These three are the multi-belt tensioners for Volvo/Marc heavy-duty trucks. Among them, 23669027 and 21454379 are completely interchangeable, while 21404578 is another common model.
1. 23669027 / 21454379 (Same model)
Applicable engines
Volvo: D11, D13 (12.8L)
Marc: MP7 (10.8L), MP8
Cummins: ISM
Applicable vehicle models (2008–2018)
Volvo: VNL, FH, FM
Marc: CHU, CXU, CXP, GU, LEU, MRU
Key parameters
Wheel diameter: approximately 86.5mm
Wheel width: approximately 40mm
Bolt diameter: 30mm
Installation: 2 bolts for fixation 

 

II. 21404578 (General Model)
Applicable Engine
Volvo: D9, D11, D13, D16
Applicable Vehicle Models
Volvo: FH12, FM12, FM9, VN/VT, NH12
Exchange OE Number
20966526, 20935523, 814985 

 

III. Differences and Selection
23669027 = 21454379: Mainly used for D13/MP7, AC and generator drive end
21404578: Suitable for older models FH/FM and some engineering machines, with better versatility
IV. Replacement Suggestions
If the original vehicle is 23669027 or 21454379: They can be directly interchanged
If the original vehicle is 21404578: The former two cannot be used as substitutes
Replacement cycle: Approximately 10–15 thousand kilometers. Avoid belt slipping or breaking