Final drive ratios, how much difference do you really feel?

Grinding, replacing, filling and more in here

Moderator: Moderators

Post Reply
scheherazade
DCAWD Groupie
Posts: 727
Joined: Wed Dec 05, 2007 11:19 am
Location: nova

Final drive ratios, how much difference do you really feel?

Post by scheherazade »

So, is it a big difference going from a 3.08 to a 3.46?

I ask because my front is a 3.08.
For my LSD upgrade I would buy a single 3.08 (rear only), or two 3.46 (front and rear).

I tracked down both possibilities (found the parts at some yards), and I'm wondering which is more worth it...

Currently, 1st maxes out around 60 or so, so the 3.46 would bring that down to 53

It doesn't seem like a big difference on paper, but I've never felt it in person so I don't know how much it gives in practice...

Can anyone chime in?
Neglecting the extra shift, how much would the acceleration improve?

-scheherazade
User avatar
WRXWagon2112
DCAWD Founding Member
Posts: 3314
Joined: Mon Aug 23, 2004 8:00 pm
Location: Livin' the dream

Re: Final drive ratios, how much difference do you really feel?

Post by WRXWagon2112 »

scheherazade wrote:Currently, 1st maxes out around 60 or so, so the 3.46 would bring that down to 53
Are you saying that in first gear, at maximum revs, you're going around 60 mph? That seems awfully high.

--Alan
User avatar
ElZorro
DCAWD Founding Member
Posts: 5958
Joined: Thu Aug 12, 2004 8:00 pm
Location: USA! USA!

Re: Final drive ratios, how much difference do you really feel?

Post by ElZorro »

Zak would probably be the best person to comment, he recently converted a WRX from the stock ratio to the FXT ratio. Some of the things I've heard him mention are increased torque and decreased gas mileage, but he'll need to speak to the specifics.
Jason "El Zorro" Fox
'17 Subaru Forester 2.0XT
DCAWD - old coots in fast scoots.
scheherazade
DCAWD Groupie
Posts: 727
Joined: Wed Dec 05, 2007 11:19 am
Location: nova

Re: Final drive ratios, how much difference do you really feel?

Post by scheherazade »

I'm expecting some more torque, but I'm not really sure how much it gives.

60 does seem high, and I personally thought it was around 40 myself... But I checked on youtube and found a 0-60 video that shifted 1->2 at 60.

********************

My mistake.
I checked you tube earlier to be sure, and I mistook 2->3 for 1->2 (r-tarded).

I checked again, It is around 40.

So if it was @ 40, it'd be a@ 35 or so.
edit : 40 * 12.4894 / 14.0303 = 35.6069

auto shifting ~ 40 : http://www.youtube.com/watch?v=Eh4xllMM ... re=related
manual shifting ~ 40 : http://www.youtube.com/watch?v=hqE3zudV ... re=related



Gear Type 6 Speed Manual
Final Drive 3.08:1
1st Gear Ratio 4.055:1
2nd Gear Ratio 2.396:1
3rd Gear Ratio 1.582:1
4th Gear Ratio 1.192:1
5th Gear Ratio 1:1
6th Gear Ratio 0.872:1

(1st total : 12.4894)

Gear Type 6 Speed Auto
Final Drive 3.46:1
1st Gear Ratio 4.17:1
2nd Gear Ratio 2.34:1
3rd Gear Ratio 1.52:1
4th Gear Ratio 1.14:1
5th Gear Ratio 0.87:1
6th Gear Ratio 0.69:1

(1st total : 14.4284)



MT 1st w/ AT 3.46 final drive would be 14.0303


-scheherazade
User avatar
zaxrex
DCAWD Founding Member
Posts: 6350
Joined: Mon Sep 06, 2004 8:00 pm
Location: asiandale

Re: Final drive ratios, how much difference do you really feel?

Post by zaxrex »

I don't know about no 6-speed conversion. To my knowledge, the 6-speed only has had one ring and pinion combination for the final drive, but if those lists of ratios are true, then I am wrong.
As far as the 4.11 FD in place of the 3.9 for the 5-wpeed, there are noticeable differences.
First gear is more of a joke now. The higher final drive lowers the load on the engine and causes boost to be built later. My highest boost is ~19psi and I have not seen more than 13 in first before running out of revs. Besides, it is over too quick to really need to push it, I can just short into 2nd and let that take over.
Either I wore down the synchros in the old ‘box just the way I liked it, or the new double cone ones just don’t go far enough to make 2nd to first shifting easier.
80mph takes 3500 rpm, but in commuting to work and interstate driving, I am getting 26-7 mpg. In that rev band though, there is no boost lag or needing to drop to a lower gear. I find myself reaching higher speeds more easily now without really trying.
Patience is the ability to idle your motor when you feel like stripping your gears
scheherazade
DCAWD Groupie
Posts: 727
Joined: Wed Dec 05, 2007 11:19 am
Location: nova

Re: Final drive ratios, how much difference do you really feel?

Post by scheherazade »

zaxrex wrote:As far as the 4.11 FD in place of the 3.9 for the 5-wpeed, there are noticeable differences. [...] I find myself reaching higher speeds more easily now without really trying.
That sounds good. I'll just make sure that the two final drives can be direct swapped. I found a yard that has a front and rear 3.46 set with only 42 miles on them, but they want double what the other yards want... If I can talk them down then I'll jump on it.

-scheherazade
scheherazade
DCAWD Groupie
Posts: 727
Joined: Wed Dec 05, 2007 11:19 am
Location: nova

Re: Final drive ratios, how much difference do you really feel?

Post by scheherazade »

Ok, this is what I got lined up.

(OPTION A)
3.46 final drive ratio
Rear carrier : $1000
Front carrier : $800
+ $250 shipping
42 miles on the originating car

OR

(OPTION B)
3.08 final drive ratio
Rear carrier : $750 shipped
10'080 miles on the originating car (engine fire killed it)


+ $1450 for the Quaife LSD
(Keep in mind I'd just buy the LSD if my ring gears weren't welded, which the older production dates had bolted)

Tell me, zaxrex, is lowering the ratio (personally, in your opinion) worth an extra $1300?

I'm thinking $750 vs $2050 is a hell of a deal... but I'd have to pass on the steeper ratio.

-scheherazade
User avatar
zaxrex
DCAWD Founding Member
Posts: 6350
Joined: Mon Sep 06, 2004 8:00 pm
Location: asiandale

Re: Final drive ratios, how much difference do you really feel?

Post by zaxrex »

Well, I didn't plan on going this route. I just kept growing parts all over the place and found that I had assembled all the pieces necessary to do the swap. In the end, it did cost me dearly though.

If I had not already had the parts, then it would not have been a big enough driving difference for me to want to do this. If you are an auto-x rat, short course fanatic, or stoplight racer, then this would have much more value. In retrospect, I should have left well enough alone.

For a cheap way to approximate the difference, fit small wheels and small tires on your car and see how it behaves. Effectively doing the same thing, but not as expensive and completely reversible.

My opinion for my driving style.
Patience is the ability to idle your motor when you feel like stripping your gears
scheherazade
DCAWD Groupie
Posts: 727
Joined: Wed Dec 05, 2007 11:19 am
Location: nova

Re: Final drive ratios, how much difference do you really feel?

Post by scheherazade »

Fair nuff, that's all the push I needed.
I'll just pick up the cheaper 3.08 and make it happen.
Thanks man :)

-scheherazade
User avatar
zaxrex
DCAWD Founding Member
Posts: 6350
Joined: Mon Sep 06, 2004 8:00 pm
Location: asiandale

Re: Final drive ratios, how much difference do you really feel?

Post by zaxrex »

No wonder the gear ratios look so funny, they are from BMW. I forgot when I read this post, but then got wise when you were getting info from RJ on your other thread.

Smart>me :oops:
Patience is the ability to idle your motor when you feel like stripping your gears
Post Reply