What gear oil to use?

G

gfrease442

New Member

Aug 3, 2005

2

0

1

Oct 24, 2005

#1

• Oct 24, 2005

• #1

I have a 1990 Mustang LX 5.0L with the 8.8 rear end. I have to change the gasket in the differential cover, because of a leak. I don't know what gear oil to put back into the differential once I change the gasket. I want to put the Royal Purple 75W-140 synthetic, but I'm not sure if that would be the right oil. Also, do I have to put the friction modifier in the Royal Purple 75W-140 synthetic gear oil? Is 75W-140 the right gear oil?? Or is some other weight gear oil better?????? Any input would be appreciated. Thanks

 

Mavrick

Founding Member

Aug 29, 2002

2,264

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46

Collingwood, ON

Oct 24, 2005

#2

• Oct 24, 2005

• #2

I went with Royal Purple 75-90, it had friction modifier in it already.. the product should tell you on the bottle whether or not you need to add friction modifier.

 

T

tjm73

Founding Member

Aug 3, 2000

2,418

2

48

Rush, NY

Oct 24, 2005

#3

• Oct 24, 2005

• #3

Any name brand 90 weight will do. Almost all name brand hypoid gear oils have the friction modifyer in it. Just look for it onthe label. I use Valvoline any time I'm in my diff. Don't get the old stuff on any clothes you like. It stinks bad and it will never, ever, stop stinking if you get it on your clothes.

 

maverick0716

Founding Member

Jan 12, 2002

3,924

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56

Chilliwack, BC, Canada

Oct 24, 2005

#4

• Oct 24, 2005

• #4

I use Redline 75W90 in mine. Most synthetics already have the friction modifier in it.

 

D

Duro5341

Member

Sep 24, 2005

86

1

7

Oct 24, 2005

#5

• Oct 24, 2005

• #5

Castrol...........80W-90 hypr.......bah, bah
it's ceritifed to use in our posi rear ends
also buy the fristion modifier from FORD, it's like $5.00

Duro

 

Shakerhood

20+ Year Stangneter

Oct 28, 2004

3,356

208

114

Ohio

Oct 25, 2005

#6

• Oct 25, 2005

• #6

Ford Service Manual calls for 80W-90 with Friction Modifier