4.7 vs 4.9 FD in a S80

JDM_DAVE

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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
 

b16 mini

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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
 

samphier

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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
 

JDM_DAVE

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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
 

firebass

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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
 

JDM_DAVE

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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
 

kellsled

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4.9 to short for any motorway runs, my built box was a nite are on motorway will a full js racing exhaust haha
 

JDM_DAVE

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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?
 

jesse888

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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.
 

Rossco155

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The speedos are not 100% accurate aswell would it not be better using a satnav speed or something?
 

JDM_DAVE

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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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