AU IRS front diff support bush upgrade

[CAT600]

Got a SOLID job done today.

When I pulled the tailshaft off to remove the gearbox hence engine, I was sort of relieved to find a part failing on the IRS of the car.

I say relieved because several months ago I had the original diff rebuilt after 140,000kms and some dragstrip action and I was concerned that something was not installed 100%. My concern started when I found what originally appeared to be a loose (vertical movement) front diff support bolt, but when I checked the bolt with a spanner, it was tight into the subframe. On closer inspection the top diff mount bush had been hammered by the launches at Heathcote and the front of the diff was able to bang up and down about 8-9mm, kind of like a slide hammer effect on a launch. Now this is the movement that kills halfshafts on the B-series cars and I was keen to resolve it. So I took some measurements off a new bush (pictured) and then made the solid steel spacer with a protruding top section.

Old vs New:





Now normally the standard bush would have a large gap all around the outside of it and only have contact in the middle where the threaded weld-in spacer hangs down from the subframe around 9mm, but my new setup, combined with a 5mm disc of rubber (to insulate NVH) will transfer the reactive torque of takeoff through the whole subframe tube AND spacer:





This is a prototype and was made a bit thicker to correct a slight tailshaft alignment issue on my project car, but if the design works, I am happy to produce a few of the correct alignment design for anybody that may want to buy one for their AU.

Not a money making exercise, just a bit of a hand for anyone that wants to drag race their IRS AU a bit more confidently

[RG]

1) RG

[FTe342]

1) RG
2) FTe342

[BlacklistedXR]

1) RG
2) BlacklistedXR
3) Fte342

Nice!
Definetly will be in. Diff is out atm so may as well upgrade the diff support bush.

EDIT: Beat me to it!

[CAT600]

No worries, be good to get 10-15 as a minimum to get costs down so I will see how we go.

BlacklistedXR, what timeframe are you working to?, I will get a "STD" version made soon but I would like to get the machine shop to knock out 20 in one hit to keep costs down.

Daniel

[BlacklistedXR]

Originally Posted by CAT600

No worries, be good to get 10-15 as a minimum to get costs down so I will see how we go.

BlacklistedXR, what timeframe are you working to?, I will get a "STD" version made soon but I would like to get the machine shop to knock out 20 in one hit to keep costs down.

Daniel

Cheers Daniel.
Im waiting to receive my swaybars from Wilkinsons before i put it back in. I don't really have a timeframe atm, i dont mind waiting abit as i've lost my license and will be building the XR8 in the meantime. I would like to get a non standard version made if it will mean it will be stronger and handle more abusing then the standard version.
Do you have an estimate on how much it will cost Daniel?
Thanks mate,
Chris

[CAT600]

Originally Posted by BlacklistedXR

Cheers Daniel.
Im waiting to receive my swaybars from Wilkinsons before i put it back in. I don't really have a timeframe atm, i dont mind waiting abit as i've lost my license and will be building the XR8 in the meantime. I would like to get a non standard version made if it will mean it will be stronger and handle more abusing then the standard version.
Do you have an estimate on how much it will cost Daniel?
Thanks mate,
Chris

Sorry Chris, when I say "STD" I mean the same type of solid bush but set up at the original dimensions to suit a standard application..... the prototype I made for mine was a bit thicker as the pinion was sitting a tough too high as it was.

The litmus test will be in a few months time when my car is back on the road and has done some strip time.

Cost is an unknown as yet but It cost me $140 to get two bushes made but even allowing for a bit of my time to chamfer the leading edge of the top hole recess and the rubber bush spacer for NVH they should still end up around the $100 mark each plus shipping.

I'll keep you in the loop.

Daniel

[FTe342]

1) RG
2) BlacklistedXR
3) Fte342
4) pstap

[CAT600]

Thanks Shayne

I am going to get the second one I made modified to refect the OE required dimension and then get a locked in price for a batch order. By the time I have a fixed price for you guys, we will get the numbers close to where we need them I will have cut all the rubber bush pads and the machining will be done. Then it's just a case of hand finishing the spacers and send them off.

Daniel

[FTE217]

Question please...mine will hardly hit the 1/4,infact I'll say never as it just isn't me tbh but I do intend getting myself to Wakefield EC whenever I get myself organised.
I highly doubt I'll work my motor but again never know.
In saying that would I need this support bush at all with my above scenario ?

[CAT600]

Honestly the dragstrip would be a must have, but a racetrack is far more forgiving and you would be OK.

The best thing you can do is get under the car, grab the pinion flange (where the driveshaft bolts on to the diff) and push up and down. If there is a touch of movement I would not be too fussed about it (rubber compliance).

If there is a lot or it thuds up and down, you should put your name on the list.

Daniel

[UU TS50]

1) RG
2) BlacklistedXR
3) Fte342
4) pstap
5) Congo XR8

[FTE217]

Thanks Dan will check it out over the week.....

[BIGJB]

I would be interested as long as you are prepared to post to NZ.
Mine is well and truly shagged and I was just in the process of seeing what
is out there to replace the original one with.

[CAT600]

Originally Posted by 99GHIA

I would be interested as long as you are prepared to post to NZ.
Mine is well and truly shagged and I was just in the process of seeing what
is out there to replace the original one with.

Really? what was actually wrong with it? just the outside edge bent upwards?

Can you get me a photo of it as well?

I will post to NZ no dramas, the freight wont be much.

Looks like we have a definitive price on the bushes, with the machining of each spacer coming to $70, and my time (and material for the rubber bush) working out to $25 each means that each one will be $95 plus postage.

Daniel

[BlacklistedXR]

Originally Posted by CAT600

Really? what was actually wrong with it? just the outside edge bent upwards?

Can you get me a photo of it as well?

I will post to NZ no dramas, the freight wont be much.

Looks like we have a definitive price on the bushes, with the machining of each spacer coming to $70, and my time (and material for the rubber bush) working out to $25 each means that each one will be $95 plus postage.

Daniel

As soon as you can get one made Daniel then let me know and i will come and pick one up.
Thanks mate.

[bloggs24]

is this only beneficial for V8's? I do some drag racing in my VCT, will i benefit from it?

[CAT600]

Originally Posted by bloggs24

is this only beneficial for V8's? I do some drag racing in my VCT, will i benefit from it?

Any IRS car will benefit at the drags, If you are leaving the line hard then that bush is copping a hard time.

Daniel

[BIGJB]

Originally Posted by CAT600

Really? what was actually wrong with it? just the outside edge bent upwards?

Can you get me a photo of it as well?

I will post to NZ no dramas, the freight wont be much.

I will throw up a pick of it when I get the chance to get the car on the hoist.
To be honest it almost looks like it's be run over by a train lol.
It's just totally flogged and bent.

[CAT600]

Originally Posted by 99GHIA

I will throw up a pick of it when I get the chance to get the car on the hoist.
To be honest it almost looks like it's be run over by a train lol.
It's just totally flogged and bent.

That's it.

Mine was bent upwards like a bowl after less than 500kms and 10 passes at the drags.

A pic would be great later on.

Daniel

[bloggs24]

Yey, i think i might need this aswell, so MAYBE count me in.

1) RG
2) BlacklistedXR
3) Fte342
4) pstap
5) Congo XR8
6) Bloggs24

[CAT600]

Ok, a bit late but the bushes are done.

I have just done 10 for now but they will make more later if required.

I will post up some pics later and some bank details for payment

Daniel

[BIGJB]

I better add my name to this list.
Will send you a pm with my NZ address if you can please find out postage for me mate.

1) RG
2) BlacklistedXR
3) Fte342
4) pstap
5) Congo XR8
6) Bloggs24
7) 99GHIA

[xr393]

I might as well grab one too.
1) RG
2) BlacklistedXR
3) Fte342
4) pstap
5) Congo XR8
6) Bloggs24
7) 99GHIA
8) xr393

I'll pay in cash and pickup if that's all right?

Steve

[CAT600]

Ok then.

Bushes are done and payment details are as below:

Bank: Police and Nurses Credit Society
Account name: Melanie and Daniel Otway
Account no#: 183779
BSB: 806-015

For those that will pickup and pay by cash I will mark you paid when you get the bush.... it will come to $95.

In W.A. that want postage it will come to $100 even.

For those interstate the freight is going to be $10 standard (4-5 days) or $15 express (1-2 days) plus the $95 so let me know which way.

And lastly international to NZ is going to be $20 registered (4-5 working days) which totals $115 shipped

Now just a couple of photos to show the stock vs damaged stock vs what I have ready to ship:

Stock brand new:





Brand new one with 10 passes at Heathcote under its belt in the T1:





The new bush setup with rubber pad:









Now as you see it in the photo above, the RHS of the bush (where the top recess is relieved with a carbide burr to clear the weld on the subframe tube) is tapered down to match the angle of the diff support casting underneath. The smallest part of the taper (16mm thick) faces to the front of the car. The rubber then sits under that and the whole assembly sits on top of the diff casting.... then simply loctite the bolt and install/torque to 75lbft and away you go.

Daniel

[UU TS50]

Cheers Daniel will be in touch over the next week to organise pick up and payment

[CAT600]

1) RG
2) BlacklistedXR PAID TAKEN
3) Fte342 PAID SHIPPED
4) pstap
5) Congo XR8
6) Bloggs24
7) 99GHIA
8) xr393
9) Congo XR8

[BIGJB]

I'll organise some cash over the next week for ya mate.
Just trying to juggle a few things atm.

[CAT600]

1) RG
2) BlacklistedXR PAID TAKEN
3) Fte342 PAID SHIPPED
4) pstap
5) Congo XR8 PAID TAKEN
6) Bloggs24
7) 99GHIA
8) xr393

[UU TS50]

Cheers for the part Daniel
and had a nice chat while i was there