Radius Arm - Cotter Pin hole

[WheelHorse]

I have a '77 that I just installed a 2.5" WH lift and ordered all new hardware as well. I know the '77 radius arms don't have factory holes drilled for the cotter pin/castle nut combo as the '75 and earlier years.

Would someone be able to run a dial caliper measurement so I know how far to crank the castle nuts down and drill a hole for a cotter pin?

 

[bronkenn]

I have a 72 and the hole is .4025 inch down from end. Ken

 

[Apogee]

I have a 72 and the hole is .4025 inch down from end. Ken

Dang...that is a super-precise measurement. I was going to say it's a fat 3/8", give or take, but the end of my F150 radius arms look like they've take a few shots over the years.

 

[jrwyant]

Subscribed. I'd like to do the same, but didn't want to drill in the wrong spot and mess things up...

 

[bronkenn]

That was from the end to the center of hole. Ken

 

[bronkenn]

A fat 3/8 or a small 7/16. That was from the end to the center of the hole. Ken

 

[WheelHorse]

I wonder if the threaded portion is longer on a '77. I got my dial caliper out and set it to .4025 and it seems like I wouldn't have enough preload on the poly bushings.

 

[bronkenn]

Can you mock it up and see if that measurement would be close enough to get the cotter pin in the castlenut? Ken

 

[jckkys]

I replaced my '77 bushings by simply torquing the nut to 100 ft./lbs as per the shop manual. The shoulder on the radius arm stops it. I've yet to see one come loose, so I can't help but wonder why a cotter pin is needed?

 

[DJs74]

I have a '77 that I just installed a 2.5" WH lift and ordered all new hardware as well. I know the '77 radius arms don't have factory holes drilled for the cotter pin/castle nut combo as the '75 and earlier years.

Would someone be able to run a dial caliper measurement so I know how far to crank the castle nuts down and drill a hole for a cotter pin?

Might be better to torque your nut down to it's positive stop with your specific setup, then mark the spot for the cotter pin hole and drill them with the arms installed. Your particular combination of bushings, radius arm angles, frame mounting brackets & nuts might vary some from another combination. This way, you can place it exactly where you want/need it to be.


DJs74

 

[Apogee]

Or you could...

1. ...drill the nut and the radius arm mount and safety-wire it.
2. ...run a locknut (nyloc or all-metal). Mine have Class C type all-metal locknuts, but I don't know if those were original or not.
3. ...add a jam nut.

Of all of the supension fasteners, those are some of the easiest to check and I've never personally had once come loose on its own between my '77 F150 (owned 23 years) or '77 EB (owned ~15 years).

 

[BUCKWILD]

go with a locknut you can adjust how much preload you have on it

 

[Tiko433]

Does preload effect "Bronco Lean " ?

 

[broncnaz]

No the preload is just for the bushing compression. Lean typically comes from the C bushings.