I'm still trying to wrap my head around the appropriate oil type for this transmission. Vehicle is a 1985 Ford F-250 4x4 w/ 4 speed manual. Unit is a Borg Warner T19.
Owners manual suggests straight 50 weight motor oil, or GL-4 80W-90 gear lube. Straight 50 weight is proving impossible to find, and 80w-90 gear oil is almost always of the GL-5 type which I've heard/read is corrosive to the yellow metals used in the synchros. Based on my experience trying different oils, the transmission is sensitive to oil weight in cold weather.
When I first bought the truck, I used Pennzoil Synchromesh, whose viscosity as I understand it, is on the thin side; probably closer to ATF than 80w-90 gear oil. This oil was GREAT in cold weather, but I was unsure of compatibility with this tranny, so I drained it and tried SAE 90 GL-4 manual transmission lube. The 90 weight is miserable in cold-- if it's below 15F in the morning, I can hear the bearings in the tranny, and the engine RPM of a cold idle (high idle during warmup) drops about 200 RPM just turning the tranny internals until the fluid begins to circulate / warm up sufficiently.
I'm at a loss as to what I can use for good performance in cold weather. With the 90 weight lube, shifting in cold (below freezing, without a 10-15 minute warm-up) is like trying to drag a spoon through frozen molasses. With the Synchromesh, it was effortless at any temp. But when I drained the Synchromesh, I thought I saw a silver sheen to the drain oil, indicating that there's a lot of extra wear metal, leading me to believe it's not the proper lube for this application.
Any input, suggestions, info, tips, experiences, etc. would be much appreciated!
Owners manual suggests straight 50 weight motor oil, or GL-4 80W-90 gear lube. Straight 50 weight is proving impossible to find, and 80w-90 gear oil is almost always of the GL-5 type which I've heard/read is corrosive to the yellow metals used in the synchros. Based on my experience trying different oils, the transmission is sensitive to oil weight in cold weather.
When I first bought the truck, I used Pennzoil Synchromesh, whose viscosity as I understand it, is on the thin side; probably closer to ATF than 80w-90 gear oil. This oil was GREAT in cold weather, but I was unsure of compatibility with this tranny, so I drained it and tried SAE 90 GL-4 manual transmission lube. The 90 weight is miserable in cold-- if it's below 15F in the morning, I can hear the bearings in the tranny, and the engine RPM of a cold idle (high idle during warmup) drops about 200 RPM just turning the tranny internals until the fluid begins to circulate / warm up sufficiently.
I'm at a loss as to what I can use for good performance in cold weather. With the 90 weight lube, shifting in cold (below freezing, without a 10-15 minute warm-up) is like trying to drag a spoon through frozen molasses. With the Synchromesh, it was effortless at any temp. But when I drained the Synchromesh, I thought I saw a silver sheen to the drain oil, indicating that there's a lot of extra wear metal, leading me to believe it's not the proper lube for this application.
Any input, suggestions, info, tips, experiences, etc. would be much appreciated!
