3.7 EA 5MT with 28" Tyre?

Dane · Post by **Dane** » Thu Apr 29, 2010 3:07 pm

G'Day Suba Dudes,

I've done alot of reading through the archives at not much work today.

I am curious about the gearing of a 3.7 EA 5MT box behind an EJ22 turning 27" or 28" rubber. (In a Brumby)

What are your thoughts? Is the gearing too low for the highway (ie is the engine rpm too low to drive comfortably?)
Keeping in mind for offroad, I would be going from standard low range to an L low 1.59.

Just tossing ideas out there.

Any opinions are greatly appreciated.

twilightprotege · Post by **twilightprotege** » Thu Apr 29, 2010 4:18 pm

i've got an ea82t with the 3.7 gearbox and 27" tyres and only the 1.19 low ratio. it's ok and good enough for everything i want. the gearing would be better going to 3.9 or even 4.11 (4.11 and 29" tyres (235/75/15) gives stock driveability gearing wise), but it's more than manageable.

downsides are takeoff (you just have to ride the clutch a little more than you would normally) and have to drive around the city in 4th, and go back to 3rd often. highway in 5th is fine for me since that's within the turbo on full boost range

Dane · Post by **Dane** » Thu Apr 29, 2010 4:30 pm

I don't mind shifting gears. Would you say you need to ride the clutch because of being off boost?

Current setup is 3.9, 4 speed with 27" tyres with an EJ22. I've got a 100k old L series 3.7 box sitting there. And considering up a tyre and rim size. Hence the questions. Wondering if I would improve my fuel economy on the highway too.

twilightprotege · Post by **twilightprotege** » Thu Apr 29, 2010 6:18 pm

ride the clutch mainly because of the gearing - it just takes a bit longer for the car to get moving. i dont mind shifting gears either, but others do.

you do get pretty good economy in some cases - ie highway - but around town not so much because you have to use more throttle to get moving and to go up hills.

on my speedo (reads less than what i really do) i get around 300-350k's out of a tank around town, so probably up to 400k's in reality. that's pretty good for a turbo i think, but then again when i get those figures, i granny drive a bit

if i had a choice of everything, i'd get 4.11 gearing and 235/75/15 tyres.

twilightprotege · Post by **twilightprotege** » Thu Apr 29, 2010 6:33 pm

i should add, my off boost isnt that bad because it's the NA compression ratio (9.5 or 9.7 or something like that) vs the turbo compression (7.7)

brumbyrunner · Post by **brumbyrunner** » Fri Apr 30, 2010 6:47 am

Your Brumby 4 speed already has the 1.59 low range so no gain there.
I wouldn't do the swap just to get 4th gear, the gearing will end up worse than it is now. If you want to make a decent improvement, get hold of a 4.11 front gearset for your 5 speed. They are probable the least desirable/easiest to find ratio which makes them cheap.

Dane · Post by **Dane** » Fri Apr 30, 2010 8:24 am

I thought that the Brumby 4 speed was slightly higher? From reading wiki anyway.

T81W 4WD 1st Revision
Gear Ratios: 1st 3.636 2nd 1.950 3rd 1.193 4th .769 Rev 3.583, Low Range 1.462
Usage: 1982-1989 Subaru Leone 1800cc and 1982-1993 Subaru Brat (EA-81 engine only)

Gear Ratios: 1st 3.545 2nd 1.947 3rd 1.366 4th .972 5th .780, Rev 3.416 Low Range 1.59
Usage: 1985-1994 Subaru Leone and 1985-1989 Subaru XT 1800cc

http://en.wikipedia.org/wiki/List_of_Su ... nsmissions

I am likely to believe you from the experience you've got though.

On a side note, is it possible to change the final ratio on the gearbox from 3.7 to 3.9? My second gear crunches when my girlfriend drives it and doesn't rev match. Would be possible to put the low km L box in with the final drive from my MY 3.9?

Also should add that I was saving the L box Low to go into a GEN1 3.9 Lib box I have. Maybe I should bite the bullet and combine those. I've never split a box before. I'll have to have a read of AP's build thread.

I'm running early L series hubs, so does the later model L series splines (hub end) match up with Lib box stubs?

I'm getting way off topic, sorry for those following. Fell free to comment on either.

brumbyrunner · Post by **brumbyrunner** » Fri Apr 30, 2010 11:25 am

You could well be right on the Brumby low range. The difference isn't going to be noticeable.
I think you're asking if the 4-speed crown wheel will fit in the 5-speed case? The answer is no.
I don't know what you're budget is but I leave gearbox building to the experts.
Send a pm to Jeff (Crossbred Performance) and see what he reckons. He just had my 2 racing gearboxes freshened up.

Dane · Post by **Dane** » Fri Apr 30, 2010 12:08 pm

I will do.

I've been speaking to Jeff about the AWD box in the past. I'm sure he's been watching this thread to

Thanks for the input.