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Possibly Dumb C6/Driveshaft Question

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  #1  
Old 06-18-2018, 12:33 PM
68AZ
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Possibly Dumb C6/Driveshaft Question

I recently picked up a 1968 F100, 390 auto with C6, 2WD LWB.
The transmission is bad and I am trying to get it back on the road ASAP.
My problem is that the local wreckers tell me the working F100 transmissions they have are different than mine despite being in the 68-72 period.
The issue is that my transmission has a flange instead of a yoke. (pic below)
If I buy a transmission from a 1971 that has a different yoke on the tail shaft, could I simply buy the half of the driveshaft that would work since my driveshaft is two pieces?
Or would I be required to modify what I have?
Any help would be appreciated. I am new to Ford trucks and trucks in general.


 
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Old 06-18-2018, 09:46 PM
baddad457
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Yes, you can replace the 2 pc driveline with a 1 pc. You'll have to measure the difference between the two transmissions and subtract that from the overall length of your 2 pc set. Then either find a longer shaft from a different application or have a new shaft made to fit your truck.
 
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Old 06-20-2018, 12:22 AM
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Well, I found a solution. I bought a C6 with a slip yoke and will buy the driveshaft that fits it if I can.
 
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Old 06-20-2018, 06:00 AM
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You're going to need a speedo cable for a car application too. The one in the pic isn't going to work. I'm also going to guess you have a long wheel base truck. Look for a driveshaft for an E series van, those are the longest.
 
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Old 06-22-2018, 12:06 PM
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Originally Posted by baddad457 View Post
You're going to need a speedo cable for a car application too. The one in the pic isn't going to work. I'm also going to guess you have a long wheel base truck. Look for a driveshaft for an E series van, those are the longest.
Yup. LWB. Thanks for the info. That speedo cable issue could have been an unhappy surprise.
 
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Old 06-22-2018, 03:11 PM
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Originally Posted by 68AZ View Post
Yup. LWB. Thanks for the info. That speedo cable issue could have been an unhappy surprise.
Anytime, good luck ! The transmission mount should be the same as what you have now. You might have to move the crossmember, but that's an easy mod, just slide it and redrill the frame holes. I have a LWB E150 van, I can measure the driveshaft on it to see where you're at there.
 
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Old 06-23-2018, 12:42 AM
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Originally Posted by baddad457 View Post
Anytime, good luck ! The transmission mount should be the same as what you have now. You might have to move the crossmember, but that's an easy mod, just slide it and redrill the frame holes. I have a LWB E150 van, I can measure the driveshaft on it to see where you're at there.
Well, thanks to you I think I will attempt to swap the guts from the good transmission to the bad one which is original to the truck. 😁
Too many modifications/complications otherwise.
Your input is very appreciated.
 
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Old 06-23-2018, 08:04 AM
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Originally Posted by 68AZ View Post
Well, thanks to you I think I will attempt to swap the guts from the good transmission to the bad one which is original to the truck. ��
Too many modifications/complications otherwise.
Your input is very appreciated.
The mainshaft won't swap. yours is quite a bit shorter and is threaded for the retainer nut. Might be easier to just have yours rebuilt.
 
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Old 06-23-2018, 03:25 PM
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Originally Posted by baddad457 View Post
The mainshaft won't swap. yours is quite a bit shorter and is threaded for the retainer nut. Might be easier to just have yours rebuilt.
I figured I would have to keep the tail shaft on the original and use everything else from the good one.
Is that not an option?
 
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Old 06-23-2018, 05:17 PM
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Originally Posted by 68AZ View Post
I figured I would have to keep the tail shaft on the original and use everything else from the good one.
Is that not an option?
I don't know, I've never rebuilt a C6. I just know the mainshafts or is it the tailshaft ? Are different lengths and one is splined the other threaded.
 
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Old 06-23-2018, 07:45 PM
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Originally Posted by baddad457 View Post
I don't know, I've never rebuilt a C6. I just know the mainshafts or is it the tailshaft ? Are different lengths and one is splined the other threaded.
I think that's the tail shaft and you are correct. The flanged one is allegedly held on with a snap ring (part 7070) and the nut (351165-S) while the slip yoke is held on with a snap ring and something else.
According to one guy who claims to have done the swap, the flanged tail shaft will come off as a unit. I will test that soon and report back.

 
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Old 06-23-2018, 08:23 PM
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Originally Posted by 68AZ View Post
I think that's the tail shaft and you are correct. The flanged one is allegedly held on with a snap ring (part 7070) and the nut (351165-S) while the slip yoke is held on with a snap ring and something else.
According to one guy who claims to have done the swap, the flanged tail shaft will come off as a unit. I will test that soon and report back.

That snap ring holds the rear bearing in place. The nut retains the rear flange on the shaft..
 
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