wow that is soo much more floor cut out than i expected it to be
And so it begins,,,,,, 5-speed Duster swap!
- Thread starter darndart
- Start date
-
goldduster318
Overzealous Car Modifier
6-speed in my case is big. Really big.
yeah i would want a 6spd.. but damn
darndart
Well-Known Member
Another piece of the puzzle arrived today. Direct fit speedo cable from Silver Sport Transmission(great people to deal with).
A question to you if you don't mind. When you cut the original floor tunnel cross member out, did you notice any undue flexing of anything? In other words, when I get ready to do mine, would it be recommended to maybe weld in some braces?
goldduster318
Overzealous Car Modifier
Yeah, the floor flexes A LOT.
I had the torsion bars backed off, had the car as leveled as possible on the floor before I started cutting. Used the lower crossmember piece to hold the bolt holes all together when I started with the welding of the top piece. I wasn't worried about the car bending after that but the floor will still flex in areas not by the crossmember until its all tied back together.
The floor is then tied into the upper crossomember and then I had patched the 4-speed hump back to an automatic floor and modified from there. I bought a new automatic carpet kit and it isn't noticeable. There is a slightly bunched area on the passenger side right at the front edge but it's fine generally.
Keep the updates coming 
darndart
Well-Known Member
Where did you get that upper torsion bar crossmember piece that you used on your car. It looks like it is pre-fabricated.
goldduster318
Overzealous Car Modifier
Toddron Restorations made it, its for the T56 swap, bottom and top crossmember.
darndart
Well-Known Member
Turned out the 4-speed hump was screwed to the floor with a bunch of screws and seam sealer. Once the screws were removed, I was able to take the hump out by hand.
darndart
Well-Known Member
I unwound the torsion bars completely before I started cutting on the torsion bar crossmember. My little air saw did not bind at all while cutting so I don’t believe there is any pressure on the crossmember with the torsion bars unwound.
darndart
Well-Known Member
I ended up putting the transmission up into place about four times as I measured and cut the floor pan. Now I just need to figure out what I’m gonna use to support the torsion bar crossmember and then go ahead and patch the floor back up.
jbc426
Well-Known Member
I used a similar 1/4" plate on the bottom as shown in your photo, and added another 1/4" plate on top of the floor. above the torsion bar cross-member. Sandwiched like that, it is very strong and doesn't flex.
I also fully welded the seams of the torsion bar cross-member to the floor pan, welded in a compete US Cartool Chassis Stiffening Kit and put in a partial roll-cage.
I also fully welded the seams of the torsion bar cross-member to the floor pan, welded in a compete US Cartool Chassis Stiffening Kit and put in a partial roll-cage.
darndart
Well-Known Member
I finally got a chance to do some work on the Duster. I decided to go with a 2” wide 1/2” think piece of steel for the torsion bar mount brace. I had the metal shop bend it to exact width and make it extra long, so I could cut it to length. It fits perfectly in the existing torsion bar mount. I welded it into place and welded the existing floor pan to the mount also. I am also going to weld the floor patch panel to my new torsion bar mount brace, to make it as strong as possible. I honestly don’t think I’ll have any issues.
That looks pretty stout. Just a question. please. How similar in size is this transmission to the Tremec T5? Thanks.
moparlvr166
Well-Known Member
jbc426, I know you modified the trans tunnel already from the posting already, my question is do you think the 4L60e would fit without surgery to the tunnel?
goldduster318
Overzealous Car Modifier
Not trying to be mean, but, It's quite weak actually, especially for the thickness of material used.
No 3D shape and right angle bends without any gussets or triangulation, There is pretty low torsional stiffness and bending in the transverse direction on the car would be pretty easy. These cars are basically trying to twist the car at the center of the transmission tunnel because that crossmember taking the load to hold the car up.
Compound that with only welding at the ends to what is essentially just sheet metal, that area is going to be highly stressed and bend easily.
The crossmember I used in my case is the way I would have designed my own if it wasn't available, basically 3 pieces together making a "c" type cross-section like the original, truck frames, etc. It's overlapped for a signifigant part into what is left of the original crossmember, and can be welded in place there.
You could use something like 1/4x1 flat stock on each end and lap over both ends and blunt the corners a bit and then it would be very strong.
No 3D shape and right angle bends without any gussets or triangulation, There is pretty low torsional stiffness and bending in the transverse direction on the car would be pretty easy. These cars are basically trying to twist the car at the center of the transmission tunnel because that crossmember taking the load to hold the car up.
Compound that with only welding at the ends to what is essentially just sheet metal, that area is going to be highly stressed and bend easily.
The crossmember I used in my case is the way I would have designed my own if it wasn't available, basically 3 pieces together making a "c" type cross-section like the original, truck frames, etc. It's overlapped for a signifigant part into what is left of the original crossmember, and can be welded in place there.
You could use something like 1/4x1 flat stock on each end and lap over both ends and blunt the corners a bit and then it would be very strong.
darndart
Well-Known Member
It’s quite a bit larger than a T5. Lengthwise they are identical. I’ve got a couple fox bodies with T5’s in them. They are a good trans.
So you don't think what appears to be 1/2" bar stock is very strong?
Would you be willing to give some undercar dimensions of the tunnel when you are done? I may want to duplicate the size in case I ever do a transmission upgrade later. Thank you.
goldduster318
Overzealous Car Modifier
Not at all. You'll find nothing made like this anywhere. You'll find a lot of C, U, H, I shapes but not this for a reason that its only stiff if it only took load in the driection of the 2" (as if it was a floor joist in a house or something) which this is not doing at all.
The tie in to the existing structure is bad, only as good as the weakest point (which is the sheet metal itself), right angles without gussets is bad, and it has low stiffness. 1/4" bends super duper easy by hand and even with double the thickness you can see it was cold bent, not sure what they used but a lever arm of a couple feet you could probably do it manually pretty easily.
The original part is the way it is for a reason. Even if this was made out of 1x2" rectangular tubing with mitre cuts and welds to get around the crossmember with decent welds it would be fairly stiff.
My plan is to take two stock upper cross members, section them and make a larger one.
darndart
Well-Known Member
I’m not sure about the tunnel itself, but the torsion bar brace that goes around the top of the tunnel would have to be removed for sure.
Along these lines....and forgive me if I'm derailing somewhat......I see SilverSport transmissions has a transmission cross member for an early A body for the TKO and TKX. Do yall know if the Tremec T5 will utilize the same cross member, or if it is close enough to modify? Thanks.
jbc426
Well-Known Member
I'll know in the next 48 hours, and post here..
Last edited:
-
