Gearbox ratios - new build

[El_Freddo]

G'day,

Since blowing second in my gearbox I'm looking into ratios a bit more closely.

I'm specifically looking at the SF and SG gearboxes from the foresters, these are the basic ratios as stolen from offroadsubarus:

SF:

1st = 3.545
2nd = 2.111
3rd = 1.448
4th = 1.088
5th = 0.871

FD = 4.111:1

SG:

1st = 3.454
2nd = 2.062
3rd = 1.448
4th = 1.088
5th = 0.780 for 2.5L version
5th = 0.871 for 2L version

FD = 4.111:1

Between both gearboxes it seems that the 2L low range is 1.447:1 and for the 2.5L is the dodgy 1.19:1

I've been using the rpm/speed calculator for each gear to do comparisons from this website. Yes it's a VW conversion site, but keep scrolling down to the calculator. It also has a list of JDM and US ratio specs for WRX/Impreza/Liberty boxes as well.

So from this I've worked out the following:

At 2000rpm--1st------2nd------3rd-----4th-----5th (0.871)

SG-----------18.2-----30.5-----43.4----57.8----72.2km/h

SF-----------17.74----29.79----43.4----57.8----72.2km/h


Then revs @ 100km/h in 5th:

0.871--------2770 rpm

0.780--------2480 rpm

^ quite a difference there. I'm thinking the 0.871 would be the go as I'd prefer the higher revs for long distance cruising at speed over hills.

Thus far I've been talking about the 4.111:1 diff ratio above.

This then got me thinking what if I took the dive to the 4.44:1 diff ratio.

At 2000rpm-----1st------2nd------3rd----4th----5th (0.871)----5th (0.78')

SG--------------16.86----28.24----40.2---53.5----66.85---------74.6km/h

SF--------------16.43-----27.58----40.2---53.5----66.85---------74.6km/h

Then revs @ 100km/h in 5th with 4.44s:

0.871--------2992 rpm

0.780--------2679 rpm

To put it all together you have the following:

At 2000rpm----1st------2nd------3rd-----4th-----5th (0.871)---5th (0.78')---Final Drive

SG--------------18.2----30.5-----43.4----57.8----72.2-----------80.6 km/h---4.111:1

SG--------------16.86---28.24---40.2-----53.5----66.85---------74.6 km/h---4.44:1

SF---------------17.74---29.79---43.4-----57.8----72.2----------80.6 km/h---4.111:1

SF---------------16.43---27.58---40.2-----53.5----66.85---------74.6 km/h---4.44:1

So if I'm going with 4.111:1 diffs I'd want the 0.871 5th ratio; but if I'm going to go with 4.44:1 diffs I'd definitely want the 0.78 5th ratio. I reckon the turbo 5th ratio of 0.73 would be too low for what I want, even with the 4.44:1 diff ratio at 100km/h you'd be pulling 2507rpm - not bad if you're running an EJ25.

All of this information is relevant to my setup - EJ22E (I believe) running 27 inch tyres (685.8mm for the calculator) in an L series.

I'm looking at the SG box, even though 1st and 2nd are *slightly* taller, I've heard that they've got better synchros and a stronger 1st gear. Plus it's a younger box as such - not by much but it's better than an 80's unit!

Cheers

Bennie

[yarney]

Bennie are you going to go awd or just use the gear sets?
It would be a better car to drive with awd and you wouldn't need to strip the box if you use 4.11. With an ej22 you still have the power:) i was happy with the 2.0l Forester in the rougher tracks

Jan

[Venom]

I'd definitely be going 4.44. It'll compensate, probably more than, the slightly longer ratios of the SG box. Certainly need to be cruising in the powerband at 100 so its not bogging down at all.

[taza]

Do not use a SF Forester gearset... between us WA boys we have broken 1st, 2nd and Reverse over 5 boxes... The mainshaft is very weak on them! I have sinced moved onto an SG/Gen 4 Outback box..
5th gear does 2400rpm at 100km/hr in my Forester verse the 3100rpm at 100km/hr with the SF box.

I picked up a 2007 Outback box from a rolled vehicle for $250 inc freight from NSW to Perth. It's done 92k km.. Should last the life of my Blue SF.

[AndrewT]

How much mechanical sympathy are you giving these gearsets? The SF gearbox I'm about to use has 280k + on it and works fine, how bad can they be?

[taza]

They seem fine behind a stock 2.0l. As soon as you throufh a ej22/25 behind it and start adding extra loads in soft sand or towing the mainshaft lets go.
This isnt just my abusive driving either. Some if the other guys who are gentle have done reverse amd 1st.
I towed my boat offroad up in Geraldton... only a few km along the beach.... getti stuck once. After using the maxtrax and airdown tyres to get out 1st gear whined ever since. 12months later it let go on a soft gear change.

[AndrewT]

this was a low kms box with fully completed service history?

[AndrewT]

Wow Bennie that's far more research than I've ever done on the subject I'm sure you arrive at a winning combination.
I'm keen to see what you come up with. While I rekon I'll hopefully get a good run out of this box but possibly not based on what I expect from the dyno run.

[El_Freddo]

Bennie are you going to go awd or just use the gear sets?
It would be a better car to drive with awd and you wouldn't need to strip the box if you use 4.11. With an ej22 you still have the power:) i was happy with the 2.0l Forester in the rougher tracks

Already AWD Jan So in this case I'll just be using the gearsets.

I'd definitely be going 4.44. It'll compensate, probably more than, the slightly longer ratios of the SG box. Certainly need to be cruising in the powerband at 100 so its not bogging down at all.

I'm keen for the 4.44s - but it's a cost thing at the moment. First I need to source the 4.44 ring and pinion gearset, then I need to have it cut and shut onto the locking centre diff pinion shaft. To me the second part is where the $$$s are. And if I can do it locally in Shepp it'd be a lot easier for me to follow it up etc.

Do not use a SF Forester gearset... between us WA boys we have broken 1st, 2nd and Reverse over 5 boxes... The mainshaft is very weak on them! I have sinced moved onto an SG/Gen 4 Outback box..
5th gear does 2400rpm at 100km/hr in my Forester verse the 3100rpm at 100km/hr with the SF box.

Taza, the SF box is the same strength of a stock WRX box - so I don't know what you're doing wrong, but you and your mates should really look at the mechanical sympathy you give your machines!
Yes this comes from someone who's blown a gear in the box, but I truly believe this is due to fatigue of the gearbox, being that it was a turbo box in a previous life I wouldn't be surprised if second was well abused on hard launches.

I picked up a 2007 Outback box from a rolled vehicle for $250 inc freight from NSW to Perth. It's done 92k km.. Should last the life of my Blue SF.

What's the ratio of the box? From what I've read a lot of Outbacks and Imprezas seem to have 3.9:1 diff ratios and slightly different forward drive gearsets. I'd be double checking that and even swapping in the 4.111:1 diff ratio if needed - the broken boxes should supply you with plenty of parts to be playing with gearbox bits. You should also have a good selection of 5th gear ratios to play with too!

Wow Bennie that's far more research than I've ever done on the subject I'm sure you arrive at a winning combination.
I'm keen to see what you come up with. While I rekon I'll hopefully get a good run out of this box but possibly not based on what I expect from the dyno run.

Yeah I wanted to make sure I was making the right choice with the SG gearbox as the donor for the parts. And I wanted to get 5th ratio right for my application - I don't want to be changing down gears on long hills on the freeway, or even have the revs dropping too far off from cruise. I'm happy to have the engine revving a bit higher, so long as it's not 3250 rpm I'll be happy. 2800 would be good I reckon so the 0.871 5th ratio would be good for both the 4.111:1 or 4.44:1 diff ratio.

Really I couldn't have checked out these ratios as in depth without having stumbled across that gear ratio calculator from subarugears.com/FAQ/FAQ.something

Unfortunately the design of the Subaru gearbox sees the clusters of 1st & 2nd , 3rd & 4th mated together so you can't change gear ratios individually with these gears. More to this 1st and 2nd are cast into the input layshaft, 3rd & 4th are cast to the output layshaft. 5th is independent of both shafts.

I've found a 3.64:1 first gear ratio, but there's two issues with this. The first issue is that the second gear is 1.95:1, the second issue is that this is in a single range gearbox. It's from an Impreza 2wd gearbox.

This got me thinking - can the input shaft be modified for the dual range - but then once again, I'm stuck with that low 2nd gear ratio. When it all boils down to the 2000rpm engine input, it gives just under a 1km/h difference slower than the SG 3.454:1 first gear ratio.

So really I'm just getting too picky. Just need to secure the SG box then go from there.

I'm also hoping the speedo drive from the SG box will match the L series instrument cluster - time will tell on that one. We ran a 3.9:1 diff ratio speedo drive gear when the box was built and this made the speedo out by 10%. Much better than the original 18% of the stock L 3.7:1 diff ratio speedo drive gear.

I wouldn't mind adding a second oil feed over 1st gear for down hill descents. 1st gear in the old box would whine when off throttle after our trip to Walhalla, I put it down to the engine braking and lack of oil over the 1st gear on the steep inclines we were driving.

Also Andrew, I've read somewhere that the SG 1st gear is physically wider and thus a bit stronger than previous generation's gearbox's 1st gear - or that the slightly taller ratio makes up the strength. Not sure which one it is but I'll check it out anyway. Nachaluva also tells me that the synchros in the SG box are better than previous generations - something I didn't know about.

Cheers

Bennie

[Venom]

Ah yeah forgot you had the L series locking centre. So what it has 3.9 now? That's kinda shit.

Before investing in a custom pinion for the 4.44 I reckon you would want to serious look at DCCD. Your tailshaft will be shorter, and going short is fairly cheap and easy. Linkages should be fairly straight forward and the manual dccd controller will do the job. Between the cost of the pinion mod and the replacement of that oh so rare locking centre that likes to self destruct I think the cost might be comparable and the end result as good for performance and much more reliable.

Oh yeah crossmemeber too. Hmm well maybe not. Off-topic but there's definitely a line for potential mods on the MY/L series where they quickly go from simple but effective and jump to tricky, not so straight forward and custom/modified parts. So many more options with an EJ platform.

[Alpinebarry]

Trying to get an adaptor plate for my ej22/ ea82 ea conversion so I can get my L series 85 sports wagon mobile . Can any of you guys assist.Barry

[AndrewT]

Tailshaft modding isn't *that* cheap to have a quality job done. Mine was $550 a few weeks ago (shorten front section 65mm to suit full EJ gearbox into L series), replace all unis in the front section with new Holden jobbies. Also replace the entire rear section with a brand new one, also with all new Holden unis.

The crossmember to make an EJ gearbox fit in an L series is easy though, should cost only you a few bits of scrap metal and some welding wire. No need to over-engineer and it's quite easy to put together.

How are you finding the old locking centre Bennie?



BTW - Alpinebarry - best you start a new separate thread re engine adaptors, but try contacting RSR555 (Paul at RSR Performance), I believe he can do you an adaptor. Also do a search for a DIY guide I wrote up a few years ago on here if you are keen to make one, it was easy.

[tambox]

If you can break a 4.11 (unless it was a twisted tooth to start with) you will destroy a 4.44 or the rear diff axles.
I have seen quite a few stripped teeth (non WRX) Subaru boxes, a lot of them have had one twisted tooth. You can see the wear pattern on one tooth is different to the rest. We assumed these had come out of crashed cars. Yours went a bit further than only a couple of teeth, so it would be hard to work out.
This includes crw and pinion.

The lower the ratio diffs, the more "force" you put to the road and hence the drive-line.

Never seen anybody do the machining work required to use a 2wd gear-set in a 4wd box. It would probably be a weak point.
There was an engineering place in Benalla or Wang that reckon they could weld the pinion.

Oil insertion at the correct points is good, but 1st should get enough splash, only the high/lows need oil. From production some boxes are noisier than others, especially first, like late model L's.

Cutting and welding tailshafts is not that hard, extending them may be. Holden uni's would be a nice mod though.

Have fun with the speedo gear, there are many sizes available. The number of teeth on 3/4 speedo drive varies as well. If you have a known set of gears and speedo reading, work it out from there.

[Alpinebarry]

Hi guys thought I would send in a pic or two of my project

[El_Freddo]

Trying to get an adaptor plate for my ej22/ ea82 ea conversion so I can get my L series 85 sports wagon mobile . Can any of you guys assist.Barry

G'day Barry - off topic but as Andrew T has said - contact RSR555 or look up the "procedure" Andrew T wrote (use the search function). It's pretty straight forward.

Or do what I did - get a Gen1 AWD liberty gearbox, use the front casings of the gearbox to house your L series gearbox internals. You use the L series rear housing at the back of the box. This allows you to use EJ clutch and starter, yet keep the L series gearbox crossmember so it's all plug and play. Worked a treat for me - and still is with this gearbox build!

How are you finding the old locking centre Bennie?

Yeah mate LOVE it!! The AWD onroad makes a huge difference in the wet (when it's most noticable!) and knowing I have a proper mechanical lock when offroad is just like the original PT4wd box... But with these gearboxes I reckon you NEED a front LSD, otherwise spinning one front wheel on the black top even when dry is pretty easy.

If you can break a 4.11 (unless it was a twisted tooth to start with) you will destroy a 4.44 or the rear diff axles.

Not the diff - a worn out second gear in a turbo box. You should know the turbo box's abuse/issues with time. Rear diff stubs/shafts are easy to replace in my mind. I'm keen to see what happens anyway.

I have seen quite a few stripped teeth (non WRX) Subaru boxes, a lot of them have had one twisted tooth. You can see the wear pattern on one tooth is different to the rest. We assumed these had come out of crashed cars. Yours went a bit further than only a couple of teeth, so it would be hard to work out.

Mine's gone a bit further from driving on it for ~10km in another gear - things would have still be smashing around in there even without using the damaged gear as the drive gear.

The lower the ratio diffs, the more "force" you put to the road and hence the drive-line.

I think you've got this the wrong way around. A taller diff ratio allows the engine to apply more power/torque to the road with less stress to the drive gears in the gearbox. A shorter ratio applies more stress to the drive gears. So my 3.7:1 original diff ratio loaded up the drive gears more. Using low range compounds this further in both situations.

My gear would have popped in either low or high range - I believe it was waiting to happen.

Never seen anybody do the machining work required to use a 2wd gear-set in a 4wd box. It would probably be a weak point.

You're probably right there - the real weak point will be my wallet

There was an engineering place in Benalla or Wang that reckon they could weld the pinion.

Sourcing a good 4.44 ring and pinion for a good price looks like the first big hurdle

Oil insertion at the correct points is good, but 1st should get enough splash, only the high/lows need oil. From production some boxes are noisier than others, especially first, like late model L's.

I'm thinking of doing it as it was only AFTER the Walhalla trip that my 1st gear would whine OFF throttle!

Have fun with the speedo gear, there are many sizes available. The number of teeth on 3/4 speedo drive varies as well. If you have a known set of gears and speedo reading, work it out from there.

What's the 3/4 speedo drive gear?

I guess the known set of gears would be the current 5th (turbo L series - 0.73?), 4.111:1 diff ratio and 685.8mm tyre diametre is 10% under at 100km/h.

Ah yeah forgot you had the L series locking centre. So what it has 3.9 now? That's kinda shit.

No, got the 4.111:1 already. So it's pretty good!

Before investing in a custom pinion for the 4.44 I reckon you would want to serious look at DCCD. Your tailshaft will be shorter, and going short is fairly cheap and easy. Linkages should be fairly straight forward and the manual dccd controller will do the job. Between the cost of the pinion mod and the replacement of that oh so rare locking centre that likes to self destruct I think the cost might be comparable and the end result as good for performance and much more reliable.

I'm confident in the locking centre. It gets locked when ever it's wet or I hit dirt. I make sure my tyre pressures are equal and that the tread wear is relatively even. I've not had any issues with my centre diff. Although I would like to have a couple of new housings machined up to have on the shelf if something does go wrong with the locking centre.

Oh yeah crossmemeber too. Hmm well maybe not. Off-topic but there's definitely a line for potential mods on the MY/L series where they quickly go from simple but effective and jump to tricky, not so straight forward and custom/modified parts. So many more options with an EJ platform.

You've met Ruby Scoo right? I'm pretty sure I've JUMPED over that line!! Now I think I'm into the refining the capabilities of this vehicle offroad.

I don't know if I'll get to the 4.44 this time - but it will always be at the back of my mind if I don't... But from what Rick has reported I'm keen for it - it's just the $$$s or the $$$$ that's involved

After this it will be time to look into the rear diff - get something better than an open unit!

Cheers

Bennie

[tambox]

Not the diff - a worn out second gear in a turbo box. You should know the turbo box's abuse/issues with time. Rear diff stubs/shafts are easy to replace in my mind. I'm keen to see what happens anyway.

Starting with a worn gear is not the best, especially with how you are using it. Its nicer to use gears out of a known box, hard to do sometimes.

I think you've got this the wrong way around. A taller diff ratio allows the engine to apply more power/torque to the road with less stress to the drive gears in the gearbox. A shorter ratio applies more stress to the drive gears. So my 3.7:1 original diff ratio loaded up the drive gears more. Using low range compounds this further in both situations.

I'll clarify that a bit, I only ever broke driveline bits once I had converted the lockable box to 4.11.
3.9 or 3.7 was ok.
4.11 gave the abilities to 4wd "harder", when things broke, it was when I had lost traction, then got it back suddenly, generally on steep rocky climbs. The 4.11 allowed the spinning wheel/s to accelerate more quickly, so the shock applied to the driveline was greater when traction was suddenly gained. Its not "normal" driving, as you said above, that causes this to happen.
I used to run the lowest L 1,2 gears with the taller 3,4,5. You have many more options these days.

What's the 3/4 speedo drive gear?

The 3rd and 4th one piece gear on the pinion shaft, this has the speedo drive spiral in the centre of it. The spirals vary, you need one of the selection of speedo gears to work with that spiral. Seeing you are loving ratio calculations at the moment, do this the spiral/speedo gear to get the speedo correct (ish). There are a few different l series plastic speedo gears OEM, depends on diff/gbox type and wheels/tyres OEM.

I don't know if I'll get to the 4.44 this time - but it will always be at the back of my mind if I don't... But from what Rick has reported I'm keen for it - it's just the $$$s or the $$$$ that's involved

The 4.44 is fantastic off road (re Rick), you just have to learn to 4WD with a great deal of respect for the driveline, like Rick does:)

[vincentvega]

when I changed the speedo gears in my now deceased auto box I just went with the outback part numbers from the equivalent year model.

I figured the stock gears were set up for 24" tyres, the outback gears 26" tyres and that they always read slow from the factory. Ended up with a speedo that was bang on with 27" rubber.

easier in an auto though as diff ratios dont affect the speedo. the drive is on one of the output shafts.

[El_Freddo]

Ok, time for an update on this thread. Here's a pic of the munched second gear if you've not already seen it:



I'm not going to go for the 4.44:1 diff ratio at this stage - two reasons, first is cost (that I've not looked into, I don't have to as I know I can't afford it at the moment) and the second is the availability of a good front 4.44:1 ring and pinion gearset for modification.

Here's why I'd need some custom work on the pinion shaft - the lower gearbox is my locking centre diff box with the longer pinion shaft:



Also for comparison the Gen1 Lib and 5spd EA 1st gear is 12.5mm wide excluding that funky thin gear that runs with the 1st gear cog. The SG 1st gear is 15.7mm wide as it is. Here's a pic of the Gen1 Lib 1st and the SG 1st side by side - these are the lower shaft gears:



And the "juicy" SG gearsets:



I'm also hoping that this SG box will bring my speedo into line - it's a long shot but I'm going with the matched speedo drive from the SG box for the 4.111:1 diff. The drive spline is the same thread count but about 1.5mm wider in total compared to the EA drive thread.

I'm yet to find out if I need to mod the input shaft low range gear to make my 1.59:1 low range fit the SG's top shaft. I remember from Apline Raven's and PeeJay's thread that they needed to machine down the gear a bit to fit the retainer clip. And I need to find the details of torque specs for the upper and lower shaft's retainer nuts etc

I must say that I'm still hungry for 4.44s... I'll get there some day!

Cheers

Bennie

[El_Freddo]

And I need to find the details of torque specs for the upper and lower shaft's retainer nuts etc

An old thread (of mine!) turned up the goods via Toonga's links to FSMs.

The XT manual is about 1,140 pages in one go. I downloaded that and the 2003 Foz gearbox section of the manual

Thanks for that link Toonga, it's come in handy once again!

Now to get over this silly season and crack into the rebuild...

Cheers

Bennie

[El_Freddo]

Ok, need some advice

When I put the front cases together I can't select reverse.

But when I've got it split I can sometimes get reverse, if I have one shaft or the other removed I can get reverse to where it should be when fully engaged everytime.

I'm really over pulling this thing apart, done it three times now and it's driving me nuts! I first found out that the SG reverse gear has a longer tooth, so swapped over to the L series unit but forgot to check it's engagement with both shafts installed, it tested well with the pinion gearset installed - this seemed to be the one that wouldn't allow engagement the first time around.

Is it just that when on the bench you can't easily select reverse like the other gears with the front cases installed?

I'm struggling for ideas other than bolting it all back together and installing it - just don't want to put in all that work to find I can't reverse the car out the shed

Cheers

Bennie