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9 1/4 to 8 3/4 swap #2659720
05/27/19 07:15 PM
05/27/19 07:15 PM
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Iowa
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tt76400 Offline OP
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I have a 1985 D-150 360/727 with an 9 1/4 axle, I have a 8 3/4 out of a 1974 D-100 that I am swapping in, I know I may need a different driveshaft, my main questions are do I need a center brake hose (rubber) from a 74 or an 85? U-bolts the same? The 8 3/4 has 10x2.5 drums on it, I plan to swap an 11x2.5 drum brake setup from a small bolt pattern 9 1/4 (1979) on it as they are all new, backing plates/ bolt on to the 8 3/4? I know the 9 1/4 is strong enough for my street toy, but I have several 8 3/4 SureGrip centers, and just prefer them, just want to know any issues that may arise. I have already converted the front to small bolt pattern, so the small bolt pattern of the 8 3/4 will be a plus as well. Thanks!

Last edited by tt76400; 05/27/19 07:22 PM.
Re: 9 1/4 to 8 3/4 swap [Re: tt76400] #2659751
05/27/19 08:55 PM
05/27/19 08:55 PM
Joined: Jan 2003
Posts: 10,558
Freeport IL USA
poorboy Offline
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Originally Posted by tt76400
I have a 1985 D-150 360/727 with an 9 1/4 axle, I have a 8 3/4 out of a 1974 D-100 that I am swapping in, I know I may need a different driveshaft, my main questions are do I need a center brake hose (rubber) from a 74 or an 85? U-bolts the same? The 8 3/4 has 10x2.5 drums on it, I plan to swap an 11x2.5 drum brake setup from a small bolt pattern 9 1/4 (1979) on it as they are all new, backing plates/ bolt on to the 8 3/4? I know the 9 1/4 is strong enough for my street toy, but I have several 8 3/4 SureGrip centers, and just prefer them, just want to know any issues that may arise. I have already converted the front to small bolt pattern, so the small bolt pattern of the 8 3/4 will be a plus as well. Thanks!


If the brake hose is different, it will only be different in how to attaches to the axle and the possible length. The line connections are still the same. If your concerned, I would get which ever hose is needed (length wise) for the truck and figure out how to make the axle attachment if its different.

As far as the brakes are concerned, do both rear ends have the same wheel bolt pattern? The 11 x 2.5 drums will need to match the wheel bolt pattern.The backing plates will interchange, but unless you are running the green beatings, you will need to have the axle adjuster lock for one of the backing plate bolts for the 8 3/4" on the one side.

Both axles use the same U bolts, as long as both axles mount either above the springs or under the springs. If one mounts above the springs and the other mounts under the springs, the U bolts and the U bolt plates and axle saddles are different. Gene

Re: 9 1/4 to 8 3/4 swap [Re: poorboy] #2659775
05/27/19 10:00 PM
05/27/19 10:00 PM
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Posts: 162
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tt76400 Offline OP
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9 1/4 in truck now is large bolt pattern, but I have a small bolt pattern 9 1/4 with all new brakes that I would swap the brakes to the 8 3/4 if they would bolt on the housing, so I maybe should get a brake hose for the '74 8 3/4 housing, both axles mount under the springs, so no issues with that.

Last edited by tt76400; 05/27/19 10:02 PM.
Re: 9 1/4 to 8 3/4 swap [Re: tt76400] #2660030
05/28/19 02:13 PM
05/28/19 02:13 PM
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Posts: 10,558
Freeport IL USA
poorboy Offline
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Both hoses may be the same part #. Probably time for a new rear hose anyway. Gene







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