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Flex plate
Customer was going down the interstate when the coach quit pulling and they rolled to the side of the road. Engine still running, until they shut it off. Tow truck later and some hours later…The flex plate had came apart, therefore separating the engine from the transmission for movement
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17 Replies
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Year or coach? Any evidence it was used to pull an oversized stacker trailer?
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Now what?
Replace the flex plate and they are good to go?
Or does the trans have to be disassembled, thoroughly cleaned, inspected, and put back together?
Jon … I’m putting my money on someone try to trying to “rock the coach” when it got stuck at some point in its life.
Jeff: is that apart in your shop?
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Ouch, that cuts! Is there any other kind of stacker trailer? Maybe DD gets their flex plates from Pratt and Whitney.
Seems like a pretty rare failure, I’ve never heard of one like this on a Prevost.
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2012 with just under 200k miles…This is not common but has happened to other coaches..
Yes this is at my shop…
No trailers or vehicle behind coach
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I think Dick may have hit the nail on the head.
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I doubt that since it has happened to multiple coaches…
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The reason I said “rocking the coach” is because a racing friend of mine bought a used 40′ (or maybe 38′ … either way NO tag axle) diesel pusher to pull his 24 to 28′ race trailer. I gave him some “things to be concerned about” when he asked my thoughts ahead of the purchase. I think he bought in spring and in late summer the transmission “went out” and asked where I thought he should take an Allison. Not sure of the trans model.
The shop he used here in Wisconsin apparently does lots of Allison work and the tech said the transmission looked like the coach had been “rocked”. I don’t know why he felt that, but he probably had seen it before. I’ll send the pictures to my friend. He sold the coach the next year and said “I bought it right, all in all I came out OK”.
Just for the record, being born and raised and now living where I do I’ve rocked a few cars, trucks, and SUVs when stuck over my lifetime. But I think I know how to do it “right”. I’m reluctant to rock an automatic transmission. A manual trans with a clutch is much easier. The automatic takes too much time to “lock up” to do it safely and effectively. If you can’t rock it effectively, trying to rock serves NO purpose.
I would never, ever rock the coach. If I get wheel spin ONCE in something soft, I’ll lift the tag and try to crawl out. If I experience wheel spin again, I’ll call a tow truck. A big tow truck. Probably a customer of John Hawkins.
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If you are experiencing some wheel spin and you have not dug yourself in, it doesn’t take much of a tow truck to get you out. If the truck has solid ground and a tow cable, it’s surprising how little pressure it takes to get you moving again. I was in just that situation and “Joe’s Tow” got us and our neighbor moving in no time. We also got dug in deep (long story how and why, but not my fault!) and a good farm tractor and tow cable got us moving out of that mess as well. There just needs to be good solid land somewhere for the tow to begin.
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My friend’s Allison problem was not the flex plate, it apparently was internal. It was pulled and exchanged for a reman and he doesn’t know what the rebuilder found.
Does this coach have Jake Brake or a transmission retarder?
We’re getting pictures of areas of a coach that 99% or more of us will never ever see.
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This happened to my extended family’s entertainer XL a few years ago. They were towed back to Prevost Nashville. At the time they were told it was extremely rare. The mechanics could only remember that failing on one other entertainer coach.
I remember my cousin telling me the engine was running fine and it just quit pulling. They first assumed it was a transmission failure of some kind.
Interesting coincidence, their drummer at the time had been on the other bus when it happened. Any drummers on board, Jeff?
Davy
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Jeff: Any thoughts on what happened to the flex plate?
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The failure is not only on Prevost coaches…It has occurred on some fiberglass coaches with the same style flexplate. Although it is not common place it does happen…This is also something that is hard to track how many it has really happened to..The units are typically out of warranty. This is a item that you do not have to go through Prevost for. So unless you could access the data base of Allison there is no way to know. I do know that although the parts were not all available locally, they were available in the system. So one could assume that they sell enough of them to have them available.
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This was a fairly common issue on 7.3 Ford diesel pickup trucks. It is caused by harmonic vibrations created by the engine. It may be the engine in this case had a miss or weak cylinder which set up some unusual vibrations causing the failure. It would be interesting to know if the part number has been superseded. If so they may have identified an issue.
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“Rocking the Coach” is not the cause of this.. only the driveshaft , gear set and axle shafts get any stress reversing and driving foreward in that situation . This is a Allison part and Allison failure . Could be a heat treat failure from manufacture, harmonic failure , over/undertorqued flywheel bolts. Put 265,000 miles on our last coach 2000 H-3 , towed stacker , Jeep’s trailers with Jeep’s and anything else . 12.7 60 Series set at 550/1850 .
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Agreed. Flexplate/converter doesn’t know or care if bus is moving in fwd or reverse.
Likely most stress on the flexplate and bolts are under lock-up in higher gears at full boost.
One advantage to an Eaton Roadranger
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