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Thread: Homemade Double Mount Diff Cover

  1. #1
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    Homemade Double Mount Diff Cover

    I think the pics are pretty self explanatory. I had a spare diff lying around and decided to sacrifice the cover.



    Drilled out the left mount holes with a 3/4" drill bit on the drill press.


    Started cutting with the 4 1/2" cut off wheel:



















    Now it's off to the welding shop to get welded up (I can't weld aluminum). Next I'll source a dog bone diff mount from charbel, fill the bushings with poly and fab up a mount on the chassis to bolt it to.
    Last edited by jrcook320; 05-06-2009 at 01:29 AM.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  2. #2
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    Looks sick man!

    Nice work. Can't wait to see it all bolted up, they look intense!

    /M3/4/5

  3. #3
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    That's Intense!

    Robert


    If you're trying to make me feel better about this scenario, give it up....

  4. #4
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    I was going to have some steel plates plasma cut to do the same thing. Never got around to it as usual.

  5. #5
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    I took measurements to do the same thing and have it drawn in cad if you're interested. I liked this route better, under the car it will look stock.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  6. #6
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    Well played sir. I'll be interested to see how this goes. My extra diff mount is just chillin. Good luck with having it welded. These aluminum castings sometimes hide little treasures of porosity and junk. Looks REALLY good though.
    Last edited by TheNeek; 05-06-2009 at 10:21 AM.


  7. #7
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    Sweet.
    I anted up for the alpina copy a while ago and have an extra 3.9 diff that is laying around. As usual your work is great...

    Josh if you make some poly mounts for yours, I could probably use some from my alpina copy...let me know if you want to make me a set as well.
    "..Horsepower is a measure of work done over time, or the rate at which work is done."




    http://www.cardomain.com/ride/579694/1


  8. #8
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    This, I like.

    I need more hours in the day, I don't know where you guys get the energy to do so much work, after work.

  9. #9
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    Quote Originally Posted by blitzed310 View Post
    I don't know where you guys get the energy to do so much work, after work.
    Tell me about it, my back is killing me after just doing an oil change last night. Some of these guys have wives and kids too, amazing.

  10. #10
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    lol.. I started at 8 pm after messing with my lawn for a couple hours and worked until 12:30 am. Once I get started on a project it's hard for me to call it quits and go to bed. I pay for it the next day, everything is sore today.

    Fitting this piece up took me 2-3 hours. I also welded up a few pinholes I found in my exhaust, cleaned up a few surface rust spots and stone chips and fogged black engine enamel in a few areas under the car (on my subframe and fuel tanks). I've decided I'm going to do the whole undercarrage with black paint after a good degreasing while the trans and diff are out. Right now its just black undercoating and oil sticks to it and softens the undercoating over time, if it were painted I could just wipe it off with a rag.

    I also started with my heat tape in a few areas, on the rear spare tire well where the exhaust gets real close, between the turbo compressor housing and manifold, and I wrapped the turbo inlet pipe. The pipe took about 1 hour to do.

    No kids yet, my wife works 2 days a week so when she's on nights (like last night) I go balls to the wall in the garage. I have a 3.45 LSD to rebuild, seat webbing to replace and a clutch to get in the car before the power tour in 5 weeks. On top of that my truck needs brake lines and some undercoating, the 323i needs detailed and a service.

    Then comes all the house projects that are stacking up...

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  11. #11
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    ^ Yeah Ok, I think I'm getting lazy!

  12. #12
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    I get every other friday off. That's when I mash on the car.


  13. #13
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    Now I need to find a cheap and easy way to add cooling fins. I'd like to find a finned 1 piece casting that can just be welded onto the bottom of the cover rather than adding a bunch of pieces to each existing fin. Something like an air cooled briggs cylinder head... or like the lawn boy I just threw away last week. crap.

    I'll go to the scrap yard and look around.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  14. #14
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    Why not just run a real cooler? I honestly think it's mild overkill because it shouldn't create huge amounts of heat unless you're doing track days with many laps in succession.


  15. #15
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    Since you're doing all this work, why not add a hinged door for easy banana input?

  16. #16
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    Quote Originally Posted by TheNeek View Post
    Why not just run a real cooler? I honestly think it's mild overkill because it shouldn't create huge amounts of heat unless you're doing track days with many laps in succession.
    This car does see occasional track time. 30 minutes all out on a real track reveals many weaknesses that autox does not.

    I don't want to spend money on a cooler, I'd need a pump and heat exchanger, fittings and a place to mount all that stuff which is not really worth it right now. Slapping an extra set of fins on the bottom of a cover is easy and I think will be enough for what I need.

    Quote Originally Posted by Layne View Post
    Since you're doing all this work, why not add a hinged door for easy banana input?
    lol, now you're thinking!!
    Last edited by jrcook320; 05-06-2009 at 01:05 PM. Reason: Automerged Doublepost

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  17. #17
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    I've been itching for a reason to build one of these
    http://www.backyardmetalcasting.com/index.html
    and do some projects with it. Maybe a big fin dual mount diff cover is the right reason.

    Milo

  18. #18
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    lol, awesome. I was talking with a co-worker about making our own blast furnace and doing aluminum casting over lunch today.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  19. #19
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    The more I learn, the more I want to start modifications at the "beginning". I want to be able to fix stuff in the desert on a plot of land with no one around, and no grid to work from. Maybe my neighbors won't mind if I build one on my back porch?

  20. #20
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    Quote Originally Posted by jrcook320 View Post
    Fitting this piece up took me 2-3 hours. I also welded up a few pinholes I found in my exhaust, cleaned up a few surface rust spots and stone chips and fogged black engine enamel in a few areas under the car (on my subframe and fuel tanks). I've decided I'm going to do the whole undercarrage with black paint after a good degreasing while the trans and diff are out. Right now its just black undercoating and oil sticks to it and softens the undercoating over time, if it were painted I could just wipe it off with a rag.
    I painted the undercarrage of my car with "Galmet" paint, satin black. It contains rust inhibitor. Its been about 3 years or so since I painted it on, and with a quick wipe back its comes up good as new.

    Its not cheap stuff, but its worth looking into or looking into similar products. I'm sure you have all this planned out, but I thought I'd throw in my .02 and see if it helps!

  21. #21
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    Great - one more up grade for me to put on the list of things to do to the race car - - Oh and the street car ...... I guess that adds up to two things to put on the list'sss.


















    Really though JR, very GOOD idea, nice piece of well thought out work and a really great way to do this. With all the cars in the junk yards, finding an extra cover should be easy. Just need to find a tig welder and weld it up.


    Always FUN TO DRIVE - Build Thread & Tech info - 79 320/6 track car build thread -- Videos of track car -Adam in car Auto-x video - Start-up video - 4/2011 Adam's TOP BMW time San Diego BMWCCA - 4-5-15 Dyno break-in run new M20B25 - Exhaust Thread - Link

  22. #22
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    Quote Originally Posted by OLD MAN View Post
    Just need to find a tig welder and weld it up.
    Just to add really quickly, I just messed around with OA welding aluminum with flux cored filler rod and it worked really really well. Good strength, it was really easy (compared to stick welding aluminum), and more people have an OA setup at home than a tig setup. If you can't source the rods I can get them for $1 each and I'll ship them to you for cost+shipping, or you can call Gordon's welding in Burbank CA at (818) 558-3232. That's where I get them.

    Takes some practice but it seems to be really tolerant of contamination unlike tig, so it'd be a good skill to cultivate. I'm wating for a transmission casing or Bell housing crack that I can just weld up while in position rather than taking it apart stripping it and then TIGing it up.

  23. #23
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    aaaahhh I wish I had a tig. I could convert my mig to weld aluminum with the right gun and gas, but it's not worth it when I can take it to a welding shop here in town and get pro results.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  24. #24
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    All this talk of welding...pfht...


    crazy glue and duct tape man, crazy glue and duct tape

    Cool mod btw

  25. #25
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    lol. good idea. I'll jb weld it.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

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