Rear Diff Break-in

REAR DIFFERENTIAL RING & PINION BREAK-IN PROCEDURE

The greatest damage to any new ring & pinion gearset usually occurs during the first hundred miles. During this time, the new gears are bedding-in which generates quite a bit of heat and if driven hard you will raise this temperature even further and may cause irreversible damage to the gears. This is because the gears need some run-time to allow the machine surface finish to wear itself to its final match. The ring & pinion gears are now lapped in but they still must have sufficient run-time to allow the surface finish to properly develop.

Over the course of a few thousand miles the gears will bed-in, increasing the load bearing surface area while polishing themselves up nicely to where they are smooth and shiny. This improved MSF (machine surface finish) reduces the heat that is generated and the larger load bearing contact area increases the overall durability of the gearset. It is wise to let the transfer case ring & pinion gears bed-in before pushing them to their material limits.

Recommend procedure for breaking-in your ring & pinion:

Follow the rear differential filling instructions provide on the FAQ section of this site. It would be best to keep vehicle speeds should stay below 60 mph for the first 100 miles. Drive the vehicle 10-20 miles, stop and let cool for 30 minutes. Repeat this process a few times before driving the vehicle at highway speeds. Do not abuse or dump the clutch or do any hard acceleration, let the ring & pinion bed-in gently. If you take it easy on a new ring & pinion and perform regular oil changes it will last much longer. Use caution when letting out the clutch, as aggressive high rpm clutch dumps can fatigue parts and may lead to eventual failures.

New or recently rebuilt rear differentials should have the oil changed somewhere between 500 to 1000 miles and again after 5000 miles. TRE adds a Moly assembly additive, do not be alarmed by the color of the oil when you first change it. Vehicles that are being road raced require race car maintenance and all drivetrain oils should be inspected after each race and changed if the oil is dark or stinky. Road racing applications may add an additional pint of oil to the rear diff for added lubrication and cooling.

Rear differential oil recommendations

DSM

89-94 DSM: The recommended oil for the rear axle of all the Mitsubishi DSMs GL-5 90w Hypoid gear oil.

REDLINE 80W-140 GL-5 GEAR OIL We highly recommend using Redline 80W140 GL-5 Gear Oil. Their part number is # 58104.

REDLINE SHOCKPROOF HEAVY If the vehicle is going to be drag raced Redline Shockproof Heavy is an excellent oil for the transfer case but make sure temps are 45*F or warmer because the oil is not thin enough for cold weather use.

Friction modifier type additives are not necessary being that the DSM has a viscous coupling type limited slip.

 

EVOLUTION

IF YOUR EVO HAS A TRE REAR COVER WITH THE OIL SIGHT GLASS YOU WANT TO FILL IT NO HIGHER THAN 1/2 WAY.

96-07 EVO: Mitsubishi recommends that the rear axle that is found in the EVOLUTION be filled with their factory oil, Diaqueen LSD Gear Oil part# MZ320345 or a high quality GL-5 or higher 90w Hypoid LSD gear oil. These oils contain a friction modifier that will reduce noise associated with friction disc type limited slips.

REDLINE 80W-140 GL-5 GEAR OIL We recommend using Redline 80W140 GL-5 Gear Oil. Their part number is # 58104. For road racing applications, use Redline 80w-140.
REDLINE SHOCKPROOF HEAVY If the vehicle is going to be drag raced Redline Shockproof Heavy is an excellent oil for the rear axle but outside temps should be 45*F or warmer because the oil is not thin enough for cold weather use.

 

Do not use GL-3/4/5 gear oil in the rear axle

When it comes to the rear axle that is found in the Mitsubishi vehicles, do not make the fatal mistake of using any oil that is spec’d as a GL-3/4/5 gear oil. These one size fits all type oils are not recommended anymore than a one heat range fits all spark plug and they are notorious for ruining the ring & pinion gears.

Hypoid ring & pinion gears

The rear axle features hypoid gears, commonly referred to as ring & pinion gears. The word hypoid is short for hyperboloid which refers to the design of these gears. Hypoid gears don’t share a common axis, run quiet (for the most part) and they are very strong by design. Yet by this design, the gear teeth must slide across one another during their meshing and this is why you must use the correct gear oil with at least a GL-5 rating in the rear differential and transfer case. Use the wrong oil and the ring & pinion gears will be ruined almost immediately from the intense heat that is generated.

Filling the rear axle

Change the rear axle oil every 5k-10k miles. Vehicles that are being road raced require race car maintenance and all drivetrain oils should be inspected after each race and changed as needed. Road racing applications may add an additional 1/2 pint of oil to the rear axle for added lubrication and cooling. New or recently rebuilt rear axles should have the oil changed after the initial first 500-1000 miles. New upgrades are available for the EVO rear differential.