Final Drive Ratio

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Makaveli_se7en

Member
In the not so distant future I will be buying a new final drive to replace the stock one in my cog box. This throws up the question of what ratio to get? I've spent a long time playing around in excel working out speeds in gears at certain rpm's and its not really getting me anywhere (beginning to feel like I'm racing 2-stroke motorbikes :doh:) so could do with some practical advice.

Basically I will be running a Quaife gear set (assuming standard ratios) that’s 1st 2.615, 2nd 1.765, 3rd 1.238, 4th 0.917 and 5th 0.741. I’m intending to rev to 8500-9000rpm approx. with boost from around 3800rpm (hopefully). And more than likely will be running a 17” rim to fit the brakes under. I will be using the car for mainly fast road and some minor track use.

I was thinking of going slightly longer than stock, say 4.05 as currently I tend to find myself a bit stuck in no-man’s land between 3rd and 4th on some of my favourite roads, but that’s with 16’s and a stock rev limit. Any advice and thoughts would be much appreciated.
 
Trip

Trip

New Member
Are you sure you can do this ?

if so, you will need two. one for the front and one for the rear.
 
Trip

Trip

New Member
as it says on the tin

"The PPG final drive assembly is a 4.066 ratio final drive, designed for use with either the stock gearset or the PPG set."

That is a standard ratio. If you can alter the ratio, you need to alter for both front wheels and rear wheels. How/If it can be done is beyond my knowledge in gearboxes.
 
S

skiddusmarkus

Active Member
I thought thats what the centre diff was for Trip.

As good as planning ahead is Maka, I think you'd be better off driving it 1st with the new setup and see how it feels then.
 
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johnsy

johnsy

Active Member
i was gonna ask danny 'redreading' if it was possible to make the final drive on an rb box longer, or what ever it would take to give it a higher top speed
 
red reading

red reading

Active Member
1st Gear :49.25MPH 2nd Gear :72.97MPH 3rd Gear :104.03MPH 4th Gear :140.45MPH 5th Gear :173.81MPH 4.066 final drive

This is for a 7500rpm rev limit and a 205/45/16 tyre





1st Gear :59.33MPH 2nd Gear :87.91MPH 3rd Gear :125.33MPH 4th Gear :169.2MPH 5th Gear :209.39MPH 4.05 Final Drive

This is for 9000rpm and a 205/40/17
 
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M

Makaveli_se7en

Member
Hi Danny, I've done the same calcs but doesn't really tell me what it will be like to drive. Just to check stock final drive is 4.125? or is that the RB box?

I'm leaning towards 4.066 as its off the shelf so hopefully cut lead times and should give a motorway cruise around 80mph without being on boost.

skiddusmarkus said:
As good as planning ahead is Maka, I think you'd be better off driving it 1st with the new setup and see how it feels then.
Click to expand...
That would be ideal but I only have a finite amount of time/money/patience for removing and rebuilding gearboxes.
 
M

Makaveli_se7en

Member
As a side I reckon to pull 209mph in a Pulsar (with stock body work i.e. Cd = 0.39, assuming frontal area of 2sqm and a rolling resistance factor of 0.01 and 25% transmission loss) you would need around 700bhp. GTX35r it is then :lol:
 
red reading

red reading

Active Member
4.125 is rb i think too edd, With the spread of power your going for i can't see the ratios being a problem tbh, especially as you are going for the raised rev limit too.

And gtx35r sounds good, but trust me i have had a pulsar upto 175ish mph and it is scary and dangerous so much so that i had the speed limiter set to 165 on my car! The car started to lift off the road and became very very unstable especially when braking.
 
M

Makaveli_se7en

Member
I know what you mean, I've V-maxed my current set up (on a private road obviously) and above (indicated) 150mph you really get the feeling you wouldn't want to stop in a hurry
 
Trip

Trip

New Member
in this regards, is it possible to swap final drives on our cars for a different final drive ratio. Let say i want to go for a 4.4 final drive to get more acceleration.
 
P

punkcav

New Member
Trip, the gearbox in the bluebird sss attessa the turbo sr20det four wheel drive carries a 4.3 final drive and the box fits straight into the pulsar
it also has a front limited slip but it is built different to the the pulsar so getting the transfer box to fit the pulsar might be a little tight
 
red reading

red reading

Active Member
Trip said:
in this regards, is it possible to swap final drives on our cars for a different final drive ratio. Let say i want to go for a 4.4 final drive to get more acceleration.
Click to expand...
Depending on which make of gearbox yes you can change the final drive, I would be careful using the bluebird final drive as it has a steeper cut on the helical which won't help our gearcase's.
 
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