Manual transmission gear oil

[can0fspam]

Hello Bullnosers!

I have a 1983 f-150 with the New Process 435 four speed granny gear transmission. I bought the truck a year ago and I've since changed all the fluids, except for the front diff and the transmission. I checked the transmission by sticking my finger in the fill hole, and it came out smelling of garlicy gear oil and with a red fluid on it. So I know that something's in there, but I have no clue what it is or how old it is or if it's right.

Anyways, I want to change my transmission oil just to make sure I'm not running on something super watered down or old, and to see if I can improve my shift feel a little. I read that this tranny takes 80w90 gear oil, but I've heard conflicting things about whether or not to get a GL-4 or GL-5 lube.

I can't find any GL-4 oils in the stores near me. Once I found a GL-4 marine lube, but it was very expensive. If the normal GL-5 oil will work, that would be cheapest. But, I know that some GL-5 has sulfur in it and that will corrode brass and yellow metals. What I don't know is if the NP435 has said yellow metals in it or if it will otherwise be harmed.

I looked at www.Novak-Adapt.com to read about the transmission, and they just have the same cookie cutter blurb on every four speed transmission saying to avoid high sulfur oil, but then they go ahead and recommend any GL-5.

I'm trying not to worry too much about things that don't matter, but obviously I don't want to put in something that's going to cause more damage to the transmission than just doing nothing.

Sorry for the wordy question. But has anyone else on here gone through this experience and changed their four speed oil? I'm looking for some pointers on what to do.

Thanks,
Jake

[1986F150Six]

Go to the thread labeled: WHYDTYTT

Page 43 [about 1/2 way down] and look for posts made by Dyn Blin, Gary Lewis  and 1986F150six.

[Gary Lewis]

Sounds like someone put ATF in on top of gear oil.

Anyway, the section from the factory shop manual on the NP435 (Driveline/Transmissions/Manual Transmissions/NP235) says on Page 12 to use ESP-M2C83-C.

 I found several lube companies say that their gear lube meets that.  For instance, here's Royal saying their Gear Lube TL meets it, and is a GL4. And Oleon says their GL5 meets it.

But I don't know those brands.  So I just looked at my inventory and Royal Purple's SynchroMax says it is the right stuff for manual transmissions.  And Mobil One Gear Lube LS says it is good for manuals.

I think part of the issue is that when the NP435 was built the best out there was GL4, but now the companies have migrated to a later, greater oil spec - GL5.  So since Ford's ESP-M2C83-C is a GL4 spec we can't find something later that says it meets that spec.  They've just forgotten the older specs.

For me, I like the Royal Purple.  It is pricey but is specifically said to be good for manual transmissions and, therefore, should not hurt the synchros.

[Gary Lewis]

Good memory, David!  But that is hard to get to, so here's a link: http://forum.garysgaragemahal.com/WHYDTYTT-What-Have-You-Done-To-Your-Truck-Today-tp148p8541.html

[ScubaSteve]

They make a red tack gear oil too. It’s popular for heavy truck transmission and axles. Not saying that’s what you should use but it may explain the red gear oil that’s in there.

[Dyn Blin]

Mine was exactly the same (red and garlicky smelling) and thick when it came out.  I used the M1 and it's been a very smooth shifting experience since.

Somewhere I found some photos of brass exposed to various gear oils at high temps, and I recall the samples exposed to Mobil 1 fared well.

Be sure to verify both bolts loosen before you drain.  It's awful to find the filler is frozen after you drain it all.

I personally found it was easier to fill through the cab than trying to pump it in from under the truck.

YMMV.

[can0fspam]

Alright guys, I went and changed the fluid today.

I found some valvoline full synthetic limited slip oil at the Advance Auto Parts near me. It looked good on the back, says it's good for all manual transmissions where gl-5 or mt-1 is needed. It seemed like the best option I had near me. I put in 6.5 pints and the new oil looks much cleaner than what came out. It drives pretty much the same as before. I'll keep an eye on it, thanks for all the advice.

[Frank Wyatt]

I'll be changing the gear oil in my T-18 maybe in the spring sometime. I've been looking at the Schaeffer Oils Supreme Gear Lube 75W-90. They also have a  Extreme Performance Full Synthetic Oil in 75W-140 that is listed as being for use in Harley-Davidson V-Twin transmissions and high performance differentials, aftermarket 5-speed and 6-speed separate motorcycle transmissions and final drives, including standard and limited-slip differentials and shaft drive transmissions requiring the use of a hypoid type gear oil. Before I make my final decision on the gear oil viscosity I'll contact one of their reps and discuss it with them. I would be interested in how the lube you used performs as well as I have been looking at other gear oils as well.