'85 F250 4x4 T-19, trying to figure out what lube goes in it. It appears to have gear oil in it now, 'cuz it's leaking out the output shaft seal and it smells like gear oil. The FSM says it should take 50W engine oil; the owner's manual is very non-specific. I found this page: The Borg-Warner T18 & T19 Transmissions - Novak Conversions with a sidebar about using 50W optionally. Did a little searching here, and it sounds like if you opt for gear oil, it should be GL-4 rather than GL-5. Still not sure what would be best, or what others are running.

Along with the leak, what I'm noticing is that it's having trouble coming out of first gear when cold. It's _not_ the clutch; the clutch fully disengages. The shifter just won't pull the tranny out of first after I launch. If it let _up_ on the clutch a little, while pulling the shifter toward me, it pulls out. Problem goes away after 2-3 minutes. It also helps (someone suggested this as a diagnostic) if I put the t-case in neutral and leave the tranny in first while stopped; that turns the shafts in the tranny and stirs the oil and the problem goes away faster. So I'm wondering, after getting the seal fixed, should I fill it with something like the Amsoil 75-90 GL4, or should I find a synthetic 50W?

 

I always read a stuck shifted means bad pilot bearing. putting a new one in as soon as my clutch gets here so i'll let you know if it helps

 

But wouldn't a bad pilot bearing mean that the clutch wouldn't disengage?

 

i always thought it took gear oil, which most of us call 90 weight but is usually 80w90 or 75w90.

because your shifting difficulty is only when cold, its probably because your oil is cold and thick enough that it makes things hard to move until they warm up a little.

if you were to swap to a slightly thinner oil like that 50 you mentioned in the first post, that would help it out a little in the cold.

i had a similar shifting difficulty in a toyota that called for 75w90 but had 80w90 in it. that difference of 5 when cold made a real difference.

if you want to, you could try adding a pint of 50w to thin out the rest of it just a little and that should improve your cold shifts

edit: i forgot to mention, that a pilot bearing won't prevent your clutch from disengaging, as it only stabilizes the tip of the input shaft against the engine. personally, i doubt its your problem anyway.

 

Pilot bearing won't prevent the clutch from disengaging, like joshofalltrades said.
It will however, cause problems when shifting, like grinding or slow shifting. This is cuz it will keep the input shaft spinning more when the clutch is pressed, and the synchros will have needs more time to overcome that additional speed. Can make it hard to get into first or reverse.

But really I'd try changing the fluid. Chances are its old and crappy anyways. Put some new stuff in, whatever spec you decide on, and it will likely be much better. RedLine makes some good MTL (manual tranny lube) that worked nice in my VW, I've been too cheap to spend the extra few buck to try it in my ford, but might.

 

As far as lube... GL-4 - it's cheap, plentiful and works. I went through this whole debate for my SM465 in my YJ... GL-4 is spec and works great.