Coming across conflicting information on NP203 oil viscosity recommendation Haynes book is saying 140w gear oil, other web sources are saying don't you dare use heavy gear oil, but use 10-40w motor oil.... The stuff it leaks looks to me like a 10-30ish motor oil...... And I know there are numerous different setups for the 203, mine being divorced with axles and grease zirks as far as the eye can see .... Any input is appreciated, I will keep poking around the web ........

 

The Ford 1976 truck shop manual: Transfer case-New Process Model 203; Above +10F-SAE 50 engine oil. Below+10F-SAE- 30 engine oil. 9 pints.

 

Guess a 40W would fall into that temp schedule, thanks for the reply ....

 

FWIW the scales for engine oil and gear oil are different. SAE 90 gear oil has viscosity properties close to SAE 40 engine oil.

I don't know correct lube for a 203... but the conflicting recommendations are not so different in terms of viscosity.

 

That makes sense, thanks

 

That xfer case set up it a "sling lubed" and you need a thinner oil. So yes motor like 10W30 and NO 80/89 gear lube like a normal NP-205 or Dana 60 uses.

Also at least one a month lock it in 4wd and drive it on NON hard backed surfaces for a bit. Dirt, gravel, sand, mud, what ever is fun.

Talk about it..https://www.bobistheoilguy.com/forum...Number=1610032

Good info here! New Process 203 Transfer Case Tech: Off-Road.com

NP203 case lube? - Off-Road Forums & Discussion Groups

 

Awesome info, thanks for the links
Wanted to add some more links for anyone else poking around for NP203 infos
http://ramchargercentral.com/vehicle...plug-location/
http://www.fourwheeler.com/how-to/47538/