Just need some thoughts on what you guys are running in ya rear rear diffs ratio wise.

My questioning comes from some experience as follows:

When I did my Cossie conversion (T5 standard box / internals) I put the engine & box into a car that was originally 2.8i and so had a 3.45:1 diff ratio. Now this was not a good combo - the engine was completely standard at this point and with that diff it was like pulling away in 2nd gear all the time and I felt the car could not pull top speed as it did not have the power to pull the gearing.

I swapped to a 3.64:1 ratio diff - from a 2.3 and this made the car completely drivable. This transformed it even with the stage 3 conversion. It behaved on the road and on track. So I am now running Cosworth Saph ratios and its a good combo.

My question is..... I know many people like the 3.9:1 diff ratio. I never tried this as I could not find a 2.0 donor car. The ratio of these was 3.89:1. I have since ripped appart my arse end and now I use Cosworth diffs and so can get what I like to fit.

My thoughts about fitting a 3.9:1 would be that you are always changing gear, 1st gear would literally just get you moving and top speed would be about 90mph. The car is predominantly for track use but thinking of putting it back on the road.

I want to get a Gripper build and would like to know your opinions and experiences with both 3.9:1 and standard 3.64:1 ratios. I don't want the expense of buying say a 3.9:1 CW&P, have it built for it to be crap.

Discuss......

 

You will probably find if for track, people will recommend the 3.9 ratio! IIRC top speed is limited to around 140mph

 

Tony@turbosystems said a 4.1 would transform my car with a T4 on it.

Steve

 

rolling circumference of your tyres is required before any one can really comment
and 140 sounds very low james for a 3.9 on the average wheel tyre combo and max yb engine rpm used

 

It just seems that my jump from 3.45:1 to 3.64:1 was fantastic. The jump from 3.64:1 to 3.9:1 is even greater tho but obviously the opposite way - can't help feel that it will run out of legs and on track I will be changing gear all the time. Getting to top speed will be rapid no doubt but I'm not interested in flat out top speed - corners stop that anyway lol.

 

Hi Tony,

using 210/640/18 slicks mate.

 

just stuff a 3.9 in it in then and give it large
you'll love it unless you want to beat Rods top speed of course lol

 

Not interested in top speed - I can get a brand new 3.9:1 CW&P. Might just do it tbh.

 

if you have turbo sytems yb power get yourself a few cwps as you'll need them roflol
we can always solve this for you with one of our supra diff conversions

 

Only 400bhp. I cant go Supra without mahoooosive work. It may be the way to go - have to see. This is all in a MK2 Granada remember and so nothing off the shelf - lots of home fabbing here.

Will have the cwp shot peened prior to fitting. Best bet for the money without going drastic sucha as Jag / Supra.

 

the supra diff conversion we do replaces the std 7.5 cosworth diff

and bolts straight in with the kit we supply
so if you have a 2wd diff in the arse you can simply un bolt it and bolt in the big supra diff we do

 

Lee Catermole aka TiB reached a peak of 172mph on a 3.9 rear diff so they aren't that short a ratio. He will have had an 8.2k rev limit though I think.

 

Cheers for that

 

I've got a 3.9 on my car on 18s it sits at 80ish at 3500rpm irrc. Certainly feels nicer to drive pulls away easier but I am on 18s and the final ratio (or whatever its called at the wheels) was quite high.

 

I would not expect the 3.9 cwp to last very long in a mk2 granny with that weight and turbo power lol

 

It weighs about 1100kg lol - about 400kg less than a saph

 

I lengthen my ratio by fitting 19" wheels with 225/40/19 tyres a 3.9 diff will pull 204mph @ 8.2k if you have the power to pull it.

 

youve done a fair bit of work then

 

Indeed I have. Its in a sad state at the moment due to not turning a wheel for 6 years and being stood outside.

Just did all the fuel system revamp with new lift pump, new bigger swirl pot with -10 feed for the 044 instead of the -6 etc and tightened every union.

Swapped the wheels over so have normal tyres as I'm gonna try and put it back on the road. Took all the hubs, brakes etc of and cleaned, fitted longer studs (can use open nuts) repacked front bearings.

It has a starting issue that I can't resolve though - I get a clicking starter - just once and that it. I have a brand new battery, brand new hi torque race starter, all earths are good but still getting the issue - will try all the switch side of the system as this may be a concern however it is firing the starter solenoid etc.

Just need to clean it out now, wash it and then take it for a pre MOT. Wanna do at least one track day this year.

I will take some pics when its a little more presentable.

 

We're do you get them from mate?