Gearbox ratios - new build

YouTube · Post by **El_Freddo** » Mon Mar 09, 2015 9:02 pm

Ok, after talking ideas with RSR I ducked out to the shed to compare the two cases.

Turns out the SG case mounts the reverse slider gear further away from the main shafts and runs a larger gear - same number of teeth with the same spacing as the old L series unit I had, just larger teeth.

The difference between the two slider gears is interesting but even when using the smaller L series gear it still won't engage - so something needs to be machined to fit.

I'm thinking it will either be the slider gear or the first/second selector ring which runs part of the reverse gearing system.

Distances between the input shaft bearing's outer edge and the edge of the slider gear's shaft:

Phase 1: 1.88mm
Phase 2: ~2.00mm (once I found a difference I didn't measure accurately :/)

Small difference but it'll count.

Now to work out what needs modification to make this set work!

Cheers

Bennie

tambox · Post by **tambox** » Mon Mar 16, 2015 9:38 pm

That reverse shaft is problem is a headache, I have seen it a couple of times when fixing boxes, never bothered to find out what the boxes came out of.
I just swapped the cases to match the gears, the people who wanted the boxes didn't care about ratio's.
You can also end up with the opposite, heaps of backlash, seen that as well.

YouTube · Post by **El_Freddo** » Wed Mar 18, 2015 11:21 pm

Yeah I'm still not 100% sure where we're going to go with this yet. RSR and I are trying to nut something out. Worst case scenario I end up using the 8 bolt cases as it looks like I'll easily be able to move the cable clutch fork to this case.
I'll have to get the oil feeders welded in and sort the diff specs but otherwise everything *should* just drop in and go...

Cheers

Bennie

YouTube · Post by **El_Freddo** » Sun Mar 29, 2015 10:48 pm

Now decided to go with the SG cases...

Stay tuned (but don't hold your breath! This has taken way too long already

)

Cheers

Bennie

longy99gt · Post by **longy99gt** » Mon Mar 30, 2015 10:31 am

nice work,
In similar news i have been collecting parts for my Low Range Conversion in to my 2007 2.5 XT Forester,
Currently have the SG 5MT non turbo box in pieces, removed the 1.19 ratio low range and have the 1.44 SF low range ready to drop in,
I will then pull the gearset (2nd-5th) from the XT and drop them into the low range box,
I will finish with the SG non turbo low range case, SF 1.44 low range, 4.11 final drive ratio, and XT gears,
that will give me a reasonable low range, and lower RPM accross all gears and finish with just over 2500rpm on the highway, down from almost 3000.
will also pull the rear LSD from the XT to put into the 4.11 rear diff,
hoping to find a front LSD to complete the box.

I'll stay tuned to see how yours goes,
Adrian

YouTube · Post by **El_Freddo** » Tue Mar 31, 2015 8:14 pm

longy99gt wrote:I will then pull the gearset (2nd-5th) from the XT and drop them into the low range box,

You can't pull second. It's cast on the input shaft with 1st gear. You can change 3rd, 4th, and 5th. I'd highly recommend swapping fifth for a ratio that puts your revs where you want them to be on the open road at cruise speed.

Make sure you have a good press available as that lower 5th gear is one hell of a nasty sucker to remove! To put it back on shove it in the oven for 20-30 mins at 200 deg (makes the kitchen smell, err, lovely!) and it will just drop in place and lock on. MAKE SURE you have the woodruff key in place!

What final ratio do you have currently? 4.111:1 or 4.44:1? If 4.44:1 try and use this ratio as it will give you better crawling ability over the 4.111:1, but you will probably have to shave the crown wheel to clear the low range gearset.

Sounds like you're well on your way to a good build for what you want anyway!

Also, what ratios does your XT have at the moment?

Cheers

Bennie

YouTube · Post by **El_Freddo** » Tue Jul 07, 2015 11:17 pm

Ok, FINALLY the gearbox is in and here are the results:

I ended up using the SG cases to overcome the SG reverse gear not working in a phase 1 set of cases (With SG cases). Everything works smooth in the SG cases.

I swapped 5th ratio. Am now wondering what I swapped it to as the calculator I used has not returned the expected revs to the real world revs at cruise.

So at 100km/h I'm pulling ~3000rpm or a tad over and at 110km/h I'm revving at ~3250rpm. Higher than I wanted! I'm yet to hook up the cruise as I need to pinch some borrowed parts back from Redback to make it work again.

I'm sure I dropped the 0.871 5th gear ratio in, so I don't know what I did wrong there, OR the other thing could be that my tacho doesn't read perfectly accurate with the EJ conversion.

The choice of running the stock SG speedo drive for the 4.111:1 ratio was a better one over the last one used. My speedo now reads about 4km/h UNDER the speed I'm doing - so it's a real trap for speeding which I want to avoid! With that said sticking with the last speedo drive (liberty 3.9:1 unit) may have been better as the driving gear changed between the SG and my original gearbox setup, main reason for this is that the previous gearset was an EA set, thus the driving gear was slightly smaller but with the same number of teeth.

I'm now going to see if I can mess around with the instrument cluster to have the speedo read with more accuracy, and it seems to "get stuck" at times while accelerating up to speedo or when accelerating hard which I'd like to sort out.

I've found the gearbox pretty sensitive as in it requires more precision in gear selection from second to third; a number of times I've gone 2nd to 5th

This could also be due to driving Redback with a large "throw" to the right from 2nd to 3rd.

This gearset is also much closer together than the last. To keep the same sort of space between gears that the last box had I reckon I would've been better off going with a dual range Impreza gearset.
I'm not complaining about this, it's just different. I can easily be in fourth comfortably by the time I'm pulling 40km/h, but I can also rev 3rd out to 100km/h and not be on the red line. Yes I've tested a few things out in the short runs I've done

The next test will be to try it out offroad - which will mean sorting out the low range as I've locked the box in high range while I make a better arm for my low range lever...

Cheers

Bennie

vincentvega · Post by **vincentvega** » Thu Jul 09, 2015 10:20 am

well done mate. impressive work

longy99gt · Post by **longy99gt** » Mon Jul 13, 2015 3:38 pm

those readings are correct for that 5th gear,
.871 is a very short gear, you should have sourced the 0.78 from the SG set,
or even the 0.738 from the SG XT set,

as i am doing a similar build, i have checked all the ratios extensively.
there is a phone app called gear calculator you canget for free and put all the info in. seems pretty accurate,

I am going with the SG case (NA) and using the SF 1.4 low range, then as much of the SG XT (07) gearset (3/4/5th) while keeping the 4.11 final drive ratio.

have everything except the new clutch and gearbox oil.

Longy.