[william]

Does synthetic oil (50w synth) work in the np435? I know it doesn't work well in the 833's because of synchro incompatability, making them difficult to shift. Is there a friction modifier I can add to a synth. oil in my 435, or is it necessary? What are y'all running?
William

 

[1990RamMan]

I run Amsoil synthetics in all of my vehicles. Have been ever since i started driving. Might be because there the best damn oil in the idustry. That and i get it at cost!

 

[s ǝoɾ]

may i ask what is the cost for amsoil? i ve been considering it for a while. and more importantly, can i really run it for upto 25,000 miles like they say? even if thats bogus i hear the stuff really helps against wear. as far as the np435 goes i have no idea.

 

[3/4tonYJ]

my experience is that synthetics generally leak more than standard gear oil in trannys, transfercases and diffs.......this is why don't use it myself. but i do know acouple folks that swear by Amsoil also (without complaint)

don't know about an np435 first hand myself........but i'm not planning on puttin it in mine

 

[Desert_Dog]

Make sure is is GEAR oil you put in the NP435.

DO NOT USE 50W motor oil in a standard transmission, unless you LIKE pulling and installing 200 lbs. of deadweight, because the tranny will not live very long if you do...

I recommend Lucas Gear oil for your NP435.

Mike

 

[william]

If motor oil is bad, why does the FSM recommend 50w motor oil?
William

 

[william]

I just talked to one of the largest manual tranny/ transfer case shops in Western Canada, and they said either gear oil (synthetic is best; 75-w80) but also said the 50w motor oil would be ok, maybe easier shifting in cold weather. No ill effects. I'm not saying I believe it, just a lot of conflicting information on this subject.
The guys on the ford list swear by 50w, they say gear oil is no good. Why can't anything be easy?

William

 

[Desert_Dog]

I would hesitate to put MOTOR oil in a GEAR case.

Lucas also make a synthetic GEAR oil, as well as Mobil and Valvoline.

Let me ask you this... would you put 50W motor oil in your differentials?

Mike

 

[william]

The reason 50w oil was originally recommended by the manufacturer for the NP435 is because gear oil contained sulfur compounds that may damage synchros and brass parts. These are the same sulfur compounds that are used in hypoid gear oil, for hypoid gears (ex: ring and pinion) to prevent galling under extreme pressure. Since the np435 doesn't use hypoid gears, the sulfur compounds served no useful purpose. As far as viscosity, 50w motor oil and 85w-90 gear oil are approximately the same. Now, fast forward 25+ years... Modern gear oil uses low sulfur and additives to combat the ill effects of the sulfur on these older transmissions. So, we can use gear oil in the np435 without any worry. Now that we are on a "level" playing field, which works better?
I know that in 833's, you are supposed to use motor oil for the reasons I mentioned above; but, you can't use synthetic oil because it will not shift properly (not compatable with synchro's and sliders). There are friction modifiers you can add to motor oil to make it work, but most people just use GL4 or GL5, because it works.
So, I guess we can conclude that both 50w and gear oil will work. I have heard that many people find that their 435 shifts smoother, especially in cold temps with the 50w oil. Maybe there is no hard and fast rule on this one, sure is interesting though...
William

 

[1990RamMan]

may i ask what is the cost for amsoil? i ve been considering it for a while. and more importantly, can i really run it for upto 25,000 miles like they say? even if thats bogus i hear the stuff really helps against wear. as far as the np435 goes i have no idea.

On adverage it cost between 50.00-60.00 to do the oil change on my truck with amsoil. The drain interval is 25,000 miles however you do have to change the filter at 12,500. It seems to do the job though. My temps have went down at least 25 percent. And the fuel economy and performance is unsurpassed. WE've been running it in the van since it was new in 84 and it has almost 400,000 miles and the motor is still going like it was new. It has never had anything done but normal maintence.