My build sheet say that my truck has a Shift-on-the-Fly,231HD Transfer Case but while under it today i looked at the tad and it said 231D

Dear John:

Thank you for contacting the Dodge Customer Assistance Center in regards
to your 2001 Ram 1500.

We are pleased to provide vehicle build information per your request.

According to our records, your vehicle was equipped from the factory
with the following:

Sales Code Description
*R1 Premium Cloth 40/20/40 Bench Seat
-AZ Agate
ADAP Light Group
ADJ Heavy Duty Service Group
AGG Sport Group
AHC Trailer Tow Group
AJKP Convenience Group
APAS Monotone Paint
ASPP SLT Decor Group
AWK Travel Convenience Group
A07P 5.9L Engine(EML)/4Sp Auto Trans(DGT)
BAZP 136 Amp Alternator
BCQP 750 Amp Maintenance Free Battery
BGJS Pwr Disc/Drum Rr Anti-Lock Brakes
CBEP 40/20/40 Split Bench Seat
CGDS Front Height Adjust Shoulder Belts
CGWS Next Generation Front Air Bags**
CGZS Passenger Air Bag On/Off Switch
CHEP Deluxe Headliner
CKEP Front Seat Area Carpet
CLAP Front Floor Mats
CSPS Passenger Assist Handle
CUSP Overhead Console w/Trip Computer
DGBS All 4-Speed Automatic Transmissions
DGT 4-Spd. Automatic 46RE Transmission
DHAP Lock-Up Torque Converter
DHKS Shift-on-the-Fly,231HD Transfer Case
DJCS 195MM Front Axle
DMH 3.92 Rear Axle Ratio
DRBP Corporate 9.25 LD Rear Axle
DSA Anti-Spin Differential Rear Axle
EAAC All Engines
EAGC All Gas Engine
EML 5.9L V8 MPI Engine
GACS Tinted Glass Windows
GJDS Rear Fixed Window
GNKP Rear View Auto Dim Mirror
GNVP Sun Visors w/Vanity Mirror
GTSP Power Heated Mirrors, Fold-Away
GVBC All Vehicles W/Power Mirrors
GXM Remote Keyless Entry
HAAP Air Conditioning
HGAS Hood Insulation
HGBS Dash Liner Insulation
I23S Route 23 - CSX, Jessup, MD
JAYS Instrument Cluster w/Tach
JCBS 120 MPH Primary Speedometer
JHAS Var Intermittent Windshield Wipers
JJAS Cigar Lighter
JJBS Dual Note Electric Horns
JJJS 12V Auxiliary Power Outlet
JPBP Power Locks
JPDP Power Windows, Driver One-Touch
JPV Power 8-Way Driver Seat
JRDP Power Driver Seat
KRAP STRIPE/BADGE/MOLDING/COLOR
KTAP STRIPE/BADGE/MOLDING/COLOR
LBAP Map/Courtesy Lamp
LBCP Glove Box Lamp
LDAS Underhood Lamp
LMAS Halogen Headlamps
LMEP Halogen Quad Headlamps
LNJP Fog Lamps
LPES Cargo Lamp
MBPP Body Color Front Bumper
MBQP Body Color Rear Bumper w/Step Pads
MDAP Front License Plate Bracket
MFNP Body Color Grille
MHAS Black Windshield Moldings
MUZP SLT Badge
MVJP Sport Badge
MWDS Removable Tailgate w/Caliper Latches
NAA Federal Emissions
NBKP EVAP Control System
NFWS 26 Gallon Fuel Tank
NHBP Auxiliary Transmission Oil Cooler
NHMP Speed Control
NMCP Heavy Duty Engine Cooling
PB3A Intense Blue Pearl Coat
QB3S Intense Blue Pearl Coat
RAAC All Radio Equipped Vehicles
RAZ AM/FM Cassette Compact Disc Radio
RCEP Infinity Speakers
RDDP Fixed Long Mast Antenna
SBAS Power Rack and Pinion Steering
SCVP Leather Wrapped Steering Wheel
SFBS Front Heavy Duty Shock Absorbers
SGBS Rear Heavy Duty Shock Absorbers
SHAS Front Stabilizer Bar
SUAP Tilt Steering Column
TBBS Full Size Spare Tire
TBMP Tire Carrier Winch
TXWP P265/75R16 OWL On/Off Road Tires
TZAP Goodyear Brand Tires
WDB 16X7.0 Chrome Wheels
WLBP Steel Spare Wheel
WLYC All Steel Wheels
WMJP Center Hub
XBSS Pickup Box
XCMS Vendor Painted Cargo Box
XEFP Transfer Case Skid Plate Shield
XFHP Class IV Receiver Hitch
XFKP 7 Pin Wiring Harness
XFLP 7 to 4 Pin Wiring Adaptor
YAAS Build To U.S. Mkt. Specifications

 

It also says you have rack and pinion steering but you don't.
It says that for all of them though.

 

Real possibility the t-case has been changed out in the past. They do tend to grenade the case when the snap-ring on the output shaft lets go.

 

Which is a better the better t-case to have in there the 231 hd or the 231 d? what is the differance? Which is a better t-case to put in it for say the common uses and to be able to hit the mud and trails with out giving out.