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Front 75W-90 gear oil or 75W-140gear oil

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Old 08-29-2014, 09:49 PM
7racecar7 7racecar7 is offline
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Front 75W-90 gear oil or 75W-140gear oil

Seen a few posts on this topic just wanted to get some advice, below is what manual says for a 2001 F250

Differential lubricant
Differential lubricant
Front axle SAE 75W-90 QL synthetic gear lubricant
Rear axle
Ford 10.50 inch axles. SAE 75W-140 GL synthetic gear lubricant*
Dana 80 axles SAE 75W-90 QL synthetic gear lubricant*
Dana 135 axles SAE 80W-90 QL synthetic gear lubricant*

The differential has been collecting a drop on the bottom since I picked up the truck about 3 months ago, going to fix it.

Found this deal with a step by step but looking for what oil to use...I might be splitting hairs here but just want to be sure...is SAE 75W-90 QL the right stuff for the front seen a few where ford now says 75W-140 in the front too?

The Step by step
Welcome to guzzle's Front Differential Maintenance Web Page

Thanks for any help
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Old 08-30-2014, 06:30 PM
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Krewat Krewat is offline
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I don't think my 2001 required synthetic in the front.

The Ford "Sterling" 10.25/10.5" rear axle REQUIRES synthetic. Synthetic for these is usually only available in xxx/140 oil. (see note below)

The Dana front axles (or any Dana for that matter I think) do NOT require synthetic.

Plain old 75/90 gear oil will work great in the fronts.



Note: I think the Ford Sterling axles require it because early on in their life, they had a lot of failures using plain 75/90 gear oil. I truly believe it has to do with the small front pinion bearing, and who they sourced it from. But that's just my own suspicion. To counter all the failures they were seeing, a synthetic oil solved the problem.

In my experience, every Ford diff I've ever seen used a non-Timken front pinion bearing, and they all showed inordinate amounts of wear and scoring early in their life - at less than 75K miles, they all showed a lot of heat. Synthetic solves that.

No so in the Dana diffs.
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Old 08-31-2014, 02:54 AM
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75W90 is GL-4
75W140 is GL-5


since GL-5 damages soft metals, I would never use it when GL-4 (the correct gear oil for boxes with soft metals) is called for.
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Old 06-06-2015, 01:53 PM
Sausage327 Sausage327 is offline
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I know its an old thread, but hopefully you can/will help me. Does anyone know the torque specs for the rear end bolts if I'm replacing the cover with an aluminum cover from a 2008 Super Duty; Ford part# 8C3Z4033A? Not a big fan of aluminum or "flashy" crap on my truck, but for the price it was a really cheap replacement to the original metal, completely rusted through, hole havin', leaking factory cover i have leaving oil spots everywhere. Thanks in advance for the input...
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Old 06-07-2015, 11:08 AM
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I just tightened mine by hand when I installed my 08' aluminum cover. It is differential cover bolts not main bearing caps on an engine, just don't snap them off. Not rocket science.

Use Permatex "Right Stuff" to seal the new cover. Some other types of sealants will seep oil.
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