This mod has the sounds of a Caterpillar, model 3408 V8 eight cylinder engine, with the most realistic torque
You will find seven horsepower options for this engine ranging from 400HP up to 800HP. 
It also includes a 15 speed compound transmission with 6 final drive ratio options (from vanilla 3.23 up to 4.63)

1. 3408 T DI: 400 hp @ 2100 rpm, 1200 lb/ft @ 1400rpm
2. 3408A TA: 450 hp @ 2100 rpm, 1460 lb/ft @ 1400rpm
3. 3408B TA: 500 hp @ 2100 rpm, 1616 lb/ft @ 1400rpm
4. 3408B TA: 540 hp @ 2100 rpm, 1746 lb/ft @ 1400rpm
5. 3408E TA: 600 hp @ 2300 rpm, 1950 lb/ft @ 1400rpm
6. 3408E TA: 700 hp @ 2100 rpm, 2250 lb/ft @ 1400rpm
7. 3408E TA: 800 hp @ 2100 rpm, 2600 lb/ft @ 1400rpm

Available for the following trucks:

International
9400 (Slava1)
9900i (SCS)
9900i (Cartruck)
9300 (Panther)
Freightliner
Argosy (Harven)
Coronado (Stas556/Dmitry68)
FLB (Harven)
Classic XL (odd_fellow/BSA)
FLC (XBS)
FLD (Harven)
Autocar
AT (XBS)
Kenworth
K100 (CyrusTheVirus)
K100e (Overfloater)
T610 (GTM)
T680
T800 2016 (Yanred/GTM)
T800 (GTM)
W900
W900a (Bigddady)
W900b (GTM)
W990 (Harven)
Peterbilt
359 (Outlaw Transport)
379 (Stas556/Fox071rus/dmitry68
389
567 (GTM)
579
Mack
Superliner (RTA)
Chu613 (FranckPeru)
Ultraliner (CyrusTheVirus)
Titán (GSC/Mahad110)
Volvo
VNL
Western Star
4900 (Yukonjack/Alpi0120)

Credits: eeldavidgt