Hi Everyone. I really want to tune my 2009 H3T 3.7L using HP tuners but as it is AWD it won't fit on my dyno which has a maximum wheelbase of 133 inches & the H3T is 134.2. Is there anyway to disengage it, literally so I can run it 2wd to tune it? Any help is appreciated

 

Drop the front drive shaft is as fair you can get beside that there a way to put the t-case in neutral but that's used for 2 wheel truck haul or a flat tow.

 

The short answer is NO.

Could you remove the front drive shaft? Yes, but what kind of tune are you going to get with the T Case split power appx 60% output to the rear wheels and what is the TCCM going to do with no input from the front wheels? In other words, Traction Control is not going to allow that to happen.

 

If you just pull the front driveshaft, all the power split goes to the front and it doesn't move. You have to put it in 4Hi-Lock to get the power to the rear wheels. Jack up the rear in your driveway and see if traction control kicks in with the front stopped.

 

Besides the above, you'd be almost doubling the torque on the rear diff and axles at full power, and there's no way of knowing if they'd fail because of it.

 

Incorrect, the only way to have the rear receive any power with the front shaft removed is to place the Tcase into 4HI Lock or 4LO lock. This will distribute the power 50/50 front/rear inside the Tcase.

I've been driving for 4 weeks so the front shaft and in 4HI lock waiting for parts.

 

Under normal driving I agree, but you're not driving around at full load and max engine rpm. The dyno will increase load on the driven axle until max engine output power is reached. As I understand full-time 4WD, the torque split in the t-case is mechanical via gearing and, unless there's a torque-sensing clutch in the t-case, in "4H lock" the full 240+ ft-lb could go to the rear if the engine is driven to full load

 

First of all, I'm not worried about 242/242 going through the driveline to the rear axle. These are regular off the shelf GM parts (well the T-case is different) that are in all sorts of 2wd vehicles putting out up to and over our power level. Secondly, in 4Hi-Lock, the T-case is locked in a 50/50 split. You won't overpower the driveline components. Third, how long is a dyno pull? One minute? Two? I've towed trailers up long grades in my H3 for that long with the pedal floored. Its not gonna blow up from stress on a dyno pull.

 

i think you will find/realize that in "lock" mode the tc is "locked front to rear.
that means that each gets the SAME torq. call it 50/50 .
the reason its called 60/40 in open mode is because the torq split actually takes place because of the 60/40 gears in the tc planetary diff.

ya really gotta look hard at the tc breakdown to see it. fun stuff.

and,yeah,when does it really see all that torq,,,never!!

 

Removing the front drive shaft and placing the differential in lock, low or hi, would allow 100% of net engine torque available to the rear drive shaft since there is 0 load on the front even if the design is for a 50/50 split; since the split can only happen when theres load on the front.

There are simple ways to prove this- increased acceleration times, increased fuel economy, ability to do burn outs...if u have stock or h/t tires.

It comes down to basic physics: force, even angular force, can only be applied if work can be done. Hence, if the front drive shaft is pulled and the only mechanical link fron the pistons to the wheels are to the rear wheels, then the engine is working only to move those wheels, thus all net engine torque goes to the rear wheels.

Unless our transfer cases use some sort of all wheel drive hydraulics or slip plates...