I recently rebuilt my 3-speed manual transmission. At first I put GL5 80w-90 gear oil in it because my dad used it since he restored the car 30 year ago. I only recently read about GL4 and GL5 gear oils, what the differences are, and their effect on the yellow metal in the tranny i.e. synchronizers. I drained the GL5 gear oil and put GL4 85w-90 gear oil in, assuming it would be better. Since I put it in however, the gears seem to 'stick' a little when shifting. Should I not have used the GL4 gear oil? Any input greatly appreciated.
Like any conversation about oil products, 10 people will have 20 different opinions.... I saw a recommendation for Red Line GL4 gear oil when rebuilding the toploader going into the '57. I've been very happy with the performance.
If I remember correctly, the recommendation came because people had something of the opposite issue you describe. More modern oils were too "slippery" to allow synchros to work well?
I would imagine there are different properties to oils under the same classification (i.e. GL4). Was the GL4 oil you used recommended for older gearboxes? I ask because I'd imagine a good oil for an "old" 1990's car might not be perfect for an "old" 1950's car even though, by today's standards, they're both "old"!
On the Toploader 4 speed in my 59, I am using Brad Penn GL4 80-90 gear oil. I have had several transmission rebuilders tell me the "modern" GL5 gear oils contain an additive that is corrosive to the brass/bronze syncronizer rings. Modern manual transmissions typically use paper lined syncros (similar to automatic transmission clutch plates), or carbon fiber, or other synthetic materials, unaffected by the additive.
81TTA, I used CRC Sta-Lube 85w-90. This is what the description says, "GL-4 Hypoid Gear Oil has low pour points and high temp properties to provide lubrication over a wide temperature range. This versatile lubricant contains anti-rust and anti-wear EP additives to provide the corrosion protection in drives and hypoid gears. It is not corrosive to copper, bronze, or other non-ferrous alloy bearings and bushings."
I would think it would be the right oil for my transmission.
Ive been using the StaLube 85-90 in my T85 also. It does seem to be a little sticky on the first few shifts going into second gear until it heats up a little. I agree about using GL4 and stay away from the GL5.
Since we're talking gear oil..............it reminded me to call Yukon about which oil for their unit, if different than a Ford's needs. Well, the 80-90 GL5 is actually what they recommend, so that's good since that is what I put in a month ago.. He advised not to bother changing that out with 90w conventional (made to GL4). He did say it does need the friction modifier, 2 4oz bottles. I found the Motorcraft brand, which is what he recommended, at a local Oreilly's. So, in the near future I'll try to syphon out 8oz to make room for it. Hopefully that'll eliminate the low speed noises I'm hearing. A friend who has good hearing walked around the parking lot following my car, and said the noise sounded like it was coming from the back pinion area.........so...... :006:
Rich for what it's worth the people who built my rear end and thats all they do said using GL5 is fine as long as the pinion and axle seals are new. I've had no problems so far..
Rear differentials contain no brass or bronze components, so I can not see any reason that GL5 would cause any problems. A manual transmission with brass or bronze syncro rings are a totally different situation.
I use Amsoil Toploader/Saginaw GL-4 when I rebuilt my Granada Overdrive Toploader I put in my 59.
Shifts like butter!20220520_070422.jpg