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Old 12-13-2020, 07:47 AM   #21
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Right. Transynd is far and above a better fluid then dex3. But is it necessary?

Truthfully, rather then switching to a fluid that better handles high temps, you should install more or better coolers to avoid the high temps to begin with.

Even though transynd handles higher temps better, the transmission still doesn't like them.

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Old 12-13-2020, 07:52 AM   #22
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Quote:
Originally Posted by turf View Post


that my opinion!

every other transmission has a mechanical lockup at highway speed. the 545 depends on a fluid lock up of the torque converter. IMO, i want the thickest glue i can run to keep the T/C together and limit slippage.

if you factor in the heat, i still want the thicker stuff in a 545.

yes, the seal issues were on other transmissions, not the 545.

IMO ... clean fluid is more important than slick fluid.....

when i had the 545, i tried both trnsynd and dex 3.

i burnt the transynd off going up mountain grades, replaced with dex3 after adding a cooler.

now i have a locking at1545 and i'm running the dex 6.

i haven't over heated the new trans so i haven't changed the fluid, but i'd be fine with dex3 in the old girl next time.

its 4 gallons with my cooler and tes295 or the dex6 can really add up.

(just a foggy side note..... i seem to recall the military using 30w which would be similar to the hydraulic link i think)

did you know that allison actually recommended rotella 15W40 ENGINE OIL for their mechanical transmissions incurring severe duty applications.. more than one school director ran it in their AT540 series transmissions, the biggest issue incurred was super cold weather the vehicles had to be warmed up for awhile before the oil was thin enough to even engage the transmission.



unlike the GM series transmissions the allisons use a concentric gear type pump. (esentially like an engine oil pump on most diesels). so the extra thick oil wouldnt break the pump.. now if the converter clearance was set wrong you could strip the pump gear of its drive ears but properly installed there were no issues..



at some point GM started using 10 and 13 Vane pumps in their transmissions and fluid viscosity became a real issue.. 700R4 in 82 maybe started it? anyway the GM pumps were (are) fragile bastards.. pump too thick liquid through one of those and rev the engine and you break the vanes off..



the allisons will pump anything you put in them.. the newer electronic ones are more sensitive as those pumps have regulators designed to provide full pressure at a much wider RPM range so more constant fluid viscosity is important to them ...


im running standard Dex-III in my MT643 and ive run the bus in some pretty damn hot weather over hills and through valleys alike and the fluid is still beautifully clear and red


im running Transynd in my allison 1000 as that transmission was not only built with all the latest 2017 Specs it also is built as a high performance application, therefore line pressure regulation is all important... my Busses see a Huge range in temperatures. . from 105 degree texas heat to -10f or colder in winter if I travel to northern places in winter.. I dont worry about the MT643, its a literal TANK.. the little DTA360 in front of it makes that transmission say "is that all you got?"


my allison 1000 was easy to use Transynd as it was dry when I got it.. some Trans-gel assembly lube and the clutches were soaked in transynd and that was it.. brand new and empty it made easy sense to use it from the start.. I couldve done the same with the MT643 however I had a 5 gallon bucket of Dex-3 in my garage so I used it...


the biggest thing about whatever you decide to run in your transmission.. dont let it get low and dont get it hot...




-Christopher


P.S.


if you are changing your fluid and filters because you notice your transmission starting to act different.. ie laggy shifts or seemingly less crisp shifts, late shifts, etc. . then you wont help it one bit by changing the fluid and filter.. your transmission is already on its way to the graveyard... it may seem better at first but it will soon fail.. its already a goner.. Trans fluid whether it be transynd or Dex-III or Dex-VI has detergents in it.. if theres enough clutch material blocking your filters that you are losing line pressure or the friction discs are worn enough that slightly low line pressure wont stop the drums then the detergents will soon finish off the rest of the friction discs.



here is an ebay listing for an AT500 series rebuiold kit.. on the right are the steels.. on the left are the frictions.. you have spinning drums that contain planetary gears inside... if the center shaft and the gears in the drum all spin together you have a non engagement.. ie just passthrough.. stop the drump and those planets are forced to spin and provide some degree of gear ratio up or down from the center input shaft.. so you stack steels and frictions alternately on the outside of the drum. the steels engage the case with their outer teeth, and the frictions engage the drum itself with their inner teeth. the valve body sends fluid up into the case where a large "piston" presses down on that pack of frictions and steels.. causing the drum to stop and forcing the gears inside to spin. that is part of a 'shift' from one gear to another.. most likely at the same time some other drum may disengage and be allowed to spin again.. when the thin little material wears off those friction discs then they have a harder time engaging.. and you get a "slip" or shift that seemingly takes forever to complete.. just like slipping a clutch in a stick shift car because you let the clutch out very slowly you make heat and wear things faster..



https://www.ebay.com/itm/Allison-AT5....c100677.m4598
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Old 12-13-2020, 09:16 AM   #23
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Sometimes flushes, fluid and filter changes can restore performance. I've seen issues with slow shifts, torque converter shudder, and delayed engagement fixed by that.

But, if you're trans is shot, no fluid change is going to fix it. No magic elixir in a bottle will fix it. You have hard part failure, which can only be fixed by replacing those hard parts. A thing you didn't talk about, is glazing the clutches. Which is caused by overheating and slipping. Once the trans is overheated and the clutches slip the first time, the friction surface becomes somewhat inefficient at holding the steels, and then they slip more, causing more heat and damage.

The moral of the story is to change the fluid and filter at the appropriate time, and to not overheat the transmission. Overheating one does more damage then just trashing the fluid.
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Old 12-13-2020, 01:35 PM   #24
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the final straw on my 545 was the freefall that a long downhill would send the truck into.

i don't know what parts do what things....but, i feel like i had sheared some vanes internal to the T/C trying to engine brake the trans. on one trip home i remember hearing noises like broken glass and metal coming from the trans on a pretty reckless downhill stretch of I-70 coming into Denver. after that i never had any downhill braking from the 545.

i caught my brakes on fire twice, then i swapped out the 545.
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Old 12-13-2020, 02:52 PM   #25
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Originally Posted by EastCoastCB View Post
I'm saying there usually a spin on filter somewhere on the transmission's oil lines. Its usually called "hydraulic oil filter" cause its just a generic filter added by the chassis manufacturer. Mine's a napa I'll get a pic when it warms up a bit outside and there's more sun light.

Not sure if what you're looking at is a power steering or transmission filter. Just trace the lines and see what its connected to.
Well it says hydraulic filter on it. The filter i purchased to replace it suggested by cross-referencing on the wix site jus says oil filter, part number 51259. Did you get a chance to look at the vid I uploaded?

I'm starting to get confused trying to research all the helpful info. So, if this current hydraulic filter has nothing to do with the transmission or fluid, where is the transmission filter? With one line coming from it to the bottom of the radiator and the other one going through the top of the transmission what's its purpose? Cooling? I'm lost at this point but I guess if I cross-referenced it with the one the wix site suggested then at least its changed. Just would like to know of there is an actual transmission filter that's a spin on that I might be missing.

I also remember Booyah saying

Quote:
Originally Posted by Booyah45828 View Post
51259 comes back as a spin on transmission

51551 comes back as a hydraulic filter.

Both do the same job.

Both are similar in diameter, gasket size, 10 micron rating, and have the same 1 inch - 12 thread.

51259 is 5.5" tall

51551 is 5.2" tall

Go with whatever you feel is best, they're the same filter as far as I'm concerned.
I just wanna get pass the filters and get it over with but I don't wanna screw nothin up
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Old 12-13-2020, 03:33 PM   #26
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that is your spin on transmission filter.

the line goes to from the transmission to the heat exchanger near the radiator, then comes back to the filter and returns to the transmission.

the heat exchanger keeps the trans fluid the same as the engine temp. if you add a cooler, you add it before the heat exchanger.

the fittings on your filter look new. so it looks like its been replaced or worked on.
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Old 12-13-2020, 03:48 PM   #27
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Quote:
Originally Posted by Booyah45828 View Post
Right. Transynd is far and above a better fluid then dex3. But is it necessary?

Truthfully, rather then switching to a fluid that better handles high temps, you should install more or better coolers to avoid the high temps to begin with.

Even though transynd handles higher temps better, the transmission still doesn't like them.
For me its an easy choice- my reman 545 came with Transynd.
For me- my engine and trans are both clean and almost new. As new as I'll ever get anyhow. If I'm putting time and money into this bus I'm going to try and make this 545 last and thrive. Mine doesn't seem to slip much at all, so that's cool. But yeah for me being in FL and wanting to run highway speeds Transynd AND an additional cooler are what I've decided on. I have the cooler, just need to mount it.
Adding a cooler is a GREAT thing to do for any 545 owner.
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Old 12-13-2020, 04:01 PM   #28
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Originally Posted by turf View Post
that is your spin on transmission filter.

the line goes to from the transmission to the heat exchanger near the radiator, then comes back to the filter and returns to the transmission.

the heat exchanger keeps the trans fluid the same as the engine temp. if you add a cooler, you add it before the heat exchanger.

the fittings on your filter look new. so it looks like its been replaced or worked on.
Thanks for clearing that up. Is it hard to add a cooler? I've been reading and trying to grasp everything you all have been discussing about the 545 overheating and it's gotten me to worrying. Or does my 3800 have one built in? How can you tell? Hoping it does
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Old 12-13-2020, 04:04 PM   #29
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Adding a cooler is a GREAT thing to do for any 545 owner.
So no bus make/model comes with it built in to the radiator? Probably a stupid question, ha!
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Old 12-13-2020, 04:24 PM   #30
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So no bus make/model comes with it built in to the radiator? Probably a stupid question, ha!
the radiator IS the transmission cooler. But the transmission creates heat, so cooling the fluid before it gets to the radiator makes for lower operating temps for both the trans and engine. Adding an auxiliary cooler can be added for not a ton of money. I've got the nicest one Tango could find/research and he sold it to me before he passed away. (RIP TANGO!).
Its an "Earl's" unit. I just need to rig up some brackets and plumb it into the line.
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Old 12-14-2020, 05:26 PM   #31
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Originally Posted by EastCoastCB View Post
the radiator IS the transmission cooler. But the transmission creates heat, so cooling the fluid before it gets to the radiator makes for lower operating temps for both the trans and engine. Adding an auxiliary cooler can be added for not a ton of money. I've got the nicest one Tango could find/research and he sold it to me before he passed away. (RIP TANGO!).
Its an "Earl's" unit. I just need to rig up some brackets and plumb it into the line.
Go it. Thanks
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Old 12-15-2020, 06:33 PM   #32
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Out of the 2, the smaller one is the drain bolt, right? For a while I had my mind set on the big one because I never saw the small one until just now. Just wanna confirm
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Old 12-15-2020, 07:00 PM   #33
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the lowest one is the drain.

the bigger one goes to the same pan. it is a fitting for the dip stick tube. i think the dipstick could go on either side..

i installed my trans temp sensor in the larger bung.
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Old 12-15-2020, 07:07 PM   #34
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the lowest one is the drain.

the bigger one goes to the same pan. it is a fitting for the dip stick tube. i think the dipstick could go on either side..

i installed my trans temp sensor in the larger bung.
How does that work? You run some sensor from that big bolt al the way into the bus dash? My dip stick is under the hood right next to the oil dip stick
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Old 12-15-2020, 07:17 PM   #35
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Video on servicing the AT545 transmission. Starts at 10:51........

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Old 12-15-2020, 07:19 PM   #36
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yep thats the factory location for the sensor whichever side of the deep pan didnt get the dipstick can accept the sensor.. its a 2 wire sensor on navistar (not sure what other chassis manufacturers used).. and it goes to a dashboard gauge in the factory cluster..



my red bus had it on its original transmission.. its part of the computer on the new transmission so I didnt need the pan sensor anymore
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Old 12-15-2020, 07:54 PM   #37
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i used an aftermarket temp gauge and ran the wire.....


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Old 12-16-2020, 03:08 PM   #38
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i used an aftermarket temp gauge and ran the wire.....


Nice, where'd you end up getting it?
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Old 12-16-2020, 05:03 PM   #39
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Not sure anyone mentioned this but you can download copies of the Allison service manual and operator's manual from the internet free of charge. Each covers a range of Allisons transmissions including the AT545. Having them won't make you an expert but they do provide a lot of the information being exchanged in this thread. I know for me it's helpful to see stuff in print as well as get it from others, both are useful.

I did Google searches for "Allison at545 transmission service manual" and Allison at545 transmission owner's manual".
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Old 12-17-2020, 11:37 AM   #40
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Not sure anyone mentioned this but you can download copies of the Allison service manual and operator's manual from the internet free of charge. Each covers a range of Allisons transmissions including the AT545. Having them won't make you an expert but they do provide a lot of the information being exchanged in this thread. I know for me it's helpful to see stuff in print as well as get it from others, both are useful.

I did Google searches for "Allison at545 transmission service manual" and Allison at545 transmission owner's manual".
Thanks. I always check online before I ask and if I'm not sure after that then I ask just to be on the safe side. Don't think I can afford screwing up. I went on then Allison website a few times first and was kinda confused. But the more I read up here, what's on their site makes more sense

Edit: Thanks for the tip on the service manual!
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