I was wondering what gear oil everyone recommends for a 1952 3100 with Muncie 3-speed column shift (my apologies if this topic has been beaten to death). The shop manual calls for straight 90 weight, but good luck finding that. After some searching, most seem to run an 80w90. I've come across the GL-4 vs. GL-5 debate, too, and I'm just not sure. Are synthetics too slippery for these transmissions (i.e. something like Royal Purple Maxgear 75w90)? I'm new to vehicles of this vintage and want to be sure I'm getting the right stuff. Thanks in advance, H.A.M.B.-ers!
get the cheapest lowest grade oil you can find, and it'll be better than what they used back then, and it already lasted almost 70 years. There's a whole nuther thread about gear oil right now, https://www.jalopyjournal.com/forum/threads/33-dodge-rear-gear-fluid-type.1159576/#post-13187165
Let me explain the Dual rating of oil.... 80w90.... 80 weight, it flows like a straight 80w oil. 90... The crushability (if this is a word) of a 90wt oil. So 80w90 flows like a straight 80wt lubes, sticks or crushes like a 90 wt oil. 75w 90 same deal. The big concern with the lower W number is leakage. Since it's a lower viscosity it can be more prone to leak.
Using a high quality of 75W-90 synthetic gear lube will not only help soften the seals, and make the transmission run cooler, but it will also make the shifting much smoother. I have also used 20W-50 synthetic racing oil in some heavy haulers, to solve heating problems. The temperature of the transmission was lowered by 50 degrees. We used spectromatic ****ysis to monitor the wear, and the oil was still good at 200,000 miles. As long as the transmission is in good condition when you install the oil or gear lube, the transmission will be just fine. The one thing that will never work, is adding a good product to a piece of **** and expect it to make a difference. Transmissions do not have the same metal to metal load as the rear end or the cam and lifters in the engine, so it isn't a gamble. A good quality, certified synthetic has up to 7 times the film strength of the old standard gear lubes. I have over 35 years experience with automotive and aviation oils, and have been a user of synthetics in aviation for over 40 years. Bob
You've probably seen the the br*** blocker rings used in older manual transmissions. The blocker rings in newer transmission are a completely different animal. I've seen some that looked to be a metal stamping with the wear surface coated with something that looks like the clutch material used in automatic trans clutch disks and bands. These newer manual trans require ATF or special synthetic lubes in part to allow the blocker rings to work as designed without excessive wear. Your older trans has no need for these special lubes or additive packages. Some synthetics can in fact be "too slippery" for the br*** blocker rings to work properly and can result harder shifting and gear clash when shifting. Like Squirrel already stated, save your money and go with a good conventional 80-90 gear lube and your trans will work as good as it ever will ***uming it's in good mechanical condition. Change it every couple of years if you really put some miles on it. The current conventional lubes are already better than what was in use when the truck was built.
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