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Old 05-08-2016, 10:56 AM   #11
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when i got my bus, there was a burnt scent to the atf fluid. the first service home was a change to brand new fluid and filter.

after several trips in to the mountains, lots of funny noises, and a gut wrenching sense that im gonna have to replace that transmission before i get to the bottom of this hill. again the fluid smells burnt @ 12,000 miles post fluid change.

i'd like to hear comments of any that have changed to synthetic.
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Old 05-08-2016, 11:45 AM   #12
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Synthetic can handle heat better than dino, but if you have been running in the 300 range, it is probably too late to do much good. 250 is really max and anything over that wrecks the oil rapidly...then the trans. Any good trans tech will tell you that 90% or more of all transmission failures are due to fluid issues. Most commonly...overheating breakdown.

Once again...check out the chart below. It is about the same as the one Allison puts out for conventional fluids.

Transmission temperature/failure chart.

And if you are up for quite a bit of reading/research, there is a long discussion with "Mr. TranSynd" himself over on the DuraMax forum. Covers lots of ground including effects on seals, temps, proper flushing techniques and much more. Way too much to include here but you can see it below...

Former Allison Transmission Fluids Engineer (Mr. TranSynd) - Chevy and GMC Duramax Diesel Forum
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Old 05-08-2016, 01:40 PM   #13
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If anyone does decide to change to synthetic. How big of a concern is it to drain all of the old oil from the low points, pockets that don't drain from the pan like the torque converter and bottom of the cooling coil before you start mixing the two different types? I know the two will mix as circulation happens but will the original change need to be changed sooner because it is mixed? Just something in my head?
I have tried a few time and haven't found a drain plug on my torque converter and pulling hoses to drain is not that big of a deal but time consuming and worth it if it matters? Or just spend money and change the fluid earlier?
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Old 05-08-2016, 01:54 PM   #14
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For anyone willing to take on a fairly long read...below is a link to a discussion on the DuraMax forum that goes into a great deal of detail on tranny fluid. It was started by Tom Johnson who was the Transmissions Fluids Engineer at Allison Transmission from 1990 until his retirement in 2009. Very informative and authoritative. Covers heat, flushing, changing and lots more.
Former Allison Transmission Fluids Engineer (Mr. TranSynd) - Chevy and GMC Duramax Diesel Forum
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Old 05-08-2016, 02:37 PM   #15
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that was a good read, i got 10-12 pages in and was about all i could take.

by that account, he reccomends a double drain and fill.

drain and fill, change filter,

run the truck 20-30 mins and

drain and fill again.

so that puts us up at about 8 gallons to change.

the other link tango gave has a link to a trans cooler. very reasonable compared to a few gallons of the synthetic.

with out looking, does anyone know it the 545 uses 3/8" cooler lines or 1/2" lines.
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Old 05-08-2016, 04:09 PM   #16
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Have you notice any leaks started ? synthetic is so much thinner, I heard of leaks starting in oils seals
No leaks.Now I need more stupid words to so I can post my answer.
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Old 05-08-2016, 05:38 PM   #17
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where and how omn an AT545 are the best places to put sensors?

I figured I'd place on on the pan (standard location).. but where is another port to install a sensor? my bus currently has no trans temp gauge.. though an insert exists for my IHC dashboard cluster.. so I plan to add 1 or 2.. there are plenty of open slots on the cluster to place gauges..
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Old 05-09-2016, 10:50 AM   #18
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Turf, check that your tv cable is correctly adjusted, that will overheat a transmission in no time. Especially an old mechanical one like the at545.

Synthetics are great. They're more stable, better protecting and last longer. But I'd use only If you need them. My bus moves less then 500 miles a year. So it's not necessary in my situation.

As far as compatibility goes and which fluid to use. You'll have to research. The Allison 295 spec'd fluids are probably some of the best atf fluids on the market. They work awesome in all the newer transmissions. How well it will work in the older ones is anybody's guess. Seal leaks are a pretty valid concern as well. Even though numerous people and manufacturers say it's not a problem. Here's a short story on my experiences.

When GM switched from dex3 to dex6, every pickup that used an Allison that we swapped over developed some sort of leak, or had the pressure switch board go bad. Allison conveniently changed the seal materials in all the transmissions spec'd for dex6, but GM says dex6 is backwards compatible with older trannies. I blame the fluid, but gm says that isn't the problem. And they didn't happen overnight either, all were about 3-6 months after the swap. Most of them, after we fixed them, were swapped back to either dex 3 or Shell Spirax S6 A295. After that fiasco, I use nothing but the Spirax S6 in the newer alllisons, whether spec'd for Dex 6 or not, while the mechanical ones still get dex 3.
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Old 05-09-2016, 10:58 AM   #19
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Quote:
Originally Posted by cadillackid View Post
where and how omn an AT545 are the best places to put sensors?

I figured I'd place on on the pan (standard location).. but where is another port to install a sensor? my bus currently has no trans temp gauge.. though an insert exists for my IHC dashboard cluster.. so I plan to add 1 or 2.. there are plenty of open slots on the cluster to place gauges..
-Christopher
Like somewhereinusa found out, Trans temps will vary wildly depending on where you measure them. A large number of oem's put it in the valve body along with the rest of the pressure sensors and switches. I've also seen them put in the output line after the pump, right after the cooler, and in the pan. Which one works the best? Hard to say. I'd imagine that being in the pan would give you the most average temp, but being in the valve body would be the most accurate. I wouldn't rely on one right at the torque converter telling you much, because I think that one might swing pretty wildly depending on how you're driving at the time.
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Old 05-09-2016, 11:01 AM   #20
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Quote:
Originally Posted by Booyah45828 View Post
Turf, check that your tv cable is correctly adjusted, that will overheat a transmission in no time. Especially an old mechanical one like the at545.

Synthetics are great. They're more stable, better protecting and last longer. But I'd use only If you need them. My bus moves less then 500 miles a year. So it's not necessary in my situation.

As far as compatibility goes and which fluid to use. You'll have to research. The Allison 295 spec'd fluids are probably some of the best atf fluids on the market. They work awesome in all the newer transmissions. How well it will work in the older ones is anybody's guess. Seal leaks are a pretty valid concern as well. Even though numerous people and manufacturers say it's not a problem. Here's a short story on my experiences.



When GM switched from dex3 to dex6, every pickup that used an Allison that we swapped over developed some sort of leak, or had the pressure switch board go bad. Allison conveniently changed the seal materials in all the transmissions spec'd for dex6, but GM says dex6 is backwards compatible with older trannies. I blame the fluid, but gm says that isn't the problem. And they didn't happen overnight either, all were about 3-6 months after the swap. Most of them, after we fixed them, were swapped back to either dex 3 or Shell Spirax S6 A295. After that fiasco, I use nothing but the Spirax S6 in the newer alllisons, whether spec'd for Dex 6 or not, while the mechanical ones still get dex 3.
I dont know alot about commercial transmissions.. but every GM transmission I ever used. . fromm 200-4R, 4L60E, etc i always ran Type F.. gave me firmer shifts and the transmission seemed to run cooler.. now maybe thatd ruin an Allison I dont know.. it sure worked in the consumer grade trannies and I beat the &%^%$ out of those transmissions
-Christopher
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