Driveshaft length ...

Discussion in 'Transmission & Driveline Topics' started by donaldy, Jan 16, 2009.

  1. donaldy

    donaldy New Member

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    Background: My project involves restoring a 1970 RS Z28 Camaro. It is originally an automatic THM400 but I am converting it to a Muncie 4 speed. So far, I have collected 80% of the parts or are coming. I have a Muncie 22, 27 spline input and 32 spline output and a 12 bolt rearend. I will be reusing my THM400 32 spline yoke.

    My question is:

    Do I need to lengthen, shorten, or leave the driveshaft the same length? Somebody must have done this exact conversion already. I rather not lengthen my original driveshaft. Leave it alone in case one day I sell my car and the next owner wants to return it to factory original. I have the factory original THM400 sitting outside my garage (covered).

    Don
     
  2. Steve's 74

    Steve's 74 Veteran Member Lifetime Gold Member

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    probably not the answer you want to hear but... with the tranny and rear installed measure the distance between the u-joints cL to cL and have a new ds cut. It's really the only way to get it right given the tolerances on these cars. You don't want to use someone else measurements and end up 1/2" short.
     
  3. donaldy

    donaldy New Member

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    OK, fair enough. If that what I need to do then I'll have to do this. I'll keep my original driveshaft and buy another one for modifications or better yet, buy one that is exactly the length I need. One question. In measuring from u-joint to u-joint, should the front yoke be pushed all the way in? or partially?
     
  4. retorq

    retorq Veteran Member

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    Measure the difference in length between the two trannys, and if you originally had a 12 bolt then that's the difference you need. If you swapped from a 10 to a 12 there will be a difference there.
     
  5. donaldy

    donaldy New Member

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    Good idea. I originally had a 12 bolt (70 Z28). So I take the difference in length between the original THM400 and the muncie and that is the length I need to add (if lengthen) or remove (if shorten).
     
  6. retorq

    retorq Veteran Member

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    Correct, it will at least get you in the ballpark ...
     
  7. yobin67

    yobin67 Veteran Member

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    The best thing to do is push your yoke all the way into your tranny,pull it out exactly 1",measure center to center,and have one made.
     
  8. Orange71

    Orange71 Veteran Member Lifetime Gold Member

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    Yes, that and make sure the rear suspension is loaded, not hanging down. :)
     
  9. Dave Nelson

    Dave Nelson Veteran Member

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    I did this exact swap on 2 cars,used the same driveshaft, no changes needed.
     
  10. DCL70

    DCL70 Veteran Member

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    The 1970 Camaro driveshafts w/4-spd., 3-spd. and TH350 measure 49.20" (center to center u-joint caps). The slip yoke has 27 splines, 1.50" dia. shaft (about 3.5" long) and measure about 5.5" from the center of the u-joint cap holes to the end of the shaft. When assembled the measurement from the center of the rear u-joint cap to the end of the slip yoke at the front is about 54.7" (49.2" + 5.5" = 54.7"). The 49.20" driveshaft was only used in 1970.
    The 71-up Camaro w/4-spd. driveshafts measure 48.5" (c/c u-jts.) and use the same slip yoke as the 1970. The reason is that the 1971-up Muncie tailshafts are about 0.7" longer than the 1970 Muncies. The 71-81 Camaros use both 48.5" and 48.0" driveshafts depending on the transmission used.
    My "1970 Chevrolet Passenger Car Specifications" (dated Feb. 1970) manual states that the driveshaft length is 49.20" (C/L of u-joints) for All Transmissions for the 1970 Camaro but I am not sure if this is totally accurate as I have never measured the length of an original driveshaft from a 1970 Camaro w/TH400 transmission. The 1970 Camaro TH400 slip yoke is substantially different (larger dia. and longer shaft, I believe) from the 4-spd. slip yoke.
     

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