I am wondering what is the correct gear oil to use in my truck's rear-end? I have a '97 F-150, 4.6, 5-spd, 4 whl drv, orp, 3.55 gears. I've seen some people say they are using amsoil 75/140. My owners manual says 80/90 rear, and 75/90 front. Any help would be greatly appreciated.

 

There should be a tag on the rear diff. specifying the weight and synthetic/conventional. The tag should be attached by one of the pan bolts. If you have a Limited Slip remember to add Fords friction modifier!
If your not sure which rear you have check the axle code on the door pannel the codes for the F-150 are as follows:19 = 3.55 non LS
18 = 3.08 non LS,
H9 = 3.55 LS,
B6 = 3.73 LS
Hope this is helpfull.



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97 F-150 XLT Ext.cab
5.4 auto o/d, 3.55 LS
Elct. 4x4, Tow Pkg.
Capt. Chairs, Console
Two Tone paint,Black on Silver, Rancho RS 5000's
Ford Bed Liner,Soft Tonneau
Bug sheild
Sony xplode CDX-600,MTX 325watt amp, 2 10" JBL subs.