Is it just me? Trans issues 87 4wd 2.6 5 speed long bed 150k miles

[SubGothius]

What spec of gear oil did you fill it with? These trucks spec GL-4 "or higher" but GL-5 wasn't yet developed then.

When GL-5 came out, it turned out to be unsuitable in many ways for gearboxes spec'd for GL-4 or earlier -- too slippery for many older-style syncros to work properly, and some of the additives can corrode yellow-metal (brass/bronze/copper) components.

The general rule now is to only use GL-5 for gears that specify it, and only GL-4 for gears that specify that, but gears spec'd for GL-1 through GL-3 can safely update to GL-4.

[96meo]

What spec of gear oil did you fill it with? These trucks spec GL-4 "or higher" but GL-5 wasn't yet developed then.

When GL-5 came out, it turned out to be unsuitable in many ways for gearboxes spec'd for GL-4 or earlier -- too slippery for many older-style syncros to work properly, and some of the additives can corrode yellow-metal (brass/bronze/copper) components.

The general rule now is to only use GL-5 for gears that specify it, and only GL-4 for gears that specify that, but gears spec'd for GL-1 through GL-3 can safely update to GL-4.

Kinda was afraid of this I have been using GL-5 as it’s what my work has in bulk and what the parts store had in stock was told GL-5 was superior and supersedes GL-4. I’ll get some GL-4 in it and start looking for another trans as the damage has been done. Once this ones out I’ll tear it down as well as trans 1 see if I cant rebuild a good spare. Hoping I can get the correct fluid and limp it through winter. It’s hard to find a trans that doesn't come with the whole truck and I ran out of storage space. One of these months I’ll get some photos, document the truck, and donate. This site has made it possible to bring this truck back to life and daily drivable. Thank you for the response.

[SubGothius]

Kinda was afraid of this I have been using GL-5 as it’s what my work has in bulk and what the parts store had in stock was told GL-5 was superior and supersedes GL-4. I’ll get some GL-4 in it and start looking for another trans as the damage has been done. Once this ones out I’ll tear it down as well as trans 1 see if I cant rebuild a good spare. Hoping I can get the correct fluid and limp it through winter. It’s hard to find a trans that doesn't come with the whole truck and I ran out of storage space. One of these months I’ll get some photos, document the truck, and donate. This site has made it possible to bring this truck back to life and daily drivable. Thank you for the response.

If it hasn't been running the GL-5 very long, there probably won't be much if any damage/wear due to that alone, mostly just poor syncro function in use, which could explain the straight-cut impression and even the slipping out of gear. Redline, AMSOil and Royal Purple all offer top-quality synthetic GL-4 gear oils.