Using synthetic oil in rear diff ok?

[unclejemima]

Changing the rear diff oil on my 84 YTM225DX. It calls for SAE 80 API GL-4 or SAE80W90 hypoid gear oil.

I wanted synthetic, and all I could find was some 75-90 GL5 Synthetic gear oil from the parts store.

Is this stuff ok to use in the rear diff?

Does the GL4 and GL5 matter? I`m assuming the GL5 is just a new rating system.

Thanks,

[harryredtrike]

go with the hypoid oil its great for that application,used in boat lower transmission

[Dirtcrasher]

There's no clutch in there, just open gears............ I wouldn't sweat the synthetics in my differential....................

[tecat-z]

There's no clutch in there, just open gears............ I wouldn't sweat the synthetics in my differential....................

I agree...

[unclejemima]

Thanks. The only reason I want to go with the synthetic is because it stays more fluid at lower temp.

Will the 75-90 work the same as my 80-90? What do these numbers mean anyway?

Thanks,

[big specht]

We have had 75w140 full synthetic in the big reds for 2 or 3 years now with no leaks or noises

[rdlsz24]

Thanks. The only reason I want to go with the synthetic is because it stays more fluid at lower temp.

Will the 75-90 work the same as my 80-90? What do these numbers mean anyway?

Thanks,

The first number is the weight of the oil when cold, the second is the weight once warmed up. You want a thinner oil on startup so it gets into tight places, and then it thickens up. At least that's how I have always understood it.

Rob