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    Driveshaft length.

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    79treemaster
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    Driveshaft length.

    Post  79treemaster on Fri Nov 08, 2013 11:04 am

    I will be measuring for my driveshaft tonight and taking it to a local shop for cutting, welding, balancing and new u-joints. They said out the door for 120.00 so I guess that ain't too bad. The 8.5 is longer than the 7.5 rear end I replaced it with so I have to get another driveshaft or fix this one. I will let everyone know what the length is when I pick it up to let everyone know how long it is with a 350 Turbo trans.

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    Re: Driveshaft length.

    Post  79treemaster on Tue Dec 10, 2013 12:19 pm

    From the center of the front to the rear joint cups it is 57" long. The distance from the center of the rear cup on the joint to the lip seal on the trans is 59 1/2 ".
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    HeavyChevy77
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Tue Jan 20, 2015 9:13 pm

    79treemaster wrote:From the center of the front to the rear joint cups it is 57" long.  The distance from the center of the rear cup on the joint to the lip seal on the trans is 59 1/2 ".
    The driveshaft I got from the very end the u joint ear to the very end of the opposite joint and I got 56" maybe 55 15/16"

    Overall length was 60 1/4"
    At 57" is the seat of the yoke (?) The tube w/splines is 3 3/4" long
    Would I have to cut my driveshaft? Or would I need a longer slip yoke (and cut to size about $80 on summit and I got a chop saw) to make sure it won't slip out during suspension travel.
    Anyone w their experience on the swap
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    Re: Driveshaft length.

    Post  GM B-Body Forum on Tue Jan 20, 2015 10:21 pm

    The 8.5 is exactly 1 inch shorter than the 7.5, when i did the swap i had the drive shaft shortened 1 inch and it lined up perfect with the wear line on the yoke and the oil seal.


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    Re: Driveshaft length.

    Post  HeavyChevy77 on Tue Jan 20, 2015 11:33 pm

    I wonder if the lip seal that 79treemaster mentioned is the part where the tailshaft ends from the transmission ( where u say the wear line is) then that would be 3/4" of the slip yoke shaft going into the transmission
    From end to end is 60 1/4"
    He said his driveshaft from end to end (not including yoke) was 57" and mine measured 56" that would leave about 3/4" of the slip yoke to go in and out of the transmission during suspension travel (which I'm questioning if its enough) IF not would a longer slip yoke work and just cut the excess. I really need to get under and measure what I have on now.
    And admin do u know ur exact driveshaft length
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Wed Jan 21, 2015 1:32 am

    The lip seal is the base of the yoke where the shaft w/splines start (57"+2.5"=59.5")(mine measured 56"+2.5=58.5") (the 2.5" is the end of u joint ear to the base of the yoke shaft)
    79treemaster/admin your application is like mine sbc/th350/8.5" rear so we should have same driveshaft length
    Where I scratch my head is the base of the yoke shaft (tube w/splines ) measured 59.5" and 59.5" on my driveshaft has me on the yoke shaft with about 3/4" to spare.
    I read that the transmission needs at least 3" of input shaft ...so would a yoke with a 6 3/4 output shaft (vs my 3 3/4" shaft) effectively solve my problem.
    The driveshaft is already balanced to 140mph from factory (95 impala ss) so I don't wanna cut/mod it but if u get a longer yoke shaft would that affect the balance.
    I hope someone can make sense of this. Thanks for helping guys.
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Thu Jan 22, 2015 4:20 pm

    https://i.servimg.com/u/f38/18/98/28/33/image15.jpg
    This is where I started to measure at the end of the u joint ear 56"

    https://i.servimg.com/u/f38/18/98/28/33/image16.jpg
    This is the overall length 60 1/4" maybe 60 1/8" 

    https://i.servimg.com/u/f38/18/98/28/33/image17.jpg
    This Is the length of the u joint ear to u joint ear (not including the yoke)

    So his yoke seal (that I think he means the base of the shaft w/ splines) measured 59.5" from the very end of the u joint ear.
    At 59.5" it's on the shaft w/splines and only 5/8" - 3/4" of the shaft left

    I read that the transmission needs at least 3" of the shaft inserting into the transmission. They mention that it only moves about 3/4"-1" back and forth.

    Summit racing sells yokes (27 spline for th350) up to 8 3/4" yoke (8" from center of u joint to end of yoke) vs my 6 1/4" one (3 3/4 shaft)

    Would this yoke work 
    8 3/4" - 6 1/4" = 2.5" more shaft extension and plus the 3/4" it would already insert with tho one I have now it makes 3 1/4" extension overall. Just enough.
    I'm pretty sure it would work just want your guys 2 cents.
    Hoping 79treemaster chimes in with his answer
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Thu Jan 22, 2015 6:27 pm

    Bump
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Fri Jan 23, 2015 2:57 pm

    http://www.summitracing.com/parts/axe-xlt8/overview/

    I was thinking of this yoke
    It has 6 1/4" shaft only $60
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    Re: Driveshaft length.

    Post  GM B-Body Forum on Sun Jan 25, 2015 9:47 am

    Wish i knew what to tell you, but i dont. TBH i think that yoke is a few inches too long, you def dont want it bottoming out in the transmission but you def dont want it too short. And suspension travel is less than an 1/8 of an inch from what i measured. I measured with the car on the ground then measured with the rear wheels off the ground and there wasnt much movement at the slip yoke. I think my yoke is maybe 2 to 3 inches inside the transmission, that i didnt measure and idk why i didnt.


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    1979 Caprice Sport Coupe, 400hp Vortec 350, Th350, GM 8.5 w/disc brakes, 3.90 gears Detroit Truetrac, 2.5" stainless duals w/ x-pipe, Dynomax race bullets.
    1984 Caprice Sedan, 305 motor, 700r4
    1978 Caprice Sedan, 305 motor, th350
    1993 L99 Caprice, 4.3 v8, 4l60 trans
    1972 Ford F-100, 302 windsor, c4 trans
    2001 BMW E46 330i, 3.0L
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    Re: Driveshaft length.

    Post  HeavyChevy77 on Fri Mar 20, 2015 3:47 pm

    I measured my axle from the flange where he diff cover goes to the head of the bolt on the u-joint strap it came out to 15 1/4" and i measured the impala axle and got 15 1/4" :0??
    measured the lower trailing arm and the were both 24 3/4" 

    Now im wondering if i even need to change my drive shaft *59(ujoint ear to ear)*58(u joint center to center)
    the impala one is way shorter *55 1/2 (center to center)
    most likely because bigger trans but i wonder if i just need to swap the axle and the shaft will fit 
    The yoke only moved about 1/4" raised and lowered
    please chime in with opinions 
    i got everything i need for the swap(rims,master,comb. valve) except being 100% sure itll fit

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