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Technical Rear axle end play

Discussion in 'The Hokey Ass Message Board' started by Texas57, Dec 20, 2015.

  1. I've got a Ford 9" with late style tapered roller open big bearings. I am converting to disc brakes. The end play/preload is apparently determined by the bearing retainers. The oem bearing retainers were removed and replaced with the caliper mounting brackets, which will now control that end play.. I've gotten several references to shim to"proper end play", but I don't know exactly how much or how little is acceptable. So, that's my question...what's an acceptable range? I have a feeling I'm opening a can of worms here, but hopefully not.
    Last edited: Dec 20, 2015
  2. rails32
    Joined: Oct 29, 2008
    Posts: 110


    who's rear disc brakes?
  3. Summit/StainlessSteelBrakes. It uses an '88 T-Bird caliper. Kit seems to be made very well, the "problem" is coming from the differential I had narrowed and changed to 31 spline trac-loc.

    This is going to get into the can of worms I was trying to avoid opening, but...I know ( or, I was told) most of the bearings in the 9" differentials are the sealed type with an internal seal. Long story, but even though I requested the old style big bearings ends, mine somehow ended up being the late style big bearing ends with the tapered open bearings and an external seal so that the lubrication is provided from the differential oil. The end cap was however drilled for the old style bolt pattern. I never would have known had I not pulled the axels to have the registration hub machined to match my rotors. The brake kit I got was specifically for the old style big bearing ends, and although all the diameters are the same, the bearing/external seal height is different than what the kit was designed for, so the provided shims which normally should give the proper end play have to be adjusted for the different style of bearings.
    My car is not being built for racing, just street use. I don't think having the tapered bearings is going to be a problem in a nonracing application, so I'm just trying to get thru my ignorance and get it assembled correctly with the proper end play. I just need to find out what "proper end play actually is. Sorry for the long winded explanation.
    Last edited: Dec 20, 2015
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  4. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,269

    Dan Timberlake

    Seems like the more the end play, the more that cornering will cause the caliper pistons to be "knocked back" even with a floating caliper, which a few online pictures suggest it is.

    I wonder what the t-bird spec is. I did not stumble on it when surfing. Well, actually Google did not stumble on it.
  5. 55willys
    Joined: Dec 7, 2012
    Posts: 1,604


    It should be a set 10 or set 20 bearing that is a tapered one piece set up that doesn't need to be shimmed. just make sure that the axle doesn't bottom out against cross shaft
  6. This is what I got when I removed both axles. Somebody else remarked also that they were a set and should not be separated. It took very little pressure to remove the axles from the housing. One or two taps with a nylon hammer. Obviously the outer race stayed in the housing. I didn't see anything that indicated it was a non separating set. rear axle 002.JPG
  7. I should have mentioned right now I have the end play at .013, and it just feels like too much to me, but getting it less than that is going to require some parts being machined.
    I should have posted a pic of the housing.... axel housing 003.JPG
    Last edited: Dec 20, 2015
  8. deathrowdave
    Joined: May 27, 2014
    Posts: 2,160

    from NKy

    Bearings should not be separated . All the taper bearings I have worked on were one piece . Not bearing and race in separate pieces (2) . My thoughts are you need new bearings replace with sealed bearings and good to go .
  9. fordor41
    Joined: Jul 2, 2008
    Posts: 917


    dump question but shouldn't there be a bearing retainer between the bearing and the axle flange? What holds the brg in the housing?
  10. There is a bearing retainer, but it is a 2 piece that is a combination caliper bracket and bearing retainer. Being split, it goes on after the axel is in the housing. It's that split bracket that is shimmed to get the correct end play.
  11. saltflats
    Joined: Aug 14, 2007
    Posts: 10,176

    from Missouri

    Being a tapper bearing it should have 0 end play just like a front wheel bearing.
    sunbeam likes this.
  12. Perhaps I'm overthinking this, but I agree the roller bearings should have no play. However, what I keep trying to figure out...look at the bearing in the pic I posted. It would seem to me if the case were stood on end and the bearing just set into the race with it's own weight, the individual rollers would all have contact with zero play, but the sheetmetal casing that holds the rollers would have some play in it. The casing can't interfere with the rollers moving freely, but it is the casing that has the pressure applied to it by the bearing retainer, so it would seem to me if too much pressure was applied to that casing around the rollers, it would cause the rollers to bind up. I think that is the reasoning behind the "proper end play".
    All this thinking is wearing me out...I may just change to the normal sealed bearings and be done with it as Deathrowdave mentioned. The bearings that are on the axle now are brand new, as everything in the differential is, I guess I'm just being stubborn replacing the bearings just because I don't understand the assembly at this point.
  13. I prefer the straight-roller sealed bearings myself. And shims between the flange and backing plate would give more end-play.
  14. The circular shims are between the bearing retainer and the bearing/seal. There is a circular depression in the retainer that fits over the bearing/seal, and that's where the shims go, decreasing the end play.
  15. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,269

    Dan Timberlake

    It is hard to differentiate between zero endplay and actual preload. Preload increases the stiffness of the bearing assembly so is useful and necessary in some applications, like bearings supporting hard working ring and pinions.
    But at some point preload can cause bearings to heat up, which can increase the preload and cascade into a big problem.
    I think "regular" wheel bearings call for minimal end play. 0.001" to 0.007" here.

    Some of the truck adjustment procedures are similar, except specifically calling for "verifiable" end play, and a frequent preventive maintenance check. Yet another use for a mag base dial indicator.
    pitman likes this.
  16. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,517

    seb fontana
    from ct

    Above is really close to what I remember..If you look up the bearing it may show what is up/wrong.
  17. Thanks for posting that, Dan exactly the info I was looking for. Since my last post, I called some places I couldn't over the weekend, mainly a differential supply house.
    First...I was going to post a pic/ad for the Timken roller bearings that are on the axles, but they are shown at the top of the link that you posted, Dan. They are not a "shouldn't be separated" set as some had told me, but in fact come as a set of separate components. The differential supply house I called strongly recommended I not change the bearings to the sealed type, that these were a better setup. They were also "very familiar" with the disc brake kit I'm using and said there should be no problems with using the shims as supplied with the kit. According to them, I was wrong in my thinking the tapered bearings were a different height than the sealed bearings. He did tell me to double check the bearing race in the axle housing to make sure it was fully seated.They told me there should be no in/out play, I needed to tighten the bearing retainer until the in/out play is gone, or just about gone, all the while checking the rotation of the axle to make sure it's not binding.
  18. saltflats
    Joined: Aug 14, 2007
    Posts: 10,176

    from Missouri

    The only thing I read in the Ford manual says there is a different in the seal between a drum brake and a disc brake.
  19. 56-f100
    Joined: Nov 28, 2017
    Posts: 1


    texas57 I found this from you I'm having problems with to much axle end there any way I could talk with you on this?
  20. First, welcome to the forum. I see this is your first post. I always try to help when I can, but this is almost assuredly a question I probably can't help with. I kept rereading this old thread trying to jog my memory, but I just barely remember working on the differential. Old age memory not working again. In the first place, this was my first build, so most everything I did was with the help of forums and friends to get it right. (14k miles on the car since this thread, no problems, so whatever I did works, I just don't remember what that was I did on the differential).
    Sorry for the long winded explanation, but I didn't want to just ignore or blow you off on your first post. I'd either ask the question/state the problem here or start a new thread and let some of the knowledgeable guys here help you out.
    You wouldn't know from reding this thread, but I had my differential totally built and assembled by a local shop. I just ran in the posted problem trying to assemble the disc brake kit to what should have been a completed assembly with the brake kit just bolted on. My problem arose when I ordered a wrong version (late vs. old big bearing) of the brake kit and was adapting to fit.
    Last edited: Nov 28, 2017
  21. pitman
    Joined: May 14, 2006
    Posts: 4,932


    Small amount of lash is better in bearing setups. A film of oil is quite thin. It is more demanding when you get into specs for an opposed pre loaded pair, like a lathe headstock. Hard to estimate/calc., w/o knowledge of load, service life, bearing quality, typ. fits, tols...
    Last edited: Dec 4, 2017
  22. Off topic, Pitman, but I love your location. I'm an ex New Englander, so I know exactly where that is, lol.
    pitman likes this.

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