300+ rebuild

[Geoff Weeks]

You can disagree with Eaton, that is fine, I went to the source to make sure I gave the correct info.

further more it is a used box, so you have no idea what it was filled with.

Eaton doesn't mention a need to "flush" if a different or unknown lubricant is being replaced by something else.

 Synthetic has better heat qualities than SAE 50 which has better than GL-1. Each is a step up.

 In this application, which is so far down the scale from the transmissions rating, SAE 50 would be fine. Even GL according to Eaton would be ok, but I would not recommend it. They list it as acceptable in other parts of the world (in the same transmissions)! 

Edited yesterday at 01:19 PM by Geoff Weeks

[Freightrain]

I thought I saw specs that say it was okay to use. I also understand that changing now would likely not be a good idea.  But, the fact that this transmission was never shifted would alter that fact slightly.  The discs are still permeated with synthetic oil.  So I guess I will change my bucket out.

[Geoff Weeks]

I wouldn't give SAE 50 a minute of thought before filling the trans with it. Your call. SAE 50 is listed as approved. 

Any used transmission syncro is going to "be saturated" with what ever was run before, It will not make a difference, but as I say, your money, your call.

[BottleHauler84]

57 minutes ago, Geoff Weeks said:

You can disagree with Eaton, that is fine, I went to the source to make sure I gave the correct info.

further more it is a used box, so you have no idea what it was filled with.

Eaton doesn't mention a need to "flush" if a different or unknown lubricant is being replaced by something else.

 Synthetic has better heat qualities than SAE 50 which has better than GL-1. Each is a step up.

 In this application, which is so far down the scale from the transmissions rating, SAE 50 would be fine. Even GL according to Eaton would be ok, but I would not recommend it. They list it as acceptable in other parts of the world (in the same transmissions)! 

I know you like to argue with people,  and its ok because most dont take it personally...including me. I respect your knowledge. 

Will you point me to the section of your information that deals with drains and refills? I was referring to what Eaton currently recommends (PS-386), and the idea that you dont mix mineral based oils with synthetics. It never has and still isn't a good idea. Will it work, yeah im sure it will. Along with 80w90 gear oil, 50w engine oil,  iso32 hydraulic oil, vegetable oil, maybe just put a grease zerk on it and fill it with grease. 

Why not just put back in it what eaton calls for?

[Geoff Weeks]

19 minutes ago, BottleHauler84 said:

Why not just put back in it what eaton calls for?

Eaton calls for many choices, it is right there in their manual. I am not recommending something that Eaton does not. Larry wasn't happy about paying the expense for synthetic and according to Eaton it isn't required.

 I found no info saying flushing was required at any point in the manuals I read when changing lube, if it isn't there (it may be and I missed it?) I can't point to it. If you can point to where it is required, I will accept that.  

When you made the the statement that syn was required it was something I had not heard or read, so I went to the source to see if my understanding was incorrect, it was not. So I linked the source material for all to read. 

IF you want extended drain intervals and you want Eaton to warranty it, then and only then does Eaton require its use for warranty purposes.  

On a used transmission none of those apply. All the oil I listed are approved by Eaton for their HD manual transmissions. 

By your reasoning deleting the oil cooler would also void any factory warranty. But they are not required below 350hp, although you pointed him to the delete plate. By the title of this thread, he is well below that.

Transmission lube has an easy job compared to other boxes, no combustion gases, no hypoid or amboid gearing, little chance of moisture accumulating, just spur gearing, roller bearings and one double ended syncro. 

Edited yesterday at 02:24 PM by Geoff Weeks

[Freightrain]

Just my .02 worth of knowledge and synchros (in car transmissions).  The old brass blocker rings worked better with mineral oil.  Synthetic was too slippery and it would rake gears.  Most new automotive transmissions use a version of ATF and with fiber blocker rings it shifts fine.

I don't know what Eaton uses for synchros today?  I think the old boxes were brass when it used mineral oil.

 

I agree with not mixing fluids.  I take that as using 1/2 syn and 1/2 mineral persay.  Topping it off with one while it still has something else in it.  Mine is very dry right now so there would not be any "mixing" of fluids 

[Joey Mack]

The Eaton Synchro is a pair of steel rings that engage each on apon assembly. The friction material is on one rings inner diameter, and the outer diameter on the other ring. The friction material engages the range gear that is selecected. The range gears have a ground surface that the friction material rides on to maintain gear speed to match road speed, and engine sped during range shifting..  I prefer the Eaton synchro over Macks because of ease of installation and low cost, and if the back box is in reusable condition, no special tools are needed to repair it in chassis.  I have lost count on how many I have done.  

With all that I posted....  You need to see a picture of what I have described to get a real perspective...  

[Freightrain]

I looked online and it basically looks like the same basic set up as a car transmission has.  Cone shaped engagement.  It is the friction material that makes or breaks the engagement depending on what fluid is used.  Just like I mentioned in the post above.  They use material that works well with lighter fluids today compared to the 60-70s.

Newer car transmissions can't use thick gear lube due to small roller bearings and the clearances they work with.  The old loose fittings gears allowed thick gear oil.

This falls in the same kind of category.

[Geoff Weeks]

Larry, SAE 50 (synthetic or mineral) has the same viscosity range as 90 GL.  40 SAE is close to 80 GL  so no change in "thickness". Gear lube and engine oil are "rated" on different scales. 

EP additive package in GL increases "tackyness" in the lube so it tends to stay on the gears (and syncro) better, not an advantage with syncro's. An important thing in hypoid and amboid gearing. 

SAE 50 or 40 are approved by Eaton and I have used both. 

SAE oils have better heat tolerance then gear lube and are preferred for that reason. Synthetic oil has better heat tolerance than mineral based SAE oil. 

If you look though what Eaton has put out about lube for their heavy manuals, all three types of oil are approved  depending on market.  When run in the highest heat load conditions, over 1950 ft/lbs and/or extended drain, Eaton says that the top tier of oil has to be used if you want them to warranty it. You also have to keep the oil temp below their limit with and oil cooler. If you are running below those limits and follow "std" oil change protocol, they will warranty with mineral oil as well.

 In third world regions they still allow gear lube to be used.  Every step up in oil is better but not required for proper operation as long as oil temp is kept below X (I'd have to go back and re read to find the limit).     

In short, the syncro still works with all three types of oil.