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Discussion Starter #1
I'm about to swap a 8.8" rear into a fox body Ford that came factory with a 7.5"(with a 302 and automatic transmission-C-4 in my case. I was under the understanding that both the 7.5" and 8.8" rear use the same driveshaft. I just recently read that the 8.8" rear uses a driveshaft that is 1" shorter than the 7.5". Summit racing has an aluminum driveshaft for the fox Fords. They show it to be 54.5" long and they claim it will fit both the 7.5" and 8.8". Does anyone have any first hand experience with this or know if this is true?
 

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I am currently in need of a tranny rebuild because of the driveshaft length issue. I ran around for 5 years and probably 20,000 mi with the stock 7.5 driveshaft. I tow dolleyed the car to the track, only to get the car home and find out I didn't have 2nd, 3rd or 4th gear anymore. Upon tranny disassembly I found exactly what I expected. The mainshaft had tried to weld itself to the input shaft(T-5) overheating the entire tranny. I was able to save about 1/2 the parts, just not any of the expensive ones. Again this didn't happen until it was on a dolley, but that goes to show how little play there is. Get the car at an angle and hit some bumps and your tranny will be toast.
 

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Discussion Starter #3
It seems that although both the 8.8" rear and 7.5" rear use a very similar driveshaft,(with a transmission-C4, AOD etc. the slip yoke spline count of 2
they are not really interchangeable. It looks like that you cant use a driveshaft from a 7.5" on an 8.8" rear, because the 7.5" driveshaft is 1" too long(55.5&quot
. However, you must be able to use a driveshaft from a 8.8" on a 7.5" rear because it is 1" shorter(54.5&quot
. If I am wrong on this please someone correct me. I think that I'll look into a new aluminum driveshaft from Ford racing.
 

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I believe you are correct and would go with the 5.0/8.8 length no matter what you decide. I know I am.
 

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I just measured up the driveshafts from '88 Mustang's with 8.8" (I'm doing a swap)

Manual(T-5) - Total - 53.5"
Driveshaft 45"
Trans Side 6.75"
8.8 Side 1.75"

Automatic (AOD) - Total 53.875"
Driveshaft 45.625"
Trans Side 6.5"
8.8 Side 1.75"

Hope that helps.... I also noticed that the 2.3 T-5 had the same length (not including trans side) as the AOD shaft.
 

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I used the stock driveshaft for my 85Mustang for both rearends. When I switched over to the C-4 trans., I installed the Ford alum. driveshaft. No problems with either one.
 

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Discussion Starter #7
I'm also going to go with a new aluminum Ford Mortorsport driveshaft, with a 3.5" diameter for the 8.8" rear. Summit gets about $160.00. It seems a smarter choice than having to cut down and reballancing my smaller diameter 7.5" driveshaft which I think was something like 2.67" in diameter. I understand that it would cost about $90.00. Just for information, theres a aluminum driveshaft up for bid on e-bay right now, in case anyone is interested...Now if I could just figure out why all those stupid "smileys"appeared in my above comments???
 

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I also put an 8.8 and a FMS aluminum driveline in my 85 GT some years ago, it fit perfect, I measured the part of the yoke that was showing behind the seal of the T-5, with the 7.5 and steel drivline, installed the 8.8 and the aluminum driveline, and if I remember correctly had virtualy the same measurement. In factafter I was T-boned in it and put the drvietrain in a 79 Capri, sold to my cousin 8 years ago, who is still driveing it.
 

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I swapped a 8.8 in to my 85 stang and used the stock driveshaft with out any problems, that is untill I blew out the u joints. but I think that was from the slicks not the rear end
 
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