Proper weight of gear lube oil in differential

[Bob & Carol Howald`]

Bill: I've alway's used the 85-140wt. I've used it in the last 3
coach's. I change it once a year and use amsoil synthetic. Never had
a problem...Bob 93pt Illinois
>
> Twice a year seems a bit much, I think this was the first change
> for our 88. This could start the viscosity debate again.
>
>
> Bill FC Michigan no leaky read end here
>
>
> --- In WanderlodgeForum@yahoogroups.com, "mrdonut12"
> <mrdonut12@y...> wrote:
> > I've got a slight dilemma regarding which gear lube oil
> > to run in my differential.
> > I consulted an industry expert who owns a heavy duty
> > fleet maintenance shop and works on trucks all day. He
> > said that GL-5 80W90 gear lube oil would be fine in my
> > Rockwell 5.29 gear ratio differential.
> > That's what I put in.
> > Digging through my Blue Box, I accidently ran across
> > some papers that stated Rockwell advised using 85W140 oil.
> > Since my Bird is so old, I wonder if lubrication
> > technology has made that recommendation obsolete, or if
> > I should switch to that weight.
> > The lubricants made in 1981 are a far cry from what's
> > available today.
> > The book also stated that, if you drive less than
> > 60,000 miles per year, the gear lube should be replaced twice
> > a year, Spring and Fall.
> > That's what I'll do. Any experience on gear lube weights?
> >
> > George Witt
> > 81 FC 35
> > Lincoln, Nebraska (60 miles down the road from the
> > College World Series--Huskers play Friday night)