tiddy1 Posted July 17, 2008 Share Posted July 17, 2008 How much load is taken through the transmission tunnel aluminium panels due to torque loading and chassis flex and may be thermal expansion of the panels? I am wondering as on my car these panels seem to be cracking quite badly as though they are experiancing some heavy cyclic loading causing fatigue Simon Link to comment Share on other sites More sharing options...
rgrigsby Posted July 17, 2008 Share Posted July 17, 2008 That's very odd, not something I've ever heard of before. Have you got any pictures? What generation chassis is yours? centre handbrake or under dash? Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
tiddy1 Posted July 17, 2008 Author Share Posted July 17, 2008 Its a 1994 chassis with under dash handbrake, I will take some pictures Link to comment Share on other sites More sharing options...
Dickie Normuss Posted July 17, 2008 Share Posted July 17, 2008 Just a thought, but could the ali skin be taking more load because something else like part of the chassis has broken? VX HPC - Loud and proud here Watch out, whatever hits the fan will not be distributed evenly Link to comment Share on other sites More sharing options...
rgrigsby Posted July 17, 2008 Share Posted July 17, 2008 My thoughts exactly, that's the only reason I can think of for something like this to happen. Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
Irrelevant Posted July 17, 2008 Share Posted July 17, 2008 like part of the chassis has broken Cruciform structure at the back of the tunnel is a known weak point - easily inspected by removing the cover though. Link to comment Share on other sites More sharing options...
Nick Pargiter Posted July 17, 2008 Share Posted July 17, 2008 Cracking panels sounds a bit alarming, would like to see the photos. It does sound like there is a problem elsewhere with the chassis. My 94 chassis would creak and flex if driven over humps at an angle, the rivet holes through the ali panels had opened up allowing things to move around more The old transmission tunnel does not really do much other than cover the propshaft. The newer one with the centre handbrake does provide some torsional stiffness to the chassis. Nick Link to comment Share on other sites More sharing options...
tiddy1 Posted July 17, 2008 Author Share Posted July 17, 2008 My thoughts were that something must have broken but I have done a careful inspection of every tube and weld (that I can see) and it all seems in one piece. there are 4 cracks, two on each side, all about 20mm long .at the rear of the tunnel they come down from the area around the cruciform and at the front they come down either side of the gear stick opening. Iam trying to work out if they are new and hence worring as they must have grown at an alarming rate, or are slow cracks which have grown over the 14 years of hard use (62K miles) in which case not so worrying Simon Link to comment Share on other sites More sharing options...
millsn Posted July 17, 2008 Share Posted July 17, 2008 My tunnel used to flex on hard acceleration (180-200 bhp). Possibly the same thing, wasn't anything wrong with the chassis that caused it. Link to comment Share on other sites More sharing options...
Dickie Normuss Posted July 17, 2008 Share Posted July 17, 2008 Flexing is ok but cracking would suggest to me that it's taking more load than it should be. VX HPC - Loud and proud here Watch out, whatever hits the fan will not be distributed evenly Link to comment Share on other sites More sharing options...
Mavic82 Posted July 17, 2008 Share Posted July 17, 2008 All the ali skins on the chassis are stressed pannels and add a lot to the torsional stiffness. That is why in the 90's the rivet density increased to help further increase the stiffness. After a lot of use these could crack especially if the crack starts at a stress raiser such as a notch or fretting point. If the chassis tubes are all OK then replace the panel and carry on, it may be you will find loose rivets in another area which could also raise the loads in that particular part of the panel. Cheers Link to comment Share on other sites More sharing options...
Tyrone Posted July 18, 2008 Share Posted July 18, 2008 I have two splits in the ali tunnel cover on mine. They did not appear until I put the cage on, which, it is generally agreed, stiffens the whole chassis. I put the splits down to the fact that I stood on the tunnel to get out of the car with the cage on. Now the cage is off I have marked the length of the splits as a 'telltale' to see if they get worse. NE Area Rep Though cowards flinch and traitors sneer, We'll keep the red flag flying here Link to comment Share on other sites More sharing options...
CageyH Posted July 18, 2008 Share Posted July 18, 2008 It may be worth drilling a small hole at the end of the crack, as this will help to stop the crack from propagating further. Only dead fish go with the flow....! Link to comment Share on other sites More sharing options...
elie boone Posted July 18, 2008 Share Posted July 18, 2008 Beware if you drill in the tunnel panels, there are electrics, fuel and brakelines on the inside of it. Link to comment Share on other sites More sharing options...
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