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Old 04-26-2016, 06:14 PM   #1
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Allison MD3060 won't shift into overdrive

We bought a 1998 Monaco Dynasty last year and have driven it about 3,000 miles since then. Everything is fine except the Allison md3060 transmission won't shift into overdrive. We took it to an Allison shop last week and, $1,000 in diagnostics later, they tell us the transmission is fine and they do not know why it won't shift into overdrive. It also doesn't downshift automatically when you go up hills, you have to manually downshift it.

In the entire time we have driven it, we have seen it go up into overdrive twice for a short period of time.

Could it be a broken or corroded wire or plug between the ECM and the TCM? Could someone help us even locate the TCM so we could follow the wires? In everything we read, it seems like each person tells a different location.

I have searched this site and have not found the exact answer we are looking for but people here seem to be very knowledgeable and helpful and we are hoping to get some direction where to start. We really can't afford to take it to any more "experts" that can't fix it.

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Old 04-26-2016, 07:48 PM   #2
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Location: Powell River, B.C.
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Welcome to iRV2.

Your Allison 3060 has two overdrive gears 5th & 6th.
The shift into 6th gear may be limited by engine torque program and vehicle speed, and if you have changed the shift program, to economy.
My 3060 wont shift to 6th until the coach is doing over 58 mph. and I've heard of coaches with the Cummins 5.9 where the shift wont happen till 64.
The transmission ECM is located by the coach builder , and the chassis builder supplies the wiring with extra length to allow multiple locations.

JMHO: $1000 for diagnosis and no repair or even a reasonable explanation of possible problems , deserves a call to Allison Transmissions to have the shop's affiliation with Allison reviewed.
If the shop just road tested and ran a scan , the bill should have been no more than $200, and failing to deal with the no automatic down shift issue is inexcusable .

Problems with wiring should generate fault codes in the ECM.
A problem with the TPS that could lead to downshift issues should turn on a CEL when the Engine ECM, detects an issue there, as the TPS info is shared between the engine and trans.
Here is a pdf on Allison codes and a picture of the Allison ECM that may help you find it.
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99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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Old 05-02-2016, 10:41 AM   #3
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Allison MD3060 and non-functioning exhaust brake ( 1 2)

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