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Old 12-06-2019, 08:12 PM   #1
Skoolie
 
Join Date: May 2019
Location: Fresnope, CA
Posts: 154
AT545 vs AT542?

What's the difference? All I can find is that they both share gear ratios and input capacities, and that the 542 has a shallower oil pan.

It seems like all of the 5-6 window full size buses only came with one of these 2 transmissions. Are they any worse (or better?) than a Ford or Chevy trans in a cutaway? I'd really rather have the full height, like an International 3800
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Old 12-07-2019, 06:21 AM   #2
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Location: Ashtabula, Ohio
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Year: 1996
Coachwork: Thomas
Chassis: International
Engine: T444E 7.3L
They are pretty much the same transmission. Some members here don't care for it, but I have one in my bus and have no regrets or issues.
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Old 12-07-2019, 07:01 AM   #3
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,817
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
they are versions... the AT540 was the first.. then it updated to the AT542 then the AT545...



the deep pan is a nice and easy upgrade to an AT540 or AT542.. it was optional on the AT545..



one of my busses has an AT540. 2 of my other busses had AT545s (which Nuked and are now upgraded)..



the AT540 is markedly Noisier. and shifts with more purpose than my 1999 AT545 did...


my 1990 AT545 shifted tight and with purpose.. and had some whine noise but not near as much as the AT540.. its Torque converter was nice and tight...



my 1999 AT545 always shifted mushy and kick-downs werent nearly as responsive as my AT540 or 1990 AT545..



ive never seen an AT540 or AT542 in anything newer than 1988.. im thinking around that tiome was when it became the AT545.. which it remained until its discontinue in 2003
-Christopher


opinions vary and whether the AT545 is up to the task of a cross country skoolie.. I think alot depends on how the school previously cared for the transmission.. and how you care for it.. updating to a bigger cooler and keeping its filters changed goes a long way toward AT545 highway longevity..



that said.. on the 2 busses where my 545s Nuked, my trans upgrades have proven to be a game changer in the way the busses drive.. However they can also be a game changer on your wallet and doing a swap yourself requires some decent skill..


-Christopher
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Old 12-07-2019, 07:20 AM   #4
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Join Date: May 2014
Location: West Ohio
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Year: 1984
Coachwork: Bluebird
Chassis: International 1753
Engine: 6.9 International
Rated Cap: 65
They're all in the same family essentially.

I have one in mine as well. It works like it should, but I put less then 500 miles per year on mine.

Stock for stock, the at545 will be somewhat better then any of the ford or chevy early offerings. One big thing is that the at545 is 4 forward speeds while your c6/th400 is only a 3 speed. The problem, though, is that the c6/th400 can be upgraded and rebuilt way tougher then the 545. Once you get to the early electronic transmissions from ford or gm, it's a wash, and any of the later offerings from ford/gm will be markedly more reliable.
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Old 12-07-2019, 02:43 PM   #5
Skoolie
 
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Location: Fresnope, CA
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Quote:
Originally Posted by cadillackid View Post
ive never seen an AT540 or AT542 in anything newer than 1988.. im thinking around that tiome was when it became the AT545.. which it remained until its discontinue in 2003
-Christopher
Interesting...the bus in question is a '98, and he seems confident that it's a 542 after I asked if it's not a 545.

It's kinda frustrating that half of this 4 minute video is of still photos, and he only drives it a few feet forward and reverse, rather than an on the road test drive.
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Old 12-07-2019, 03:08 PM   #6
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,817
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
its possible the trans went bad and was swapped with a used one at some point.. an AT545 lasting a whole tenure of a school bus is somewhat unusual..



the AT545 in my 1990 was not the original.. there was a note that when the Bus engine was replaced with a Jasper reman , the trans was changed also..



the one in my 00 appears similar, it had a tag on it where it had seemingly been purchased from a scrap yard..


the AT540 in my 1978 has a reman Tag attached to it where it had been Rebuilt / Reman..



some schools run their busses till they are worn out then scrap them.. and they pull good tires, drivetrain parts etc to be used for repairs on existing units..



but then being navistar it totally wouldnt surprise me if they had some wierd option to get an AT542 in 98.. ive seen stranger things in school busses..
-Christopher
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