Here are some possibilities and suggestions, ranging from simplest to more complex:
1. Linkage Issues (Most Likely):
* Shift Linkage Adjustment: The most common cause is a problem with the shift linkage. This could be a bent or broken component, a loose bolt, or simply misadjustment. Carefully inspect the linkage from the shifter to the transmission. Look for anything bent, broken, loose, or disconnected. Consult a Jeep CJ/Wrangler repair manual or online diagrams to see what the linkage should look like. Adjustment may involve tightening bolts, replacing worn parts, or bending slightly bent linkage back into shape (carefully!).
* Clutch Adjustment (Manual Transmission): If you have a manual transmission, improper clutch adjustment can sometimes interfere with shifting. A mechanic or repair manual can guide you through adjusting the clutch cable or linkage.
2. Transmission Internal Problems (Less Likely, but More Serious):
* Shift Fork: A broken or bent shift fork inside the transmission prevents the gears from engaging properly. This requires transmission removal and repair by a mechanic.
* Damaged Gears or Synchronizers: Worn or damaged gears or synchronizers within the transmission could also be the culprit. This is a more serious and expensive problem, usually requiring professional repair or a rebuilt transmission.
* Low Transmission Fluid: Check the transmission fluid level. Low fluid can cause shifting problems, though usually more erratic than being stuck in one gear. If low, add the correct type and amount of transmission fluid as specified in your owner's manual. If the fluid is dirty or smells burnt, you likely have more serious issues inside the transmission.
3. Other Possibilities:
* Stuck Shift Lever: Sometimes debris or something else can physically jam the shifter in one position. Inspect carefully around the shifter and try gently working the lever back and forth.
What to Do:
1. Visual Inspection: Thoroughly examine the shift linkage. Look for anything bent, broken, loose, or disconnected. This is the best starting point.
2. Consult a Repair Manual: A repair manual specific to your 1979 Jeep Wrangler is essential. It provides diagrams and detailed instructions.
3. Seek Professional Help: If you're not comfortable working on your vehicle or after visual inspection reveals a problem beyond simple adjustment, take it to a mechanic specializing in older Jeeps. Trying to fix internal transmission problems without experience can lead to more significant damage.
Important Considerations:
* Year and Model: Specific repair procedures vary slightly based on the exact year and model of your Wrangler (CJ-7, etc.).
* Transmission Type: Knowing if you have a manual or automatic transmission is crucial.
* Safety First: Remember to prioritize safety throughout the process.
Don't attempt to force the shifter. This could cause further damage. A careful and methodical approach is key to diagnosing and fixing the problem.
