I have a 2010/11 Ford Ranger manual model and I’m having trouble getting it into fourth gear. I tow a trailer regularly and recently had it serviced and found that the oil was a little low in the gearbox, about half the amount there should have been.
Can I try something like an additive before I go to a gearbox specialist?
How did you determine the gearbox oil was low? An additive won’t do anything for you, except maybe fix a leaking seal, but you don’t say if there is a leak present. Take it to a mechanic.