Frequently Asked Questions: Detroit Truetrac

Find answers to your questions about Detroit Truetrac here. 

What kind of oil should I use for my Detroit Truetrac? Can I use synthetic? Do I need friction additive/modifier?

  • A quality, petroleum-mineral based, GL5 rated 80w-90 gear oil should be used.
  • Synthetic oils are not recommended for Truetrac applications. While some customers have found that synthetic oils works well in this application, Eaton has not confirmed under test conditions that all synthetic oils are compatible with Eaton Truetrac applications.
  • Friction modifiers should not be used because they will decrease performance (reduce differential bias).

What is the warranty on my Eaton Performance differential?

Eaton Performance differentials (including Eaton ELocker, Eaton ELocker4, Eaton Posi, Detroit Truetrac, and Detroit Locker) are warranted for one year against manufacturer defects. The full warranty document can be found here.

Can I use the stock bearings?

In most cases, the Truetrac units work with the factory (stock, OE) bearings. Exceptions include the “10 bolt” 8.5 \ 8.6 GM models, the “performance” Dana 35 & 44, and GM “12 bolt” with 35 spline axles. The units require unique bearings either for retro-fitment or to accommodate larger than stock axle shafts. 

What kind of break-in is required?

While Truetrac units do not require a break-in for operation, the gears do “lap” together. While the time required to fully lap the gears will vary depending on driving style and loads, the units will operate smoother with age. 

Does the Detroit Truetrac lock up?

The Truetrac is a helical gear limited slip differential, not a “locker”. The Truetrac operates by transferring power from the spinning wheel to the wheel with the most traction. If one tire breaks traction, the amount of rotation (or spin) is controlled by transferring the lost traction to the higher traction wheel. The Detroit Truetrac operates on the principle of "torque biasing”: the typical Truetrac aftermarket differential will consistently deliver approximately three-fold the torque of the slipping wheel to the gripping wheel.

I use my car on the street and on the strip, will the Detroit Truetrac hold up?

On the street, the operation of the Truetrac will be transparent. You will not know it is there until you need it. In racing situations, the unit will apply torque to both tires and launch straight as an arrow, time after time. The Detroit Truetrac is manufactured with forged and heat-treated cases with extremely high-quality gearing. The Truetrac is designed to be the strongest component in your axle assembly.

How much horsepower and torque will the Truetrac handle?

Detroit Truetrac is designed to handle more torque (power) than the axle shafts it drives. Horsepower has little influence on the differential since it is more of a function of engine RPM. Each model of Truetrac is designed to unique torque capacity specifications; however, they are all developed to handle the extreme torque loads typical in professional racing and military applications. The torque limit is largely limited by the “barrel” diameter (the inside diameter of the ring gear) but is also limited in c-clip models by the reduced pinion gear sets due to the c-clip installation pocket. Since these parameters are dictated by the axle design and ring gear strength, the Truetrac differential should not be the limiting component in the axle’s torque capacity. 

Can the Detroit Truetrac be used in the front axle of full time 4-wheel drive Jeeps and trucks?

Yes, and front axle applications are extremely popular. Truetrac differentials are very smooth, offer near-zero steering feedback, and greatly aid in traction / mobility enhancement. Eaton manufactures the Truetrac for front axles, rear axles, and inter-axle drive systems.

Can the Truetrac be repaired?

The helical cut gears inside a Truetrac are “maintenance free”, only requiring regular lube changes. Any failure of the Truetrac results in irreparable damage to the differential case – typically scoring the pinion gear pockets. Therefore, they are technically not rebuildable. Failure is generally the result of insufficient lubrication or poor lube quality due to age or contamination. 

My Truetrac has more internal “lash” then an open or plate style limited slip differential. Is this normal?

Detroit Truetrac differentials are a helical gear style limited slip differential. From a high-level system view, the units are constructed similarly to an open differential – except all gears are helical and the “pinion” gear is split into two intermeshed gears. Because of the three gear tooth mesh interfaces, the design must have lash. While all Truetracs (and helical gear differentials in general) have internal lash, units with preload are less noticeable. Typically, Truetracs have a maximum lash of three to four degrees side-to-side between gears. This is normal and required for the superior torque transfer design of the product.