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Old 04-30-2012, 09:48 PM
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Transmission Tunnel body work -- will cutting weaken the car?

Hi guys,

When I installed my T56 into my Jag XJ6, I had to cut the transmission tunnel opening wider, as well as extend the tunnel rearward. The cuts werent the best, and I'm in the process of trying to make them a bit nicer so i can rivet a new plate on. However, because of the design of the jaguar's tunnel, there is a circular hole that is present for the old automatic transmission shifter linkage.

To make the hole flat enough to be able to put a piece of patch metal over, I'll have to cut into the hole -- will this mess with the structural integrity of the car's floorpans? If i had a welder, I'd just weld a new piece of metal to bridge the hole but since I don't, will cutting the transmission tunnel hole bigger on this one side cause me any grief? I really want to get the hole patched up to stop the hot stinky air from rising into the cabin, and reducing the noise -- but i'm just nervous with how this cut will affect integrity...

Thanks in advance!

Tyler

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Old 04-30-2012, 09:54 PM
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Not knowing the car very well I can't say how much you could cut. But generally speaking you could cut the living crap out of a transmission tunnel and it would do next to nothing. Post some photos of what you are planning.

Brian
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Old 04-30-2012, 10:51 PM
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ill get some photos of the area in question, and post them tomorrow -- its kinda hard to know what im talking about without some visuals ;-)

Thats good to know about the cutting -- sounds like i'll be ok, and at the very least i can weld-patch it later.
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Old 05-01-2012, 03:47 AM
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I would think that if the car is a unibody, it would affect it more than if the car has a full frame
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Old 05-01-2012, 08:01 AM
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xj6

The jag is a unibody, I've dropped a few ifs and irs out of them but never paid any attention to the trans areas . They use reinforcements in various areas. If you are cutting thru reinforcements instead of just floor skin you should add new ones, you could shape channel , angle etc then use drill point metal barn screws, primer the spots before and after screwing it together.
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Old 05-01-2012, 10:24 AM
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i'm not going to be cutting through anything thicker than the trans tunnel material, its not very thick. I certainly wont be cutting through anything that is reinforced.

Since you're familiar with the body, do you know the hole that I'm talking about? Its on the driver's side, its where the old automatic shifter linkage slipped through the floorboards from the cabin.
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Old 05-01-2012, 10:47 AM
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The Jag is unibody. The rockers provide most of the bending stiffness, but the trans tunnel adds to that. I would strongly recommend WELDING new metal, not riveting.
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Old 05-01-2012, 11:26 AM
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Here is a pic of the XJS model getting the same treatment as I gave my car:

http://dl.dropbox.com/u/24984984/Shifter%20A.JPG

http://dl.dropbox.com/u/24984984/Shifter%20B.jpg

I drew arrows so you can see what metal would be affected. In essence the hole with the lower arrow on Shifter A would merge with the top hole, becoming a "super hole". What do you think? Weld, or leave it as is?

As for the riveting:

It was going to be just over the small hole where the shifter comes through the floorboards (the top area, around the shifter tower) -- but now that might possibly cut the hole a bit bigger, i'll have to either have a combination of riveted top hole & welded side, or just leave the area alone altogether. I'll post some additional pix up at lunch -- if ya'll could let me know what you think... if its necessary to even patch the hole or not, that'd be really helpful.

Last edited by tylerwerrin; 05-01-2012 at 11:36 AM.
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Old 05-01-2012, 12:59 PM
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Another option is to stiffen around the opening. Craft a piece of metal as thick (or slightly thicker) than the floor pan material you are removing. Cut the piece into the shape of an oval, that is, with a hole that will match your floorboard cutout. Weld around the inside of the oval, and the outside, with the oval clamped snugly to the floorboard. The width of the oval (if you make the outside profile an oval as well) should be at least twice the minor diameter of the opening (I assume it's ellipse-like, I cannot reach the link right now). The idea is to stiffen up around the opening, since you've removed some stiffness by cutting it in the first place.

Pat
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Old 05-01-2012, 02:05 PM
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Quote:
Originally Posted by joe_padavano
The Jag is unibody. The rockers provide most of the bending stiffness, but the trans tunnel adds to that. I would strongly recommend WELDING new metal, not riveting.
X2 on this, incidental riveting done with things like blind rivets simply aren't good enough. To carry loads on rivets you need to be able to rivet like they do on airplane structure where the rivet is a press fit in the hole with the shank hammered flat while the head is backed up (bucked). If you don't have this capability the best and better thing to do is weld so that the patch actually carries structural loads.

Bogie
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Old 05-01-2012, 02:22 PM
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rivets

When I was an Engineer at Ford I wrote a few Repair Standards, In certain applicaations Stainless Steel Pop Rivets were approved for repairs, but they are hard to set with a hand squeezer,
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Old 05-01-2012, 03:39 PM
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Here's a crappy mock-up that I did in Microsoft Paint. The gray area is area that has already been carved out. The black is the proposed area, so you can get an idea of how big the hole will become:

http://dl.dropbox.com/u/24984984/Shifter%20C.jpg

Like i mentioned above, the only place I plan(ed) on riveting is the hole directly around the shifter tower. It's sounding more and more like I'll need to weld the whole hole back up. What are the dangers in driving with the hole unsealed? The welder is about 5 miles from my house...

Last edited by tylerwerrin; 05-01-2012 at 03:49 PM.
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Old 05-01-2012, 08:07 PM
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co leaks

With a leaky exhaust you could get carbon monoxide poison. drive with the windows down. I've driven a lot of miles in my horless carriage Model T ford with leaky wood floors and the original T 's and A ' s
were leaky.
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Old 05-02-2012, 03:57 PM
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Here are some photos of what the hole looks like in my car:

http://dl.dropbox.com/u/24984984/Hole%201.JPG

http://dl.dropbox.com/u/24984984/Hole%202.JPG

http://dl.dropbox.com/u/24984984/Hole%203.JPG

As you can see, the hole extends from the top of the tunnel down the side. What's a bit shady is the black plate that you can see in a couple of the photos isn't welded into the car -- it's simply screwed down in a couple places. I can always rivet it down, or add a couple more self tapping screws, but as it looks now there isn't a way to attach it to the tunnel, aside from welding.

I've asked a couple welders in the area if they'd be up for doing the job -- their main concern is with the wires/carpet in the car. You can see there wire harness in the photos that might get in the way.

Any ideas?
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