Offroad gearbox build

NachaLuva said:
Have you worked out final drives in each configuration? eg, is 2nd low higher or lower than 1st high?
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2nd low is marginally higher than 1st high but with the 4.44s is marginally lower than standard sf 1st high.

Last weekend was another big gearbox weekend. Pulled the box out and pulled it apart. Checked over everything and changed the bearing on the lower transfer gear. Also checked the front diff setup. I also installed the low range and 1st gear oil feed whilst I was at it as I had completely forgotten about that on the first assembly. Put it all back together and put it back in the car. Not bad for 2 days work. I havent been able to tell it it was making any noise until today though as I had a front wheel bearing gone which was making a hell of a noise. Now that the wheel bearing is fixed I am happy to say it sounds nice and quiet now :)

On another note I love the new ratios in this gearbox with the 4.44s, perfectly suited to my gutless motor and with the taller 5th there is no real change in freeway rpm. Fuel efficiency, not sure about yet as I cant get my speedo corrector to work for some reason, just wont pick up the input signal from the gearbox no matter what I do. The other thing about this box which is a huge improvement is the 35:65 torque split, so much fun on and off road.

I still haven't had a good chance to test the box offroad but I am expecting great things with the twin LSDs and lockable centre.

Finally a few pics from the build. Completely forgot to take photos for most of it though...

Making the replacement coil for the centre diff
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4.44 gear almost completely shaved, a small amount more came off after this.
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And finally everything assembled in one half of the case
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Wow, you're getting professional !

I think that you can start upgrading gearboxes for the other members of the forum !
 
Yeah dude awesome job, especially fixing up that DCCD centre. Can say the twin LSDs and DCCD centre is a great combo. I'm stoked to see more people focusing on drive train and suspension and not just various combo's of springs and lift blocks!
 
You've done a great job :monkeydance:

Doing that coil must've been fun lol, glad its all working well now :biggrin:

Venom said:
I'm stoked to see more people focusing on drive train and suspension and not just various combo's of springs and lift blocks!
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Fortunately you've paved the way for this & shown us what works :biggrin:

Dedman said:
I also installed the low range and 1st gear oil feed whilst I was at it as I had completely forgotten about that on the first assembly.
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I'd been meaning to ask if you were doing that. IMO a very good idea. Originally I was going to do mine wired into the LR light so the oil feed automatically came on when LR was selected, but it was pointed out that I don't want it on while descending a steep hill as it would run dry

Now that the wheel bearing is fixed I am happy to say it sounds nice and quiet now :)
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:woohoo:

On another note I love the new ratios in this gearbox with the 4.44s, perfectly suited to my gutless motor and with the taller 5th there is no real change in freeway rpm.
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Awesome!

The other thing about this box which is a huge improvement is the 35:65 torque split, so much fun on and off road.
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So how does that affect the handling? Oversteer?
 
jf1sf5 said:
Wow, you're getting professional !

I think that you can start upgrading gearboxes for the other members of the forum !
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Haha I dont think it would be worth the amount of work that I put in, unless they paid me big dollars.

Venom said:
Can say the twin LSDs and DCCD centre is a great combo.
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Yeah I cant wait to test it out. The only short test that it has received so far I am pretty sure there was fuse blown on the DCCD as it was not as good as I was expecting off road with a wheel lifted. In all other situations it was better than the original box though. Im also very interested to see how the rear suretrac goes off road, so far the signs are good.

NachaLuva said:
Doing that coil must've been fun lol, glad its all working well now :biggrin:
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Yeah it was hell, 3 hours of meticulously winding wire neatly, hand were very sore by the end of it. Would have been impossible without the guide I made up on the ****ty wood lathe

NachaLuva said:
Fortunately you've paved the way for this & shown us what works :biggrin:
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Still to see how long the front diff lasts. I think it should be fine but a fair amount came off. Not quite into the contact pattern yet but close.

NachaLuva said:
Originally I was going to do mine wired into the LR light so the oil feed automatically came on when LR was selected, but it was pointed out that I don't want it on while descending a steep hill as it would run dry
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Im planning to make a variable speed controller that turns the pump on at a low speed with the low range light an then have 2 tilt switches, one that turns the pump on at a higher speed when climbing steeply and one that turns it off when descending steeply

NachaLuva said:
So how does that affect the handling? Oversteer?[/QUOTE

Well on gravel it certainly does, its great to be able to cut real hoops in a Subie but my rather sad motor really doesn't have the go to get it to do much on the black stuff unless it is wet. It does corner better at speed though with minimal powering with a much lower tendency to under-steer when you take a corner to fast. The 3 diffs give it a much nicer more controllable feel and have no ill effects of on road driving that I have found as of yet.

As I just mentioned my motor is getting quite sad, it has done what I like to call a Taza, ie burning a ****load of oil around 5L of oil between changes... Looks like a new motor or an upgrade is on the agenda not to far in the distant future
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Yeah its an AP suretrac. I have been trying to understand how they work/how effective they are but have not been very successful as of yet. Will be very interesting to give it a good off road test.
 
Thanks for the link Ratbag !

Seems to work like a clutch type differential (Cusco, Kaaz…) but not as "oversized" as these.
 
Hi Ratbag

From what I have read the suretrac in Subarus is a different diff to the one you linked. It is made by a different company, AP Racing and not Eaton and the internals look like the image jf1sf5 posted although some pictures of the internals do not have the spider gears and just the little pieces of metals as shown in the below link, not sure which version the Subarus have.

https://www.mycaterham.com/66828/117416.html

Again how it works I am not really sure...
 
Dedman said:
Yeah for an SG box a complete transfer case swap would be your best option. Bare minimum you would need the diff, both transfer gears and rear of transfer case housing.
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Do you need the DCCD rear housing or can the DCCD fit in the stock SG rear housing?
 
You need the dccd rear housing
 
NachaLuva said:
Do you need the DCCD rear housing or can the DCCD fit in the stock SG rear housing?
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The transfer case is made up of two section, the main bit and the back plate that has the bit the tailshaft goes into. As far as I know you could use the main section of the SG case but you would have to drill a hole for the DCCD wires. You will however HAVE to use the back plate for the transfer case from the DCCD box. You are far more likely to obtain a complete transfer case than just the back plate so I would just use the complete transfer case case from the DCCD box as it is far neater. The only thing is the DCCD box has the return to centre spring for the gear selector outside the box where as the SG has the internal version. I swapped it over so I had the internal version but I think the earlier sfs had the external spring anyway.
 
NachaLuva said:
OK thanks guys. Had an offer of a DCCD but no housing. Think I'll wait for a complete DCCD unit
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If your Foz is a '97-'98 (122hp), then you can take the DCCD without the housing, but its easier with the housing :icon wink:
 
My thoughts on DCCD

After playing around with this box a fair bit I thought I would share some of my experience with this DCCD that everyone raves about. My overall thought is that it is and excellent upgrade however I would still rather a locking AWD box for offroad. On road the DCCD is great and the 35:65 torque split is beyond brilliant in turning an annoyingly under-steering car into something that is great fun to drive even with the pissy little ej20. The car corners much better and I have not found it to tail happy.

Where I would prefer a true locking centre is in offroad driving under certain situations, in particular when balancing on diagonal wheels. In this situation the car will often transition between more traction from the back wheels to more traction to the front wheels and back again. The way the DCCD works means that to transfer from sending all the torque to the rear to sending all the torque to the front wheels means the diff has to fully unlock and then relock. This unlocking and relocking only takes about a quarter of a turn of the diff to go between fully locked and fully locked but as this happens the diff jolts the driveline somewhat. If you are in a situation where the amount of traction is distributed 35% front 65% rear and fluctuations in front to rear traction constantly causes the diff to transfer between Lock forwards and lock rearwards sometimes very rapidly which I think is less than ideal.

Maybe one day I will find one of these locking EJ AWD boxes...
https://offroadingsubarus.com/trihybrid_gearbox.html
 
Thus why I'm going 20kg. I find with my GT when you lock it there is non of this at all and it changes the cars offroad ability.
Wanna swap? I wanna go DCCD for onroad.

that is very interesting what your saying. I thought once it was electronically locked that was it. Possibly because you have the gen 1 DCCD diff that it does this. Or maybe your custom coil or controller.
 
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Nah I definitely would prefer the DCCD over the 20 kg. If the 4kg is bad on road for understeer the 20kg would be terrible. Plus I am just being picky with the DCCD. In terms of decreasing off-road ability the 1/4 turn from unlock to relock is only equivalent to 1/16 of a turn of wheel slip. It's just the slight jolt through the tranny when it's constantly changing between the two that I'm not a fan of.

100 % sure that is how the diff works. It requires a slight rotation of an output shaft faster than the diff casing to multiply the force produced by the locking coil (Force multiplied through some balls rolling in cams). When the output shafts want to rotate the other direction in relation to the casing then it naturally has to unlock and relock in the other direction as the balls roll down the cams in one direction and up the cams in the other direction.

The only effect that my rewound coil and controller might have is that it might not lock as effectively as a stock one. That being said I tested its locking ability by removing the rear tail shaft and seeing if I could spin the front wheel which I could on hard packed dirt without any issues. If I lock it on the black stuff and turn a corner I sometimes get tyre skip and sometimes clucking as the diff is overcome and unlocks but this what I've heard happens from everyone with DCCD who has tried it and is really expected as the front wheel are trying to push the car backward and rear wheels trying to push the car forwards all with very high traction thus creating far more load on the diff than would be experienced by just looking traction on one axle offrroad.

The other thing I am interested in is the life of those clutch packs in the diff. Only time will tell on that one...
 
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