RE: [ihc] 13" clutches ...I think it is possible

[John Hofstetter <hofs@xxxxxxxxxxxx>]

At 10:12 PM -0700 11/9/03, John M. Adams wrote:
> I look back through my maintenance notes and see that both my manual
> transmission and transfer case have GL-4, not GL-5. Back then - my
> truck is recently back on the road after an 11 year "rest" - I had
> some reason for using GL-4 in the cases, and GL-5 with an additive
> in the diffs. Don't remember the details, and I don't have any product
> lit saved, can't read the labels...  Anyway, my question:
>
> To purge the transmission and transfer case of the old GL-4 gear oil,
> you're suggesting I run a 15w-40 diesel oil for a while, then switch
> to the Mobil-1 15w-50. Is that because you can't mix the old GL with
> the synthetic Mobil-1, or just because it's a cheaper flush? In other
> words, if I don't mind throwing out 6 quarts of Mobil-1 after a 2K
> "rinse", can I go straight to Mobil-1 and skip the dino oil?

Absolutely.  I'm sure that Dennis was only thinking of a cheaper 
flush. Because of it's detergency, the Mobil 1 synthetic would be a 
very good, albeit expensive, flush.


> Also, I read this on the Mobil website:
>
> "Mobil 1 Synthetic Gear Lubricant 75W-90 meets the most severe API
> Service MT-1 and GL-5 EP gear oil service classification."
>
> Should I therefore consider running their 75w-90 synth in my diffs -
> it does say EP - and the 15w-50 in the transmission and transfer case?

Again, in my opinion, absolutely. That's what I run in my Scout 
diffs.  I won't change it until I'm concerned about having gotten 
water in the diff, either from stream crossing, or condensation 
inside the case. I need to run vent hoses up from the diffs to an 
always-dry spot higher in the vehicle.

Somewhere in the digest archives is a very good explanation by Jim 
Grammar or Eldon or ? about the reasons for motor oil or gear lube. 
At the risk of getting myself corrected, which happens all too often, 
the basic reason is that gear oil has additives for gears that kind 
of slide against each other like rings and pinions. For gears where 
teeth engage without sliding, the motor oil, or in some cases ATF is 
the right choice.


> Thanks, all of you... this is real helpful input I'm getting.
You're welcome

John

--
John Hofstetter
www.goldrush.com/~hofs