Guys,
I did a search on the correct gear oil for the Lightning differential and did not really find a concrete answer listed in any of the threads I read. It seems that we are relatively all in the same state of confusion, including the dealers and SVT. To summarize:

1. The standard F150's with the 9.75" rear end (all F150's with the 5.4L have the 9.75" rear end) requires 75W-140 gear oil. This is listed in the F-150 Owners manual.
2. The Lightning has the same 9.75" rear end (I believe that it is the exact same rear). However, the SVT F-150 Lightning Owners Guide Supplement states the use of 80W-90 gear oil for the rear end.
3. The metal tag affixed to the differential housing on the rear end on my Lightning also lists ths use of 75W-140 gear oil and not 80W-90 as listed in the SVT Lightning Owners Guide Supplement.

The tow ratings for my L are about the same as my F-150 4x4, so why is SVT allowing the use of 80W-90 oil instead of 75W-140???
Mind you, I will never tow with the L, but nonetheless, Ford has designed it to allow for towing.

Has anyone researched this and found an answer. Very shortly I am going to change the differential oil with Amsoil, but am confused which weight to get. I am tempted to use 75W-140 since I know it won't crap out the bearings and gears but would rather use 80W-90 if it is truely specified correctly by SVT.

Any further knowledge on this subject?
GDG

 

Another thing I just noticed is that the capacity for the differential as listed in the standard F-150 Owners Guide is 2.6 liters, whereas the Lightning supplement lists the capacity as 3.3-3.8 liters? I am certain that the 9.75" rears are all the same.

What is going on?
GDG

 

Good Questions

I know you also need a bottle of friction modifier as well...

I would us the stuff listed on the tag...

When Shaun from JDMs shop fixed my leaking rear cover afew weeks ago he used 75W-140, just like the tag called for,

Doug

 

I'm using the 75-90 mobil one synthetic and a tube of friction modifier. I have about 5 quarts in there. I only have have about 2K miles on it with that oil...but have had no problems.
The mobil 1 is about 1/3rd the cost of the 75-140.

 

I am interested too in any knowledgeable 'answers'. In my thinking, the 80-90(or 75-90) would offer less resistance with a bit(tiny?) more performance/gas mileage than the 75-140?.

I plan to use a synthetic(probably Mobil 1) when I change mine out--let us know about the 'quantity' amount too.

Thanks,

Dan

 

Well,
For the record, I decided to go with the Amsoil 75W-140 since it is used in all the 9.75" rears (except for possibly the lightning per the SVT specs) instead of the 80W-90. I know the stuff works for the long haul since I have used it with great success in the past.
GDG

 

Here's a interesting thread ...


https://www.f150online.com/forums/sh...erential+fluid

 

Hey DL,
Yeah, I have talked to Pyle Brothers in the past when I did a 4.10 swap on my 4x4. I even bought a part from them (i.e. read rear pinion nut - for those who know what I am talking about). He also explained to me their philosophy on gear oils. I can't really remember it now since it seemed to be more opinion than fact, but I do recall him saying that he was OK with synthetic. Looks like the confusion continues onward!!
GDG