Which Axle Drives the Truck?

tandamaxleMany heavy-duty truck have what is referred to as tandem axles. That is, there are two axles with differential assemblies, one is just an ordinary differential and the other has a power divider attached.

There is a lot of confusion about which differential is working when. We’ve heard arguments from people saying it’s the front, or the rear. The answer is: both of them are working all the time.

Both axles drive the truck, just like both the left and right tires drive a rear-axle pickup truck — as long as there is no loss of traction.

When the differential or power divider lock is engaged, each axle now drives the truck whether the other axle has traction or not.

Later axle models may also include wheel differential locks so that each wheel will turn, regardless of traction conditions.

A not of caution: driving on a surface with good traction (like a road) with the differential lock engaged is a sure-fire way to dust one or both of your differentials.

The power divider contains a nest assembly that compensates for minor variances in tire wear. Locking the axles disables this compensator, which will cause damage to one or both of your axles.

And never lock in your axles when one wheel is free-spinning. In fact, it’s safest to lock in your axles when the truck is stopped.

Rebuilt Clutches: an Economical Alternative



With many older trucks having only a limited operating life in California, rebuilt clutches provide a low-cost alternative to new.


We care an extensive inventory of rebuilt clutches, and if we don’t have it, we can usually rebuild it.

We carry all standard clutches, including cast 15-1/2-inch,  cast 14-inch , and stamped angle-spring 14-inch in both single- and double-disc.

Most models include new discs and center plate and completely rebuilt and tested covers.

We also offer in-house flywheel servicing while you wait.


Make Clutch Pedal Freeplay Part of Your Routine

clutchpedalProbably the most common cause of a clutch replacement is running a clutch out of adjustment. As the clutch discs wear, the throw out bearing assembly moves forward, and eventually begins to press against the clutch release fork.

Eventually, the fork will actually prevent the clutch from fully engaging, increasing the chance of the clutch discs slipping. Once the discs beging slipping, the resulting heat quickly deteriorates the clutch friction material.

Including a regular and frequent clutch pedal freeplay check in your maintenance schedule will go a long way to ensure long clutch life. Also, show your operators how to check the clutch pedal freeplay themselves, as they may notice a hard clutch pedal before you do.

CARB Releases DPF Pamphlet

dpfpamphletThe California Air Resources Board has released a pamphlet, titled a Truck Driver’s Guide to Care and Maintenance of Diesel Particulate Filters (DPFs) to address the many problems related to this transitional technology during the implementation of more stringent air quality regulations.

The pamphlet details causes of many issues and a procedure to deal with these problems.

The pamphlet is available from their website.

Product Line





Rebuilt Transmissions and Differentials:

  • Eaton/Fuller Heavy Duty
  • Eaton Midrange
  • TTC
  • Meritor
  • Dana/Spicer


  • New Fuller Clutch Assemblies – all common part numbers
  • Rebuilt Clutches.
  • Complete clutch rebuilding facility – have a hard-to-find clutch? Give us a call, we can probably rebuild it.
  • Flywheel servicing while you wait.


  • We keep a complete inventory of drive line parts and materials, from 1000-series PTO shafts, to 1710 slip lines, to the latest Meritor RPL series and Spicer SPL90, SPL 140, SPL170 and SPL250 series.

NewStar PTO Assemblies:

  • We now carry NewStar new PTO Assemblies. Call us with your part number for a quote.

We specialize in differential and transmission repair, and we have an in-house drive line shop and clutch rebuilding shop.

We can also removed and replace your transmission, clutch, drive line or differential and repair them in-house.