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My 1981 F150 has the SROD 2WD transmission that doesn’t like shifting into second gear when the nighttime temps get below 40 degrees F.
After replacing all of the seals bearings and brass parts I filled it with straight 90 wt. gear oil about 500 miles ago.
The longer I drive it on cold mornings the better it gets but the first two or three times trying to shift into second gear while rolling is really tough and occasionally it will grind a tooth before final engagement.
Do I need to add a block heater to the transmission or did I miss something on the rebuild? Or can I swap to a lighter gear oil?
The clutch is adjusted fine and I’ve tried double clutching and not using the clutch at all with the same result.
During the hot summer it was easier to engage second gear but it’s never been as easy as third and fourth
Be vary careful on the oil used.
I think the GL3 and older is what you want to use and all you can find is GL4 now think it is.
The reason is the newer oil eats yellow (brass) metal and turn the rebuilt into junk.
I went with Red Line MT-90 as it's safe for yellow metal and made my transmission shift easier.
It's also what's in my over drive unit as it came with it.
Dave ----
Synthetic gear oil should give you some improvement and make it shift a lot better in all temperatures. Its not cheap though. About $12-$14 a quart at Walmart, but if you can find the Walmart brand it's about $9 a quart.
WARNING: All modern gear oil available today in local retail outlets is GL-5 grade. GL-5 grade gear oil contains sulphur compounds that attack brass and bronze.
WARNING: All modern gear oil available today in local retail outlets is GL-5 grade. GL-5 grade gear oil contains sulphur compounds that attack brass and bronze.
I thought so and why I said something as not every one knows.
After draining the gear oil out of the NP435 over night I refilled it with RL MT-90 that I ordered on like as no one has it on the shelf around me.
It also is not cheap but safe for yellow metals
Dave ----
Follow that link to see several other readily available sources for the (hopefully) correct lubricant, and some important details about GL-4 versus GL-5 oil for an older design manual transmission. There's lots of misinformation out there, so be careful about what you read. Basically, don't use GL-5 in place of GL-4 because it can cause accelerated wear of the brass synchro rings. GL-5 doesn't exactly attack brass. The link above explains what actually happens. However, the Pennzoil Synchromesh Fluid mentioned earlier says it's compatible with yellow metals, so in theory it should be okay. Myself? I'm not sure I'd want to risk it, especially when the stuff originally specified can be easily found if you know where to look.
I used CRC Sta-Lube. NAPA carries it, so it is readily available across the country. It may not be on the display rack with the newer stuff, so you might have to ask. It's also available online from the usual sources such as Amazon, etc.:
I certainly see how the synchromesh may be less than optimal, but I learned of it by way of the Jeep forums; and those guys are a different breed to say the least…
I will report when my NP435 blows, So far so good!
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