NP 435

[hiball3985]

I have a 1966 F250 with a NP435 trans that requires 50w oil. I can no longer find any 50w. What are the recommended alternatives?

Thanks, Jim

 

[JimPghPA]

RedLine makes some outstanding gear oils.

One of the problems you may be running into is weather the 50w you refer to was meant to indicate an engine oil that could be used in a trany, or a gear oil.

Here is some information about one of RedLines gear oils. Note that they refer to it as being equal to a 30w motor oil, or a 80w gear oil.

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Lightweight ShockProof®
Film thickness greater than an SAE 75W140, yet low fluid friction like 80W gear oil or 30W motor oil
Excellent low-temp flow, improved cold shifting
For racing differentials under moderate loads
Popular in racing transmissions like Hewland and other Road Racing dog-ring boxes, Bert and Brinn for Stock Cars, G-Force, and Liberty clutchless for Drag Racing

LightWeight ShockProof Gear Oil - quart - $15.49
LightWeight ShockProof Gear Oil - gallon - $61.95
Quantity

ABOUT RED LINE GEAR OIL FOR MANUAL TRANSMISSIONS
Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)
Red Line offers lubricants to pinpoint nearly every transmission application
MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears
Excellent gear and synchro protection, balanced slipperiness for easier shifting in cold climates
Excellent for high- and low-mile transmissions
Compatible with petroleums and other synthetics
ALSO AVAILABLE FROM OUR DEALERS
58404 - LightWeight ShockProof Gear Oil - quart
58405 - LightWeight ShockProof Gear Oil - gallon
58406 - LightWeight ShockProof Gear Oil - 5 gallon

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If I were you I would give RedLine a call. If this oil is not the correct oil for your application, they probably can match you up with something they make that would work well.

 

[AITG]

Kendall makes a product called SHP Synthetic Transoil 50. It takes the place of the old 50 wt. motor oil spec that HD manual transmissions used to require.

The additives in gear lube aren't friendly to synchronizers in manual transmissions.

 

[JimPghPA]

From another web site:

Originally Posted by smithriver101
I did not see what year your truck is but the factory manual for my 1966 f100 with the np 435 lists 50 wt motor oil for the transmission. I have not changed mine yet but I picked up the oil just a couple days ago. I suspect that an 80/90 wt oil may make it harder to shift, primarily when the fluid is cold.
Actually gear oil and motor oil are rated differently. 80w-90w gear oil has same flow characteristics as straight 50w motor oil. I use Lucas 80w-90w in my NP325 tranny, Dana20 transfer case and 9" and dana44 differentials. It is rated GL3,4,and 5. Makes it nice and simple. Has improved shifting in both tranny and transfer case. If I was heavy towing in hot weather all the time, I would step up to something heavier in the rear end.

 

[JimPghPA]

Back in the early 70's when when working on 4 speed manuals for Camaros, I remember when we put some manual tranys back together after swapping in parts from other similar tranys to replace the broken parts, we use to fill them with motor oil.

I think RedLine would provide you with an outstanding gear oil for your trany.

 

[Zaedock]

I use Coastal 75W90 in my Muncie SM420(this tranny is in my trail Jeep mated to an AMC 2.5L four cylinder). It's GL3/4/5 rated. It shifts smooth and flows pretty well when cold. Of all the oils I've tried over the years, it has worked the best and is cheap at Advance Auto. If you wanted to stick to motor oil, I'd bet you could get away with a 20W50.

 

[Chris142]

Napa has valvoline sae50. My IHC pickup calls for SAE90 gl-1 oil or SAE50. I have been running SAE 40 in it for decades since the 40 is in every store

 

[229]

GL-4 rated as light as you can find.

 

[hiball3985]

Thank you gentlemen, that is a wealth of good information that will get me on track. I still have 50w in it but haven't changed it in years. It's been on my to do list for a while.

Thanks again, Jim