Project Tundra, Getting More Grip with an Auburn Gear HP Limited Slip Differential

Project Tundra: Getting More Grip with an Auburn Gear HP Limited Slip Differential

by Mike Kojima

Supercharging Project Tundra is one of the best things we have ever done to any project vehicle in the MotoIQ fleet.  The TRD supercharger has proven to be totally reliable in thousands of miles from towing up hill in blazing heat to driving all over the place.  It has also proven to be economical as our normal driving gas mileage has not changed at all.  If anything, the large amounts of power have had only one negative effect on the truck: no traction.  To help deal with this we obtained the only limited slip diff on the market for late model Tundras, the Auburn Gear HP Limited Slip Differential.

Traction was a big issue with Project Tundra.  Our engine could easily break the big 295 Nittos loose from a roll all the way up to 50 mph.  The wheelspin was so violent, the truck's traction control, stability control and electronic Limited Slip were going crazy.  Not programmed for so much power and big grippy tires, the truck would sometimes get into violent oscillations where the electronic nannies fought to control the power to no avail. It was scary, your options were to let off the gas or crash.  

Since the stability control and electronic Limited Slip work by using the brakes to either add understeer or slow the rear tire spinning faster than the other, the added power and the fact that the electronics were coming on all the time were killing the brakes, especially the rear brakes.  In addition the electronics were causing irritating things to happen like what we would call Auto Bog. This is when you stepped on the gas hard to make a right or left turn with oncoming traffic.  You would gas it to speed up and the truck would shoot into traffic, only to have the electronics bog the motor and the truck would just sit with no throttle control as on rushing traffic would come closer and closer.  This was not only annoying but potentially dangerous.

The spinning tires would also generate huge amounts of wheel hop when the electronic LSD would try to vary the torque from side to side.  Not only would this affect traction but the pounding was putting a lot of stress on the drivetrain.  Now the stock truck is affected by all of these issues as well but the addition of the supercharger with its big injection of power and torque makes it much worse.

We figured an LSD Differential would help all of this and after doing some research we were surprised to find that only one company made an LSD for late model Tundras.  Auburn Gear has an HP model differential that fits all Tundra's from 2007 on up.   We obtained one of these diffs and proceeded to install it.

 

The Auburn Gear HP Differential fits the Tundra's huge 10.5″ ring gear.  We think this is the beefiest differential of any 1/2 ton truck on the market.  The diff has a strong cast nodular iron case with precise machining for easy setup as we found later.
The Auburn Gear HP diff is very different than your typical limited slip that usually uses clutch packs loaded by cross shaft torque.  The Auburn HP Diff uses the side gears which are machined with cone like backs to provide locking torque.  The side gear cones are forced into the differential case by these springs and retainer plates when the rear wheels start to turn at different speeds.  To us, this seemed like it would not have very much lock up.  Would this diff be able to lock up with our big tires and 500 plus hp?  Read on.
Our Tundra is so big, it won't fit on our lift so Howard Watanabe had to work on the floor with jackstands.  The first step is to remove the wheels.

 

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