NPR (Isuzu); W35/3500, W4, and W45/4500 (Chevrolet/GMC) 1995-2022
NQR (Isuzu) and W55/5500 (Chevrolet/GMC) 1999-2022
NRR (Isuzu) and W55HD/5500XD (Chevrolet/GMC) 2005-2022
- **From July 1995 for diesel engines; from October 1995 for gas engines.**
- See remarks for general guidance on where springs were used. Dates are in Month/Year format.