cossie51

Dropping my 2WD diff off in the morning to have a Quaife ATB installed as the standard one broke the planet gears.

Do you notice much difference in acceleration if you change to 3.9 CWP ? As this would be the ideal time to have it changed.

Mark Shead

A very good mod as the stock car is overgeard

Mark

smiley

Mark what are the options for front diff on a 4x4 running 3.9 in the rear i remember you said quaffe what power are these rated to? and if under 700 is thier an option beyond that?

markk

iTrader: (2)

Fit a std front, thick wall case, strengthened steel plate, super finish the CWP. Will be fine, you must fit a set of drop gears in the transfer.

Or the RnD 7" sized diff from Barra, again, needs to have the drop gears.

Caddyshack

Bara built me a 3.9 thick wall quaife so I didn't use drop gears. I use 16 inch wheels and a close ratio long box by Oppliger (built by Bara) I love the car on this set up and feels very keen the whole time.

smiley

So they do a 7" in 3.9 mark? Thanks for the info mate

markk

iTrader: (2)

Nope, thats why you use the drop gears, i wouldn't use the 3.9 cwp, too small a tooth profile

Turbo Zetec

iTrader: (1)

i believe the 2.0 dohc 4x4 sierras came with 3.9 front and rear diffs as std.

smiley

Thanks mark, yes zetec turbo thats right but im looking to bullet proof as will be over 700 bhp

cossie51

Dropped mine off at CTS this morning and decided to bite the bullet and go 3.9 CWP. Having new bearings and seals and a Quaife ATB fitted so hopefully I shouldn't suffer to much wheelspin at 400 bhp as it's 2WD

ajamesc

Fit r888's and your have almost no wheel spin the the dry with warm tyres

richard youll

I ran a 3.9 2wd for a short time and reverted back to 3.6 after chewing up several cwp, they go very noisy very quicky , 3.6 lasts a lot longer

cossie51

At what power were you having the issue with the cwp chewing up and becoming noisey ?

dan le moignan

Guys how bad is the 3.9 at motorway speeds?
most of my driving is in the forest and single carriage ways with 50/60mph limits.
Only go on motorways to get to shows etc then it's a fair drive etc, say 2 hrs each way.
Heard the fuel bill goes out the window on motorway as guess you are not on closed loop at the rpm the 3.9 sits at?.
what sort of cost is it to convert a 4x4?
Parts wise the drop gears and chain seem to be approx £250, and a non lsd 3.9 cwp diff about £100 them swap the cwp into your own lsd 7" diff?.

turbotrev

You won't notice a huge difference in topspeed mate, going higher than 4 then yes you'd significantly notice it

Cheers Paul