Toygasm and others with CBs that suffer from extemely short range:
Are you using fibreglass antennas? ie. Firestick, Skipshooter, Diesel...
Most of the problems I've seen with this style antenna have been caused by a missing plastic spacer. This spacer isolates the chrome antenna base from the metal mount (which is grounded). When your antenna strikes objects such as branches over a period of time, the impacts can crack the spacer and it can fall out. Most people do not realize (or forget) that the spacer even existed, and merely tighten the antenna down when they perceive that it's become "loose". This shorts the antenna to ground and will cause extremely poor reception and can damage your radio if you transmit while this condition exists.
This problem can be seen as a high SWR reading, but if your spacer is missing, no amount of adjusting your antenna will lower your SWR.
The spacer looks like a washer, but is "stepped" so that the small side rests in the mount hole, and the large side butts against the base of the antenna.
Even if you are using a different-style antenna, I'd say that most problems are antenna-related, so your antenna system is still something to check.
For any 4-wheelers considering buying and installing an antenna:
I recommend a base-loaded antenna with a whip and a shock spring. ie. Larsen or Sinclabs. These antennas perform well and are not overly tall or expensive. The shock spring helps prevent bent whips when evergreen branches drag over them.
Mount the antenna away from reflective surfaces such as your A-pillar, spare tire mount, or back of your cab. Ideally, the antenna should be at the highest practical point, and not have any metal in its path. For these antennas, which are "loaded quarter-waves", the mounting location requries a good "ground plane", or somewhat flat area of metal. The best location is the center of your metal roof, but most do not want to drill that hole. For pickups, the next best place is the center of your hood (again, that darn hole), and the next best is on the fender in a somewhat central location (not too close to the A-pillar).
Stay away from the 1-foot tall center-loaded mag mount antennas, and any antenna that comes with the 2mm-thick coax cable. Do not install dual antennas unless you can mount them 9 feet apart (and even then, I don't recommend them). Stay away from fibreglass antennas unless you 'wheel in tree-less areas.
Use quality coax, such as Belden, Amphenol, or Larsen. Look for tight shielding and a stranded center-conductor (stranded is less susceptible to damage from vibration than solid). Even better, dual-shield coax that has a foil shield around the braid will further reduce loss and will also help reduce interference to your stereo or other radios. The coax must be 50-ohm impedance (ie. do not use cable-TV coax, which is 75-ohms). The exception is when you have dual antennas; then each feed must use 75-ohm coax.
Use a quality PL-259 connector such as Amphenol. Ensure that the coax braid is soldered to the connector body. Do not use crimp-type connectors as they WILL fail. Do not use acid-core solder.
Do the installation right the first time, and it'll always work when you need it.