4.7 vs 4.9 FD in a S80


JDM_DAVE

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Nov 13, 2013
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Hey guys, looking to see what you recommend going for! My 96 DC2 wont be a daily driver but will be used on motorways and bypass roads when I do decided to drive the car. Is there a major difference in revs in 5TH gear between the two? I was just going to go for the 4.7 out of the 98spec box but before I did, i just wanted to have your opinions on running the 4.9 FD... Is it worth it? cheers
 
I'd recommend the 4.7 as it's still fine on the motorway and a noticeable difference over the 4.4,
I've not had a 4.9 but some do say it's a bit to short for longer distance motorway use

I can't remember what rpm 70 mph was now but it's worth checking out the m factory gear calculator to get an idea of the difference
 
Had both. 4.9 topped out at 118 with a 96 spec box.

4.7 was 132. Much nicer to live with and plenty short enough
 
Well it seems like the 4.9 is better for track use.. think ill stick with the 4.7 as it looks the be the best all rounder. thanks chaps
 
so far is the 4.7 is the balance of all fd in b series , stick with it, i got a 4.9 but i m lazy to change and there are times that i regret that i have cz this how i bought my engine, 4.7 is for everything daily, tracks, drags, cruises !!!! just my opinion
 
Im running a 96 s80 with the shorter 5th so going off the Mfactory table im going to stick with the OEM gears and 4.7 FD
 
4.9 to short for any motorway runs, my built box was a nite are on motorway will a full js racing exhaust haha
 
My plan was to buy a 4.7fd from a 98spec dc2 but before I do im not sure what I have.. took my car out for a drive for the first time yesterday and at 70mph my rpm is around 4200rpm. the stamp on my gear box says 4JHd so its definitely a 96spec box.. Is this the right rpm at 70mph?
 
4200rpm for 98 spec is coming up 78mph
96spec 79mph.
That's with 195/55
It's hard to tell the difference between them at that rpm according to the calculator.
Perhaps do 70 in 3rd and tell us the revs then?
Preferably 100+mph in 5th would show up the differnece more.
 
The speedos are not 100% accurate aswell would it not be better using a satnav speed or something?
 
I should state that i have 16inch wheels with 215/45 tyres, not sure how much this would influence it... iv done the speed on sat nav today and 70mph on the car was 67mph on sat nav
 
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