M-809 transmission fluid upgrade?

[my blood flows OD]

I'm looking to change my trans fluid in my m-813a1.
I want to use the best option avalible cause the transmission show signs of a ruff life. I also spoke to the chief at the fire dept that formerly used my truck as a tanker and he told me the reason they sold my truck and went to the m-923 was that the younger volunteer firemen can't shift a standard.
so I'm looking for advice on what would be my best option for fluid?
Amsoil? Anyother synthetics? Do I use 80/90? I've heard that the GL 3 or GL 5 isn't the transmission manufacturers recomended fluid. It was said that using 30w motor oil was better?
Any info will be awesome.

 

[mdemars03]

I am assuming it has the original Spicer transmission. If so here is what Spicer's website shows:

Spicer SAE 50 Synthetic Gear Lubricant for Manual Transmissions

Spicer SAE 50 synthetic manual transmission lubricant is specially formulated for extended drain and severe service in heavy duty manual transmissions that require a non-EP gear or transmission lubricant. It is specially formulated to protect the higher-torque manual transmissions coupled with increased horsepower engines.

•Exceptional high-temperature lubrication for extended drain intervals
•Less friction and drag in the transmission
•Potential improvement in fuel economy
•Reduced maintenance and replacement costs
•Less gear wear as vital transmission parts are lubricated quickly

Here is link I followed:
http://spicerparts.com/lubricants/oil/SAE-50

 

[simp5782]

The valvoline 5 gal bucket is part number VV706035M. Maybe your local parts store can has it but doubtful.

Mobile delvac is available thru walmart.com by the gallon. Or other stores using Google

Sent from my SM-G860P using Tapatalk

 

[davo727]

That mobil delvac 50 wt synthetic is 50 to 70 bux a gallon depending on where you get it

 

[my blood flows OD]

I don't mind spending the money on good fluid if it will help smooth the shifting a little.
I understand if the transmission is on its way out no fluid is gonna bring it back but if I can lube it up I can get it to shift a bit easier then it will prevent any more damage

 

[Scar59]

FWIW; I just serviced my M813A1 and put 80/90 back in the trans & transfer. Axles are next. The truck does not see severe service any longer.

 

[Lukes_deuce]

Im interested to hear what other oils have been used. 50wt synthetic is hard to find.

 

[red]

I run 80-90w as well in my 816. Smooth shifts into all but 3rd gear, have to be quick with that shift.

 

[davo727]

Amazon will drop it off at your front door

Im interested to hear what other oils have been used. 50wt synthetic is hard to find.

 

[my blood flows OD]

Amazon has Lucas and moble. Anyone got a favorite?