Before you begin, consult a repair manual specific to your 1991 Chevy Blazer 4WD. This will provide diagrams and crucial details particular to your vehicle's transmission type (e.g., 700R4, TH350, etc.). The exact procedure varies slightly depending on the transmission.
Here's a general overview of the process. Remember this is a general guide, and you MUST use a repair manual for your specific Blazer's transmission.
1. Identify the Problem:
* What's wrong? Is the shifter imprecise? Are certain gears hard to engage? Does it not go into park properly? Understanding the specific issue helps focus your adjustment.
* Visual Inspection: Check the linkage for bends, broken parts, loose bolts, or worn bushings. Look for excessive play in any joints.
2. Access the Linkage:
* You'll likely need to remove some components under the vehicle to get a clear view and access to the linkage. This often involves removing the floor console or parts of the console. Refer to your repair manual for specific instructions on removal.
3. Adjustment Points:
There are usually several points of adjustment. These are typically:
* Shift Linkage Rod: This is the rod that connects the shifter lever to the transmission. There may be threaded adjusters (nuts and bolts) on this rod that allow you to change its length.
* Transmission Shift Lever: Some transmissions have adjustment points on the shift lever itself, accessible after removing the linkage.
* Bushing Replacement: Worn bushings can introduce slop in the system and are often the root cause of imprecise shifting. These will require replacement rather than adjustment.
4. Adjustment Procedure (General):
* Start with the engine OFF.
* Engage the parking brake firmly.
* Locate the adjustment points. Your repair manual will clearly show these.
* Place the transmission in Neutral. This is your starting point for adjustment.
* Carefully adjust the linkage rod using the nuts and bolts. Small adjustments (1/8 to 1/4 turn at a time) are best. After each adjustment, check the shifter position in each gear.
* Check for proper alignment: Ensure the linkage is aligned correctly throughout its range of motion. Forceful engagement of any part of the linkage is a bad sign.
* Tighten all fasteners securely.
5. Verification:
* Test Drive: With the adjustment made, test drive the vehicle carefully and thoroughly. Try shifting through all gears, making sure each engages smoothly and correctly. Pay close attention to Park and Reverse.
* Repeat if needed: If the shifting is still not ideal, make small adjustments as needed, always testing after each change.
Important Considerations:
* Repair Manual: A factory service manual is essential. Improper adjustment can cause serious damage.
* Safety: Always work in a safe environment with the vehicle secure. Use jack stands, not just a jack.
* Transmission Type: The specific adjustment procedure will depend on the transmission type in your Blazer.
* Professional Help: If you are uncomfortable performing this repair, it's best to take your vehicle to a qualified mechanic.
This is a complex procedure. Improper adjustment could damage your transmission. Do not attempt this unless you have mechanical experience and are confident in your abilities, or if you are working with a qualified mechanic. Use your repair manual as your primary guide.
