Synthetic 140
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Senior User
Joined: Aug 2004
Posts: 165
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From: NEBRASKA
Synthetic 140
I've got an early '99 Superduty. I want to change the rear diff. gear lube, but there is a tag on the pumpkin that says to use 140 weight synthetic. I have been to every parts store, tractor supply, and international shop in town and no one carries it. The head mech. at international couldn't understand Ford's reasoning for using it. Can I get away with using a lighter weight synthetic?
Posting Guru
Joined: Nov 2002
Posts: 2,440
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From: Ventura County, CA
Can I get away with using a lighter weight synthetic?[/QUOTE]
Use the recommended gear oil spec. 75w/140 isn't that hard to come by. I've seen it at local Kragan's and Auto Zone stores, also at Wal-Mart from time to time. I got my Royal Purple from Summit Racing online. If you're going to change the gear oil yourself, make sure you have enough clearance to refill, and make sure you have a replacement gasket or sealant for the melon.
DS
Use the recommended gear oil spec. 75w/140 isn't that hard to come by. I've seen it at local Kragan's and Auto Zone stores, also at Wal-Mart from time to time. I got my Royal Purple from Summit Racing online. If you're going to change the gear oil yourself, make sure you have enough clearance to refill, and make sure you have a replacement gasket or sealant for the melon.
DS
Postmaster
Joined: Jan 2005
Posts: 2,753
Likes: 3
From: Phenix City, AL
If you have the rear LS, you need to use the synthetic. The conventionals don't have the shearing properties to hold up well with the LS. You'll wear the clutches out much faster and cause yourself some bills.
As mentioned above the multi-viscosity stuff will work fine, but try to stick to the recommended weights. That way no warranty issues from Ford.
As mentioned above the multi-viscosity stuff will work fine, but try to stick to the recommended weights. That way no warranty issues from Ford.
Tuned
Joined: Jun 2005
Posts: 421
Likes: 1
Ford saids with Synthetic rear ends oil they are replacing less rear end do to warranty defects. Ford is all so saying the rear bearings and gear sets are lasting much longer.
I changed the rear end axle seal in my old 1999 Expendition 4X4 and I asked the same qustions mainly Synthetic rear end oil is pricey I was advised though rear end shops Gear heads and Ford run Synthetic oil you be glad you did in the long run.
I am a aircraft mechanic the way I look at it if most all Aircraft run Synthetic oils there a reason for it if good for aircraft it should work great in my truck.
I changed the rear end axle seal in my old 1999 Expendition 4X4 and I asked the same qustions mainly Synthetic rear end oil is pricey I was advised though rear end shops Gear heads and Ford run Synthetic oil you be glad you did in the long run.
I am a aircraft mechanic the way I look at it if most all Aircraft run Synthetic oils there a reason for it if good for aircraft it should work great in my truck.
