U-joint doesn't match rear end...

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Nov 3, 2001 | 08:38 AM

guitars2

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U-joint doesn't match rear end...

The u-joint receiver on the differential is about 1/2 inch wider than the u-joint itself. It looks like someone has possibly put a 3/4 or 1 ton rear end in this old 1973 F-100 Now what do I do? Is there such a thing as a u-joint with different sizes for the driveshaft and differential? Help!!

Nov 3, 2001 | 04:53 PM

Supercab

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From: Palm Bay, Florida

U-joint doesn't match rear end...

I'm not sure what to tell you IF someone put a F250-350 axle under your truck,one easy way to tell is it will have 8 lug studs instead of the 5 lug that would be on a stock 9" rear end found in F100-150s.
If this is the case did you pull anything out or did you buy the truck not running?? if you pulled out an old joint take it with you to your auto parts guy & he can probably match it.
My thinking is this (there are 2 different yolk sizes on 9" rears,one is the same size both ways,one is wider on one side for use in the "bigger" yolk) a lot of parts guy don't know this, & give you the smaller one.
Hope this helps you, Rick

Nov 3, 2001 | 05:03 PM

fordmando

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U-joint doesn't match rear end...

Although both share the same size u-joint cap, one is about 1/2" longer than the other (per side.)

They might make an adaptor u-joint, or you can just replace the yoke on the rearend.

BTW, either size u-joint can appear on almost any F-100/150 of this vintage. I think they just had a bunch of different size yokes in a common bundle, and grabbed whichever was on top, and made the driveshaft to fit.

fordmando
70 F-100 Ranger XLT 400 C6
78 F-150 4x4 400 4 on floor
George

Nov 4, 2001 | 07:33 AM

guitars2

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U-joint doesn't match rear end...

Thanks guys, I was able to find the correct u-joint with one axis longer than the other. Problem solved!! Thanks again!!

Nov 4, 2001 | 12:40 PM

dfisher1

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U-joint doesn't match rear end...

Guys,
The difference is C-4 driveashaft to C-6 Driveshaft. There just a little different.
Good Luck, Have Fun,
KingFisher

Nov 5, 2001 | 06:19 PM

Kenny

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From: New Egypt, New Jersey

U-joint doesn't match rear end...

Nov 5, 2001 | 09:29 PM

MSTRAWN

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U-joint doesn't match rear end...

Guitars2, There are many different u-joint sizes for the driveshaft to differential yoke on a ford. I ran across this when I installed a 9" Lincoln Versailles rear end into my 66 mustang. What you need to do is measure ( with vernier calipers) the width of the yoke on the rear end and the diameter of the yoke where the caps of the u-joint fit. Then take the same measurements on the drive shaft. Forget Autozone, O'Reilleys, etc for this one. Find a Drive line specialist. Give them the measurements and they will find a U-joint for you. Just remembe to jot down the part number for future ref.
1977 F-100
300 I-6 / C-4 (soon to be AOD)
Offy C intake w/Edelbrock 500CFM
Hooker Ceramic coated headers w/duals, turbos, tips, and 02's
MSD6A w/Blaster Coil
Headlight relay system (Delanty style)
Overhead Mount FM-CD etc.
R-134 A/C system (I'm cool)