99 Pete 379, 60 series Detroit, 840000 on miles. Just had full rebuild with new crankshaft (spun a bearing) When we took to the shop jakes were working perfectly, now half the time they are not working more specifically while on the HWY. Mechanics says maybe computer?? But we took it to the shop with no problem with the jakes! Oil pressure is also acting up but after testing the pressure on the motor and the gauge it is said to be running correctly. Just don't know if these coincide together so wanted that to be thrown in there. Any help would be greatly appreciated! We are new to the trucking industry and still learning.