---
title: What Rear Gear Ratio Works Best With My BluePrint Engine?
description: Learn how rear gear ratios affect drivability, cruise RPM, throttle response, and performance on BluePrint crate engine combinations.
---

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# What Rear Gear Ratio Works Best With My BluePrint Engine?

### ***Can The Wrong Rear Gear Ratio Cause Drivability Problems?***

**Yes.** A rear gear ratio that is too tall can cause:

- Engine bucking at light throttle
- Surging while cruising
- Poor throttle response
- Excessive clutch slipping during takeoff
- Engine lugging
- Difficulty maintaining speed in overdrive

A rear gear ratio that is too aggressive can cause:

- Excessive cruise RPM
- Reduced fuel economy
- Increased engine noise during highway driving

Why Does My Engine Run Better In A Lower Gear? If your engine runs smoothly after downshifting, but bucks or surges in a higher gear, the engine may be operating below its preferred RPM range. Performance crate engines are designed to make power in a specific RPM range. Operating significantly below that range may result in poor drivability even when the engine is functioning properly. Common examples include:

- 5-speed overdrive transmissions
- 6-speed transmissions
- Deep overdrive automatic transmissions
- Tall rear axle gears
- Large displacement stroker engines

How Do Camshafts Affect Gear Selection? **Larger camshafts generally require more RPM and more gear.** Engines equipped with larger camshafts typically:

- Produce less vacuum at low RPM
- Prefer higher operating RPM
- Require deeper axle gearing
- Perform best when not lugged

Mild street engines are generally more tolerant of taller gearing and lower cruise RPM. What Should I Consider When Selecting Rear Gears? Consider:

- Engine displacement
- Camshaft size
- Vehicle weight
- Tire diameter
- Transmission type
- Intended use

Ask yourself:

- Is the vehicle primarily street driven?
- Will the vehicle see highway travel?
- Is maximum acceleration important?
- Will the vehicle tow or haul loads?

The answers help determine the best balance between acceleration and cruising comfort. Are Overdrive Transmissions Always Better? **No.** An overdrive transmission can improve highway cruising, but pairing an aggressive overdrive ratio with tall rear gears may place the engine below its ideal operating range. Common symptoms include:

- Bucking
- Surging
- Constant downshifting
- Poor throttle response
- Engine lugging

How Can I Tell If My Gearing Is Too Tall? Signs include:

- Vehicle struggles to accelerate in high gear
- Engine bucks at light throttle
- Frequent downshifting required
- Poor response from low RPM
- Cruise RPM feels excessively low

If these symptoms improve after downshifting, gearing should be evaluated before changing carburetor or ignition settings. What Should I Check Before Changing Gears? Before replacing rear gears, verify:

1. Ignition timing is correct.
2. Mechanical advance functions properly.
3. Fuel pressure is within specifications.
4. No vacuum leaks exist.
5. Spark plugs are in good condition.
6. Transmission and clutch operation are normal.

A tune-related issue can mimic a gearing problem. 

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