MD3060 buzz and “do not shift”

[Cougarkid]

1998 Overland Larado
Cummins 6CTA 8.3L
Allison MD3060
119,750 miles

Stuck in driveway. Been parked fo a month. Getting ready to head out.
Key on and a rhythmic “buzz” from under the dash. “Do not shift” warning light on dash is keeping time to the buzz. Selector “wtec ii” is flashing a zero (0) with an X and a + inside it, matching the rhythm, also.
No response from the selector.
If I let it buzz in for a minute or so, it will stop buzzing and return to normal mode. It might stay that way, or revert to buzzing again.
After returning to normal mode, if I start the Rv, all is good, until I put it into gear. At that point, the selector goes bye-bye, the buzzing resumes, and I have to turn the RV off to get it to reset and go back to neutral.

So far we have:
Checked all connectors. Unplugged and reconnected.
Checked all fuses we could find.
Checked relays in control box under dash.
Disconnected battery and reconnected.
Checked tranny temp gage at dash.

We managed to get it to go into gear, but it clunked a bit, like it went in and out. Not the normal sound. still in buzz and do not shift mode.

Any help would be appreciated!

[Cougarkid]

Finally managed to get a 35 00 code out of it. Battery voltage interruption.
Out to check all the wires from the battery to the tranny. Should be fun - it it packed in there pretty tight and wires going everywhere!

Still looking for advice.

[deandec]

Measure the chassis battery voltage at the battery terminals for at least 13.2 dcv.

Try starting your generator and then the engine, using the chassis battery boost, to see if all works well.

Could be you have a failed battery or alternator.

Transmission needs solid voltage to operate during a trip.

The engine only needs voltage to start.

The generator can help provide the needed voltage on my rig.

When my alternator failed during a trip, I connected the two positive posts of the chassis and house battery. Then I started and ran the generator all the way home about 150 miles with no problems.

[Cougarkid]

Interesting idea with the generator. I’ll remember that one!
Actually ran jumper cables from 2nd vehicle (running) to try to boost voltage, but no help.
Chassis batteries are 9 months old and holding charge, but only at 12.8 volts.
Alternator is only holding batts at 12.8 volts, not really charging. That is in the list to get checked out, too.

[deandec]

12.8 volts is either fully charged 12.6 dcv plus a 0.2 float charge remaining.

If you alternator is running and charging at about 13.6 dcv then it is ok.

My 13.2 volt erroneous comment should have been 12.6 dcv for a charged battery and 13.6+ dcv for measuring the charge to the battery from the alternator.

It is possible that your battery cannot carry the operating load of the chassis starting sequence and therefore cannot power the transmission afterwards.

If you continue to have a problem, you may want to have the chassis battery load tested even if it is newer.

You probably know all the above but thought it might jog some ideas to get your rig going.

[Cougarkid]

THANK YOU for the info/thoughts!

Disconnected and checked batteries - both at 12.6 volts.
Hooked up again and had to “emergency start” to fire up Rv. (BTW, 3rd day of testing/checking/running)
Got a 12.6v reading while running.

Alternator!

Pulled it out and off to parts store.
Tested and voltage regulator bad.
Putting out 11.6 volts.
Cheered at having to replace it!

New one will be in tomorrow am. Will install and “hopefully” be on my way at last.

I will let you know.

[Cougarkid]

Well, alternator replaced and pumping out the volts!
With that said, I am still stuck with the same tranny issues.
Had an hour long conversation with
The service manager, Steve, at Pacific Power Group in Kent, WA.
After following his instructions to test power and ground wiring, it looks like the ECU and/or selector is bad.
Will be at his door at 7:00am Tuesday for testing. If bad, new one is $3500!

This will be our 1st major repair (over $500) in the 8 years we have owned it.

[NHRA225]

Hold your Horses !- Call these Guys ! best in the Business if your not in a Hurry and want it repaired Right !
>>>>https://www.transmissioninstruments.com/

[Cougarkid]

Well, went and saw Steve. Hooked up my ecu and selector and both appear to be good. Tranny health is excellent. He doesn’t want to sell me one if I don’t need it.
He gave me a used ecu to take back and use for a test to see what happened. Got the same issue with it. After some more testing and phone calls, looks to be bad power somewhere in the system.
Had to leave the Rv and am headed 2000 miles to Missouri by van with my son and family for wife’s father’s funeral on Saturday. She flew out Saturday.
Time WAS against me.
Will have to come back and resume repairs in a few weeks.

[Cougarkid]

To clarify the above power statement:
We previously checked the power and ground wires from the batteries. This was done per Steve’s direction, following Allison’s procedure, by the numbers. All readings came back good. Voltage and ohms.

There is no good way to check the power wires while it is running. We are going to have to run new wires from the batteries to the ECU and splice into the connections to check things out. We will run temporary wires outside the Rv to check and install permanently if that corrects the issues.

For future reference:
Allison states that 9.6 volts minimum are required for proper transmission operation.

[RKins]

Originally Posted by NHRA225

Hold your Horses !- Call these Guys ! best in the Business if your not in a Hurry and want it repaired Right !
>>>>https://www.transmissioninstruments.com/

X2 on contacting John and talking to him about what you're seeing/experiencing. His specialty is repairing TCM but he really understands how the system works. I sent my TCM to him, he tested it to include putting the TCM in the freezer and testing it again the next morning. He found nothing and there was no charge except for freight both ways. He did send me a wiring addendum that fixed my problem which was PacBrake not working.
It can't hurt to contact him through their web site, leave your phone # and he'll call you back.

[Cougarkid]

So, back in town again. Only 3 weeks later.

Talked with transmissioninstruments today. Told them my saga of flashing, codes, ECU swap and wire tracing. Ran their testing and came up with a clean bill of health on everything. Shifter good, ECU good. Their take, bad power/ground wire somewhere, but no way to tell where for sure.

All my flashing/buzzing/clicking comes down to the VIM under the dash. All tranny power seems to go thru it. 6 relays, with only 2 of them marked (neutral and back-up warning) and a 3rd for pac-brake, unmarked. Both 10amp fuses are good. All 6 relays in there (all as far as I can tell) are clicking on and off in rhythm with the flashing of the selector.

I can replace all 6 and see if that solve the problem.

If not, I'm down to running new power and ground wires from the battery to the front of the coach and tapping into the VIM power wires. Maybe a bad wire that is shorting under load.

We will see...…..

[Cougarkid]

So, another day of testing. Jumper wires, multimeter, sockets, screwdrivers, etc.
Chased it down to an issue with the VIM. Power in, but only partial, intermittent power out. Making the neutral relay click off and on.
Used the cigarette lighter, a power plug and some crimp connectors to create power “out” of the VIM to the ECU. Jumpered the neutral safety.
Coach fired right up, cat eyes gone, N on shifter. It will now go into gear and move!
Going to hard wire it up for now. Will look into getting the VIM checked out and possibly a replacement.
I’m for now, at least I can move and travel if needed.

[rschreifels]

This may not solve your problem, but it doesn't hurt to try it.

Unplug the connectors and use a conductive grease on the pins and then put dielectric grease on around the connector shell/seal to keep water out of the connector. But Do Not use dielectric grease in the pins.

If you have used dielectric grease on the pins in the past, you need to clean it out and use conductive grease on them.

IMHO from past experience.