GC8 DIFF Bush Inserts

abeiq
Probationary Driver
Posts: 85
Joined: Sat Jun 06, 2015 10:05 am

GC8 DIFF Bush Inserts

Postby abeiq » Mon Jul 25, 2016 11:49 pm

Hey all,

Did a little DIY on the weekend - been meaning to get to this for ages, i didn't take many pictures of the process because i didn't think i would get this far but now im done and im happy!!!

Being 18 years old, my 98 GC8 rear diff bushes began to get flogged out and noisy, after putting in the Hardrace engine, tranny and pitch mounts i was over the moon in the lack of movement in the drivetrain but still felt there was a little more to be desired - and this was it - now shifts are smooth, down shifting/rev matches are perfect!!!

I will use pics from google where possible, but try to explain best as possible.

the diff bushes wearing is a common issue with the GC8 and short of removing the rear subframe, this was the only feasible resolution. which makes this harder is that there is no diff inserts to suit the GC8 available.

Be warned, i am not responsible for any damage to your car as a result of installing these/installation issues!

This is probably one of the easiest mods i have done to the car to date and yielded the best results - there is no noticeable NVH - well i dont notice it - Acceleration is straight on, taking off from a stop feels fantastic and as above, the rev matching feels amazing - i cant recommend doing this highly enough!!!

Lets begin;

Parts and tools:
- Jack
- 17mm spanner/socket
- breaker bar/ratchet if applicable
- Superpro Rear Differential Support Mount 'Void Filler' Bushing Set SPF4297K - These are made for newer rexies - see below
- sharp knife for trimming to fit
- Grease (preferably lithium grease/bushing grease)
- washers large enough to cover majority of diff bush insert - i grabbed mudguard/mud flap washers from bunnings - my kit did not include the washers
- step drill bit/large drill bit to widen the hole in washer to suit diff bolt diameter

My diff bushes may be different to yours as i have a early build 98 GC8 - not sure if there are any differences see pic below from google of bushes similar to my ones

Image

1. Get the back in the air, high enough to work your way around under the car (i used DTM low ramps for sufficient room)
2. Jack up the Diff slightly so there is an even gap in the diff bush
3. Prepare washers by widening hold in center to fit over duff bolt diameter
4. prepare diff inserts, this may take a little bit of testing and trying - cut bush inserts narrower and thinner to slip inside diff bushes - i made mine just narrow enough to fit in voids and just thick enough to need to be forced into place

The red spots in this image is pretty much the cut lines, you want to cut down these until you hit the bottom of the insert without cutting through the insert - i will try and take mine off to show the detail a little better

Image

Cutting is necessary as there are to my knowledge, no inserts to suit GC8's (and i did a crap load of looking) - these inserts are made for newer 08+ rexies and will not suit GC8's in their standard form.

5. remove nut from diff bolts using 17mm spanner/socket - these are done up FT from factory (F**king tight) so prepare to need some decent force
6. grease up bush and attempt to slide in
7. this may require a great deal of force to get in - i ended up greasing the crap out of the bush, putting it into place, slipping the washer back over and using the nut/washer to force the insert in. i then backed this off all the way to ensure that the insert was seating in the bush correctly
8. Reinstall nuts and tighten down to FT specs.
9. Finished install - see pics
Image

10. Take the car for a drive and enjoy.

11. Drive 100kms and double check tightness of nuts :)

This also removed the knock from the rear of my car. If anyone is interested in getting these but is concerned about modding the bushes, i can probably buy a few of these and cut them into shape and test on my own car, i can also provide suitable washers etc and probably do them for $50 shipped to your door if there is any interest.

Please provide any feedback :)

Cheers

mv75
WRX STi Driver
Posts: 840
Joined: Sat Dec 27, 2014 9:26 pm
Location: Brisbane Northside.

Re: GC8 DIFF Bush Inserts

Postby mv75 » Tue Jul 26, 2016 4:39 pm

Nice dude. I got the orange AVO ones on the gc8. Had to trim them down too. Pretty much went the same way you did, except the washers were already a perfect fit, used a breaker bar on the nuts to get them off, and since my car is standard height, didn't need to jack it, all done on the floor. :)

I had a thump from the rear when using the throttle while at speed, these fixed it right up. Is a good mod. Gave the standard bushings a good inspection, no splits or anything, they're just too soft. These are also a much cheaper alternative to the diff brace, and do the same thing. That is if you have bushes that can take inserts, doesn't look like my 2003 gd can. :(

abeiq
Probationary Driver
Posts: 85
Joined: Sat Jun 06, 2015 10:05 am

Re: GC8 DIFF Bush Inserts

Postby abeiq » Tue Jul 26, 2016 9:00 pm

Thanks mate :)

for some reason this kit didnt include washers -_________-

for the nut, i ended up using another spanner on the back of the 17mm one to get the leverage - it was nuts (literally - hahaha get it)

yeah mine had no splits either they were just flogged out from age but not physically broken :D.

my diff use to make tonnes of noise when going over bumps? and now is gone :D

damn that sucks dude, apparently subaru have a tool to do it without subframe removal, i'd say its some kind of puller would be nice to have.

In terms of getting the car up, i only did it because i was doing my RSB then remembered i had the bushes and decided it would be perfect timing as i had my rear diffuser off to get the RSB in.

LilSaint28
Learner Driver
Posts: 3
Joined: Sun Aug 21, 2016 7:26 pm

Re: GC8 DIFF Bush Inserts

Postby LilSaint28 » Thu Feb 23, 2017 8:17 pm

Hi all. pretty new here. just wanted to know if there is any guide on how tight should the bolts be for the diff? Planning to DIY my 07 WRX as car service from the dealer is far expensive. Thanks heaps.

mv75
WRX STi Driver
Posts: 840
Joined: Sat Dec 27, 2014 9:26 pm
Location: Brisbane Northside.

Re: GC8 DIFF Bush Inserts

Postby mv75 » Thu Feb 23, 2017 9:15 pm

LilSaint28 wrote:Hi all. pretty new here. just wanted to know if there is any guide on how tight should the bolts be for the diff? Planning to DIY my 07 WRX as car service from the dealer is far expensive. Thanks heaps.


You'll probably need this instead for an 07;

viewtopic.php?f=102&t=86113

LilSaint28
Learner Driver
Posts: 3
Joined: Sun Aug 21, 2016 7:26 pm

Re: GC8 DIFF Bush Inserts

Postby LilSaint28 » Tue Mar 14, 2017 12:32 am

Thanks man. All good now.

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