james kiely

iTrader: (5)

can anyone advise me on the merits of using a 3.9 quaiffe atb[locked at 90% which i dont understand to be honest ]over a standard ratio of 3.6 quaiffe atb on a road going saff.how would it drive on a 3.9 for fastroad use .or would it be purely a rally diff .

any help appreciated guys

JonnyBravo

Quaife ATB is not a plate type lsd so from what I'm aware could not be set to 90% locked for example, its also not a rally diff at all as with one wheel off the ground it will lose drive where as a plate type wont.

Great road diffs though but make sure you know what it is your buying as it doesn't sound like one but if its a road setup you want then a Quaife is ideal as it doesn't need regular servicing.

As for ratios first thing I would do if I ever owned a Cosworth is ditch the 3.6 and go for a 3.9, totally transforms the car.

james kiely

iTrader: (5)

cheers johnny,great info mate

i have a 3.6 got but ive been offered this ,

would it give better acceleration johnny and what top speed would it limit the car to?

JonnyBravo

It will effect top speed a little yes but people forget how long geared Cosworths are.

My mates one came out of TiB's 3 door which did nigh on 180mph at Brunters, he only changed as he wanted a bit more top end iirc.

We found on my mates that when on track where you would usually have to use 2nd and not have great traction you could now use 3rd and have a more controllable car, that and the fact the drop off in revs keeps the engine in the power more.

Here is 2 videos to compare the 2, the only mod being the 3.9 fitted in the Bedford clip, car is a 3 door running a little under 400hp.

3.6 Ratio

http://www.youtube.com/user/dyAlpina#p/u/16/3E3QF1QcuuM

3.9 ratio

http://www.youtube.com/user/dyAlpina#p/u/10/P6OzD2qTuPQ

Mike Rainbird

iTrader: (3)

On a road car, I personally wouldn't bother - I'd prefer the relaxed cruising that the 3.64 gives. A car used regularly on track is a different kettle of tuna .

james kiely

iTrader: (5)

thanks johnny and mike ,where would it leave the revs at motorway cruising?


i just watched the video johnny,fookin hell looks like another 100bhp,reminded me of the 500 touring cars

thats it i have to tell the wife more lies

thanks mate

JonnyBravo

It certainly is relaxed.

I wouldn't say its that bad with the 3.9 fitted, Dave quite happily cruised to Germany without being deafened or sitting at too higher rpm.

I'd still have one on a road car, at the end of the day you don't buy a Cosworth to drive to the shop and back, you buy it to use it and it does really does help make the most of the power you have without spending thousands.

ALL IMO ofcourse.

Just for the record Mike sells Quaife ATB's although I am suprised he didn't mention that. Prices are on his website

james kiely

iTrader: (5)

cheers johnny ,and tuv approved aswell i hear

JonnyBravo

I'd say its definitely like you have gained another 50hp, totally blew us away how much faster the car was round a circuit and as it is used on the road it helps when you want to have a bit of fun.

As for what rpm I'd need to ask him for you, it is noticeably higher but not 5k @ 70mph for example.

Oh and at the Touring Car comment, Dave will be very happy to hear his car and driving ( and gloves ) were compared to that

JonnyBravo

"were" TUV approved

Craig J

iTrader: (1)

3.9 is good when using std gear ratios, but if you have intentions to use a close ratio box then all becomes a little too short IMO.

james kiely

iTrader: (5)

it would be used with astandard ratioo quaiffe big tooth box aswell craig

Mike Rainbird

iTrader: (3)

Speeds in gears assuming 215/40 x 17 and 7000rpm gear change points:
3.64 gearing:
1st Gear Ratio 2.95 46.10mph
2nd Gear Ratio 1.94 70.10mph
3rd Gear Ratio 1.34 101.49mph
4th Gear Ratio 1.00 136.00mph
5th Gear Ratio 0.80 170.00mph
85mph cruising rpm = 3500rpm

3.9 gearing:
1st Gear Ratio 2.95 43.03mph
2nd Gear Ratio 1.94 65.43mph
3rd Gear Ratio 1.34 94.73mph
4th Gear Ratio 1.00 126.93mph
5th Gear Ratio 0.80 158.67mph
85mph cruising rpm = 3750rpm

james kiely

iTrader: (5)

cheers mike,an extra 250 rpm isnt to bad at cruising speeds really,and i dont think i will be going for 170mph .its just the acceleration i would like

Mike Rainbird

iTrader: (3)

My close ratio dog 'box has a shorter fifth gear and with the 3.9 gearing, 85mph is just under 3900rpm, which I personally find a PITA for distance work (I like driving my car LOL).

james kiely

iTrader: (5)

would it be important to have the car mapped with the diff you were more likely to use?

james kiely

iTrader: (5)

anyone else running a 3.9 ?or their views please

Gary F

iTrader: (1)

I'm considering it myself.

james kiely

iTrader: (5)

did you look at johnnys videos gary

silky16v

iTrader: (1)

James i take it this is for the 2wd cossie as your (my old car) 4x4 saph already has 3.92 diff's in it already

james kiely

iTrader: (5)

hi matt ,yes mate its for g88,i have a 3.64 quaiffe atb off mark already and will be picking it up in a couple of weeks ,i just got offered another one with 3.9 and was wondering how it would drive matt

what are you driving at the minute matt?

mark r

which diff uses the 3.9 ratio the one from the 2.9 24v bob granny?

JonnyBravo

No, its was a granada 2l iirc

I believe I know someone who has a few cwp's if you are after one.

philram

iTrader: (3)

if i wanted to fit a 3.9 cwp to my 7.5 cossie diff, would it have to be a specific one or would one out of any 7.5 diff fit.?

JonnyBravo

Its a direct swap iirc

philram

iTrader: (3)

cheers..