sagaris 3.73 / 3.9diff cr gearbox
Discussion
I know this has been discussed before but I still find myself agonising over it, to cut a long story short I have a 3.73 diff on my sag which was on it originally, last year I decided to have the cr box fitted, my first impressions where oh s
t what have I done! as 1st gear does seem really high until you get going then the thing really flies, 6 months on im still not totally convinced that the really high 1st is for me, I have 2 options either resort back to the std ratio gearbox or I stick with the cr box and get the 3.9 diff fitted, Anyone been in the same boat? Does the 3.9 diff really help to lower 1st gear, very little of my driving is on track so the emphasis is on fast road use (when safe to do so of course).
Many thanks in advance.
t what have I done! as 1st gear does seem really high until you get going then the thing really flies, 6 months on im still not totally convinced that the really high 1st is for me, I have 2 options either resort back to the std ratio gearbox or I stick with the cr box and get the 3.9 diff fitted, Anyone been in the same boat? Does the 3.9 diff really help to lower 1st gear, very little of my driving is on track so the emphasis is on fast road use (when safe to do so of course).Many thanks in advance.
Ian, I recall a ride around Oulton Park in Daftlads Sagaris which was fitted with a 3.9 diff & CR box and it was extremely impressive showing a significantly quicker acceleration than my Sag. It is a route that I would probably have taken had I been keeping my car. The gear changes were more frequent and it will have an effect on top speed and revs on the motorway but apparently the car still works fine for touring. I suppose you other option is to go back to a standard box.
Just a couple of thoughts. If the car is for road use would changing to the 3.91 diff mean more noise at normal road speeds. Also, you mention that it flies in first gear, but only once you get the revs up. Could the car benefit from a re-map to give you a bit of lower down torque ?. If you're prepared for more noise going down the 3.91 diff route, why not think about a de-cat as from my experience this with a re-map (on my 3.6 SP6) really gave me extra low down grunt. Also, how about the CR box with the 3.46 diff ? - allegedley this is the worst combination possible, but again from personal experience I think that combination works really well as that's what I've got ( have a look at my vids from Fighting Torque) posted on here. 60 in 1st, 90/95 ish in 2nd, 125+ in 3rd, 155+ in 4th - awesome as Britney would say. I wouldn't dream of changeing my CR/3.46 diff combo.
KillerJim said:
Had the pleasure of getting a blast in a 3.9 diff Sagaris not so long ago. The acceleration is noticably quicker (which is saying something for a Sag) than my standard one but as I`m a non-tracker user I`d never make the change.
It was not a 3:9 Jim it was a 3:73, so if that was quick then a 3:91 will blow you away. Still believe that the best ratio for every day and track is standard box and 3:73 ratio.The standard sag diff is not a good mix with the c/r box and is one of the reasons you see clutches going at 12000 miles imo
Anyway Jimbo where were you for the Trackday last Monday best turnout for a while.
B
A 3.9 differential will have no affect on road driving, you will get no whine and it will not wear the clutch out, Best to have a 3.7 or a 3.9 only if you have a CR box. the benefit of the 3.7 0r 3.9 is purely to get away quicker, but you loose top end but anything over 140 is pointless anyway. Look at it like the gearing on a bike pulling away from a standing start. Who will get to 10mph quickest the person in fist gear (3.9) the person in second gear (3.7) or the person in 3rd gear (3.4). The down side as I said is the person in first runs out of power quickest before he needs to change gear.
You certainly wont need a remap your not changing anything under the bonnet.
You certainly wont need a remap your not changing anything under the bonnet.
A few mixed messages on here, it seems.Sharing my own recent development experience...
A lower diff always gives you better acceleration in every gear not just 1st, but your gear changes come a little more frequently and you have a lower top speed (mine's still over 160 with a 3.9 diff, which I find sufficient!) so is still a compromise.
Obviously there's not a vast % difference between a 3.73 and 3.91, but still makes a difference - whether good or bad depends on your priorities!
Agree there's no noise difference in diff ratios, or even most lsd types, but a semi-straight cut c/r box like a Quaife is noisier.
De-cats improve top end (only) marginally.
A re-map is helpful if you've got a sub-optimum chip in the first place (my 2004 chip couldn't be improved on when TVR Power tried others in it, on the standard 3.6 engine) OR have made other changes to breathing/exhaust etc. such as de-cats.
Iv got the standard box and diff... this is the only area iv yet to 'play' with, as always its hard to take advice from others as everyone has their own driving style, from what iv read i am tempted to swap to the 3.7 diff and keep the standard box, it seems it is the most sensible all round combo to improve the response/feel of the car without spoiling what is already a fairly good set-up. my car is a trackday/touring/daily drive so no drastic changes needed.
hollowpockets said:
Iv got the standard box and diff... this is the only area iv yet to 'play' with, as always its hard to take advice from others as everyone has their own driving style, from what iv read i am tempted to swap to the 3.7 diff and keep the standard box, it seems it is the most sensible all round combo to improve the response/feel of the car without spoiling what is already a fairly good set-up. my car is a trackday/touring/daily drive so no drastic changes needed.
No sense in letting those pockets sit there filling up. 
willtvr said:
Get mine back from HHC in a couple of weeks with 3.73 diff(standard box) fitted so will add some comments once driven.
It will feel quicker & be quicker than previous, although you'll lose a bit off the top end.So what, be honest when was the last time you went over 170mph???
Just enjoy your better acceleration
I had a 3.73 diff & std box before I changed to c/r & 3.9.
For info the change is about the same again
tail slide said:
hollowpockets said:
Iv got the standard box and diff... this is the only area iv yet to 'play' with, as always its hard to take advice from others as everyone has their own driving style, from what iv read i am tempted to swap to the 3.7 diff and keep the standard box, it seems it is the most sensible all round combo to improve the response/feel of the car without spoiling what is already a fairly good set-up. my car is a trackday/touring/daily drive so no drastic changes needed.
No sense in letting those pockets sit there filling up. i have my name for a reason! Just aswell im off on a 3 weeker this time! 
hollowpockets said:
iv just made a call and when i collect my car from the service/re-spray/re-map it will also have a quaife diff with the 3.7 ratio.
That's my combo with standard box and quaife
Always had the 3.73 diff, but the quaife gives it that extra edge and surefooted feel.
I would call the quaife a safety option for those new to TVR's
and
A performance/tractability improvement for those who can handle power slides and tractability on demand
I must down load my racelogic performance box statistics for 0-60, 0-100 and 0-100-0;
Anyone else got some factual figures for the various combinations we have?
G
If you are in a position to have a choice and you go for the 3.7 you will always wonder how much quicker it would have been with a 3.9
I am running the c/r box with the ATB/LSD 3.9 diff, and if you would like to see how powerful that combination is I will be more than happy to take you out for some laps at Cadwell on the 27th May.
But having said all that you only get the best out of the C/R box with the 3.9 ATB/LSD diff with a 4ltr minimum RR spec. If you can get 370bhp at the wheels which equates to about 440bhp at the fly then the above combination is quite simply awesome.
I am running the c/r box with the ATB/LSD 3.9 diff, and if you would like to see how powerful that combination is I will be more than happy to take you out for some laps at Cadwell on the 27th May.
But having said all that you only get the best out of the C/R box with the 3.9 ATB/LSD diff with a 4ltr minimum RR spec. If you can get 370bhp at the wheels which equates to about 440bhp at the fly then the above combination is quite simply awesome.
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