0.825 ratio 5th gear behind EJ22

AlpineRaven · Post by **AlpineRaven** » Mon Jul 06, 2009 9:58 pm

Do you think this gearset - 0.825:1 5th gear ratio would be okay behind EJ22 with 3.7 diff, 205/70 15" tyres?

at 100kmh it would be on lazy 2450rpm approx, 85% of the time I'm on the highway mostly flat surface, 10% of the times is on hilly areas but cruising at 110kmh (approx 2700rpm) anyway (normally i would set cruise control at 115kmh anyway if im in 110zone)... so what you think?
Cheers
AP

FYI - At the moment I have 0.871:1 5th gear (2650rpm at 100kmh/2900rpm at 110kmh/3000rpm at 115kmh)

discopotato03 · Post by **discopotato03** » Tue Jul 07, 2009 11:17 am

AP that may depend upon what the other main box ratios are , namely 4th because it affects the rev drop 4th -5th .

I'd reckon if your 5th is currently 0.87 you must have the closer ratio gear set , basically the non turbo/wide ratio Lib gearset .

In the close set 4th is a slight underdrive (1.088) and the wide set 4th a slight overdrive (0.972) .
With the close set a 0.825 would be ok provided the EJ22 has the torque to pull it lower in the rev range .

I went into gearbox ratios a while back but don't recall a 0.825 , I know of 0.87 , 0.78 and I think a real tall one from one of the Impreza's with short ratio diffs . What is this one you're talking about from ?

Cheers A .

AlpineRaven · Post by **AlpineRaven** » Tue Jul 07, 2009 8:06 pm

discopotato03 wrote:AP that may depend upon what the other main box ratios are , namely 4th because it affects the rev drop 4th -5th .

I'd reckon if your 5th is currently 0.87 you must have the closer ratio gear set , basically the non turbo/wide ratio Lib gearset .

In the close set 4th is a slight underdrive (1.088) and the wide set 4th a slight overdrive (0.972) .
With the close set a 0.825 would be ok provided the EJ22 has the torque to pull it lower in the rev range .

I went into gearbox ratios a while back but don't recall a 0.825 , I know of 0.87 , 0.78 and I think a real tall one from one of the Impreza's with short ratio diffs . What is this one you're talking about from ?

Cheers A .

yeah, I think its about 150rpm@100kmh difference between 0.871 to 0.825:1... so yeah.. I know its pre-99 imreza, still trying to find out. I do know that EJ will be able to pull it easily, but not 0.780/0.738 unless I have 4.11 diff.
Cheers
AP

discopotato03 · Post by **discopotato03** » Wed Jul 08, 2009 10:36 am

Yeah , 0.738 was the one I couldn't quite remember .

In my RX L Series going from its original 0.78 5th to the current 0.87 one made quite a noticeable difference and I think I calculated it to be between 11 and 12% or about 300 per thousand in 5th .
Spare a thought for me doing 90 in 5th at 3000 ...

If you find a few sets of those 0.825's I'd like one provided they fit in a L AWD box which main gearset wise is like a 1st gen Lib AWD gearset though normally the wider turbo ratios .

Cheers A .

AlpineRaven · Post by **AlpineRaven** » Wed Jul 08, 2009 8:33 pm

discopotato03 wrote:Yeah , 0.738 was the one I couldn't quite remember .

In my RX L Series going from its original 0.78 5th to the current 0.87 one made quite a noticeable difference and I think I calculated it to be between 11 and 12% or about 300 per thousand in 5th .
Spare a thought for me doing 90 in 5th at 3000 ...

If you find a few sets of those 0.825's I'd like one provided they fit in a L AWD box which main gearset wise is like a 1st gen Lib AWD gearset though normally the wider turbo ratios .

Cheers A .

Yeah... The guy I got it from he pulled it out from 1996 WRX box that had blown main shaft, he didnt have any other 0.825 as I was planning to get another one but didn't, he has 0.780 5th, it will go well with 3.9 or 4.11 diff but not really with 3.7.

Yeah by 150rpm difference could make a big deal for long highway trips.
Cheers
AP

AlpineRaven · Post by **AlpineRaven** » Wed Jul 08, 2009 8:41 pm

AlpineRaven wrote:Yeah... The guy I got it from he pulled it out from 1996 WRX box that had blown main shaft, he didnt have any other 0.825 as I was planning to get another one but didn't, he has 0.780 5th, it will go well with 3.9 or 4.11 diff but not really with 3.7.

Yeah by 150rpm difference could make a big deal for long highway trips.
Cheers
AP

I didnt realise, That gearset needs 5mm key, whereabout our gearboxes has 4mm key, otherwise you can machine the keyhole/shaft.
Cheers
AP