flatlander757
Member
Doing a lot of spreadsheets on planning to do stupid things with stupid axles ended up forcing me down the rabbit hole of comparing 1 ton unit bearings. My plans will be revealed once I figure out exactly WTF I'm doing, but figured I'd share this to start some discussion so people with parts and actual vehicles already in progress could add to it.
I built this up using SKF's online lookup plus Rockauto for applications/etc.
Here is a link to the spreadsheet:
Things that stick out to me:
GM 99-06 HD unit bearings are 8x6.5, 33 spline, and same 4-bolt pattern as the 99-04 Super Duty stuff. Thanks to a post by Tech Tim either here, or on the old board, his post about dropping a GM unit bearing right into a Spidertrax knuckle was what got me to thinking about doing this.
Ram 2009+ unit bearings are all 8x6.5 and either 33 or 35 spline, with 33 spline available in 9/16 or M14 studs, and 35 spline available in M14. What is interesting to note is that 2wd/4wd were different applications up until the 2013+ stuff (where 2wd/4wd interchange). I was not originally sure if this was a cost cutting measure (not having to spline it), or because the 4wd bearings would come apart without the stub axle (like on TJs and most 1/2 ton and FWD car bearings). My guess is that there may be ABS differences on some year splits where dimensions are unchanged otherwise. I did look up Mopar part numbers as well and they do not have the 12/13 2500/3500 having different year splits... that is only SKF. Not sure what to think of that. 12 or 13+ is when the AAM axle went from 4 link to radius arms up front... did the 3500s get that one year sooner? If so that may be the difference? On that same note, no idea what changes exist on the 2019+ bearings.
Back on topic... Ram 14-18 unit bearings have the same 4 hole pattern as the 05+ Super Duty bearings. This could be huge if 35 spline is good enough. What is hard to find is how far from the KNUCKLE FACE to the center of the u-joint is it? I'm sure one of the two bearings can probably go one way but not the other, with the other one requiring a spacer potentially. I could swear I've seen someone selling an overpriced kit to run F350 bearings on Dodge/AAM knuckles, but cannot find it now.
Depending on how far off one bearing/knuckle vs the other is, it could be as simple as a custom stub shaft being made up to keep the u-joint pivoting within the steering axis.
Brake rotor hat offset is the other issue if you're trying to adapt to a truck, but whatever I'm doing will be all custom (lighter weight) stuff so that's not a big deal... BUT being that all the hub offsets are with ~3/8in of each other... simple spacers either between the hub and knuckle (if putting Ford hub on Ram) or between the caliper bracket and knuckle (if putting Ram hub on Ford) to keep a factory (redrilled) rotor. I haven't bothered looking into brake rotor thicknesses and offsets yet, but I'm sure that's another option too.
Hopefully this gets some gears turning,
I built this up using SKF's online lookup plus Rockauto for applications/etc.
Here is a link to the spreadsheet:
Unit bearing dimensions.xlsx
Unit bearing Dimensions 3/4 and 1 ton Unit Bearing Dimensional Reference MFR,Yr start,Yr end,Model,OK w/o stub?,SKF P/N,Wheel bolt pattern,Stud size/pitch,Hub bolt pattern,Hub bolt pitch,Splines,Hub offset,Wheel pilot,Flange Dia Ford,1999,2004,F250-350,Y,BR930420,8x170mm,M14x2.0,4X5.5118,M14x2.0...
docs.google.com
Things that stick out to me:
GM 99-06 HD unit bearings are 8x6.5, 33 spline, and same 4-bolt pattern as the 99-04 Super Duty stuff. Thanks to a post by Tech Tim either here, or on the old board, his post about dropping a GM unit bearing right into a Spidertrax knuckle was what got me to thinking about doing this.
Ram 2009+ unit bearings are all 8x6.5 and either 33 or 35 spline, with 33 spline available in 9/16 or M14 studs, and 35 spline available in M14. What is interesting to note is that 2wd/4wd were different applications up until the 2013+ stuff (where 2wd/4wd interchange). I was not originally sure if this was a cost cutting measure (not having to spline it), or because the 4wd bearings would come apart without the stub axle (like on TJs and most 1/2 ton and FWD car bearings). My guess is that there may be ABS differences on some year splits where dimensions are unchanged otherwise. I did look up Mopar part numbers as well and they do not have the 12/13 2500/3500 having different year splits... that is only SKF. Not sure what to think of that. 12 or 13+ is when the AAM axle went from 4 link to radius arms up front... did the 3500s get that one year sooner? If so that may be the difference? On that same note, no idea what changes exist on the 2019+ bearings.
Back on topic... Ram 14-18 unit bearings have the same 4 hole pattern as the 05+ Super Duty bearings. This could be huge if 35 spline is good enough. What is hard to find is how far from the KNUCKLE FACE to the center of the u-joint is it? I'm sure one of the two bearings can probably go one way but not the other, with the other one requiring a spacer potentially. I could swear I've seen someone selling an overpriced kit to run F350 bearings on Dodge/AAM knuckles, but cannot find it now.
Depending on how far off one bearing/knuckle vs the other is, it could be as simple as a custom stub shaft being made up to keep the u-joint pivoting within the steering axis.
Brake rotor hat offset is the other issue if you're trying to adapt to a truck, but whatever I'm doing will be all custom (lighter weight) stuff so that's not a big deal... BUT being that all the hub offsets are with ~3/8in of each other... simple spacers either between the hub and knuckle (if putting Ford hub on Ram) or between the caliper bracket and knuckle (if putting Ram hub on Ford) to keep a factory (redrilled) rotor. I haven't bothered looking into brake rotor thicknesses and offsets yet, but I'm sure that's another option too.
Hopefully this gets some gears turning,