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Hummer INext

Full-time all wheel drive.

Transfer case: All HUMMERs use a New Process Gear (NPG) 242 2sp transfer case. It is a full time transfer case incorporating an open differential between the front and rear driveshafts (DS). It has 4 modes, High (H), High Locked (HL), Low (locked) (L), and Neutral (N). The ratios are 1:1 in high, 2.72:1 low.

Military versions have a 50/50 split, civil versions a 48/52 split via the planetary gear differential. Military TC has a mechanical speedometer output and a larger oil cooling loop.

The input shaft and rear output shaft are co-linear. The front is a left handed output, chain driven.In H, the normal operating position, torque is evenly split front and rear via the transfer case's differential. This center differential is open and allows the front and rear driveshafts to turn at different rates to allow turning on high traction surfaces. In HL, the differential is locked (manual locker), forcing the front are rear driveshafts to turn at the same rate. This is equivalent to a part-time 4wd system. The L position forces the input shaft to turn a planetary gear assembly at the front of the case. The ring gear is machined into the front case. Low adds a gear reduction of 2.72:1. The differential is always locked in low. The N position disconnects the input from the output shafts totally. The differential is open in this position. A sensor at the rear of the transfer case (TC) is used to determine speed. Another sensor determines if the TC differential is locked or unlocked, illuminating a status light. The TC is cooled via transmission fluid flowing through an intercooler inside the TC. The engine, transmission, and transfer case are rigidly connected together. The assembly is canted slightly to the right.

Differentials: The differential case is a Dana (AMC) 20, hypoid (top entry), same as in some older Jeeps (AFAIR). The differential has a ratio of 2.73:1. HUMMERs use Zexel-Gleason Torsen torque sensing/biasing (front and rear) differentials. These are not a limited slip design or locking design. The bias ratio is 3.8:1 AFAIK. Since the suspension is independent, the differential case is connected to the frame.

Optional Eaton ELocker locking differentials front and rear.

Source: Gerald's HUMMER Page

Have you seen a better description of Hummer I on the web? Please send us the link to or post it in a comment below!

Hummer IINext

Borq-Warner 4484 transfer case.

Full-time all wheel drive with 40/60 torque distribution via planetary gear differential, which can be locked manually (Source).

Have you seen a better description of Hummer Ii on the web? Please send us the link to or post it in a comment below!

Hummer IIITop

Either the B-W 4493 or 4494 (greater low-range reduction).

Full-time all wheel drive with 40/60 torque distribution via planetary gear differential, which can be locked manually (Source).

Do you own Hummer Iii? Can you please make a photo of the car's 4x4 transmission, switches, dashboard lights, etc. and send it to ?

There are 2 comments
ERNEST NORWOOD
March 11, 2019 - 19:33

I HAVE A 2004 HUMMER H2 I HAVE HAD ISSUES WITH THE FRONT END HOPPING LIKE IS LOCKED IN 4HI EVEN THOUGH ITS IN THE AWD HWY MODE . IVE REBUILT THE TRANSFERCASE NEW SWITCHES NEW ENCODER MOTOR YET I STILL HAVEW A HOP IN FRONT END ON SHARP TURNS FORWARD OR REVERS IT IS NOT THERE WQHEN I REMOVE THE DRIVE SHAFT HOWEVER. I HAVE DONE SOME REPAIR ON THE FRONT END LIKE WHEEL BRGS BALL JOINTS CHASING THIS PROBLEM . CAN ANYONE TELL ME IS THIS THE NATURE OF THE BEAST OR IS THERE SOMETHING IM OVERLOOKING??

George
October 31, 2009 - 22:12

The torque split of the H1 is 48/52, not an even 50/50.

The Hummer II utilized the Borq-Warner 4484 transfer case.
www.rsgear.com

The Hummer III utilized either the B-W 4493 or 4494 (greater low-range reduction)