Rob has a way of getting any weight GL 4 gear oil from a small oil company in his area.
It would be in 1 gallon amounts for around $10.00 - $20.00 shipped.

Why? You ask, when you can buy it at any Trak Auto or NAPA .  85 -95 weight they sell seems to work well.

Ha HA - just check your local Track Auto, NAPA, or Poop Boys and try to find some GL 4 on the shelf. It is no longer carried or even available to order.  The only gear oil Rob's found has both GL 4/GL 5 on the label.  For this to be true means it has additives to meet GL 5 requirements.  According to Rob, the engineer at King Oil Company said the label is misleading.  The additives to meet GL 5 requirements are corrosive to transmissions made for GL 4, and proved it by looking it up in his book of oils.

I currently have the GL 4 / GL 5 in all my cars with no obvious problems, but .  I will be changing trans. oil in all of them over the next few weeks to this specific GL 4 oil.

Crusty uses GL4 period!  He gets it from a small company in Madison that says there is gallons upon gallons of it available, look in the heavy equipment world, but be careful because many tractor suppliers have only GL5.

It appears the industry thinks its like motor oil and the later the number, (kinda like the SAE rating), the better, so why carry the old stuff.  This is the first guy I meet that had it in a book in black and white that GL 5 is not intended for older cars, tractors, and heavy equipment.  For the most part the entire industry is ignorant on the subject.
This guy is real cool and is sending me a whole bunch of literature on this subject.  I'll pass it along if the list is interested.
The price is also right, under $20.00 a gallon possibly $16.00 - $18.00 shipped to me.
Now back to beer drinking and brush hogging!