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Hey guys, looking to see if anyone has experience swapping the old 51 F4 (and other big trucks) axles to something newer and more common. I would like to get more options for a wheel/tire set up and still have the widow makers on mine. Thanks.
Welcome to the forum. You are wise to replace the RH-5 Widow Makers. The general wisdom is that is is easier to get other rims than replace an axle (not saying it can't be done, but remember, you have RH-5 all around, and so that includes the front axle too, and then that leads to suspension changes, steering changes and before you know it, you don't have a classic any longer). There are options to get 19.5 or 22.5 rims with the 5 on 8 bolt pattern which opens up tire options a bit. You can also get many safer 20" options from the secondary market which would let you keep your existing tires which look to be decent and keep total expense down.
If you want to go modern tubeless, there are 22.5 and 19.5 single piece rims out there from some vehicles in the 70's/80's such as Dodge/Winnebago motor homes that use the 5 on 8 bolt pattern.
Finally, there are those on the forum who have gotten new rims from Wheels Now, American Wheel, OTR. They have 19.5, 20, and 22.5 options with the 5 on 8 bolt patterns, but some of those have a different look to them. Not exactly click and order, but a call knowing what you need size and cosmetic wise with a big checkbook and order (and shared quite regularly around here already):
Wheels Now - https://www.wheelsnowinc.com
American Wheel - https://www.amwheelspecialist.com/obsolete/ - They specifically advertise 19.5, 20, and 22.5 solutions
OTR Wheel - https://www.otrwheel.com/ - their website doesn't list our applications. One would have to investigate further.
I used the knuckles off a C4500 on my f7. The kingpins worked great the knuckles fit fine.
I changed the rear end to a dana 80 4:63 gear, its better than that 60 gear the truck came with.
Last edited by F1 coyote; Apr 17, 2024 at 04:05 PM.
Reason: add icon
FYI, unfortunately, the information from the F7 doesn't translate directly to an F4. Only the F4, F5, and F6 have somewhat of an overlap. The F7 & 8 are completely different beasts. The C4500 won't be an option.
its a meritor axle, I measured the kingpin on the f7 and it matched to a meritor axle used on the c4500 trucks. try measuring the king pin on your f4 and see if it matches a modern axle. GOOD LUCK.
Sorry I thought you might find one. Those flat nose trucks with the six bud bolt pattern is what I thought might work. I'm not sure of the names of these trucks are but I felt like they might just work.
Sorry I thought you might find one. Those flat nose trucks with the six bud bolt pattern is what I thought might work. I'm not sure of the names of these trucks are but I felt like they might just work.
Can you post pics of your truck to show the outcome please?
Does anyone know what part number or truck these c4500 knuckles are from? Any info would be helpful. Seems like if this is a possible solution for F-7/8 trucks this would be a more popular thread. I have heard of other knuckles being used but not without lots of machine work etc,ie $$$$.
This is one of my trucks for viewing pleasure. I have Dayton adapters for the front….
0 gear the truck came with.
