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Has anyone used Amsoil ATF in the hydraulic system? not sure what came out of my system that I drained.
Thanks
JD

[cwl1979]

I personally wouldn't refill a system with ATF. I would look for a quality hydraulic oil such as Chevron 5606A. Its very similar to ATF in fluidness and its also red in color, but it doesn't have a bunch of the additives that ATF does. When in a pinch ATF would be fine, however ATF has a tendency to deteriorate rubber lines pretty fast causing more issues down the line.

Just my thoughts on it, from my experiences.

[Richard]

Carl, do you have an idea of mixing the existing atf in a system with hydraulic oil? Just curious.

[johnkosir]

on 712 Newell told me any synthetic ATF

[cwl1979]

Carl, do you have an idea of mixing the existing atf in a system with hydraulic oil? Just curious.

From my previous experience with auto transport, a lot of people in the 48 states "cut" their AW-32 with a few quarts of ATF.

From my personal experiences, with older equipment and rubber lined hoses, I've had hoses delaminate and cause problems. Some of the newer high pressure low weight hose solutions are really nice using "Pex-like" liner tubing with high strength nylon wrapping and a lightweight protective outer jacket. Being in Alaska limits me to what's available, using a product like Chevron 5606A was our best option. Cold will find a weak spot and tear things up. The Chevron 5606a has a working temp of -66F to +266F, I once split the Aluminum of a 2 stage cylinder by pushing to hard at -68F. The next day I had a chat with the boss and informed him that while our equipment might be rated to work in those temps... I am not!

The main benefit of using a better fluid is the ability to use it in colder temps, while lowering the strain on the moving components. Such as the pump or cylinders themselves. 

While I know that the average Newell/RV user isn't going out in -20 weather, I wouldn't hesitate to.

[jdkskyking]

In past years when I started planning my modifications to split my hydraulic system by adding a hydraulic pump dedicated to the cooling fan hydraulic motor, I best this topic to death. 
Here’s a AI response to using TranSynd 668 exclusively. 

Great question — you’re asking whether it makes sense (or if there’s a risk) to use Allison TES-668 TranSynd (synthetic ATF) in your 2005 Newell’s hydraulic circuits (steering gear + cooling fan motor), instead of a conventional hydraulic fluid such as Dexron IV / Dexron-III equivalent.

Here’s the breakdown:
1. What TranSynd 668 Is

• TES-668 is Allison’s current-generation, factory-approved synthetic ATF (automatic transmission fluid).
  
• It is a PAO-based synthetic, fully backward compatible with TES-295 (older TranSynd), and approved for very long drain intervals.
  
• It is engineered to be shear stable, oxidation resistant, with strong anti-wear and anti-foam additives.
  
• Viscosity: ~7.3 cSt @ 100 °C (similar to ATF/Dexron III/IV).
  

2. Hydraulic System Considerations (Steering & Fan Drive)

• Many OEMs (including Newell in your era) specified Dexron III ATF for the hydraulic system because:
  • Readily available,
    
  • Compatible with seals,
    
  • Multi-purpose (same fluid family as the Allison transmission).
    
• Steering gears and hydraulic fan drives in coaches of this vintage are not picky — they typically call for Dexron III or an equivalent ATF.
  
• Key requirements are viscosity, lubricity, and anti-foam performance, all of which TranSynd meets or exceeds.
  

3. Potential Advantages of Using TranSynd 668

• Thermal stability: Handles higher heat loads (beneficial for the fan drive circuit, which often runs hot).
  
• Oxidation resistance: Longer fluid life and less varnish in valves/pumps.
  
• Cold flow: Maintains better viscosity at low temperatures than mineral ATF.
  
• Consolidation: One fluid across both transmission and hydraulics simplifies maintenance.
  

4. Potential Considerations / Cautions

• Cost: TranSynd 668 is premium-priced compared to Dex/Merc ATF.
  
• Over-spec? In a simple steering/fan hydraulic circuit, the system may never stress the fluid like a transmission does, so the extended-life benefit may not be fully realized.
  
• Seal compatibility: TranSynd is tested for compatibility with ATF seals (nitrile, Viton, etc.). No known issues in hydraulics, but always confirm if your Newell system explicitly calls for “hydraulic oil only” (unlikely for that vintage — most called Dexron III ATF).
  
• Mixing: If there is residual Dexron III/IV in the system, mixing with TranSynd 668 is generally fine (they are compatible), but you lose some of the extended life benefit until a full fluid exchange is done.
  

✅ Bottom Line
There is no technical reason not to use TranSynd 668 in your Newell’s steering and fan hydraulic system if the manual specifies Dexron III/IV ATF. In fact, it may offer longer life, better heat stability, and reduced varnish. The only downsides are cost and the fact that the hydraulic circuit may not “need” that level of performance.

If you want one common fluid across the coach (transmission + hydraulics) and don’t mind the expense, TranSynd 668 is an excellent choice.

[hypoxia]

Newell used Mobil Delvac 1 ATF TES 295 in the transmission, steering and hydraulic system when they built 1482 and were still using it a year or two ago.

[jdkskyking]

Some things never change…

[David W]

My 87 classic doesn't have any of the extra hydraulic systems but it uses Mobil 1 ATF synthetic/ tes 295 in transmission and power steering. TES 668 is the newer version. I personally still use the Mobil 1.