Changing the final drive ratios

[dumpycorsa]

Hi. I'm looking to buy a Quaife final drive for my F20 box. 4.2 ratio (standard being 3.55). I'm using the car on the road and for drag days. It'll give the car (on 195/45/15's) a theoretical top speed of 113mph @6500 rpm. Do you think this is a good idea or not? Just trying to weigh up the pros and cons.

I'll also be fitting an ATB diff with this.

[Welsh Dan]

Thats 4000rpm at 70mph, so I wouldnt really say there's any cons on the road as you can still cruise comfortably on the motorway.

Whats your current terminal speed on the drag strip?

[dumpycorsa]

Thats 4000rpm at 70mph, so I wouldnt really say there's any cons on the road as you can still cruise comfortably on the motorway.

Whats your current terminal speed on the drag strip?


I've not done 1/4 mile yet as there isn't any 1/4 tracks down here. All the spaces are filled with cowslol

I've done 1/8 mile runs and my best time is 8.918 @83mph.

Will a straight cut Quaife final drive make that "straight cut whine" you get with straight cut gear sets?

[Welsh Dan]

It'll make one of those whines yes.

It'll help your 1/8 mile runs, but you might find you hit the limiter before you hit the 1/4 mile marker.

[Geordie-Chris]

You'll be close to limiting by the time you cross the finish line on a quater, but should be fine - 90mph - 100mph max as your crossing unless your running some mega power or a LET.

[burgo]

i think thats to short imo. will deffo see the limiter before the finishing line

[Stuart]

see sig link for more info :D

DO NOT use the custom gear ratio part though... its broken lol

[dumpycorsa]

My new engine will have a rev limit set to approx 7200rpm. Thats what the cams will pull to. If it is 7200rpm then the top speed with the new ratios will be 125mph. The tyres I use on my drag days are a 50 profile so that'll help a little too.

Ideally I'd get a Quaife gear set aswell but can't stretch to that atm.

[MARTIN KELSON]

Hi

I run a Quaife straight cut syncro gear set in my F20.
On track and out for a blast on the roads its fantastic.
Only used it once on drag strip and to be honest you will be needing 5th gear by the end of the strip. Every gear change possibly costs half a second so i thought it wasnt ideal for dragging.
Also if you intend on alot of motorway use again not really well suited. I did order a year or so later from Quaife a longer 5th gear to ease motorway use.
If its your weekend toy for track and 'B' road blast and you dont mind the whine, the accelerations gains to to different ratios are worth the money and effort.

Martin

[dumpycorsa]

Hi

I run a Quaife straight cut syncro gear set in my F20.
On track and out for a blast on the roads its fantastic.
Only used it once on drag strip and to be honest you will be needing 5th gear by the end of the strip. Every gear change possibly costs half a second so i thought it wasnt ideal for dragging.
Also if you intend on alot of motorway use again not really well suited. I did order a year or so later from Quaife a longer 5th gear to ease motorway use.
If its your weekend toy for track and 'B' road blast and you dont mind the whine, the accelerations gains to to different ratios are worth the money and effort.

Martin

I was just going to use the Quaife final drive and the standard GM gear set.The car is now used as a weekend toy. I was concerned about taking it up the motorway for drag days etc but could trailer it if needs be. I've seen some SCCR boxes forsale but they seem to use a long first gear then close ratios to 5th or even 6th (if you have the £££'s). My friends MK2 escort is the same. It's like pulling away in second. I was just looking to improve 0-60 times. I think it would run out of revs on a track. Can you change the 5th gear ratios on a standard gear set or would I have to buy a full gear set?

[MARTIN KELSON]

Hi

With the Quaife straight cut synchro set i use you can only select the 5th gear ratio and final drive (that was the case when i got mine anyhow) the rest is selected by Quaife.
Mine on 15" wheels also at 70mph is doing about 4000rpm on motorway. Its not ideal but but with mine i dont do alot of motorway and when i do its Santa Pod which is about 200 mile round trip.
If its 0-60 you want to improve i would highly recomend the Quaife Straight cut synchro gear kit.