Duplex introduced the D-450 chassis in the early 1980s as a replacement for the D400. It received the Defender name. It came standard with a 5-man aluminum canopy cab, a 4-door fully enclosed cab seating up to 8 firefighters was an option.
In 1991 the enclosed cab became standard to comply with the new NFPA requirements.
The D-450-T was a tandem axle chassis intended for aerial ladder trucks (a popular pairing was a D-450 cab and a Grumman aerial/body) and other large apparatus but a single axle chassis, simply known as the D-450, was also used for pumpers and smaller trucks. Simon-Duplex discontinued the chassis in the mid-1990s.
Standard specifications in 1987[]
D-450 (Single axle)[]
- Engine - Detroit Diesel 6V-92TA
- Engine horsepower - 350 (Up to 475HP with options)
- Transmission - Spicer 1352-A
- Alternator - Leece-Neville 4725JA, 130 Amp
- Front GAWR - 13,180 lbs
- Rear GAWR - 23,120 lbs
- Cab width - 96"
- Cab length - 109.50"
- Cab roof style - Flat with canopy
- Cab doors - Full height
- Seating capacity - 5
D-450-T (Tandem axle)[]
- Engine - Detroit Diesel 8V-92TA
- Engine horsepower - 475
- Transmission - Allison HT-740
- Alternator - Leece-Neville 2800JB, 160 Amp
- Front GAWR - 18,000 lbs
- Rear GAWR - 46,000 lbs
- Cab width - 96"
- Cab length - 109.50"
- Cab roof style - Flat with canopy
- Cab doors - Full height
- Seating capacity - 5