, all new bearings and seals, also you might want to consider a new LSD as well depending on your budget.
Sadly none of this is cheap, but it's bloody well worth it, especially with supporting mods, exhaust, intake, and remap.

John

Edited by mfp4073 on Thursday 7th February 22:24

[mfp4073]

Trev,

I forgot to mention I use Castrol synthetic gear oil 75w 140, in the diff, I've found this one suits me best, and not Royal Purple diff oil,( I do use Royal Purple in the engine and gearbox)

John

[CV8revver]

mfp4073 said:

Trev,
I had a 390 diff fitted to my 05 CV8 a few years ago and it was the best performance mod I've made. The car has really woken up, 1st gear is a bit low, but all the others are great, you can actually accelerate in 6th.
I'm not sure what make of the gears are as they were fitted by Monkfish. Give Roger or Andy a call or e-mail them at Pedders Uk to find out.
Whatever you do don't buy a cheapo set as it will more than likely whine like an old bus. If I rember rightly Roger said I should only hear a low whine at around 45-50 mph, then it will fade away. He was right, I've had no problems with this mod and I recommend it.
You should budget for a full rebuild, all new bearings and seals, also you might want to consider a new LSD as well depending on your budget.
Sadly none of this is cheap, but it's bloody well worth it, especially with supporting mods, exhaust, intake, and remap.

John

Hi John.

I'll give them a email and see how I get on. Thanks for the tips and heads up!

Trev

[Lincsls1]

mfp4073 said:

Trev,

I forgot to mention I use Castrol synthetic gear oil 75w 140, in the diff, I've found this one suits me best, and not Royal Purple diff oil,( I do use Royal Purple in the engine and gearbox)

John

I am quite interested in this mod too. Although I'd like to consider an even lower ratio - 4.10 gear set?
My question is, does the speedo/ecu/whatever!? need calibrating or is the speed signal taken direct from the wheels?

[speed4u]

Spicer as fitted as std.

[mfp4073]

Lincsls1 said:

I am quite interested in this mod too. Although I'd like to consider an even lower ratio - 4.10 gear set?
My question is, does the speedo/ecu/whatever!? need calibrating or is the speed signal taken direct from the wheels?

Yes the speedo needs to be adjusted with a diff ratio change. You need to do this electronically I'm afraid.
As for a 4.10 ratio, that's great for a drag strip, but I'm really not too sure about driving with that gear set on a road, I think you will notice an increase in fuel consumption and 1st will be very low. I guess it depends on what you want from the car.

John

[Lincsls1]

Hmmm. Yeah I get what you mean about the 4:10 set, but these cars are very tall geared I think.
I reckon 6th gear would be good for over 240mph with the necessary power with the stock diff.
A much lower diff might make the car feel like much more of a torque monster.

[mfp4073]

Lincsls1 said:

Hmmm. Yeah I get what you mean about the 4:10 set, but these cars are very tall geared I think.
I reckon 6th gear would be good for over 240mph with the necessary power with the stock diff.
A much lower diff might make the car feel like much more of a torque monster.

A torque monster indeed!!!!! and an ambitious top speed to say the least.
A few years ago there were a couple of owners on here that were in the 200 mph club or there abouts.
You should look through some really old threads on this forum and see if there's any useful information you could use. I think one of the user names was Jez?
Try looking on face book, quite a few knowledgeable owners left this forum and can be found on there.
Best of luck.

John

[Janosh]

Do not buy Motive gears, they will whine and you’ll have to rebuild the diff again.

For experience, only use GM gears.

I liked my 3.7 gear as a happy medium, but 3.9 is good too, either way the diff will be a great upgrade.

4.1 would start to compromise the cars GT abilities IMO but good if your chasing times on the strip or only using the car at the weekends.

[Lincsls1]

I've been reading some info on the US forums and they generally recommend the 4:10 ratio.
I'm sure there's a calculator online which can be used to figure out the effect they would have.
For me, top speed is rather irrelevant. I know mine gets nowhere near the rev limiter in 6th, it just doesn't have the power.
I'd rather pull it all back so maybe my car could just about rev out in 6th, guessing would still be around 170mph, but feeling much more lively in every lower gear, especially under 100mph.

[Janosh]

As a reference point, 70mph with the 3.9 is about 2k revs.

This should give you an idea of how the diff affects cruising comfort, the 4.1 might start to feel a bit ‘busy’?

[vxr2010]

I did a 3.9 on my cv8 , it was more noticeable than a remap , car is a lot more user friendly and sportier , and i still got 35mpg on a long run , it’s a good mod to get done

[leigh1050]

mfp4073 said:

A torque monster indeed!!!!! and an ambitious top speed to say the least.
A few years ago there were a couple of owners on here that were in the 200 mph club or there abouts.
You should look through some really old threads on this forum and see if there's any useful information you could use. I think one of the user names was Jez?
Try looking on face book, quite a few knowledgeable owners left this forum and can be found on there.
Best of luck.

John

Jez's car was /is a twin turbo'd beast of a car that managed 208 m p h I think. There was a couple of other twin turbo'd cars about that made a heap of h.p.

Edited by leigh1050 on Friday 8th February 18:41

[fred bloggs]

The hsv gts has 3.7;1 and I find this good .I was gonna put a 4.1:1 in the car ,but instead put a kaaz 2way diff and a cam.

[Lincsls1]

fred bloggs said:

The hsv gts has 3.7;1 and I find this good .I was gonna put a 4.1:1 in the car ,but instead put a kaaz 2way diff and a cam.

Yeah, I think the 5.7 VXR also has this diff, but I still find it all a bit tall.

[mfp4073]

leigh1050 said:

Jez's car was /is a twin turbo'd beast of a car that managed 208 m p h I think. There was a couple of other twin turbo'd cars about that made a heap of h.p.

Edited by leigh1050 on Friday 8th February 18:41

Thanks leigh1050.
Ah, so my memory isn't too bad after all, well apart from losing my car keys every two minutes. There have been some great cars on this forum over the years that's for sure.

[robbyd]

CV8revver said:

Hi John.

I'll give them a email and see how I get on. Thanks for the tips and heads up!

Trev

You realise Monkfishperformance don’t exist anymore?

[Janosh]

mfp4073 said:

leigh1050 said:

Jez's car was /is a twin turbo'd beast of a car that managed 208 m p h I think. There was a couple of other twin turbo'd cars about that made a heap of h.p.

Edited by leigh1050 on Friday 8th February 18:41

Thanks leigh1050.
Ah, so my memory isn't too bad after all, well apart from losing my car keys every two minutes. There have been some great cars on this forum over the years that's for sure.

As a little update, Jez is now building the Monaro to run for a class record at Bonneville... a whole new ball game and aiming for over 250mph.

It’s a shame that this forum went quiet... there are some epic builds that would make for amazing build threads

[mfp4073]

robbyd said:

You realise Monkfishperformance don’t exist anymore?

As I said in my earlier post,Roger and Andy now run Pedders UK. I have spoken to both for advice since the clousure of Monkfish and they helped me out with their invaluable advice. Both are great guys.

John