Gear oil/shifting question

My 2009 4 cylinder access cab 5 speed has about 70,000 miles.
It has had difficulty shifting into 1st or reverse when cold for about the last 30,000 miles.
Last year, I bled the brakes and clutch slave with all new fluid and changed the gear oil with VALVOLINE 75w90 full synthetic.
It made no difference in the shifting.
My question is: Since it only does this when cold, could I simply swap over to a slightly thinner oil?
I live in south Florida. The weather is always pretty warm.
I'm rebuilding the shifter this weekend with new bushings. But I'm not sure that will do much.
Thanks.

 

Your cold and mine might be 50 degrees different .

Around zero I have some difficulties shifting then I use 85w140 .

You might have something else going on if your having problems with 75w90 even down to 30 degrees if you see temperatures that cold

Does warming up the Transmission make a difference ??

Shift to 2nd before going into 1st ??

 

I checked out in my garage.
I'd used MOBIL 1 and it's GL5 so, I'm going to dump it out anyway.
I'm going to do some experiment with Redline MT90. Since it seems to be pretty universally liked.
The temperature here is from 50 to 100 year round.
It never really gets cold.

 

I’m in GA, so my temps. aren’t very cold either. I have the Redline MT90 in my 6 speed 2011 DCSB and “feel” it shifts better. Just my .02, good luck.

 

Thanks.
WTF is GL4 so hard to find?
Most standard transmission vehicles have synchronized transmission gears.

 

When you drained the old oil out to replace it, did you notice metal particles in it. That tells a lot about your transmission.
How does it shift when you've been driving and the tranny has warmed up?
Here is my thoughts. If you replaced the oil with the Same rating as the original that came in it when you bought the truck it should be good. Now if you changed the viscosity and brand that could cause problems. I'd stick with what the manufacturer recommends. If tranny isn't grinding when you shift I would guess it's the oil you put in it.

 

Does it grind going into reverse or just difficult? There is no synchromesh in reverse so if it does not grind the clutch is releasing. You maybe on the right track with the shifter bushing.

 

No metal.
But my drain plug does not appear to be magnetic