Top gear 100km RPM

[revmax]

Had an 89 MPFI L series wagon a few years ago (not the one I am wrecking)
From memory the 100km/hr RPM was 3100 in fifth gear ( I think)
now my Brums RPM in 4th @ 100ks is 3100.
ponder! 4th gear on both cars is 1:1 engine to tail shaft ( I believe) with 5th on the L overdrive.
MY Brums final reduction is 3.7:1, is it possibe my old L was 3.9:1 final reduction or am I missing something.
any input appreciated

[Cliff R]

Not very helpful I know but my MY is 3.7:1 and at about 100ks/hr it is on about 3,100 to 3200 RPM on the factory tacho also.
I dont have a tacho on the L series but it seems less noisy at 100 (see other post re forgetting to put it into 5th)

[El_Freddo]

5th gear, 100km/h, 3.7 final drive = ~3250 according to my tacho.

I've heard that the 3.9 final drive gearboxes have different 1st - 5th ratios than the 3.7 gearbox, but that's just what I've heard, I've never looked into it.

I do know that the front wheel drive L series rev lower, just over 3g in revs from memory - it's been a few years! I'm keen to swap the 5th gear from the 2wd gearbox into the PT4wd gearbox to drop revs when cruising thus using less fuel with the EJ22

Just need the time to do it all.

Cheers

Bennie

[revmax]

(see other post re forgetting to put it into 5th)

that is what sparked my memory about starting this thread.

[discopotato03]

You have to read the factory specs .

AFAIK only Turbo Ls and some later MPFI ones had 3.7:1 finaldrives .
4th gear in L boxes is not 1 to 1 like many in line gearboxes are . While yes all L 5 speeds 5th is an overdrive 4th can be stightly lower or slightly higher meaning an under or over drive .
Long story short the turbo and later MPFI cars get the wide ratio gearset while the carby cars get the close ratio gearset .
Confused ? Well Subaru use the same first ratio in close and wide gearsets and the close set steps up in smaller jumps ie 2nd 3rd 4th 5th ratios are shorter than the wide box ones . 4th ends up being just under 1 to 1 in the close set and just over in the wide set so you can say that the wide set has two overdrives in reality .

Close vs Wide .

1st 3.545 vs 3.545
2nd 2.105 vs 1.947
3rd 1.428 vs 1.366
4th 1.088 vs 0.972
5th 0.871 vs 0.780

My bitzer L DR AWD box has the close set and 3.7 diffs and its about 2-300 revs higher in 5th than the std RX Turbo ratios (wide set + 3.7) were . For mostly round town its better but not the best for long highway hops which I rarely do .

A .

[revmax]

awsome thanks discopotato