Rally's MY04 Forrie- Poverty Pack special

That guy is an artisan with the death wheel.

He's a bit of a guru with Subaru's I have to tell you. He's the one who has done all the work on the diffs- including putting the 06 STI 6 speed front diff in a DR 5 speed. I think he was the first person to do it.

I have begun a new project with the Forrie. A gearbox and rear diff upgrade form the centre of this project. I had a spare gearbox lying around doing nothing and so I decided to have it overhauled. It will get a stronger first and second gear set from a later model gearbox. 3rd, 4th and 5th will be from a turbo box, with 5th being the tallest available 0.738 ratio. Final drive will be 4.44:1. All gears including low range will be shot peened for extra strength. I did the maths and while in gears 1-4 the gearing will be shorter, with this extra tall 5th it will cruise at lower RPM in top gear.

But the interesting part of the project is really a project in itself. I recently purchased an R180 rear diff from an MY10 WRX. I want to try and install a locking centre. The centre itself is expected to be an e-locker. Originally intended for use in a different brand of car, the plan is to see if we can get it to fit inside the Subaru R180 housing and mate it up to the axles and crown wheel. Initial investigations have shown there to be some issues which need to be sorted, but we are quietly confident we might get there. Whether or not I go the whole R180 rear end, or run a hybrid R180/R160 rear end I have not decided. While I am at it, I will look at installing a GD Impreza rear sub frame to see if that will improve the handling

Having a locking centre and rear diff, plus a torsen front diff, should give the car some pretty impressive capability. We just need to see if we can do it.

^ very interesting!

It would be the first rear diff locker...

Hmm. I'm a bit concerned about a centre locking diff plus rear locker. Could end in tears!

Perhaps better to have two LSDs? These would allow torque wind up a means of escape from the drive train when the centre is locked.

My centre locker works very well. A rear locker in combination would be ultimate! You'd ONLY use the rear locker when needed in low traction situations.

Rally, if you're building your box with the SG first/second combo in the SF cases, your reverse gear won't work once it's all bolted together and correctly torqued. In the SG box they moved the reverse slider gear about 1.5-2mm away from the drive gear. They also added a bit more meat in the diameter of the reverse slider gear and the drive gear. This does not allow you to engage reverse.

Everything else will work as it should though. I considered shaving the drive gear and slider gear to reduce the height of the teeth so it'd work. But I ended up going with the SG cases - easy to fit everything and a stronger case too.

Your build sounds good though!

I've heard about the r180 being a direct swap with the lockers. A mate told me the 4x4 Datsuns had an r180 in the front end and that some of these were fitted with the manual locker. Apparently the diff centre was interchangeable with Nissan/Datsun's rear diff that basically ran the r180 in a solid axle setup...

I never got around to messing with these. My issue would be adapting the output axles to match my factory rear shafts.

Good to see someone giving it a go. I've heard the new navaras with the factory locker runs the r180 diff setup in a solid axle configuration. In theory this should drop straight into an r180 independent diff housing and work.

Cheers

Bennie

Cheers. I am not doing the gearbox build myself. I gave the bloke doing it the gearbox code so it is up to him to get it sorted. I won't be using any SG gears except reverse.

The biggest problem with the diff conversion is axle retention. We believe we can overcome this and if so we should be good. IF.

The reverse gear issue only applies to early 4 bolt sf boxes.

I picked up the axles, hubs and rear brakes only to find that the rear axles don't fit the hubs. I had originally intended to use axles which would fit my existing hubs and the R180 diff, but went a different way which meant using R180 hubs. I may end up going back to my original plan if I cannot get the axles I need.

jf1sf5 said:

It would be the first rear diff locker...

Click to expand...

Not the first rear diff locker in a Subaru, but the first of this type. There have been around 10 (or more) Detroit lockers plus a Brumby with a 4wd locker diff modified to fit

Looking forward to seeing how this goes

NachaLuva said:

Not the first rear diff locker in a Subaru, but the first of this type. There have been around 10 (or more) Detroit lockers plus a Brumby with a 4wd locker diff modified to fit

Click to expand...

Ah, ok, didn't know that !

Any links to see how it was built ?

I spent Saturday taking the rear end out of the car. All the R160 bits have been replaced with R180 bits, plus twin piston rear callipers. Due to being sick last year, I had to take things slowly and pace myself, and I was utterly exhausted at days end. Today, a mate of mine installed the Hi-Tech exhaust system, which is the same as what I have on the Impreza from the cat back. The Impreza runs a different dump pipe to the Forester. So that is stages 1 and 2.

Stage 3 will be to install the new gearbox, which is currently being built. Stage 4 will be to see if we can install the locker.

jf1sf5 said:

Ah, ok, didn't know that !

Any links to see how it was built ?

Click to expand...

Detroit lockers are a pretty crude way of going about it. You can also unintentionally unlock them. As peter Brock discovered at the start of Bathurst once in the late 70's when it unlocked and he got swamped off the line with what effectively was a single spinner.

An update about how the project is going. Not much has really happened in the last week. I picked up some STI R180 rear axles to replace the WRX R180 rear axles. The STI ones are stronger and are a better fit. The twin piston rear callipers have now been overhauled, and along with the new discs have been installed. The brakes have only been partly bled because we ran out of time. Next weekend the car goes in to have the new gearbox installed. Only once the gearbox is installed will work be able to start on the actual diff locker project

Have you had any problems with your actual gearbox ? Or are you just wanting to play Lego's ?!

Will be very interested about the r180 rear diff locker, take some pics !

Sloppy gear change with dccd was the main issue, along with wanting to strengthen it up to cope with towing and the turbo engine. Also took the opportunity to improve the gearing.

You have an auto version of the DCCD controller ? And that made your gear change sloppy ?

Controller has nothing to do with it. It's a mechanical issue of some sort

On Saturday after a lot of bleeding we finally got the brakes to work. It has never taken me so long to bleed brakes and I don't know why. The ABS light is on. We think mucking around with the wrong axle damaged the sensor. I have a spare so I will fit that after the gearbox goes in. The exhaust is hitting the tow bar, so we need to fix that and stop it moving around so much. The axles that are in there now are only in there temporarily, as one belongs to someone else and the other is not as strong. The old plated rear diff and gearbox are now going to be sold, so if you want a better off road car check out the for sale section of this forum.

The gearbox has now been installed and the first thing you notice is the gear change is so much better. Had to replace the drivers side rear wheel bearing, due to being supplied the wrong axles as mentioned previously. I now have 2 STI rear axles and there are no problems. The new exhaust fits better, although it does drone more than the supposedly same system in my WRX. Put it down to be a wagon whereas the WRX is a sedan. So that is STage 2 now completed. At the end of the month, I am going on another camping trip. Once I come back, we start Stage 3- The E-Locker for the rear diff.