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Thread: Some interesting axle strength calculations

  1. #41
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by Warren Stramer View Post
    Out of curiosity I dug up some of my axles I had run in the past and removed for one reason or another and inspected the spline roots under magnification, This is what I found.............If you can enlarge the photos you will see a crack starting near the spline valley on nearly every spline. (I don't know how to make these photos larger here) Right click on photo and "open link in new window"?? maybe?
    As an experiment I'm going to take an axle that has not yet been subject to high torque loads and machine an undercut right at the spline end to the valley root depth, polish and shot peen that area, and see if it helps at all, as that is where my left side axles fail.
    Wow Warren great pics!!!!

    Those corners where the splines end and merge into the shaft are nasty,I dont think that could get any worse as far as a riser... that radius must be single digit thousandths of an inch...I betcha your undercutting and polishing makes a huge difference

  2. #42
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    Re: Some interesting axle strength calculations

    There are many different methods of making outside splines. How are these made? Does anyone know? The process itself might have something to do with it.

    Something I thought of while looking at Warren's pictures is that I don't think we typically engage the entire length of the spline. If this is the case, then there is room to reduce the stress risers. I truly am speculating here off the top of my head. What if the amount of splines that are not engaged are machined off? I am going to take a stab and say that maybe re-heat treating the area would be a good idea since we don't really need hardness here, we need toughness.

    Also, look at how nasty the end of those splines are! Holy cow there are TONS of stress risers! Some simple polishing might even do some good.

  3. #43

    Re: Some interesting axle strength calculations

    I dug out three more used and abused axles that where not yet broken, but show the initial signs of spline twist. The failure mode is the same on all of them. Cracks starting where the spline valley transitions to the machined relief.

    I also magnified three unmolested axles and they are fine, no cracks. So, I will grind and polish a relief back to where the splines engage the diff side gear splines and eliminate all those knarly stress risers. I will also make some small narrow paint lines to monitor twist.

    Also going to try these axle bearing/seal supports, unless someone here has tried them and had problems with them.(If so, please speak up) I think anything to stabilize the axle stub should be beneficial.
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    best 1/8 ET-6.16 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.65 sec. 8 valve NO NITROUS!!

  4. #44
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by Warren Stramer View Post
    I dug out three more used and abused axles that where not yet broken, but show the initial signs of spline twist. The failure mode is the same on all of them. Cracks starting where the spline valley transitions to the machined relief.

    I also magnified three unmolested axles and they are fine, no cracks. So, I will grind and polish a relief back to where the splines engage the diff side gear splines and eliminate all those knarly stress risers. I will also make some small narrow paint lines to monitor twist.

    Also going to try these axle bearing/seal supports, unless someone here has tried them and had problems with them.(If so, please speak up) I think anything to stabilize the axle stub should be beneficial.
    I think I get it..they replace the seals but also act as needle bearings on the stub shaft? That seems like a pretty good idea. I wonder if any OEMS do that?

  5. #45
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    Re: Some interesting axle strength calculations

    I have never personally tried them but from the allpar days those seal/stabilizer things do actually work. They are really made as a bandaid fix for the OEM open differentials where the side gears are shimmed in the carrier but either from loose factory setup or high mileage/one tire fires the side gears are a sloppy fit and that allows the axle to whip around and wear the seal out.
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  6. #46
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    Re: Some interesting axle strength calculations

    It would be nice if someone came in here and said 'oh yeah those save axles'. I bought some for the same reason but i dont have something to truly test them yet.

    Dont push the red button.You hear me?

  7. #47
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    Re: Some interesting axle strength calculations

    Doubt that this anecdote helps the thread much buuut... My 928 S4 has a front engine but a rear transmission located over the rear wheels connected by a 6 foot 'torque shaft', basically a 6 foot splined solid axle. I've had a clunk on hard launches that has gotten worse over the last couple years, talked to the local 928 specialists who have been doing the work that's outside my um, skilset Greg at Precision Motorworks knew the problem exactly, the torque shaft twists a teeny bit on every hard launch, add that up over countless launches(he said always over 80K miles but usually by 100K, Mine went 120K so I was on borrowed time) and with all the twisting the shaft begins to shorten. On our CV axle set up it wouldn't be a problem because it could just pull out a bit but on the torque shaft which is held into the flexplate and the TQ by circlips, it starts to pull on the crank and eventually will lead to main bearing failure The new shaft he has custom made with larger OD, improved radious next to the splines and larger carrier bearings, addresses all of the stress failure issues. I was dubious of the fix but sure enough the clunk and subsequent thrumming at highway speed is gone now. He showed me the original 'shortened' shaft, sure enough, the splines on the two ends don't line up anymore because there is so much twist in the shaft.

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  8. #48
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by Warren Stramer View Post
    Also going to try these axle bearing/seal supports, unless someone here has tried them and had problems with them.(If so, please speak up) I think anything to stabilize the axle stub should be beneficial.
    Yeah ummm

    The million times I have bugged people to use them, I got grief about them gawling up the axles blah blah blah they fail/seize blah blah blah too expensive blah blah you are an idiot for wasting money.

    Not sure I respect those opinions. I certainly don't care if my broken axle has some gawling. I also don't care if it costs 30-50 bucks to protect an axle.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

  9. #49
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by 2.216VTurbo View Post
    Doubt that this anecdote helps the thread much buuut... My 928 S4 has a front engine but a rear transmission located over the rear wheels connected by a 6 foot 'torque shaft', basically a 6 foot splined solid axle. I've had a clunk on hard launches that has gotten worse over the last couple years, talked to the local 928 specialists who have been doing the work that's outside my um, skilset Greg at Precision Motorworks knew the problem exactly, the torque shaft twists a teeny bit on every hard launch, add that up over countless launches(he said always over 80K miles but usually by 100K, Mine went 120K so I was on borrowed time) and with all the twisting the shaft begins to shorten. On our CV axle set up it wouldn't be a problem because it could just pull out a bit but on the torque shaft which is held into the flexplate and the TQ by circlips, it starts to pull on the crank and eventually will lead to main bearing failure The new shaft he has custom made with larger OD, improved radious next to the splines and larger carrier bearings, addresses all of the stress failure issues. I was dubious of the fix but sure enough the clunk and subsequent thrumming at highway speed is gone now. He showed me the original 'shortened' shaft, sure enough, the splines on the two ends don't line up anymore because there is so much twist in the shaft.
    Now that's German engineering at its finest.

  10. #50
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by Warren Stramer View Post
    I dug out three more used and abused axles that where not yet broken, but show the initial signs of spline twist. The failure mode is the same on all of them. Cracks starting where the spline valley transitions to the machined relief.

    I also magnified three unmolested axles and they are fine, no cracks. So, I will grind and polish a relief back to where the splines engage the diff side gear splines and eliminate all those knarly stress risers. I will also make some small narrow paint lines to monitor twist.

    Also going to try these axle bearing/seal supports, unless someone here has tried them and had problems with them.(If so, please speak up) I think anything to stabilize the axle stub should be beneficial.
    Awesome! I was thinking of paint to use as a twist indicator.

    As for those seal/bearings. I also would like to see somebody try them, however when they were brought up a while back the response was exactly like this:

    Quote Originally Posted by Ondonti View Post
    Yeah ummm

    The million times I have bugged people to use them, I got grief about them gawling up the axles blah blah blah they fail/seize blah blah blah too expensive blah blah you are an idiot for wasting money.

    Not sure I respect those opinions. I certainly don't care if my broken axle has some gawling. I also don't care if it costs 30-50 bucks to protect an axle.
    However, I can't see how they would do that damage. There is splash lube out there already and it can't be worse than the bushing that's out there now that has slop in it. The only thing I can think of is if the bearing or the shaft has a harness issue or some other flaw where a roller locks up and starts messing things up. Also, RWD applications have been using a similar design for...oh...probably as long as the automobile has been around. I would love to give it a shot.

  11. #51

    Re: Some interesting axle strength calculations

    Quote Originally Posted by Reaper1 View Post
    Awesome! I was thinking of paint to use as a twist indicator.

    As for those seal/bearings. I also would like to see somebody try them, however when they were brought up a while back the response was exactly like this:



    However, I can't see how they would do that damage. There is splash lube out there already and it can't be worse than the bushing that's out there now that has slop in it. The only thing I can think of is if the bearing or the shaft has a harness issue or some other flaw where a roller locks up and starts messing things up. Also, RWD applications have been using a similar design for...oh...probably as long as the automobile has been around. I would love to give it a shot.
    Well, How much wear could I possibly have on a drag car I'm with you.....little to none. Just wonderin if anyone had ever actually tried them. I'm putting them in. Nothing can go wrong....go wrong.....go wrong............go......
    best 1/8 ET-6.16 sec. best 1/8 speed-119.70 Best 1/4 MPH 145.5, Best 1/4 ET 9.65 sec. 8 valve NO NITROUS!!

  12. #52
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by Warren Stramer View Post
    I dug out three more used and abused axles that where not yet broken, but show the initial signs of spline twist. The failure mode is the same on all of them. Cracks starting where the spline valley transitions to the machined relief.

    I also magnified three unmolested axles and they are fine, no cracks. So, I will grind and polish a relief back to where the splines engage the diff side gear splines and eliminate all those knarly stress risers. I will also make some small narrow paint lines to monitor twist.

    Also going to try these axle bearing/seal supports, unless someone here has tried them and had problems with them.(If so, please speak up) I think anything to stabilize the axle stub should be beneficial.
    Wow! Where did you get those from? I was looking at this same issue a few nights ago and decided I'm going make a new diff bearing retainer plate that would use a radial ball bearing. Any way I think it would only help things.

  13. #53
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by lengel View Post
    Wow! Where did you get those from? I was looking at this same issue a few nights ago and decided I'm going make a new diff bearing retainer plate that would use a radial ball bearing. Any way I think it would only help things.
    32125LRB is part number. I just ordered my set from parts authority. They ran about $36 each.

  14. #54
    The moderately moderate moderator Turbo Mopar Staff
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by krut View Post
    32125LRB is part number. I just ordered my set from parts authority. They ran about $36 each.
    So they can be used on both axles or just the driver's side?
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  15. #55

    Re: Some interesting axle strength calculations

    Both sides. Auto and manual I believe. I purchased mine from Fitzall...http://fitzall.com/pins_stabilizers.php
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  16. #56
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    Re: Some interesting axle strength calculations

    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

  17. #57
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    Re: Some interesting axle strength calculations


    how long does the seal last riding on the rough portion? it cant be too happy there. does it even seal at all?

  18. #58
    The moderately moderate moderator Turbo Mopar Staff
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    Re: Some interesting axle strength calculations

    Quote Originally Posted by acannell View Post
    how long does the seal last riding on the rough portion? it cant be too happy there. does it even seal at all?
    Not long.
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  19. #59
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    Re: Some interesting axle strength calculations

    But we don't know if this is a problem for us or not. I think it's too early to poo-poo it.

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    Re: Some interesting axle strength calculations

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