Hmmmmmm. When I upgraded my springs on the 72(with a 77 rear end in it) to 11 packs. The u-bolts I ordered didnt fit around the housing. When I called the vendor they told me 77s were larger diameter and exchanged my u-bolts and all was good. Now reading this I measured the 77 housing I have on the bench and it looks like 3.25. I'll have to get under the 72 and measure that one.
Let us know. I was always under the impression that 9" axles in cars got the 3" diameter tubes and trucks got the 3.25" tubes. All trucks, which presumably included the F100/F150's as well.
Maybe there were some that got the larger 3.5" tubes after all. Never seen one myself, but that doesn't mean they don't exist. Maybe the heavy half ton trucks, or perhaps the big muscle cars?
Or maybe they sent you the smaller 3" bolts by mistake and then had to send you 3.25's in their place.
Or were you trying to use your originals at first?
Are you sure that the u-bolts that you had to order were larger diameter and not just longer? Using our springs you definitely need longer u-bolts.
No more "new" 3.25" centers though. The current crop of aftermarket housings are ALL 3" diameter because apparently nobody has ever made the truck version as it turns out. Guess they were all hot-rod companies to begin with and so only worked on the smaller tube version of the housing center.
All the housings with the larger axle tube size centers you were able to buy up to about two or three years ago had to be salvaged from junkyards.
Now that those are so few and far between, it's not worth their time to hunt them down. So everybody just uses the 3" now because they can buy those new from manufacturers.
Luckily, if you don't have 3" u-bolts, the existing 3.25" u-bolts fit these smaller tubes just fine usualy. As they're torqued down they conform enough to encompass the smaller axle tubes. Even the big-boy 5/8" ones it seems.
Definitely curious what you find.
Be nice if you had an old receipt with a part number!
Paul
