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Need help selecting fluid for hydraulic system (Steering, Fan) oil change


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I need to change the 50-55 quarts of fluid in our 2005 Exec/Detroit. In other threads, it’s been covered how some models have had a hydraulic pump leak transmission fluid into the hydraulic system causing an overflow. I had that problem and have fixed it. But, when I had the fluid tested (Blackstone Labs) the results were “off enough” that they recommended changing the fluid in the next maintenance cycle.

I’ve been doing some research and shopping, and realize I have several options: Dex III, Dex VI, or hydraulic oils in ISO 32, 48, and 64 ratings. I know that Transynd has been mentioned often, but I’m not planning to go in that direction so please don’t post that. I’m already planning to change the transmission fluid soon and I’m not buying four or five 5-gallon pails at this point. 

Now, I’ve read the owners manual and know that it says 50-55 quarts of transmission fluid, and that Dex III is the recommended fluid for “TF”. I also highly suspect that my unit came with hydraulic fluid not ATF initially, since the color initially had no red tint and only got some over time as Dex III was used to top it off, and maybe a couple of gallons of Transynd got mixed in with the bad pump. I raised my suspicions years ago with Bill D and he agreed, although there was no way to know for sure. I know that some 2000-decade models even had 15W-40 in the hydraulics, but I don’t think that applied to mine. I do suspect that the mix of hydraulic oil, Dex III, and Transynd is likely why Blackstone came back with a muddled result.

My current choices seem to be based on Tractor Supply options, but I’m still researching. Dex III is $102 per pail. Dex VI is a little cheaper, as is their “synthetic” option. They also have “universal trans/hydraulic” options, plus regular hydraulic oil in ISO 32, 48, and 64 ratings, all cheaper than Dex III. I’ve never heard of anyone using Dex VI, so that’s probably not a good choice, so I’m basically between Dex III and ISO 32 hydraulic.

Appreciate any thoughts (other than Transynd/equivalents) on this choice.

As an aside, I’m going to add a ball valve and nipple in place of the regular pipe plug in the drain, similar to what I did for the cooling system. Why Monaco built these things like the fluids would never be changed is beyond me.
 

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Mine is a 2003. It said Dex III. 

 

That is what I just out in it and it looked the same as what came out of it. 
 

 

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At the risk of contradiction or maybe added history.  MONACO used whatever was around.  I talked personally to Monaco tech support, the pump vendor and the fan motor vendor….as well as TRW….who made, probably, the power steering sector

My book said AW46.  Bought it.  NOPE….had ATF.  Went to all the above… they all said…..NO AW46.  Now, I also have a manufacturing and maintenance background and a lot of experience and knowledge about hydraulics in lift trucks and casting (metal and plastic) machines…..and installed a Preventative Maintenance program in two plants to cut down on down time and repairs…one operation had 100 plastic injection molding machines….and each machine had its own hydraulic system.

The ONLY documented use of “motor oil” was in the Elkhart plant for a year or two.  That was circa 2006 or so. Monaco in Oregon had converted to ATF.  But, some of the 2008 Dynasties have AW46. Monaco said….we converted a long time ago.

Bottom line, you have the big system.  Odds are…it WAS originally AW46. If it has been “doctored”…and this happens….I’ve seen construction equipment get hydraulic oil or ATF or Motor oil or power steering fluid.  Fluid is not “Fluid is Fluid is Fluid”.

The correct way to “fix” your system.  Drain the reservoir and disconnect hoses and drain as much out as you can.  Replace with ATF.  Look up the specs for your power steering sector or call TRW.  They will tell you WHICH DEX or fluid to use.

BUT….the techs will tell you….for maximum life and minimum wear, convert or add Transynd or the TES 295 equivalent….and buy one that Allison approves….not one that say TES 295.  The most trusted one is Delvac Mobil TES 295.  Allison tests that and certifies it. The TRW tech said….TRW decided NOT to spend MILLIONS to develop  a fluid.  We adopted Transynd.  We require it on all warranted long or high service applications.  Our warranty costs  are now half or lower what they were. Read the TRW manual.

Now….that is what I would do and what I was told and what many have done or such.  I changed my filters, twice….and added Transynd back both times.  I ain’t gonna do it again.  Got close to 70K on it….it will run for 150 K…

Your call….your rig.  That’s the history of Monaco and my comments come from moderating here since 2011 and reading just about every post since joining in 2009…

Good Luck….

 

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I'm using Valvoline Maxlife synthetic ATF.  When I bought it was $18 per gallon but has now gone up to $25.  

https://www.walmart.com/ip/Valvoline-MaxLife-Multi-Vehicle-Full-Synthetic-Automatic-Transmission-Fluid-ATF-1-GA/15125768?athbdg=L1102&from=/search

https://www.amazon.com/Valvoline-Synthetic-Multi-Vehicle-Automatic-Transmission/dp/B007VWRUQC/ref=sr_1_1_so_AUTO_ACCESSORY?crid=1NSN2MZIDDAF0&dib=eyJ2IjoiMSJ9.LZyXMO8rOwstfmNgBdEvFlnrIldjVYxMR4bfZDhMVaaDl6gj34gvJVj6rnPQepoHANidqIRmCUuLImyFEaz2CYwctblUq23pDCb2myybrw1DFuOaU2OhiM-foA1oDRPe4TugOouzLiAuE9N8VDbgpjFYIAJKtJN-7PIK2gTWxRRx5b94Y-0Wr6AGiYBLV8n6R2mqtMnaSFaheSiehnqMJE9iYNvPvp7kt2QkPjrm-LH5g8HQ8sfSAy9G498K8WI-1_iRXdTfUAoLdo1Zzj9sPJxHqOjgiPV5ubwChDvKLpU.91m4b6qNX_27mQBBG1gGL00OqN7mqCVxBBLFtydQL10&dib_tag=se&keywords=Valvoline%2BMaxlife%2Bsynthetic%2BATF&qid=1718234895&sprefix=%2Caps%2C82&sr=8-1&th=1

  • Recommended for use in the following applications: GM DEXRON-II, DEXRON-IIIm DEXRON-VI, Ford MERCON LV, Toyota/Lexus Type T, T-II, T-IV, WS, Honda/Acura, ATF-Z1, Nissan/Infiniti Matic-D, Matic-J, Matric-K, Matic-S, Hyundai/Kia SP-II, SP-III, SP-IV, SPH-IV, BMW 7045E, ETL 8072B, LA2634, LT71141, Allison C-4, Mercedes Benz NAG-1, Volvo 1161521, 1161540, 97340, 1273.41, and VW/Audi G-052-025-A2, G-052-162-A1. For CVT applications Valvoline recommends Valvoline Full Synthetic CVT Fluid.
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2 hours ago, Bob Blackmon said:

2004 Signature / Series 60. Book says Dexron III. While you are adding ball valves, put one on both sides of the filter. 

I'd be hesitant to put valves on the filter.
If one of those were inadvertently closed and the engine started, you could do serious damage very quickly.

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I was planning on valves if I ever change the fluid again but I would lock the handles or maybe just remove them. I have to dump 10 gal of fluid to just change the filter, pretty nuts.

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11 minutes ago, Ivan K said:

I was planning on valves if I ever change the fluid again but I would lock the handles or maybe just remove them. I have to dump 10 gal of fluid to just change the filter, pretty nuts.

You could relocate your filter head higher.

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Just now, 96 EVO said:

You could relocate your filter head higher.

Would need at least one new hose or extension made but sure is an option to consider. The tank is quite high and filter is at hitch hight, already scraped it once.

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20 hours ago, vito.a said:

I'm using Valvoline Maxlife synthetic ATF.  When I bought it was $18 per gallon but has now gone up to $25. 

Vito,

I think I've settled on a similar product, house brand from TSC. Around $20 per gallon ($102/5-gallon pail). Since my capacity is 12.5-13.75 gallons, I ordered it online for delivery to the local store.

22 hours ago, Chad A said:

Mine is a 2003. It said Dex III. 

 

That is what I just out in it and it looked the same as what came out of it. 
 

Chad, my manual for a 2005 model says the same thing. Page even looks the same. Good to know that 2003-2004-2005 were essentially the same, as I've always considered our coach as somewhat of a hybrid (2005 model, built early 2004, "white gloved" 4/25/24) as I've found a variety of older parts used.

I've decided to stick with ATF rather than hydraulic fluid. Ordered a synthetic ATF online.

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5 hours ago, Bob Blackmon said:

2004 Signature / Series 60. Book says Dexron III. While you are adding ball valves, put one on both sides of the filter. 

 

2 hours ago, dl_racing427 said:

I'd be hesitant to put valves on the filter.
If one of those were inadvertently closed and the engine started, you could do serious damage very quickly.

 

1 hour ago, Ivan K said:

I was planning on valves if I ever change the fluid again but I would lock the handles or maybe just remove them. I have to dump 10 gal of fluid to just change the filter, pretty nuts.

Good suggestion on the valve by the hydraulic filter, but I think I'm OK there as we've changed the filter numerous times with no drain issues. My reservoir is on the right side of the engine compartment under the rear run box, and the hydraulic filter is on the left side just below the coolant overflow tank, also about chest high. The primary fuel filter is below the hydraulic filter, and I learned the hard way that I needed a ball valve there. My secondary fuel filter came with a ball valve installed, and the coolant filter (I just use a blank these days after the conversion to OAT coolant) has two needle valves. But I will add a ball valve to the hydraulic reservoir drain, which makes it easier to drain the next time. Learned that lesson when I changed the coolant a few years ago. In fact, I wish I had it when the bad hydraulic pump was overfilling the reservoir, as I needed suction to drain out the excess.

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