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#4518204 - 09/16/17 09:30 PM Gear oil temp tolerance?
buck91 Offline


Registered: 04/17/12
Posts: 2449
Loc: 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

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#4518275 - 09/17/17 12:12 AM Re: Gear oil temp tolerance? [Re: buck91]
zeng Offline


Registered: 09/01/15
Posts: 2183
Loc: 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.


Edited by zeng (09/17/17 12:22 AM)

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#4518492 - 09/17/17 11:07 AM Re: Gear oil temp tolerance? [Re: buck91]
MolaKule Offline


Registered: 06/05/02
Posts: 19042
Loc: 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.





Edited by MolaKule (09/17/17 11:11 AM)

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#4518984 - 09/17/17 09:13 PM Re: Gear oil temp tolerance? [Re: buck91]
buck91 Offline


Registered: 04/17/12
Posts: 2449
Loc: 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.
_________________________
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#4519125 - 09/18/17 04:52 AM Re: Gear oil temp tolerance? [Re: MolaKule]
dlundblad Online   happy


Registered: 09/30/13
Posts: 9999
Loc: 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?
_________________________
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#4519137 - 09/18/17 05:30 AM Re: Gear oil temp tolerance? [Re: dlundblad]
4WD Online   confused


Registered: 09/21/10
Posts: 6351
Loc: Texas
308F for Redline - any downside?

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#4519294 - 09/18/17 10:30 AM Re: Gear oil temp tolerance? [Re: dlundblad]
MolaKule Offline


Registered: 06/05/02
Posts: 19042
Loc: 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.

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