Glad to have found this forum.I have recently been assigned a different truck,concrete pump truck on an MR 688 with an E-7 400 engine,with a T-310 transmission.The first time I range shift from lo to hi while leaving out a distinctive grind is heard from the transmission,but does not happen for the rest of the day.I believe the is the beginning of the end for the synchronizer.or am I wrong.I was taught to always pre-select ,please tell me if I am wrong,never to shift from lo to hi or hi to lo without being IN a gear.If the range select lever is changed while in neutral damage to the synchronizer will occur.This truck was operated by someone else for almost a year and I believe his shifting procedures were wrong,i.e.,range shifting in neutral.Now,with it grinding only one time in the morning could this mean there is a problem with the o-rings in the range shift valve or synchronizer cylinder due to some kind of binding or shrinkage over night?I am not sure for the proper part but the cylinder that is on the back of the transmission that has 2 air lines running to it,could the inside be dirty or scarred preventing problems in the morning?I am looking for some help although I think it is the beginnings of synchronizer failure.Any ideas?