Ok, admittedly I'm thick and completely baffled by the diff options available for my Sagaris, not even sure what the standard (if there was such a thing) diff ratio is that I have fitted to mine. Could someone please enlighten me as to the pro's & con's of each 3.46, 3.7 and 3.91 options, and what I can expect to pay for a change-out? Mine is an early car, 2005. Original plate was GX05 ENV. Thanks in advance guys.

I have the 3.91 and it cost around £1200 fitted. I was told that the 3,91 need an extra part over the 3.73 option, adding a little bit to the price.

It is the most worthwhile mod I can think of for recent model TVRs running Speed Six engines.

My Sag came out the factory with the "wrong" diff fitted (Don't know what this means though).

I have an invoice when my Sag was 15 months and 11k miles old for part number R0662 with the description Sag Hydrotrak Diff 37

Any idea which ratio diff I have fitted please guys?

I also have the close ratio box - is this a good set-up?

'twas something on here...

Only you know whether it is a good 'setup'. Do you like it? Well there you go then.

You'll need to get under the car and see if you can read the tag on the side (if it has one). I think they're all Hydrotak so that's nothing special. The 37 at the end hints to me that you may have the 3.73, but of course I actually know nothing, I'm just an Internet warrior with suggestions.

I was under the impression that all Sags came out of the factory with CR boxes.
Looking at the spreadsheet, I wonder why anyone would choose to move up to the higher ratio diffs. Is it me, or do they appear slower through the gears the higher you go up? Power delivery seems to smooth out, but is this really a good substitute to the apparent sheer aggressive response of the 3.46??? Am I missing something?

Thanks John. As I'm not the original owner, and don't have the original invoice, is there anyway I can find out what options my car came out of the factory with? Cheers.

My Sag was originally the 'standard' box and the 3.46 diff.
I recently had this upgraded at RG, electing for a close ratio box, and Quaife LSD with 3.91. Also had their lighter Simplex timing chain kit fitted at the same time.

I've yet to compare it with previous form on the track (the Quaife LSD in particular is supposed to aid in laying down the power out of tight corners), but on the road the car 'feels' a lot quicker through all the gears. Response is still linear and smooth, but the car revs a lot more freely right to the top end, and as I've said above - subjectively at least - it feels massively faster than before. Third gear in particular seems to last forever.

The CR box seems to force an adjustment in driving style .... most noticeably 1st gear is a lot longer than before, and the car doesn't like me to snatch 2nd gear as early as I used to (it'll bog down slightly if you change into 2nd too early).

All in all a very worthwhile upgrade. Not cheap though.

cheers
DR

Depends how you interpret it I guess. I see 3.91 as a higher ratio than the other two. It means my car now has a theoretical top speed of 176mph vs 195mph with the standard diff ratio. A speed it can actually attain instead of fantasy gearing.

Yes I have the standard gearbox. I've not changed it as I am perfectly happy with the combination, which IMO works very well. Maybe a CR box would be even better, I don't really care and won't contemplate changing the gearbox ratios unless the current one packs up.