I am looking for a little help trying to figure out this problem I am having. I just built a rock crawler with a 2001 4.8, TH400 manual valve body, Atlas 3.8.1 transfer case. With the transfer case in High range 2wd and with the vehicle at a standstill, if I punch the throttle to WOT starting in 1st 2nd or 3rd gear the RPMS only go to about 2500 RPMS and stay there no matter how long I hold the throttle down like its being governed or going into limp mode. If I slowly roll into the throttle from a stand still and gradually let the RPMs climb it will climb with ease till it hits the rev limiter no problem. If I build up speed in high range and go up a steep hill, it quickly falls on its face and wont get out of its own way. now here is where it gets interesting. If I drop the transfer case in low range from a dead stand still i can punch the throttle to WOT and it rips with no hesitation at all until it hits the rev limiter starting in 1st 2nd or 3rd gear. it will Climb extremely steep hills with no hesitation. it is not throwing any codes and it has good fuel pressure
the engine is completely rebuilt from block up. I have replaced the cam, cam position sensor, injectors, fuel pump, MAF. I have re calibrated the TPS and IAC and have done a crank relearn. the computer was tuned by a reputable tuner. He is stumped as well
to me it feels like a torque management issue......or something that has to do with the engine sensing a higher load that limits the RPMs. I would appreciate any advice or pointers that might help me get this figured out. I've been trying to get this figured out for weeks.
*2001 4.8L DBC with a summit stage 1 truck cam, shorty headers dual exhaust only running the upstream o2 sensors
* TH400 manual valve body
*2300 RPM TH350 stall converter
*atlas transfer case 2 speed 3.8.1 (no VSS)
* 529 axle gears
* 38" tires
*rig weight is about 5,000 LBS
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