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Thread: At a crossroad on my 55? Sell it or C4 build

  1. #31
    Registered Member chevynut's Avatar
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    Your tires won't support 4750 ft-lb of torque. They'll smoke long before you reach that level.

    Even if they could, let's assume you have a 10" lever arm from the yokes to the pinion support....I don't remember how long it is. That would result in a force of 5700 pounds upward at the bolt. Assuming you use a 1/2" bolt there the cross sectional area is .196 square inches. The shear stress would be about 29,000 PSI and a grade 8 bolt can take 170,000 PSI. There's lots of safety margin at the bolt. The urethane bushing isn't going anywhere either. We set the pinion 1/2 degree lower than the engine angle to accomodate some small movement of the pinion. I looked at the stresses on the crossmember as well and long ago went to a .188" thick wall tube. So the design is sound from an engineering point of view.

    There are other frame suppliers that use the same type of pinion support...Progressive Automotive, The Street Shop, and I believe even SRG. Newman uses a torque arm which looks nice, but as you mentioned it takes an additional crossmember. If you're using an AME center section the crossmember is already there, but it's placed too far back to use Newman's torque arm. There was a guy here and on the other site that built his "own" C4 conversion (so he says) who actually took my frame jig to his house and used my design...he used the two Newman crossmembers and torque arm. They run around $1000.

    So the torque arm isn't necessary, and it does essentially the same thing as the pinion support bracket commonly in use. The reason they used the c-beam on the C4 Corvette was to stiffen the chassis/body assembly. That's also why the C5/6/7 Corvettes use a torque tube.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


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  2. #32
    Registered Member chevynut's Avatar
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    I got this from an article I have, and I did the same calculations several years ago when I shared your concerns about torque....

    "You can calculate available traction torque using the following formula. You need to have the weight on the rear tires, plus the amount added from weight transfer.

    weight on rear tires X COF X tire radius
    Traction Torque= __________________________________
    12

    COF= Coefficient of Friction. For "normal" tires and pavement, use .7 as a "worst-case." For really sticky tires on normal pavement, use .9. For slicks and sticky dragstrip pavement, use 1.0 to 1.5.

    Radius= Measure from center of wheel to ground with tire aired up as it will be driven and the car loaded normally.

    Sample: 1993 C4 Conv. 3383 lbs, 50-50 weight Dist + 10 percent rear weight transfer (kinda on the high side), 285/40-17 tires (10.7 radius)

    1860 X .7 X 10.7
    TT= _______________ = 1160.9 lbs-ft
    12

    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  3. #33
    Registered Member chevynut's Avatar
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    Quote Originally Posted by 55 Rescue Dog View Post
    2.66 first gear x 4.47 rear x 400 ft lb engine torque = 4750 ft lbs of torque on the axel housing.
    Why are you wanting to run a 4.47 rear?
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  4. #34
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    Quote Originally Posted by chevynut View Post
    Why are you wanting to run a 4.47 rear?
    The 4.47 gear is what is in the quick-change rear, with a Muncie in my Camaro, which is the gear I use cruising around town. Runs about 2800 RPM at 45 mph. Don't know what gear is in the Dana 44 in 89 I'm getting. Probably 3.07, which should be good with a 4 speed auto. So, maybe with a auto, I shouldn't be concerned about breaking the diff housing, from lack of a torque arm. I know on the C4, that because there is no rear trans mount, that the torque arm is needed to tie the rear and trans together, in place of a torque tube used on the C5.
    Last edited by 55 Rescue Dog; 12-12-2015 at 05:52 AM.

  5. #35
    Registered Member rockytopper R.I.P 5-13-2017's Avatar
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    Dog if you are cruising around town at 2800rpm @ 45 mph you must spend your time preying on unexpecting modern muscle cars like JT does in his 56 lol.

  6. #36
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    Quote Originally Posted by rockytopper View Post
    Dog if you are cruising around town at 2800rpm @ 45 mph you must spend your time preying on unexpecting modern muscle cars like JT does in his 56 lol.
    I can't sneak up on anyone with this Camaro. Originally I wanted to do my 55 into a street legal oval track car.


    http://bangshift.com/bangshiftapex/c...rning-monster/

  7. #37
    Registered Member rockytopper R.I.P 5-13-2017's Avatar
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    After seeing that not sure you will be happy with a C4 chassis. I thank this would have satisified your desires better lol. He went with an old retired nascar under his 55.


    https://theblock.com/node/33615/lightbox2

    Last edited by rockytopper R.I.P 5-13-2017; 12-12-2015 at 03:33 PM.

  8. #38
    Registered Member chevynut's Avatar
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    Your 89 Dana 44 will probably have a 3.33 or 3.54 gearset in it unless it's been changed from stock. You can tell the stock ratio by looking at the etched numbers on the bottom of the housing.

    The 88's used the early 85-87 housing and they all had 3.07 gears. After that they went to a 3.33 and 3.54 in 89. 90's used 3.33 and 3.45 gears, 92 and later all had 3.45 gears. This is from a C4 specs book I have.

    So it looks to me like the early 89s had 3.54s, then they went to 3.33 for the late 89s through early 90's, then 3.45s for late 90's and thereafter.

    These Dana 44 HD diffs are pretty stout, and they were used in the Vipers with a very similar housing. I don't think I've ever heard of a housing breaking, and I don't understand why that concerns you. I'm not sure where the weak point is on these differentials, but the Dana 44 HD can take 3460 ft-lb short duration and 1100 ft-lb continuous. If you're only planning on 400 ft-lb, even a 36 would work for you.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  9. #39
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    Quote Originally Posted by rockytopper View Post
    After seeing that not sure you will be happy with a C4 chassis. I thank this would have satisified your desires better lol. He went with an old retired nascar under his 55.


    https://theblock.com/node/33615/lightbox2

    Since I plan on radiused rear fenders, and the fronts are not great, I can totally see pushing the wheels out a little with the C4! So much for scrub radius though.
    Last edited by 55 Rescue Dog; 12-12-2015 at 04:38 PM.

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