Author Topic: Allison Transmission Hard Shifting  (Read 3125 times)

Mike Grevers

  • BAC Member
  • *
  • Posts: 25
  • Thanked: 8 times
Re: Allison Transmission Hard Shifting
« Reply #15 on: January 03, 2023, 01:55:30 AM »
Thanks, I hope it lasts. Only time will tell and I will be sure to update everyone if it doesn’t or does.
2003 Beaver Patriot Thunder 505
The following users thanked this post: Fred Brooks, Frank Bergamo

Eric Maclean

  • BAC Member
  • *
  • Posts: 1184
  • Thanked: 442 times
  • Karen and I would like to wish you all happy trail
Re: Allison Transmission Hard Shifting
« Reply #16 on: January 03, 2023, 03:54:05 PM »
Mike
I would agree with your assumption the higher temps a first would have been slippage and the TCM would have been trying to counter that slippage by increasing clutch pressures and cutting down on clutch over lap time to decrease the possibility of slippage .
As you drove the coach with fresh fluid in it the clutch packs would eventually Purge the contaminated fluid from with in the clutch packs and the slippage would decrease the TCM would then start to return the shift schedule to a more normal ( less harsh) shift pattern .

By the way if the slippage gets out of control in any one gear the Allison TCM will command a down shift in an attempt to save the transmission.when the slippage gets out of control the TCM will also log a code for that clutch pack stating the slippage issue.

My coach uses a separate trans cooler that is mounted in front of the cooling stack ( first in line before the charge air cooler)
My trans temps run after a hundred miles or so at 148* and when climbing hard for extended periods of time will climb to 158*
And that may be due to RPM lose and related cooling fan lowered air flow through the cooling stack as the coolant temperature also increase from 188* to 196* when extended climbing so i put it off as normal.
It has worked this way ever since I got the coach 4 years ago

I'm with you on this one at this point the end game would be a rebuilt trans and you really have nothing to loose ( except maybe a tow bill if you get stranded)

Hope this helps
Good luck
Eric
« Last Edit: January 03, 2023, 04:56:22 PM by Eric Maclean »
1997 Patriot Yorktown
3126-B
2009 Chevy HHR
Roadmaster falcon tow bar
Demco Air Force one tow brake.
The following users thanked this post: Fred Brooks, Mike Grevers

Mike Grevers

  • BAC Member
  • *
  • Posts: 25
  • Thanked: 8 times
Re: Allison Transmission Hard Shifting
« Reply #17 on: February 03, 2023, 03:06:15 AM »
Update:

I took the coach on a trip from Chicago to the Florida Keys for about the last month. The transmission did well. I saw temperatures ranging from 155 to 185 from flat Indiana in the cold to the hills in southern Georgia. Although I got over 2000 miles out of the transmission, it was always in the back of my mind that it's when it will fail not if it will fail. I decided upon my return this past weekend that I will be ordering a reman transmission. I got a few quotes from $10,250.00 at the high end and the lowest at $7,900.00. I will be going with the lowest as they are a major local Allison distributor I have worked with and have a 2 year unlimited mile warranty. Just wanted to let everyone know how it went.
2003 Beaver Patriot Thunder 505

Frank Bergamo

  • BAC Member
  • *
  • Posts: 275
  • Thanked: 72 times
Re: Allison Transmission Hard Shifting
« Reply #18 on: February 03, 2023, 05:35:47 PM »
Wow,

“when it will fail not if it will fail.”  That’s just about every major component on the coach. Traveling several thousand miles with zero issues with transmission, I think I would hold off on replacing transmission. There are no guarantees that a rebuilt or remanufactured trans will be any better. Just my humble opinion for whatever that’s worth. Good luck on your decision.
Frank & Paulette Bergamo
2019-       : 2007 Marquis Topaz IV  C-15 600 HP Allison 4000
2014-2019: 2002 Marquis Emerald C-12 505 HP Allison 4000
2004-2014: 1986 Executive Diplomat 3208 250 HP Allison MT-643
Grand Junction, CO.