42RH Swap: '80 Volare

Transmissions and Rear Ends

  1. mchartier105

    mchartier105 Well-Known Member

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    I didn't see too many threads with pictures here or people who've done it so I decided to make one to start. I just finished swapping an '88 42RH into my 1980 Volare. Only the crossmember needed work to make it fit.

    The factory column shifter bolted up and works well, and I'm using a lokar kickdown. The driveshaft length with an 8.25 rear was 41.75" centre to centre. I used a GM transmission mount on a modified stock transmission mount. I'm controlling the lockup and overdrive with toggle switches for now.

    Here are a few pictures.

    IMG_20180127_094844.jpg
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    IMG_20180131_113547.jpg
    IMG_20180131_113559.jpg
    IMG_20180131_113610.jpg
     
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  2. Oldiron440

    Oldiron440 Well-Known Member

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    Looks great.
    I like swaps......
     
  3. slant6billy

    slant6billy Well-Known Member

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    That's awesome. I'm eyeing up a 42RH or otherwise known as the A500. What gear are you running in the 8.25?
     
  4. mchartier105

    mchartier105 Well-Known Member

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    I'm running 3.23s right now and turn just about 2000rpm at 110kmh, part of the reasoning for the swap is so I can throw some taller gears in, I'm thinking probably 3.90s or 4.10s. They'll still be turning less rpm than the 3.23s without overdrive.
     
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  5. BudW

    BudW Moderator Staff Member

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    Looking great!

    Before anyone makes any major crossmember work (modifications), I recommend making some measurements first – or a person (not necessarily you) will have a bad vibration that is hard to locate (and fix).

    Sense the propeller shaft slip yoke will be in a different location (front to rear) – as well as the transmission mount will be in a different location, a person can’t use either for a height measurement.

    A person can use the rear most transmission fluid pan rail for both before and after measurements (pending your old transmission mount is not broken or sitting close to metal to metal before measurement).

    Even a deviation of ¼” in height will cause a vibration. A ¼” variation side to side, well cause a vibration, as well.

    Most people don’t realize that Chrysler engine/transmissions does not sit in a straight line (parallel) to centerline of car – but is offset about 1” (or so) off-center, towards the Right side of vehicle, to reduce propeller shaft vibrations.
    It is off-set to the right and off-set in height, about 1”, in both measurements.

    The transmission height does make a big difference – so if you do have vibrations – that might be a place to look. Hopefully, you won’t need to worry about that problem.


    I know it is some work, but it would be nice, after your vehicle is done and working great, to remove your crossmember and measure it out as to what changes you made, and post here.
    There are others here wanting to do the same procedure.
    BudW
     
  6. mchartier105

    mchartier105 Well-Known Member

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    I took lots of measurements before I started and ended up putting it up and taking it down a few times to do more grinding. I'm confident I got it in the perfect spot, the angle looks good to me and is the exact same as it was with the old 904, and I have no vibrations at all so far, even using the polyurethane GM style mount.
     
  7. BudW

    BudW Moderator Staff Member

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    Wonderful!
     
  8. mchartier105

    mchartier105 Well-Known Member

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    And I'm actually about to pull it out to throw a coat of paint on it before I start daily driving it again on Monday, so I'll take some better pictures and some measurements!
     
  9. AJ/FormS

    AJ/FormS Well-Known Member

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    I too was looking at the angle issue,and wondering
     
  10. 89.Fifth

    89.Fifth Well-Known Member

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    Thanks for the pictures! This is a great thread as I've been hoping to do this one day.
     
  11. Joe12459

    Joe12459 Well-Known Member

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    This is great info. It will be very helpful to me, as I'm about to put a 3.9L/42RE in my son's Mirada.
     
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  12. Justwondering

    Justwondering Well-Known Member

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    I am completely clueless about what this means.
    I get that you are changing the transmission.
    I get that there are gears in the transmission that are bigger/smaller, taller/shorter, rotate faster/slower.
    I know I'll never do anything like this.

    You are changing the transmission because it will be faster? get better gas mileage? the new one is more reliable? or is this a racing thing?

    Yes I'm in the house where it is warm reading the forums rather than outside where it is cold changing out the instrument cluster that is failing on my 2000 Silverado. Taking the day off after a brutal week of health care. Bleh.
     
  13. AJ/FormS

    AJ/FormS Well-Known Member

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    The additional gear, allows more flexibility in rear gear selection.
    This allows for a lower rear and a little quicker off-the line acceleration. At the other end of the speed range, the additional top gear, gets the rpm back down at hiway speed.
    One could chose a rear gear to greatly increase the jump off the line, or, one could chose a rear gear to greatly reduce the cruise rpm. Or somewhere in the middle
     
    Last edited: Feb 2, 2018
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  14. Oldiron440

    Oldiron440 Well-Known Member

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    Doesn't the od transmission have a lower fist gear ratio?
     
  15. mchartier105

    mchartier105 Well-Known Member

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    Yes, lower 1st and second gear. And the reason for the swap is better mileage, taller first gears for better acceleration, and the possibility to put taller rear gears in while keeping highway rpm down.
     
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  16. mchartier105

    mchartier105 Well-Known Member

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    Also, the cost of the swap all done is about $650-$700CAD including the rebuild kit but not including the man hours of cutting, grinding and welding. I'll have to gather my receipts and do a full breakdown of the expenses.
     
  17. mchartier105

    mchartier105 Well-Known Member

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    Here's a picture of the shift linkage hooked up, the 42RH doesn't have the upper locating tab for the bracket but I used some locktite and tightened it down well and it doesn't seem to move and its been shifting well the last couple days but I'm still worried so I may drill a small hole in the case and use a screw instead to locate it. IMG_20180202_114311.jpg
     
  18. AJ/FormS

    AJ/FormS Well-Known Member

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    A500s are 2.74-1.54-1.00, same as A999s and some A998s
    A518s are 2.45-1.45-1.00, same as A727s, A904s, and some A998s
    The 2.74 low gear is 11.8% better, a little more than one rear gear size. The penalty is splits that are slightly further apart.
    The .69 od Brings the cruise down many rear gear sizes, turning a 3.91 into the equivalent of 2.70s; and the new low gear would turn the 3.91s into a 10.71 starter gear..... up from the typical 6.76 factory(2.76x2.45). It's sort off a win-win deal, but it works best in specific combos.Not the best for others. Used as the factory did, it's great!
     
    Last edited by a moderator: Feb 2, 2018
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  19. mchartier105

    mchartier105 Well-Known Member

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    Some better pics of my modified crossmember compared to an original. Mostly just grinding on the front and back along with cutting the original mount "ears" off.
    DSC_0004.JPG DSC_0001.JPG DSC_0003.JPG DSC_0002.JPG
     
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  20. Oldiron440

    Oldiron440 Well-Known Member

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    it would have been nice if Mopar had a big block OD.