[mrad77]

The recommended goto fluid would be the TES 668 full synthetic

Here is the approved list of fluids from Allison

On-Highway Fluids

Allison Transmission TES 668® introduces the next generation of synthetic automatic transmission fluids for long-haul applications.

www.allisontransmission.com

I was on the same site from Allison. I also called them. When I told them the transmission was in a Duramax, they told me I needed to call GM and should use their recommended oil as they changed the specs on some of the seals. So is this just GM trying to sell their product?

 

[OkDually]

I was on the same site from Allison. I also called them. When I told them the transmission was in a Duramax, they told me I needed to call GM and should use their recommended oil as they changed the specs on some of the seals. So is this just GM trying to sell their product?

The Allison 1000 is in the Duramax. Use what is listed in the Allison guide. As long as you use the TES fluids you are fine.

 

[STigue]

Great to have you on board and welcome . My 2019 I have been using Delvac 1 ATF doing a drain and filter change every 20,000 miles . I do this because we pull heavy and my son uses it to race in JR Street (drag racing) . I just ordered a 2024 GMC SLT . What would be your recommendation on fluid and fluid change intervals . Is the Delvac 1 great to use or should I just go with TranSyn ? We pull a race trailer and I have never had a problem with my Allisons in 5 trucks I've owned so I just want to take care of the new 10-spd

 

[Oregonnovaguy]

“Taking care” of the Allison 10 speed is going to be a little tough; GM inexplicably did away with the spin-on filter, and even worse, there is no dipstick (and therefor no way for the DIY guy to check fluid level and top off the fluid).

 

[RINGNEKS]

Anyone having tranny issues on their 2020 or newer Dmax? My buddy just lost his in a 2023 while towing up a steep grade.

 

[boaty3]

I've been away from the forum for a while, been busy and truck has been pretty flawless. Anyway, I'm wanting to do a trans service, is the TES 668 going to be ok for my 03 5-speed ALLY? I remember back in the day there was a concern using a certain fluid as it would cause issues with the seals or something in the 5 speeds. I'm considering the Valvoline Syn Gard 668 or the Mobile Delvac 1 ATF 668. Thanks!

 

[OkDually]

I've been away from the forum for a while, been busy and truck has been pretty flawless. Anyway, I'm wanting to do a trans service, is the TES 668 going to be ok for my 03 5-speed ALLY? I remember back in the day there was a concern using a certain fluid as it would cause issues with the seals or something in the 5 speeds. I'm considering the Valvoline Syn Gard 668 or the Mobile Delvac 1 ATF 668. Thanks!

Allison now recommends the 668 for the Allison 1000

 

[boaty3]

Allison now recommends the 668 for the Allison 1000

And it is safe for ALL Allison trannys? Even my 03 5-speed? I haven't been able to find anything that specifically says its safe in ALL of them. I just want to be sure before I put something in it. Like I said I remember there being a fluid that would damage seals at one point.....
Thank you for the reply!

 

[OkDually]

And it is safe for ALL Allison trannys? Even my 03 5-speed? I haven't been able to find anything that specifically says its safe in ALL of them. I just want to be sure before I put something in it. Like I said I remember there being a fluid that would damage seals at one point.....
Thank you for the reply!

On-Highway Fluids

Allison Transmission TES 668® introduces the next generation of synthetic automatic transmission fluids for long-haul applications.

www.allisontransmission.com

 

[ancho]

TES-668 is backwards compatible to 2001 for the Allison 1000. If you haven't already found that out.

 

[Rsharpe]

Tom,
I have 2007 classic 2500. I spoke to Allison tech today like you recommended, my serial number told him that my Allison was made by GM. He would not commit to telling me to change to Transyn over Dextron VI because of seals, said I would need to hear that from GM. We both know GM will recommend dex VI. He did ask why I was opposed to using dextron and I guess I’m not really opposed to it, but from what I’ve been reading Transyn is the best option for my tranny. Thoughts?

Thanks,
RWS

 

[mp06011999]

Tom,
I have 2007 classic 2500. I spoke to Allison tech today like you recommended, my serial number told him that my Allison was made by GM. He would not commit to telling me to change to Transyn over Dextron VI because of seals, said I would need to hear that from GM. We both know GM will recommend dex VI. He did ask why I was opposed to using dextron and I guess I’m not really opposed to it, but from what I’ve been reading Transyn is the best option for my tranny. Thoughts?

Thanks,
RWS

I've an 06 LBZ since new and on the advice of Tom Johnson himself from a phone conversation we had years back, I switched over to TES-295. And this is plastered all under the hood:

To each his own, but my baby is gonna make the second owner a very well taken care of ride

https://www.dieselplace.com/threads/alli-1000-seals-and-dex-vi-vs-tes-295.723746/#post-7185242

 

[Rsharpe]

Thanks mp06011999,

I didn’t realize until reading further on that Tom had left the forum, so I appreciate you passing his past words of wisdom on to me.

 

[Trey1983]

Hi folks,

My name is Tom Johnson. I was the former Transmission Fluids Engineer for Allison Transmission from 1990 until my retirement in 2009. I worked to develop and release TranSynd for Allison over a 10 year period and I also wrote the Allison TES-295 and TES-389 specifications. I had full responsibility for approval of all transmission fluids for Allison products on a world-wide basis. Since Allison was owned by GM for decades, and as part of my job at Allison, I also served on the ATF Committee for General Motors for several years. And, because Allison produces most of the transmissions for the US Army, I was also a member of the Engine Oil Review Committee for SAE Performance Review Instittute (formerly the Lubricant Review Institute.

These are my credentials. I'm here to help with your questions and to settle any arguments concerning TranSynd, Allison fluid specifications, DEXRON-III, DEXRON-VI, oil formulations, etc. So, as long as I'm not absolutely flooded with stuff, I'll try to keep up.

PS: I couldn't be involved in these forums while in my official capacity at Allison but I always thought I'd get involved once I retired. I own my own oil and coolant analysis business now and do consulting for the oil and additives industry on the side.

I recently bought my first duramax and have a few questions for you if you get the time. Thanks in advance

 

[OkDually]

I recently bought my first duramax and have a few questions for you if you get the time. Thanks in advance

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