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Gear oil temp tolerance? #4518204
09/16/17 09:30 PM
09/16/17 09:30 PM
Joined: Apr 2012
Posts: 2,586
West Michigan
buck91 Online content OP
buck91  Online Content OP
Joined: Apr 2012
Posts: 2,586
West Michigan
Related to the below discussion about Ford PTU's but does anybody have any idea when type of operating temp ranges a GL-5 gear oil is designed for? Specifically a 75w140... more specifically Amsoils SG 75w140?


2011 F150 4x4 5.0L
1996 Mustang GT 5spd/ragtop
Re: Gear oil temp tolerance? [Re: buck91] #4518275
09/17/17 12:12 AM
09/17/17 12:12 AM
Joined: Sep 2015
Posts: 2,260
Malaysia
zeng Offline
zeng  Offline
Joined: Sep 2015
Posts: 2,260
Malaysia
Adequate operating viscosity range is more appropriate than temperature range (not that it's irrelevant) in this PTU application.
Anything xxW140 may be inadequate here, and one should seriously consider and adopt a xxW190 or xxW250 gear oils with higher [email protected]*C, within the confines of system parameters.
JMHO.

Last edited by zeng; 09/17/17 12:22 AM.
Re: Gear oil temp tolerance? [Re: buck91] #4518492
09/17/17 11:07 AM
09/17/17 11:07 AM
Joined: Jun 2002
Posts: 19,242
Iowegia - USA
MolaKule Offline
MolaKule  Offline
Joined: Jun 2002
Posts: 19,242
Iowegia - USA
More info is needed in this case.

I.e, What is the peak operating temperature of Ford's PTU?

For most lubes, any sustained temps above above 70% of the flash point is going to severely degrade the lube. So for this fully synthetic 75W140, any temp > about 280F is detrimental.

As others have stated, the Ford PTU design suffers from two main issues: 1) the low volume of fluid, 2) insufficient heat rejection.

Without an external cooler, short OCI's would be in order.




Last edited by MolaKule; 09/17/17 11:11 AM.

Reading is fundamental; understanding is not a given ability.
Re: Gear oil temp tolerance? [Re: buck91] #4518984
09/17/17 09:13 PM
09/17/17 09:13 PM
Joined: Apr 2012
Posts: 2,586
West Michigan
buck91 Online content OP
buck91  Online Content OP
Joined: Apr 2012
Posts: 2,586
West Michigan
Haven't had a long trip to check yet but in local driving the ptu seems to closely correspond to the trans temp. Vehicle doesn't ever tow but does see occasional road trips.


2011 F150 4x4 5.0L
1996 Mustang GT 5spd/ragtop
Re: Gear oil temp tolerance? [Re: MolaKule] #4519125
09/18/17 04:52 AM
09/18/17 04:52 AM
Joined: Sep 2013
Posts: 10,457
Indiana
dlundblad Offline
dlundblad  Offline
Joined: Sep 2013
Posts: 10,457
Indiana
Originally Posted By: MolaKule
More info is needed in this case.

I.e, What is the peak operating temperature of Ford's PTU?

For most lubes, any sustained temps above above 70% of the flash point is going to severely degrade the lube. So for this fully synthetic 75W140, any temp > about 280F is detrimental.

As others have stated, the Ford PTU design suffers from two main issues: 1) the low volume of fluid, 2) insufficient heat rejection.

Without an external cooler, short OCI's would be in order.





Could your comment be taken as 30% below the flash point too?

Easy math.. say the flash point is 100*F, you mean anything 70*F+ is detrimental?


03 Jeep WJ 4.0 200k Castrol Edge 10w40 HM Fram XG16
02 Volvo S60 2.4T 177k M1 0w40 Mahle OX149D
97 Chevy Blazer 4.3 149k Rotella T5 10w30 Supertech ST3980

Re: Gear oil temp tolerance? [Re: dlundblad] #4519137
09/18/17 05:30 AM
09/18/17 05:30 AM
Joined: Sep 2010
Posts: 7,008
Texas
4WD Offline
4WD  Offline
Joined: Sep 2010
Posts: 7,008
Texas
308F for Redline - any downside?

Re: Gear oil temp tolerance? [Re: dlundblad] #4519294
09/18/17 10:30 AM
09/18/17 10:30 AM
Joined: Jun 2002
Posts: 19,242
Iowegia - USA
MolaKule Offline
MolaKule  Offline
Joined: Jun 2002
Posts: 19,242
Iowegia - USA
Originally Posted By: dlundblad
Originally Posted By: MolaKule
More info is needed in this case.

I.e, What is the peak operating temperature of Ford's PTU?

For most lubes, any sustained temps above above 70% of the flash point is going to severely degrade the lube. So for this fully synthetic 75W140, any temp > about 280F is detrimental.

As others have stated, the Ford PTU design suffers from two main issues: 1) the low volume of fluid, 2) insufficient heat rejection.

Without an external cooler, short OCI's would be in order.





Could your comment be taken as 30% below the flash point too?

Easy math.. say the flash point is 100*F, you mean anything 70*F+ is detrimental?



Yes. Say FP is 400F.

0.30 X 400F = 120F. 400F - 120F = 280F.

0.7 X 400 = 280F, but with fewer keystrokes.

This only applies to a full synthetic gear lube.


Reading is fundamental; understanding is not a given ability.

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