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ANOTHER ALLISON Story - Interesting - SUCCESS!


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OK....  History.  My Allison MH3000 has 63K on it.  I had a complete filter and fluid change in 2012/13 around 25K to keep the extended warranty in place.  I had that done again in early 2018 @ 54K as i was going to do an 8.5K trip across the country.  The local OTR shop did it and let the fluid drain for a while....as they completed work on the Genny and such.  Allison later told me that was no recommended as the continual drain would allow more than the "expected" fluid to be removed.  They added the 19 or so quarts that Allison said and did not do the complete warmup and fluid test.  BUT, I checked the fluid level following the service guide.  it was showing 3 Quarts low and some funky codes.  I added 1.5 Quarts or so and had a local Allison dealer check and clear the codes.  Level was fine.  I was on the phone with Allison about the Diagnostics codes and they were not much help.  They referred me to the DEALER....

OK....drove it for almost 9K and then had TGU and did not get out in 2019 save a few miles to and from the shop for service and some "warm up" drives.

Have put about 500 road miles on it earlier this year and last week.  Drove it home from Emerald Isle last Thursday in a really ugly gully washer rain storm.  There were many stretches of roads in eastern NC that were flooded or had 6" to 12" of standing water.  I slowed down and got out of the worst.  Pulled into a rest stop and thought that the Allison (not very heavily loaded and towing the Yukon) seemed a bit abrupt in the Exhaust Brake downshift.  Since it was hot, I did the Fluid Check.  NO JOY.  The countdown did not start....got an oL -- FL code.  

Ate lunch and read a little and decided that the Allison dealer would be involved.  Set up an appointment for this morning.  Read that the FL code was a FAILED sensor (there are 6 or so listed).  OPPS....that ain't gonna be cheap.

On the way home, I called Mobile Support, Dr. Frank.  He chatted and did some research. IF it was the Oil Level sensor, then you had to drop the pan and such, so that would be a new filter and fluid and probably in the $500 - $750 range.  OUCH.... I had just pulled into my neighborhood.  He had me start to get into the Diagnostics.  In order to do that, you have to first enter the "Fluid Check" mode.  (push down, simultaneously, the UP and DOWN buttons).  OPPS....before I could do that again to enter the Diagnostics mode....BINGO....the fluid level program started to count down.  NO FL.  Aborted that.  Unhooked and drove to a side street and leveled the MH.  THEN, called tech support back as the Fluid Level test was perculating.  BINGO.... Fluid Level OK and NO funky oL -- FL code.

We chatted as he did some research.  In the Diagnostic Mode, I wrote down the codes.  Had three of them.  They were "old or inactive" codes.  We, mostly HE, concluded that there had been some communications issues before....PERHAPS a bad speed sensor.....  It hit me...  these codes were, i THINK, the same ones that Allison had cleared and pronounced the Tranny OK and sent me traveling.  Next UP.  he had me clear the codes.  Drove the MH back home and got it parked.  Next day, I checked the Diagnostics.  NO CODES (you do get a D1 -- but NO followup numbers.  I had three real (inactive codes) and two DX's with --.

Bottom line.....after noodling over it.  I THINK that the water caused a shorting error.  The "shorting" error is listed as one of the causes of two of the codes.  So, that is probably the some issue in the TCM and ECM and Tranny pigtails.....but it dried up.  I DID drive in a heavy rainstorm during the western trip.  The Allison also does, I think, periodic checks....so if it did one of it's little..."Hello.....are we still connected" tests during that period, it would have thrown the codes.

Bottom line, I have fully documented the event and such in my "log" and will monitor it for the duration of the season.  We'll see how that does.  The fact that the Allison dealer had cleared the codes and since there was no "active" codes resulted in the dealer not chasing a ghost to fix...

Tip of the Hatlo Hat to Dr. Frank (if you are old enough to know what that means....God save you....I am).  Thanks for the help, Frank....

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Tom, I had a very similar issue last summer on my Neptune Allison transmission. Mine is the 2500 tranny but I'm sure very similar plugs and such. Long story short, tech at Tom Johnson in Marion concluded we had connectors at the transmission had gotten water in them and caused erratic things. Ours went crazy half way down Black Mountain and came down the rest of the way with no exhaust brake (scary). We had driven through a frog choker earlier through the Great Smoky Mountains to about Asheville and after that she went crazy. We limped into Tom Johnson on Saturday evening. By Monday morning connectors dried out, and she shifted perfect. "Knock on wood" she's been shifting fine ever since, probably 5,000 miles.

 

I did take Van Will's advice and wd-40 clean  and small amount of dielectric grease on every connector on or near the tranny. Sure sounds like what just happened to you. Good luck and hope you're good to go now.

 

Chad Y

07 Neptune

Central NC

Edited by Chad Y
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5 hours ago, Chad Y said:

Tom, I had a very similar issue last summer on my Neptune Allison transmission. Mine is the 2500 tranny but I'm sure very similar plugs and such. Long story short, tech at Tom Johnson in Marion concluded we had connectors at the transmission had gotten water in them and caused erratic things. Ours went crazy half way down Black Mountain and came down the rest of the way with no exhaust brake (scary). We had driven through a frog choker earlier through the Great Smoky Mountains to about Asheville and after that she went crazy. We limped into Tom Johnson on Saturday evening. By Monday morning connectors dried out, and she shifted perfect. "Knock on wood" she's been shifting fine ever since, probably 5,000 miles.

 

I did take Van Will's advice and wd-40 clean  and small amount of dielectric grease on every connector on or near the tranny. Sure sounds like what just happened to you. Good luck and hope you're good to go now.

 

Chad Y

07 Neptune

Central NC

That will be my next order of business if I get the phantom, non active codes again.  I THINK now that what I felt when I decelerated onto the long grade down to the rest stop was either my "it has been a WHILE since I drove this puppy on the road.." or perhaps the Allison did have some electronic issues.  Not enough to throw a visual light on the display.  When I drove it back to storage on Monday, I used the Exhaust Brake and it seemed "smoother" and less abrupt.  Next time I go out with the Yukon, I will duplicate the scenario and see if there is a seat of the pants difference in the downshift and Exhaust Brake performance.

Thanks for sharing.  OUCH on no brake.  I was traveling to TN in the mid 70's and got stranded at the foot of the Black Mountain grade (headed west into TN).  That was on a Sunday evening and 4 or 5 folks were killed and a whole lot more injured.  That prompted all the sand lots and the speed restrictions on the Black Mountain grade.  i watched a car pass me around 60 MPH going up the hill once.... and then, Mr. Smokey pulled him over.  The SHP and Deputies patrol that road a lot.  I always stay at least 5 - 10 MPH under going down as I don't want to have issues and understand the physics of Kinetic Energy.  Squaring your velocity (speed) is ugly...

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  • 4 weeks later...

OK.....a little more INFO.....obviously NOT from a tech....but here goes.  When I had the "Cannot check fluid level issue", that was the result of a very erratic and hard downshifting, using the Exhaust Brake, occurrence.  I do NOT have the REAL Jake Brake....just the simple Cummins one.

I was approaching a ramp (downhill) for a rest stop.  Routinely, I engage the exhaust brake.  CLUNK....CLUNK.  HMMMM.  So, I got to the stop and decided to check the level.  THAT gave me the ERROR CODE....actually, the Tranny said.... We AIN'T gonna do that.....we is out to lunch.    SO, after ferreting through the codes and then discussing with Frank McElroy.....as I approached home (had driven it for about an hour), the codes were cleared.

What we surmised was that all the standing water (it was a frog strangler) had shorted or got the tranny connector wet.  I have not crawled under and done the approaching sealing...

BUT, I did clear the codes and all is well.  

Today, I drove it on another trip.  I routinely engaged the Exhaust Brake.  MY MY.....how smooth and responsive.  SO.....this is what I have concluded.

When the Tranny lost contact with the mother ship or her designee (the ECM or perhaps the TCM), then the tranny just "downshifted" on its on without the data buss from the ECM or the TCM.  That loss of data buss also stopped the system from doing the Fluid Check as there are several other "Sensors" that have to be in the loop (working) for the ECM and the Tranny and the TCM to allow for the Fluid Check.  What the Tranny got was an "We done lost one of our 6 little sheeps.....and until we find that cuddly little character....we are NOT going to play nice.

Therefore.....once dried out.....the Tranny shifts (Down) fine.  There was never any upshift issues.....just the harsh downshift.  All is well.  Need to put some bulb grease on the connections....

Edited by Tom Cherry
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