Low power in 4th gear

[Nez'sRanger]

I have an 89 Ranger with a 2.9 and a FM146 tranny (4x4).
I noticed that it has plenty of torque/power in 1st, 2nd, and 3rd, but when I put it in 4th, it feels like the power gets sucked out... The engine even sounds different, almost like it's bogged down. 5th gear is also fine. In fact, when going uphill on the freeway in 5th, I needed to drop it into 4th, but like I said before, it doesn't have the power to handle the hill much better than 5th.
Is it just the gear ratio, or is it maybe something else?

 

[Transman304]

In 4th gear it is a 1:1 ratio. There in no gear multiplication so it may just be poor engine performance if it seems like it is getting worse.

 

[rusty ol ranger]

Its just a 2.9 thing.

1-3rd is fun, 4th and 5th get pretty blah.

If you worried run a compression/fuel pressure check, but you pry have nothing wrong.

 

[Dirtman]

I would do a fuel pressure check as well. Clogged fuel filter or failing fuel pump can cause the engine to get sluggish or stutter at higher speeds.

 

[Nez'sRanger]

I definitely have a dying fuel pump, which I intend to change within the month. Hopefully that clears it up. Thanks!

 

[RonD]

As said 4th gear in a 5-speed is 1:1 ratio, so there is no "gear", basically a sleeve that connects input shaft to the output shaft directly
If engine is at 2,000rpms then output shaft/drive line is at 2,000rpms

Engine issue should also effect 5th
i.e. low compression, lack of fuel, ect......

There is a 4th gear bearing in the FM146, #4, next to #12 and #13 in this drawing: https://therangerstation.com/tech_library/pdf_documents/Mitsubishi5speed.pdf

Maybe this is worn out, causing a drag when in 4th but not in the other gears