Floorpan Rust Close to Transmission Crossmember - How To Proceed

[JRHemmen]

After pulling back the carpet in my E30, I was greeted by a good amount of floor pan rust. Three spots are rusted through, while the rest was luckily just surface. On the passenger floor pan, I cut out what I wanted to remove and then realized that I was cutting within an inch of where the Transmission Crossmember bolts on. Should I cut as close as I can to the edge of the rust, or will this compromise the integrity of the trans support? My other option is cutting out the area where it mounts and then drilling and tapping a new hole.

Additionally, there is a spot of rust on the passenger side of the transmission tunnel about the size of a quarter. I punched it through and it looks like there are two sheets of metal there. How can I patch this without dropping the trans?

Pictures aren't great, but I won't be home with the car again for two weeks so they're all I have for now. The hole on the trans tunnel can just barely be seen in the pictures.

[amcp]

I have the same issue. Debating trying to path vs replacing the floorpan from a donor I have. I'm concerned with the trans mount area as well.

[15Michaeljoseph]

I literally just wrapped up this repair two days ago. The trans mount is plug welded to the floor skin, so it's two pieces. Support the trans with a floor jack and remove the trans mounts to give yourself more room. I replaced the entire mount slot with one from a donor car, and 'custom' made the patch for the floor pan itself. I'll attach the pictures I took of that area so you can kind of see what I'm talking about. (Try not to make fun of my welds, I was going for strength not beauty lol)

Don't be nervous... Just get in there and do it, you'll be fine.

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[JRHemmen]

I literally just wrapped up this repair two days ago. The trans mount is plug welded to the floor skin, so it's two pieces. Support the trans with a floor jack and remove the trans mounts to give yourself more room. I replaced the entire mount slot with one from a donor car, and 'custom' made the patch for the floor pan itself. I'll attach the pictures I took of that area so you can kind of see what I'm talking about. (Try not to make fun of my welds, I was going for strength not beauty lol)

Don't be nervous... Just get in there and do it, you'll be fine.

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This is exactly the type of response I was hoping for. Thank you!

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[amcp]

THANK YOU 15Michaeljoseph

[15Michaeljoseph]

If you have any questions about it just reply to this thread. Seems to be a common rust spot (I'd blame the heatshield trapping moisture, dirt, and salt) so it would be good to have info out there for others.

It's fresh on my mind and I'd love to help if I can.

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[Jokester]

If you have any questions about it just reply to this thread. Seems to be a common rust spot (I'd blame the heatshield trapping moisture, dirt, and salt) so it would be good to have info out there for others.

It's fresh on my mind and I'd love to help if I can.

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I did the exact same process on my vert, also did it in the trunk, was scary at first, but then you just say fuck it, turned out great in the end. :devil:

[Sunnyledge]

I had multiple rust spots between the transmission tunnel support and floor. Fortunately in my case the tunnel support was pretty solid, so I was able to fabricate and weld patches and plug weld to the tunnel support. You have to be carefull of blow thru when welding in the patches.

[JRHemmen]

If you have any questions about it just reply to this thread. Seems to be a common rust spot (I'd blame the heatshield trapping moisture, dirt, and salt) so it would be good to have info out there for others.

It's fresh on my mind and I'd love to help if I can.

Sent from my moto g(6) using Tapatalk

I really appreciate it. Did you put the heat shield back in? I have all of my exhaust out right now for unrelated reasons so I'm wondering if I should just drop it. The piece of the heatshield closest to the transmission (the fabric sheet) is in pretty rough shape anyway. Luckily the rest of it (covering the driveshaft) looks pretty good.

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[15Michaeljoseph]

I really appreciate it. Did you put the heat shield back in? I have all of my exhaust out right now for unrelated reasons so I'm wondering if I should just drop it. The piece of the heatshield closest to the transmission (the fabric sheet) is in pretty rough shape anyway. Luckily the rest of it (covering the driveshaft) looks pretty good.

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I actually did end up cleaning all of the heatshields up and putting them all back. I figure they're there for a reason, and the last thing I want is my undercoating melting off/ catching fire. The long one underneath the spot that rusted out got a few inches trimmed off the back because one of the studs got cut out with the floor patch and I didn't have time to fab up a new stud lol

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[mxtx]

great work and congrats on saving it.

i have similar floorpan rust issue, if not, worse on my Touring.

any idea on if all models share floorpan design for a donor swap? the areas are so big and continuous it would have be a huge patch almost the entire footwells.

ive never welded before...

[Sunnyledge]

I had to replace my entire driver’s side floor. Not as hard as you’d think if you template And plan properly. I recently saw a supplier in England that is supplying stamped replacement panels. It’s gonna cost more, but it will save a lot of fabrication and look factory.

[mxtx]

replacement would be amazing to find... england is a good call to search, thanks.

[tomstin]

Been there! After I repaired the rust, I used stainless hardware, washer with double nut on the bottom side, fender washer, then the shield, fender washer and locknut. Also used POR15 and seam sealer. Figured leaving some space between the heat shield and floor pan would allow water to escape and dry. Therefore, hopefully prevent future rust.