Rear Wheel Stub Axle Play - Help Needed

[RB26powered74zcar]

 

 

 Anyone have more details on where to find the mark on the upright?

 

I located the letter on the top side (as it sits on the car) of the bearing housing, right about where the spacer fits inside. They were hard to see until I put a wire wheel to use, cleaning paint/road grime off...

[74_5.0L_Z]

This is a timely revival of this thread as I am in the process of replacing my rear wheel bearings.  I replaced them once about twelve years ago, and since then I have run hundreds of autocross events with sticky tires.  Lately I have an intolerable amount of play in the rear wheel bearings so I have purchased all new rear wheel bearings. 

 

So, while measuring the spacers and the housings (both marked B, I found that spacer is right in the middle of the allowable specification (2.068) and the housing is near the maximum tolerance (2.072).  I plan to assemble everything today with  bearings and see what kind of axial play I end up with.  If I still am unsatisfied with the result, I plan to have some new spacers made at my local machine shop.  From measuring the existing spacer, I found that the OD is 1.782" and the ID is 1.310" .  Available 4130 tubing comes in the following sizes from aircraftspruce:

 

    

       OD               Wall Thickness          ID        

 

    1.625                 0.156                    1.313  

    1.750                 0.188                    1.374

 

The 1.625 tubing more nearly matches the ID and the 1.75 tubing more nearly matches the OD of the original spacer.  I was thinking that the ID will be more important to keep the spacer concentric with the axle.  Now I am trying to decide which end of the tolerance to have the new spacers made.  Do I have them made to the long end of the allowable (2.0693), or do I have them made to the short end (2.0669)?    I think either would work.  The longer dimension will push the bearings against the outer surface of the large OD races and the inner surface of the small OD races, and the shorter dimension will reverse the situation. 

 

Any thought?

Edited November 24, 2013 by 74_5.0L_Z

[NewZed]

I made a comment earlier about the bearing system being designed for hot running, but it's probably not that much of a factor in this case since all of the materials are similar.  I had transmission countershaft bearings in mind, which are set on steel shafts in an aluminum housing. and preloaded for proper clearance when they heat up.  The strut materials would all expand at close to the same rate.

 

If you look at the attached drawing you'll see that the seating area for the outer races is in line with the inner races.  I think that the distance spacer is meant to match that outer racing seat distance, to center the balls in the races when everything is assembled.  You wouldn't want the balls riding on the sides of the races since the loads on them shift from side to side and up and down.  If I was starting from scratch or "blueprinting" my struts I would measure that area, from outer race seat to outer race seat, on each strut and make the "distance piece" match it. 

 

That's where my logic takes me.  There might be more to it.

 

Edit - forgot to say that the inner and outer diameters of the distance piece probably aren't that critical as long as the ends are flat and parallel and offer a good seating area for the inner bearing races.  When everything is compressed by the axle nut the two inner races and the piece essentially form a solid tube of steel.

Edited November 24, 2013 by NewZed

[heavy85]

The spacers are clearly hardened.  Unless you have the ones you are having made hardened I strongly dont think they will hold up.  How are you planning on hardening them?

 

If the inner and outer races are in line then there is excessive play.  You need to either space the inner race out or in to take up play in the bearings.  I've played with this so know this from first hand experience not just theory.  I would space the inner race to be closer together than the outer race to take out the play.  Bearings have an effecive center that's not neccessarily through the middle of the race.  You draw a line from where the ball touches the outer race through the center of the ball through where the ball touches the inner race to the center of the shaft.  By having the inner race closer than the outer, the balls touch the outer race towards the inside and the outer race towards the outside.  This effectively makes the bearing spacing wider which reduces the load on the bearing.

 

I still cant find any markings.  Anyone have 'B' spacers that are in specs willing to sell?

[NewZed]

Thanks for correcting me.  With that in mind, and a little more digging in the FSM, you'll find that all of the information needed is in the Rear Axle chapter.  L1 and L2 in the drawing, numbers in the chart.  With the measurement tool of your choice you don't need the letters anymore.

 

 

Not to argue, but it looks like with tolerances there's a lot of overlap, but the goal (blueprint) might be to have the strut housing ~.010 - .020" bigger than the distance piece.  Just looking at the numbers.  Really though, they look pretty sloppy and essentially just centered.  Maybe those are just starting points and the "adjustment" procedure that Nissan never describes, to get preload and end play, is what sets the final distance.  If adjustment is nut torque then there's some compression of the distance piece,  If they mean disassembly and adjusting piece distance then there's more labor involved.

Edited November 24, 2013 by NewZed

[rsicard]

Thanks heavy. Good to know that I'm not the only one seeing this. I was thinking of milling about .002 off the spacer and trying that to preload the bearings as right now I don't think I am at all. Do you remember what thickness spacers you were playing with? I just want to make sure I'm in the right ballpark.

Not certain why there is ANY pre-load needed on Ball Bearings.  If there is, then that would induce excessive wear and heat on both inner and outer races of both bearings.  If there is axial play of the stub axle, then add shims to one end of the inner spacer until the axial play is 0 to .001" such that there is still NO axial pre-load on either bearing. The FSM says 0 to .0059" axial play which in other words says NO pre-load countering their pre-load specs on the same image.

[74_5.0L_Z]

Ok.  I finished replacing my wheel bearings yesterday and I also played around with the spacers.

 

My starting condition was that both rear wheel had excessive play, so I replaced all four bearings.  While in the process of replacing the bearings I re-measured the spacers and the housings.  Here is what I had for both sides:

 

                    Left Side                Right Side

Spacer          2.066                    2.068

Housing        2.068                    2.072

 

When I pulled the axles out the left side housing provided a good close tolerance / interference fit with the bearing outer races; however, the right side bearings slid out of the housing too easily.  After cleaning up the right side housing it looks like I have fretting on the inner housing to outer race surface.  Not good, but being the eternal optimist, I assembled everything to see how it felt with new bearings.

 

The left side as expected went together great.  There is no measurable axial play and the axle spins very freely.

 

The right side went together weird:  The bearings drop into the housing with light hand pressure which was not unexpected because that is how the old bearings fit as well.  What is weird is that when torqueing the axle nut, I hit 200 ft-lbs of torque and then the nut continues to turn without an increase in torque.  After about two turns at the 200 ft-lb plateau, I decided to stop.  In this configuration there is at least 0.006" end play. 

 

The torque plateau has me worried.  Am I stretching the axle (doubtful unless it is cracked in the treads), or is the fretting corrosion in the housing not letting the bearing seat all the way.  Either way, I need to re-torque the axle and see what gives.  If the axle is flawed, I want it to break on the bench.   If the fretting is preventing the bearing from seating,  then maybe the extra torque will (temporarily) fix it.

 

Either way, I need a new right rear strut housing, and perhaps a new right rear axle.  Anyone have a spare they want to sell or trade for?

 

What sucks is that the new housing will need to be sectioned to match my old one.  We all know how much fun that is.

 

Edited to use proper significant figures.

Edited November 26, 2013 by 74_5.0L_Z

[RebekahsZ]

I think you should just cut your losses and give up being a z-car guy and call me just to get that car out of your life. Think of all the fun you could have playing chess and shuffleboard as I drive your car with an evil grin on my face!😜If you decide to walk away, I could have the trailer hooked up in about 2 seconds.

Edited November 26, 2013 by RebekahsZ

[heavy85]

How are you measuring the housing so precisely?

[johnc]

I wore out a set of rear struts in a similar way (25,000 track and autocorss miles).  Over time, with large lateral loads, the hub ovals a bit and the bearing moves in the hub.  I tested it and found an inner bearing that took a little more then hand pressure to install spun from its original position in the hub.  1/8 of a turn or 200 turns, I couldnt tell. Suddenly getting end play out of spec when it was in spec before is a clue. I used Loctite Green (Bearing Lock) and it worked for a year but then the end play went out of spec again.  I replaced the rear struts.

 

And you must have a heavy, hardened washer under the stub axle lock nut.  Without it you will bottom the threads before hitting the preload or end play numbers.

[johnc]

And I've made my own spacers a few times.  I used the 1 5/8" OD 4130 tubing as listed above.  Didn't worry about hardeneing because I checked the hubs frequently, never had an issue in 2 years of racing, and the rear struts have been on a customer car for at least 5 and I haven't heard of a problem.

[74_5.0L_Z]

I should only be recording 3 decimal places (my bad). I interpolated on the spacer dimension.

 

To measure the housing, I install the inner bearing and then use my Starrett dial calipers to measure from the lip of the outer bearing to the face of the inner bearing.  I use it like a depth gage by resting the bottom of the caliper on the ledge of the outer race and let the bar extend hit the face as I open the caliper.  I repeated the measurement several times at different clocking around the bore until I was satisfied that I had a reasonably accurate measurement that could be repeated.

 

Thanks John,

 

I will have to get some of that Loctite Bearing lock and see if I can extend the life of the strut housing until I can get a replacement and get it sectioned.  I assume that this is the stuff that you mean:

 

http://www.henkelna.com/faceted-search-17046.htm?countryCode=us&BU=industrial&parentredDotUID=productfinder&redDotUID=0000000HWO

Edited November 26, 2013 by 74_5.0L_Z

[Meph]

Just an fyi, my rear bearibg on one side was actually loose in the housing. Acted exactly like a worn bearing. I wrapped the bearing once with thin tape to take up the play.... working so far!

[johnc]

Yup, 609.

[heavy85]

Got replacement 'B' spacer.  On the problem side that's had shims that didn't work so well, I tried the spacer as received at 2.068".  Same as previous experience, there was no discernable preload but you could also slightly rock the tire back and forth enought to feel it.  So removed the spacer and turned it down to 2.061" and reinstalled.  This worked great as there is still no discernable preload but also cant feel any movement.

 

PS:  Even thought they were the more $$ SKF bearings and only a couple years old, one of the bearings .... in the problem side .... doesn't roll free.  I'll be tearing it appart to see what happened.  Luckily for reasons I can't remember I had one complete set of rear wheel bearings and seals.  Gotta like those little victories.

[74_5.0L_Z]

Well I pulled the passenger side strut back out to determine why I still had play and why the torque leveled off around 200 ft-lb.  So, I loosened the nut and started to re-torque it.  Again as I reached 200 ft-lb, the torque went soft.  Well, I turned it a little more and then the torque completely went away.  All of the threads on the axle let loose.  Now I had a nut on the axle with no threads by which to remove.  Several hours later the nut is off, and I am in need of a new axle and nut.

[RebekahsZ]

While you have it apart, ask for some Chequered Flag stubs for Christmas.  Be sure to put antiseize on the threads or they will gall, as SunnyZ found out.