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Thread: Transmission Overheating

  1. #31
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    Aug 2009
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    Quote Originally Posted by JIM CHALOUPKA View Post
    Orren, my $.02 on this. I personally would go with a new original part or one just like it, the reason being the chain break always goes to the weakest link. You presently have an escape valve of sorts and I would rather have it brake than the casting it is bolted to.

    As I am sure you know mechanical failures will just move down the line to the next point that will fail.

    The area of the components appears from the photo to be quite rusted and corroded, maybe due to road salt or storage in a damp environment, be that as it may, I would clean everything up as well as possible and use a new plate and high grade fasteners all torqued to specs. Also note the elongated bolt hole next to the failure point, this suggests to me that the assembly was loose and moving. This would in itself lead me to think that improper fastening and not the bracket/plate thickness/strength was at fault, but then again, who knows ....happens and your there and I am here.
    As an aside the welded plate probably was doomed to failure from the start and should have been only regarded as a temporary repair, just say'n, please take no offense.
    Hope it all works out!

    JIM
    Excellent analysis Jim. Do you think Stress Corrosion Cracking could be the cause? Looks like a salty environment. It looks like Prevost designed the bracket to flex and absorb energy. Toughness is key. Unless this is a widespread problem, I'd do what Jim suggested. Replace it with a new part. Make sure it's nicely painted with new hardware torqued to spec. Just my 2 cents.

  2. #32
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    Good catch Orren, guess what?, Mine is also broken, found it today after church.
    Had my suit and tie on so I didn't get to do any work, just wiggled it a little and it fell down a couple inches. The break is in the same as yours, without the weld of course.
    All the bolts are still torqued tight and I have no corrosion or rust. So goes my theory up in smoke. I will treat it as a perishable item needing to be checked regularly and replaced at some interval yet to be determined.

    I use my retarder a lot and never noticed any deficiency with the broken part (looks to have been broken for some time as the break does not look fresh) (how do I know you might ask, well I just know when a crack is fresh )

    JIM

  3. #33
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    Jul 2010
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    Jim,

    When I spoke with the service manager at the local DD/Allison shop he indicated that their repair was to weld the crack/break and then gusset the mounting plate when equipment was in their shop for this repair. Since you've looked at yours, you know that in the way that Prevost mounts this valve that welding a gusset on the back of the plate is not an option. My mounting bolts were also tight and the second break was just below the mounting bolts on the transmission - the plate actually looked like it was torn in half. I'd be curious as to the amount of stress being placed on the hydraulic hoses while that 15-20 pound valve is just dangling there being actuated by the retarder. For my repair I went with a 3/8" plate and increased the width of the tapered section from teh transmission mount as it goes down to the accumulator mounting position.
    I'll post a photo when I get a chance.

  4. #34
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    Evidently this is not a common repair with Prevo parts anyway. I ordered one and it is coming out of Canada, $68.43. Could have made my own with more time, but I am preparing to get on the road soon time does not allow for fabrication.

    I do know what you mean about the gusset, looks like there is barely room for an open end wrench!

    I think there are a lot more broken out there than owners know about

    Thanks again for the warning.

    JIM

  5. #35
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    Has the transmission issue been resolved yet? Inquiring minds want to know....<g>!

  6. #36
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    Mar 2010
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    Sorry for the delay in getting the details back, it's been a busy season.

    The transmission was replaced in Billings at Interstate Power Systems, an authorized Allison dealer. They used a reman from Weller which come painted red as a trademark. The exchange price was about $7500. I also needed a U-joint, which they also replaced, and refilled with TranSyn fluid.

    The retarder accumulator bracket wasn't broken, but now that I look at the picture I can see that it has had some strain. We'll see.

    After the change, we took it out for a test drive while attached to the Allison diagnostic computer and everything looked fine. The shifting
    was a bit rough at first, but got better as the control computer learned the bus. Downshifts into 4th, when slowing down, continue to
    be somewhat rough and the mechanic said that I might have to replace the control unit to fix that. Other than that, it runs smooth
    as silk and the retarder works better than ever.

    I constantly monitor the sump temperature now using the Silverleaf box and it stays around 210 most of the time. We've since put
    over 1000 miles on it and all seems fine, again except for some rough downshifts when slowing from highway speeds.




  7. #37
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    Fred,

    I assume you are using the arrow buttons to periodically check fluid levels?

    When you pull into a level space after driving and things are up to temperature that is a good time to check. If the transmission is too warm or cool it will tell you, but if you have been driving a while it should be in range.

    Last month I had to add one quart even though I have no signs of leaking. I surmise when last filled with Transynd and it read OK it was near the bottom of the range, and after about 3.5 years this last reading finally showed it down one quart. Trying to be that precise with the dip stick is almost impossible.

    The shifting should smooth out because it takes a certain number of shift cycles before it has "learned" to match your driving habits.

  8. #38
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    Glad you got fixed up Fred, the cost was less that what I had expected to hear from you. Hopefully the hard shift will get better as time goes on.

  9. #39
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    ............

  10. #40
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    Troup
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    Any suggestions for a code 2511?

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