Escos diff ratio 3.92 0r 3.62

[MONTE 005]

hi Guys,

i'm thinking of lowwering the Diff gear ratio of my escos......
does anyone know what ratio is better....?
is it true that the sierra xr 4x4 is a lowwer ratio?

[Kelv]

Standard is 3.62.

If you step up to a 3.9 you will have slightly better acceleration but at the sacrifice of a few mph top speed.
If you change the rear diff to 3.9 then you will either have to change the front diff to match, or the preffered and stronger route is to use a step off kit in the transfer box which in turn makes the front diff rotate at the same speed as the rear.
This involves a shorter chain and smaller wheel which drives the front prop.

[MONTE 005]

thanks for the info Kelv....
is the xr 4x4 diff 3.9?

as i wouldn't like to open the gearbox for now.....

i intend getting a big tooth gearbox later on

[Kelv]

xr4x4 will still have the 3.6 ratio.

you need to find a 2.0 4x4 early sierra, these have the 3.9 diff, or failing that you could buy a 3.9 CWP to have fitted into your own diff when you go for the big tooth box.

[spiritof'76]

Maybe i should be thinking about this with a new gearbox on the horizon Don't know if i might regret missing the opportunity

[Kelv]

Julian, if your having a box made then its the ideal chance to have the 3.9 step off setup fitted into the transfer box while its apart.
all you will need to allow for as an extra budget will be the 3.9 CWP that you fit to your rear diff.

Mike R said it cost him around £500 to convert his ATB to 3.9, which included the brand new CWP, plus all new seals, bearings, collapsable spacers and a gerenal overhaul while it was apart which is pretty good imo

luckily for me i had 2 spare 3.9 rear diffs sat at home, so i sacrificed one of them to use with my new ATB.

[spiritof'76]

Hmmm.. cheers Something to think about then ! Presumably i'd need to budget a little extra for a new shorter chain etc then ? Or do they just shorten your existing chain ?

I wouldn't say the car was lacking in acceleration but would i be right in thinking the car will pass through the Lag zone quicker with shorter final gearing ? Any downsides to all this other than the obvious knocking a little off the top end speed.........

[Loader]

long motorway journeys are a pain with 3.9 so paul R has said.

Im still stuck on this choice one as i have an allready shorter 5th atm

[Richie]

long motorway journeys are a pain with 3.9 so paul R has said.

Im still stuck on this choice one as i have an allready shorter 5th atm

Yeah they are

Hence why i'm going back to 3.6s

[Kelv]

i had no issue with mine being on 3.9 ratio, motorways were still fine but obviously it still raised the revs over where they would be on 3.6 at any determined speed, but nothing to worry about.

and iirc, the road angel topped out at 146mph when it clipped the rev limiter in 5th, and it still didnt hang about in getting there.

[Richie]

i had no issue with mine being on 3.9 ratio, motorways were still fine but obviously it still raised the revs over where they would be on 3.6 at any determined speed, but nothing to worry about.

and iirc, the road angel topped out at 146mph when it clipped the rev limiter in 5th, and it still didnt hang about in getting there.

Just feels like you need a 6th gear

[dom123]

ive been thinking about doing this to my diff even tho i'm rwd as i find 1st gear is too long i think ive seen 50mph in 1st before.

i do quite alot of drifting in my escos as most my friends have jap cars and are really into it.. so i go out with them and have a crack at some of there dirty rat runs they set there up to do..usally they find roads with lots other roads coming off so there constanly having to flick the rear end over either way while keeping it spining..etc

when i have ago 2nd gear is often dead the engine cant pull it at 30mph while keeping the wheels spinning, so if i use 1st gear its a bit of a handfulll way to much power!!!

if i skid a complete roundabout depending on it size i can do those in second gear but if i get to much angle and back off i usally cant get the wheels spinning again with out another clutch kick which is annoying..

so these 3.9 diff come off which sierra? which year?

also am i right in think buy down gearing the diff will be stronger as theres less load making the wheels spin.

[Kelv]

Dom, the diffs from the sierra's in question run a 7" diff, if your running a 2wd setup and beam then your diff will be a 7.5".

and yes your are correct that there is less load.

[dom123]

oh thats a shame.. mine is a 7.5 setup.. what kind of top speed would i see with a 3.9 diff and a t5? with 450bhp?

[Kelv]

you can still buy a brand new CWP in 3.9 to suit your diff tho mate.

providing your 5th gear ratio is vaguely around the same as the 5th gear in the 4x4 box, id suspect you to be getting towards 150mph still, dependant on where your rev limit is set.