Serious Question: How fast in 4 High?

Wow, that's awesome, but even worse! The rubber on the strip is even more grippier than dry pavement.

Do you disengage 4-wheel before you leave the strip and return to the pits/parking? Might want to run it up on the grass after a run to make sure the wrap is spun out.

 

Almost right...... W/locking hubs NOTHING in the front drive train turns when the hubs are unlocked. W/ the newer Tacomas everything still turns when in 2wd but there is and can be no power delivered due to the right front axle being disconnected. If the front shafts weren't turning the same speed as the rest of the drivetrain there would be some serious grinding when engaging 4WD.

 

So what is spinning on the front end of the late model tacomas when in 2-wheel? I assumed that the front drive shaft and axles were spinning, but no torque was applied to the shaft until you flipped into 4-wheel. Therefore, I thought this engagement was accomplished inside the transfer case.

 

I'm pretty sure the 4Hi only works up to 55mph anyway - look in your manual.

 

The system is sometimes called 'Central Disconnect', and works with open differentials in front. It works on one of the front half-axles, and when the one half is disengaged, both run free (open differential) as no drive force can be delivered to either front tire.

I used to think we had 'automtaic locking hubs', but they require backing up briefly to unlock... and with a central disconnect, we have shift on-the-fly 4WD to 2WD to 4WD.

 

OP, I have driven close to 100 miles per hour in H4 (4WD-Hi). I did this on a very straight county maintained graded/dirt road in very safe conditions. Road was closed to through traffic and visibility was perfect and was in the middle of desert in the middle of summer. There was nobody else around.

^This limitation pertains only to when shifting between H2 and H4.

I have tried to shift into H4 above 65mph and the truck will not do it. There is a safety mechanism to prevent the operator from doing so. The truck will generate warning beeps. The velocity must be below 62mph and then H4 may be engaged.

 

The transfer case and the front axle are engaged when you flip the switch....

 

The front drive shaft does not rotate if in 2WD. In fact, if your truck is in 2WD (and your truck is 4x4), and parked, you can crawl under your truck and rotate the front drive shaft with your bare hands.

 

Ah...but I can turn my rear drive shaft when parked as well, so that's not necessarily true.

I thought the same thing about the auto hubs...I had an older SUV with auto hubs, so I wasn't sure how the taco was actually engaging the front axles. I'll have to read more about "central disconnects"...thanks.

 

Yeah, I understand that, but does the transfer case only eliminate the torque on the shaft, much like a manual transmission, or does the shaft stop spinning completely when in 2wd?

Without a locking hub, the axles must be locked to the wheels at all times. Therefore they will be spinning at all times. The differential is a passive device, therefore it will spin the shaft. So my understanding is that the front drive shaft spins in 2wd, but it is internally disengaged from delivering torque from inside the transfer case.

 

I answered my own question. Here's some info and verifies what David K said and auto disconnects..... http://www.dodgeram.org/tech/repair/4X4/4x4_engagment.htm

One side of the axle is hard-connected and spins all the time. It spins the differential, but since the other half of the axle is not fixed, the spider gears in the diff spin the other axle backwards. Therefore the front shaft does not spin. But it does confirm that the axles are spinning in 2wd.

 

Nice times/ speeds

I've launched in h4 before on other trucks with V8s and over 300 hp and the difference is night and day snap your neck hook and fricken go!

What are the time differences in 4 vs. 2 wd in 1/4 mile

 

I wonder if there is a difference. I get a much better launch in 4-wheel, but I wonder if all that additional rotating mass slows down the performance at the top end of the track.