This is the stock differential for most Sprites and Midgets from 1958-1967. This ratio, 4.22:1, was introduced in 1958, and was the standard gear ratio for the Bugeye through the first of the MKIV Sprites and MKIII Midgets. It produces slightly higher engine revs at speed and provides 15.4 mph per each 1000 rpms in top gear. However, this ratio provides slightly better "off-the-line" acceleration as compared to the 3.9 and 3.7:1 diffs.

This differential includes a new 4.22 ring gear and pinion or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collapsible spacer, and seals.The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable.

This is a sought after ratio for Sprite and Midget owners who want to reduce engine revs at freeway speeds. This ratio, 3.9:1, was introduced in 1968. This eased the engines revs at speed and provided 16.5 mph per each 1000 rpms in top gear.

This differential includes a new 3.9 ring and pinion gear set or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals. The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable. NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.9 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

This is a sought after ratio for Sprite and Midget owners who want to reduce engine revs at freeway speeds. This ratio, 3.55:1, was never offered as a factory option but we believe it should have been! This ratio will tame the higher engine revs at freeway speeds even better than the sought after 3.7 rear end.

This differential includes a new 3.55 ring and pinion gear set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals. The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable. NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.55 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

This is the sought after ratio for Sprite and Midget owners who want to reduce engine revs at freeway speeds. This ratio,  3.7:1, was introduced in 1977, 2 years after the MG Midget had the Spitfire 1500cc driveline installed. This eased the engines revs at speed and provided 17.9 mph per each 1000 rpms in top gear.

This differential includes a new 3.7 ring and pinion gear set or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals.  The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable.   NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.7 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

Rebuilt Sprite, Midget, Morris Minor late type differential with 3.9:1 crown wheel and pinion but with the added major upgrade of a full race Limited Slip Differential with 90/35 ramps. The EVOLUTION limited slip is a modern version of the Salisbury clutch type. It has improved clutch material and a unique design of smooth transitions between loaded and unloaded. Extremely easy and predictable to drive! This design will NOT allow the wheels to spin even if one of them loses contact with the ground. All our limited slips are pre-set for full race applications but can be changed easily for other applications. Modern engineering and design allows variations in static pre-load, percentage torque transfer and accelleration/decelleration action to be made. This facilitates tuning the diff to suit individual requirements and applications - be it road, rally or race! Static settings are easily changed by replacing one diff plate with a thicker one; a selective plate pack is available separately. Static pre-load is checked by holding the unit in a vise and checking slip-point with a torque wrench on one of the crown wheel retaining bolts. Percentage torque bias is increased by interleaving the plate configuration, but is also dependent on ramp angle; shallower ramp angles give higher percentage torque bias. The design of the cross pins and ramps in which they operate allow torque bias changes to be made. The closer to 90 degrees the ramp angle, the less action it has - so a 90 degree ramp effectively unlocks the diff making it behave like a standard diff. Conversely, the shallower the angle, the greater the locking action.

This is a sought after ratio for Sprite and Midget owners who want to reduce engine revs at freeway speeds. This ratio, 3.9:1, was introduced in 1968. This eased the engines revs at speed and provided 16.5 mph per each 1000 rpms in top gear.

This differential includes a new 10 tooth pinion and 39 tooth ring gear set or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals. The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable. NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.9 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

Rebuilt Sprite, Midget, Morris Minor late type differential with 4.22:1 crown wheel and pinion but with the major upgrade of a full race Limited Slip Differential with 90/35 ramps. The EVOLUTION limited slip is a modern version of the Salisbury clutch type. It has improved clutch material and a unique design of smooth transitions between loaded and unloaded. Extremely easy and predictable to drive! This design will NOT allow the wheels to spin even if one of them loses contact with the ground. All our limited slips are pre-set for full race applications but can be changed easily for other applications. Modern engineering and design allows variations in static pre-load, percentage torque transfer and accelleration/decelleration action to be made. This facilitates tuning the diff to suit individual requirements and applications - be it road, rally or race! Static settings are easily changed by replacing one diff plate with a thicker one; a selective plate pack is available separately. Static pre-load is checked by holding the unit in a vise and checking slip-point with a torque wrench on one of the crown wheel retaining bolts. Percentage torque bias is increased by interleaving the plate configuration, but is also dependent on ramp angle; shallower ramp angles give higher percentage torque bias. The design of the cross pins and ramps in which they operate allow torque bias changes to be made. The closer to 90 degrees the ramp angle, the less action it has - so a 90 degree ramp effectively unlocks the diff making it behave like a standard diff. Conversely, the shallower the angle, the greater the locking action.

This is the stock differential for most Sprites and Midgets from 1958-1967. This ratio, 4.22:1, was introduced in 1958, and was the standard gear ratio for the Bugeye through the first of the MKIV Sprites and MKIII Midgets. It produces slightly higher engine revs at speed and provides 15.4 mph per each 1000 rpms in top gear. However, this ratio provides slightly better "off-the-line" acceleration as compared to the 3.9 and 3.7:1 diffs.

This differential includes a new 9 tooth pinion and 38 tooth ring gear set or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals. The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable. NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.9 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

Rebuilt Sprite, Midget, Morris Minor late type differential with 3.7:1 crown wheel and pinion but with the major upgrade of a full race Limited Slip Differential with 90/35 ramps. The EVOLUTION limited slip is a modern version of the Salisbury clutch type. It has improved clutch material and a unique design of smooth transitions between loaded and unloaded. Extremely easy and predictable to drive! This design will NOT allow the wheels to spin even if one of them loses contact with the ground. All our limited slips are pre-set for full race applications but can be changed easily for other applications. Modern engineering and design allows variations in static pre-load, percentage torque transfer and accelleration/decelleration action to be made. This facilitates tuning the diff to suit individual requirements and applications - be it road, rally or race! Static settings are easily changed by replacing one diff plate with a thicker one; a selective plate pack is available separately. Static pre-load is checked by holding the unit in a vise and checking slip-point with a torque wrench on one of the crown wheel retaining bolts. Percentage torque bias is increased by interleaving the plate configuration, but is also dependent on ramp angle; shallower ramp angles give higher percentage torque bias. The design of the cross pins and ramps in which they operate allow torque bias changes to be made. The closer to 90 degrees the ramp angle, the less action it has - so a 90 degree ramp effectively unlocks the diff making it behave like a standard diff. Conversely, the shallower the angle, the greater the locking action.

This is the sought after ratio for Sprite and Midget owners who want to reduce engine revs at freeway speeds. This ratio,  3.7:1, was introduced in 1977, 2 years after the MG Midget had the Spitfire 1500cc driveline installed. This eased the engines revs at speed and provided 17.9 mph per each 1000 rpms in top gear.

This differential includes a new 10 tooth pinion and 37 tooth ring gear set or a good used set.

These differentials are rebuilt with all new bearings, cross pins, thrusts, collasible spacer, and seals.The "Core Charge" will be refunded after we determine that your old diff assembly is rebuildable. NOTE: ONLY THE LATEST STYLE BTA548/549 DIFFERENTIAL HOUSINGS WILL ACCOMODATE THE 3.9 CROWN WHEEL AND PINION. THE EARLY TYPE CASES WITH THE SIDE FILL PLUG ARE NOT REBUILD/CORE CANDIDATES FOR THIS GEAR SET AS HOUSING TYPES MUST MATCH - CORE GEAR RATIO IS NOT IMPORTANT.

This rebuilt differential for Morris Minors, Sprites and Midgets has a 4.55:1 ratio, which is good for racing applications as it keeps the engine in a good power band for quick acceleration. It produces higher engine revs at speed and provides 14.1 mph per each 1000 rpms in top gear.

This differential has a new 4.55 ring and pinion gear set or a good used one.

These differentials are rebuilt with all new bearings, cross pins, thrusts, spacers, and seals. Other parts like the planet and sun gears may be replaced at extra cost if required.

Rebuilt Sprite, Midget, Morris Minor late type differential with 4.55:1 crown wheel and pinion but with the major upgrade of a full race Limited Slip Differential with 90/35 ramps. The EVOLUTION limited slip is a modern version of the Salisbury clutch type. It has improved clutch material and a unique design of smooth transitions between loaded and unloaded. Extremely easy and predictable to drive! This design will NOT allow the wheels to spin even if one of them loses contact with the ground. All our limited slips are pre-set for full race applications but can be changed easily for other applications. Modern engineering and design allows variations in static pre-load, percentage torque transfer and accelleration/decelleration action to be made. This facilitates tuning the diff to suit individual requirements and applications - be it road, rally or race! Static settings are easily changed by replacing one diff plate with a thicker one; a selective plate pack is available separately. Static pre-load is checked by holding the unit in a vise and checking slip-point with a torque wrench on one of the crown wheel retaining bolts. Percentage torque bias is increased by interleaving the plate configuration, but is also dependent on ramp angle; shallower ramp angles give higher percentage torque bias. The design of the cross pins and ramps in which they operate allow torque bias changes to be made. The closer to 90 degrees the ramp angle, the less action it has - so a 90 degree ramp effectively unlocks the diff making it behave like a standard diff. Conversely, the shallower the angle, the greater the locking action.

This rebuilt differential for Morris Minors, Sprites and Midgets has a 4.55:1 ratio, which is good for racing applications as it keeps the engine in a good power band for quick acceleration. It produces higher engine revs at speed and provides 14.1 mph per each 1000 rpms in top gear.

This differential has a new 4.55 ring and pinion gear set or a good used one.

These differentials are rebuilt with all new bearings, cross pins, thrusts, spacers, and seals. Other parts like the planet and sun gears may be replaced at extra cost if required.