Low rpm's in 5th gear

Howdy. The son inlaw just bought a 86 4runner. It's been beat pretty good but I know Toys are good for it. My question is, it rev's just fine in every gear but 5th. Goen down a flat highway and in 5th it won't rev over 2500 no matter how much gas ya give it. It has a 22re and 31-9.50's under it. My daughter had a 86 p/u with a 22r (I believe) and 33-10.50's and it had no problem hitting 90. Is there a limiter on these things? Thought i'd ask before chasing vac lines. Thanx for reading
Mike

There is no limiter at that rpm. There is probably a speed limiter around 90 mph.

Here's some stuff to check:

Valve lash adjustment
Hot Valve clearance:
Intake 0.20 mm (0.008 in.)
Exhaust 0.30 mm (0.01 2 in.)

PCV valve
Air filter
Exhaust system blockage
Replace oxygen sensor
Fuel flow and pressure-fuel pump and filter

Spark plugs
Recommended spark plugs:
Denso W16EXR-U
NGK BPR5EY
Gap: 0.8 mm (0.031 in.)

Ignition coil, cap, rotor, wires

Charcoal canister if Calif vehicle
Brake adjustment in rear

Vacuum leaks:
PCV hoses
EGR valve
Intake manifold
Air intake chamber
Throttle body
Pulling in air between air flow meter and throttle body
Ignition timing - 5 deg BTDC at idle, short terminal "T"

Check compression
Compression pressure: 12 kg/cm2 (171 psi, 1,177 kPa)
Minimum pressure: 10 kg/cm2 (142 psi, 981 kPa)
Difference between each cylinder: Less than 1.0 kg/cm2 (14 psi, 98 kPa)

Check cam lobes
Minimum intake lobe height: 42.63 - 42.72 mm (1.6783 - 1.6819 in.)
Minimum exhaust lobe height: 42.69 - 42.78 mm (1.6807 - 1.6842 in.)

Check timing chain stretch
Chain elongation limit (3 different points) at 17 links: 147.0 mm (5.787 in.)

Check diameter of crank and camshaft sprockets with chain installed
Crankshaft sprocket minimum: 59.4 mm (2.339 in.)
Camshaft sprocket minimum: 113.8 mm (4.480 in.)

http://personal.utulsa.edu/~nathan-buchanan/93fsm/

1. has the gearing been changed to match the tires?
2. is it the original cat conv?