240 stub axles in a 280 - Tech Note

[JMortensen]

This I'm sure is the correct answer!

 

[The spacers] are there to prevent side forces on the ball

bearings just as you surmise. They do this with a

slight preload on the inner races. Being loose is very

bad in this application. The inner races are slightly

preloaded but the bearings and outer races are not.

There are two bearings there just to accomplish this

task, one would likely suffice for simple load bearing

functions. Like in a solid axle design.

If you used too small of a spacer, things would move

around and the bearing would fail from misalignment

because the inner race would be drawn out of true to

the outer race. If you use too long of a spacer, the

races would again be drawn out of alignment or the

outer race would wobble out of position and things

would wear very quickly.

 

So the spacers are there to PREVENT preload, and I'm sure the drag test is a measure of how much preload is present and if it is low enough to be within acceptable limits.

 

This is also evident in John's FSM excerpt: 3.9 in lbs preload is basically like taking your pinky and pushing on the inner race on both sides. It's just enough to take out the slop in the ball bearing, but not enough to make the ball bearings wear too quickly.

 

Jon

[nat0_240_chevZ]

How do you preload a ball bearing? If you push or pull on the center in relation to the outer race, that would just make it wear really fast, right? No preload on tranny bearings, or any sealed unit bearings used in front hubs that I'm aware of. I can't think of a single ball bearing that gets used as a straight axle wheel bearing that gets any type of preload.

 

I'm not exactly the bearing guru, but I've been around a few and sold a few in the past couple years... just never heard of bearing preload on a ball bearing.

 

Jon

 

Well i know a few types of BB that can take axial pre-load but only small amounts (about 10% of radial), they are 'Deep groove BB' either in single or double rows' also thrust collar BB take pre load when used in a positioning requirement.

 

nato,

just thought id share, think this thread is like 3 years old!!!!