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Old 05-06-2019, 08:07 AM   #1
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Odd Allison tranny error

Our coach has a Cummins 8.3 ISC coupled with an Allison MH 2000 tranny. The tranny, with its WTEC system, does an incredible job of self-diagnois.

I'm relating this to maybe help someone else that has this error.

I started to fire up to go on a trip but the engine wouldn't start and the tranny was giving this odd error. It was showing a symbol that looked like a zero with an X through it, then it would change to a symbol the looked like a slanted X sort of. I tried using the battery boost button but nothing.
After much researching and troubleshooting I was in the chassis fuse panel & had MS turn the ignition on. The voltage dropped to 5.7 v. It hit me like a bolt of lightning, the chassis batteries were almost dead!

But why, I said to the universe, why didn't the battery boost jump it? Well, on my coach the battery boost solenoid is powered by, you guessed it, the chassis batteries which were too low to engage it!

Well, after jumping it off w/ my truck I was on my way, mad with myself for not recognizing it sooner and way behind schedule. But I learned a valuable lesson: the Allison symbol for low voltage & I need to power the battery boost solenoid off the coach batteries.

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Old 05-06-2019, 08:59 AM   #2
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Glad you figured it out.
Just a side note, back in 2003 when I had my Rexhall Rose Air, I got that signal, apparently Allison calls it a "cats eye" Anyway, Very long story 'short' it wouldn't start and I had plenty of battery. Finally got it started and the problem was the wire loom from the shift panel to the transmission. It rubbed against the generator and caused an intermittent short circuit.
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Old 05-06-2019, 02:06 PM   #3
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So I was reading an Allison Service Manual the other evening and came across an interesting comment in the manual...

Allison Transmissions are shipped to their customers with their standard oil.... yet reading through there service manual they call any transmission used with an engine brake or an exhaust brake as SEVERE DUTY and require their upgraded synthetic fluid change the service interval to yearly or every 50K miles.

I can only assume this is because when the transmission ECM sees the command from the engine that the exhaust brake OR engine brake is engaged the transmission must raise the fluid pressure and lock up the torque converter and allow the power now from the rear wheels to travel to the engine for power to be absorbed and the vehicle speed to be decreased...

I know I've not followed those maintenance schedule as it lined out differently elsewhere in the information..... its the addition of the exhaust brake or engine brake that makes the different.....
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Old 05-06-2019, 06:35 PM   #4
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I think all of their transmissions, at least the 3000 and 4000 come standard with Transynd oil (It's a Castrol product)
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Old 05-07-2019, 02:41 PM   #5
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Thanks for that info, jelag. The previous owner had it changed & it was changed to synthetic, even though it only had 24,000 on it. It has a tag added to the pull stick but it may have had Transynd from the factory though as it is a mh3000.

It has an exhaust brake but it slows by partially closing off air flow in the turbo, putting back pressure on the engine. Exactly how I don't know but it works. It may raise pressure in tranny as it raises engine rpm.
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Old 05-07-2019, 08:06 PM   #6
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Quote:
Originally Posted by Joeb212 View Post
Thanks for that info, jelag. The previous owner had it changed & it was changed to synthetic, even though it only had 24,000 on it. It has a tag added to the pull stick but it may have had Transynd from the factory though as it is a mh3000.

It has an exhaust brake but it slows by partially closing off air flow in the turbo, putting back pressure on the engine. Exactly how I don't know but it works. It may raise pressure in tranny as it raises engine rpm.
The PacBrake/exhaust brake works by restricting exhaust gas flow through the exhaust pipe, post-turbo. This creates backpressure in the combustion chambers; which in turn slows the MH.
Your Allison should be a MD3060(MH version of 3000). Some have an optional retarder built into the transmission.
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Old 05-07-2019, 10:37 PM   #7
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Not only does my engine brake affect the engine (variable vane turbo in my case) but the Allison starts down shifting pretty enthusiastically. (Seeing 3000 rpm is not unheard of) THAT is where the "heavy duty" comes in.
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Old 05-08-2019, 10:34 AM   #8
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Most people don't realize that over revving an engine when 'down shifting' is actually just as bad or worse than over revving during "up shifts' I try to keep my rev's below 2,500 just for that reason. Diesels engines do no like 'high rev's'
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Old 05-08-2019, 11:23 AM   #9
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The PacBrake/exhaust brake works by restricting exhaust gas flow through the exhaust pipe, post-turbo. This creates backpressure in the combustion chambers; which in turn slows the MH.
Your Allison should be a MD3060(MH version of 3000). Some have an optional retarder built into the transmission.
Maybe it "should" be, but the manual says MH3000, I haven't crawled under to check specific numbers.

Exhaust brake: I stated I didn't fully understand exactly how it works. The manual says "The Pac Brake exhaust retard system is an auxiliary braking device that is attached directly to the engine turbocharger. The exhaust brake operates by using a dash switch. The dash mounted switch will operate the exhaust brake when dash switch is "ON" and throttle is "RELEASED."
When the exhaust brake is activated, a flapper inside the exhaust brake moves and restricts the flow of exhaust gases. This causes an increase of exhaust pressure within the engine. Increased exhaust back pressure quickly
slows engine speed, resulting in powerful engine braking action" That's the extent of my knowledge.

Thanks for your input.
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Old 05-09-2019, 05:41 AM   #10
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Allison transmissions are shipped to the vehicle manufacturers without any oil in them. The only oil in when shipped is the residual from the production test stand, which is TranSynd.
It is the vehicle or chassis manufacturer that chooses which oil to use and fills the transmission for the first time.
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Old 05-09-2019, 05:44 AM   #11
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MD3060 was the transmission designation for the close ratio 3000 before Allison started selling the transmissions classified by vocation.
Any 3000 in a motorhome after that point will be known as an MH3000.
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