Modifying gearbox mount points to chassis

[Warps]

Hi all.

While trying to identify the source of vibration in my gearbox (it's rubbing the cross member or the body somewhere) I have found the gearbox cross member to be cracked, and the rubber mount to be shagged.

As the mount is a modified RX2 item (tags welded onto it to fit the TQX gearbox) I obviously can't just grab a new one off the shelf. Because of this, I'm considering whether to repair and strengthen the cross member (extremely poor design) or bin the whole lot and fabricate something that actually works.

Upon further investigation, I have found that the gearbox cross member mounts on the body are cracked where they weld to the transmission tunnel. What I would like to do is drill these off and relocate further back, so that they line up with the gearbox mount hole, so that I can then make a new cross member that will mount the whole gearbox in a less dodgy manner (rubber mounts aren't much good at resisting bending moments - I dare say the main reason for cracking in the trans tunnel)

Now, after reading this in the CAMS manual:

(ii) Gearbox: The gearbox (and the number of ratios) is free, save for the following:
• no modifications may be made to any bodywork to accommodate a gearbox, save for the drilling of holes to support components, or to facilitate the fitting of the gear change mechanism;

I get the distinct impression I'm not allowed to move the body mounts rearward (which is a bugger, as it would give me more clearance for the gearbox, right where I suspect the box is hitting the body). Can anyone confirm that my interpretation of the CAMS manual is correct?

Funny thing is the S4 RX2 has 2 sets of mount holes, the rear most ones being pretty close to where they need to be for this to work

Or should I just be done with it in the knowledge that nobody is ever going to take a tape measure to my gearbox mounts, given I'm not about to start winning any major events.

[afifield]

I removed the mounts from the tunnel to replace the bolts, but then put them back in the same place because of that rule. To fit the S4T box I just made up a plate (50x6mm) with offset holes for the mount, and braced the angles

[Warps]

Yeh, I was contemplating whether to remove them to repair the cracking properly, or just weld it up as it sits. Being able to relocate them would give me more reason to remove and do the job properly.

So, the fact that a later model RX2 has different mounts doesn't help us at all?

Also, I don't suppose you know the bolt hole spacing where the rubber mount bolts to the S4 gearbox? I need to find an off the shef mount that I can bolt to my gearbox, then make a cross member to suit.

Thanks

[Kaptainballistik]

Originally Posted by Warps

Hi all.


• no modifications may be made to any bodywork to accommodate a gearbox, save for the drilling of holes to support components, .

So drilling holes is Ok.To support components. Like the crossmember.

Thus you use a piece of box tube that goes between the chassis rails that has the gearbox mount on it. And make sure it goes close to the rails to stop the dreadded tunnel cracking..... notch it for exhaust clearance. Big plate on top of each mount will distribute the force nicely!

The Intention of the rule is the key here, Its to disallow things like changing tunnels on Escorts to allow for the fitment of Getrags, Not to stop you changing mounts. And you can use A S4 RX2 mount as the car is type approved.

Also Motor mounts are free just not their number......( It mounts the drivetrain......which includes the motor)

Yes, Its been queried and OK'ed, Same as the Anti dive kit ,the pods........

And you guys think I ask a few questions about the VR$........... Brent Blackwell and Phil Boyd had their ears chewed off!

[afifield]

Originally Posted by Warps

Also, I don't suppose you know the bolt hole spacing where the rubber mount bolts to the S4 gearbox? I need to find an off the shef mount that I can bolt to my gearbox, then make a cross member to suit.
Thanks

It was from an older Holden. Can't remember the model, but I think it was a ute (WB rings a bell, but that may be the radiator hoses). It wraps around front and back of the rubber. Downsides are that the rubber is a bit soft, it uses imperial threads and I had to re-drill the top holes. Tried the eurathane replacement, but it failed dismally.

[oldmanbluebird]

I'm I not in the right frame of mind or what?
but to me its like the irs in a bluebird question that was asked before,
and I ask myself
"when was the last time anyone looked under a car to check IRS or engine mounts, gearbox mounts or what ever"
Its would be different if your running a wrc or with the top end of town type of people but I honestly don't think anyone cares unless you beat some knob with out a life who wants to complain about everything and anything and in that case the person would always find something to complain about.
I return a question " has anyone ever had their car picked for a alteration like that"
tell me if I'm on the wrong track and its really that strict

[Warps]

That's pretty much what I was thinking, but I'd like to keep my car in the spirit of the rules, just because that's the kind of bloke I am (yes, blindly following meaningless rules established by some random a long time ago, far, far away )

Thanks for your feedback Pete - again, you've proved to be a wealth of wisdom to us rotary tragics

Andrew - the parts dude gave me a VN Dunnydoor mount to look at, which was almost but not quite the same (was half a hole out). I'm still half tempted to choose something common, cheap and with similar bolt pattern, then make up an adaptor plate to bolt the mount to the gearbox. If I put in enough adaptors, spacers etc. then I'm sure to end up with a reliable Mazda, right