frekeyguy

Hi All:

LOVE the forum, you guys are very helpful,

2008 F-150 SUPERCREW XTL 5.4L - H9 REAR Axle.
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1. H9 = 3.55 LSD - correct ?

2. Do I need to use synthetic or conventional ? 80w90 or 80w140 (80% I don't tow/Haul, 20% it tows a 2000-2500lb trailer loaded, or 500lb-750lb bike with gear in the bed)

3. How many quarts does it need ? 3 quarts ?

4. The front will need 2 quarts ? can I run regular or do I need to run synthetic ?

JimWills

Yes H9 is a 3.55 ls capacities and recommended lubricants are in the owners manual but the quantities you list sound about right. I use the lower viscosity Mobile 1 lube as i don't do a lot of towing either, but add additional friction modifier to the rear to prevent chatter on turns. (Mobile one says its in there but its not enough) Definitely go Synthetic and you'll probably never need to change it again.

frekeyguy

I acquired this truck with 145kms / 90miles - the transmission fluid is original, im sure the gear oil is original too.

So next question:

1. Will go with synthetic, it will help with those HOT days and not having to worry as much. 80W90 or 80W140 ?? Which would you guys recommend ?

2. For the friction modifier - this is where I am not clear...how much and what brand ? or can I buy that from Ford ?

JimWills

I'd go with the lighter weight as it may slightly improve economy, the friction modifier is available through your dealer and most major auto parts stores.

There is no recommended change interval that I am aware of for the diffs as they come with Synthetic from the factory but the norm is @ 100,000 miles. I did mine at 100,000 and again at 200,000 when I changed the axle seals and bearings. (Found the bearings were still in good shape but figured while I am in there...)

techrep

iTrader: (1)

Book calls for 75-140 plus 4 oz of friction modifier... 3 qts were perfect for the rear.. I used Mobil one full syn.

homer

x2 on what Techrep said.. I bought 4 quarts and the 4th sits on my shelf unopened.


Make sure you use that friction modifier. I bought mine from Ford. If you don't, you'll get the chatter. I'm not sure if it'll wear the clutch pack quicker or not but it'll definitely chatter (some have removed the chatter by adding it after).

techrep

iTrader: (1)

And it’s $20 a quart... that’s a case of beer..

tcp2

Redline 75w140 in mine with a bottle of redline friction modifier. Changed at 75k miles. 3 quarts is plenty.