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Duramax Transmission fluid

Old 10-18-2020, 07:01 PM
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Default Duramax Transmission fluid

About to do a trans fluid change on my '06 LBZ.

Probably a dumb question, but is there any reason to get Castrol Transynd over Mobil Delvac TES-295? $54/gal for Transynd, $45/gal for Mobil TES-295.

Doing a complete service (dropping pan, changing internal filter, etc..) Truck has Dex Vl synthetic right now

Thanks
Old 10-19-2020, 07:24 PM
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No one?
Old 10-19-2020, 07:26 PM
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Originally Posted by Manoverboard123 View Post
No one?
I was following to see the consensus, as I am hetting ready to do my 06 as well. I dont think it currently has synthetic in it.

I am typically a just stick with the manufacturer reccomended oil kinda guy. They have spent millions determining correct oil
Old 10-19-2020, 07:30 PM
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also be sure you get the correct inner filter. On my 19 silverado, I could have sworn it was the deep pan, but it was the shallow. Putting both filters side by side, there is less than 1/2 of an inch difference. I beleive the nipple is a different diameter though. The deep filter was loose fitting when slid up into the shallow trans housing.
Old 10-19-2020, 07:34 PM
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Mine is shallow. All the Allison's are gonna be shallow unless it is aftermarket. A deep pan is strictly an aftermarket "mod."

GM recommends Dexron VI synthetic, but Allison recommends any TES-295 rated fluid from the Allison 1000 all the way up to the big commerical transmissions.

Castrol Transynd and Mobil Delvac TES-295 are the most popular used, I was just wondering if there was any advantage over one or the other. The guy on here Back-In-Black has mentioned how much nicer the trans shifts and what not using the Allison fluid over Dex VI.
Old 10-19-2020, 07:36 PM
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On Amazon.. 12qts of TES-295 Mobil and both genuine Allison filters for $184. With the Castrol Transynd it's a little over $200

Old 10-19-2020, 07:36 PM
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[QUOTE=Manoverboard123;14150503]Mine is shallow. All the Allison's are gonna be shallow unless it is aftermarket. A deep pan is strictly an aftermarket "mod."

Thats funny. It was easier to get the deep filter than the shallow!
Old 10-19-2020, 07:39 PM
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[QUOTE=Codycat;14150508]
Originally Posted by Manoverboard123 View Post
Mine is shallow. All the Allison's are gonna be shallow unless it is aftermarket. A deep pan is strictly an aftermarket "mod."

Thats funny. It was easier to get the deep filter than the shallow!
Yeah, a lot of guys have done the "mod" and it's really not a bad idea to be honest... Helps keep the transmission cooler. But, I'm the kind of dude that says if it ain't broke, don't fix it.... Have an '06 LBZ in our family with 965,000 miles on the original Allison transmission..... So, I see no reason to start altering it's factory build
Old 10-19-2020, 07:44 PM
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DEX VI is the stock(OEM) fluid, you can use either, I'd get the cheaper
Old 10-19-2020, 07:51 PM
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[QUOTE=Manoverboard123;14150512]
Originally Posted by Codycat View Post

Yeah, a lot of guys have done the "mod" and it's really not a bad idea to be honest... Helps keep the transmission cooler. But, I'm the kind of dude that says if it ain't broke, don't fix it.... Have an '06 LBZ in our family with 965,000 miles on the original Allison transmission..... So, I see no reason to start altering it's factory build

That's awesome that you got that many miles out of it. My 19 was my first new truck ever. I average 60k a year. i hope to get 400-500k out of it, I change engine oil every 5k. Outer trans filter, fuel, and air every other oil change.

My 06 on the other hand i bought this summer for our slide in truck camper. It had 220k on it. I had to do new heads, turbo, y pipe, injectors, water pump, glow plugs, etc. Needless to say I got a ton of money wrapped up into it,, and hope the trans lasts awhile, since the engine should be good to go.
Old 10-20-2020, 11:26 AM
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I'd order the fluid from Summit.

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Old 10-20-2020, 03:22 PM
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https://dmaxstore.com/products/?rout...&product_id=61

add the internal filter, another gallon and you’re good to go

recently changed mine in my LMM with this kit, although I didn’t drop the pan. Just did oil and spin on filter.

Last edited by GoodRun; 10-20-2020 at 03:28 PM.
Old 10-21-2020, 11:45 AM
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GM owned Allison transmission until the “bail out” that’s why up until 2008 it was totally acceptable to run regular old GM Dexron in Allison trannies. Now that they’re away from GM they specify they’re in-house Transynd (Castrol product I believe). I wouldn’t sweat it. I’ve got 320K on mine running Dex, I do change it religiously at 50K along with the main (spin on) filter.

Allison also specifies you only need to change the internal filter during “overhaul”, many do it anyway though, probably doesn’t hurt.

http://www.fccc247.com/3%20Chassis%2...mendations.pdf

Last edited by jason8251; 10-21-2020 at 11:54 AM.
Old 10-22-2020, 02:07 PM
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Go with the Mobil 1 Delvac from summit racing. Best price I found when I changed mine.
Old 10-25-2020, 05:33 PM
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I recently did a lot of reading on this. The seals used in the earlier Allison transmissions were different than the newer ones. They made a mid year change in 2006. They discovered after a lot of 2006 trucks left the factory with the old seals and Dex 6 (instead of Dex3) that the Dex 6 was damaging the seals; thus the mid year change on seals to be compatible with the Dex6. You can look up the serial numbers of which transmission got which seals and thus which won't start leaking with Dex6 in them.
When Allison wanted their own fluid the got Castrol to make if for them so it's the real deal as far as Allison is concerned. Anything else is a copy but possibly just as good.
I went with Allison Transynd in my 2005. I figure the cost isn't that much more to get the real "Allison" fluid. I haven't noticed any difference in the transmission.

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