4 speed install

topmill · Feb 16, 2015

Hey everyone, not sure where to post this. I'm going from auto to 4 speed. My question is where to cut and weld my new hump.

Adam · Feb 17, 2015

topmill said:
Hey everyone, not sure where to post this. I'm going from auto to 4 speed. My question is where to cut and weld my new hump.

Get the new hump first, I like AMD's sheet metal. Rough out the hole and use the actual hump as a template to mark the outline. It would be ideal to mock up the four speed in place, with shifter. Cut inside the outline by about 1/2 inch so you will have something to weld it to... I would drill 5/16 holes every 3 inches or so in the replacement metal flange (not thru the floor). Position the hump where you want it, then you can plug weld the hump to the floor, simulating spot welds. Apply some seam sealer and call it done. I would use a Wire Feed welder for this... careful not to start a fire under the car, undercoating, etc...

DetMatt1 · Feb 17, 2015

Couldn't have said it better myself.

challenger6pak · Feb 17, 2015

If you have a very clean floor you can metal bond the hump into place and not worry about any fire. Use the 3M brand. It works the best.

DetMatt1 · Feb 17, 2015

That's a good idea too.

topmill · Feb 17, 2015

Thanks, I do have the hump. I guess i'm just a little nervous about cutting the floor without measurements. I do have a wire feed welder so OK guys next weekend......

Adam · Feb 18, 2015

My original 4 spd Challenger is 31 & 3/4 inches b/t the red arrows. If you are working on a Cuda it will be different. One has a two inch longer wheelbase and I believe an extra inch is in the rear footwell.

Adam · Feb 19, 2015

I have used Lord Fusor body panel adhesive on a roof skin along the drip rails (I still welded the A-pillars & quarters in) The adhesive gives you very little time, but there is no heat warp-age, and it is rock solid.