Oil for 1994 geo prizm gearbox?

[HMan]

What oil should I use in a 1994 geo prizm (Toyota corolla) with a 1.6 liter engine and a 5 speed manual transmission?
The manual says that I should use SAE 75w-90 GL-4 (GM part number 12346074 Castrol Syntorq GL-4 or equivalent) or SAE 75W-90 GL-5 gear lubricant. The engine rarely sees more than 4000 rpm and I try to rev match when possible. I drive it to and from school mostly, so I occasionally have to drive 70 to get to class on time, but I typically drive 30% highway driving at 45 mph, 50% freeway driving at 55 mph, and 20% city driving at 40 mph with about 16 stoplights round trip to and from home. I drive the car hard somewhat when I am running late and need to time the lights, but otherwise I try to drive it easy. I live in ojai, lowest temperature I see is 20 F with the highest being 110 F, college is in Ventura with temperatures rarely going above 90F or below 40 F.
I'm currently running Valvoline full synthetic (SKU VV975) 75W-90 and is what appears to be a GL-5, but I'm not sure if GL-5 is good for my gearbox.
Odometer has 250K miles on it, the transmission was rebuilt less than 100K ago if the seller is to be believed.

 

[KD0AXS]

I'd use Amsoil 75W-90 GL-4.

http://www.amsoil.com/shop/by-product/tr...ar-lube-75w-90/

 

[Bandito440]

If the manual allows for GL-5, then the Valvoline you're using now is a fine choice. I happen to like Mobil 1 75w-90 and Red Line gear oils too, but you're on the right track. If you like the Valvoline and it's working for you, stick with it.

 

[HMan]

The gearbox is a bit touchy with the Valvoline, before the gear oil change it shifted smoother. It started to shift smooth again after I drove it for 250 miles at 65-70 Mph through a few mountains (the oil already had 3k on it before this,) but I still have to double clutch sometimes.
Toyotanation forum users say that the gearbox should use a GL-4 if possible because of the syncros, the bottle of Valvoline says it is good for LSD use. Not sure if any of this is true, but it is more information to work with.

 

[JavierG]

Is this the same question, different post?
https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2877753

 

[HMan]

Originally Posted By: JavierG
Is this the same question, different post?
https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2877753

That is this thread.

 

[HMan]

I have read on other forum that syncomesh gearboxes toast syncros with GL-5 gear oil, is this true?