2180 gear failure

[07cl733]

I'm looking at buying a 2000 ch with an 18 speed mack trans. I know a good bit of the history, as it is my brothers truck. It has a 460xt, 46k meritor locking rears and mack air ride suspension. My brother bought it used with around 300k miles on it. In the 200k that he has put on the truck it has been plagued with driveline issues, both in front of and between the differentials. All sections of the drive line have been replaced along with all yolks and u-joints. Shortly after replacing the driveline he was pulling a steep grade and one of the u-joints sheared 2 sides off the cross. One of the pieces fell out of the cup and melted into the asphalt.  In the last 20k miles it started disintegrating clutch brakes in less than 500 miles. Then the gears in the back of the trans started scattering, teeth were coming off and even wiped out the speed sensor. He had the back of the trans rebuilt and it lasted 2000 miles before doing the same again. He took the truck to mack and they put a remack trans in that lasted only slightly longer before exhibiting the same symptoms. That is where the truck sits now. Mack would not warranty the trans until complete failure left him on the side of the road. He never had that opportunity since he parked the truck and went back to school. I will also add that he is a good driver that knows well to pre-select ranges and does not shift to low range until moving at slow speed. He is also careful with clutch brakes, the whole clutch assembly has been replaced and we checked for proper linkage adjustment. Is there any hope for this dog, or do we need to put her down? Thanks for any thoughts.

[Mack Technician]

Have you had any “like” issues since you bought it?

[turckster]

Driveline issues coupled with synchronizer issues sounds like driveline angle/suspension ride height issues. A majority of synchro failures are from either improper shift techniques or driveline vibration (susp. ride height). The clutch brake failure is probably from improper adjustment, a bad wear surface (seal housing or throw-out bearing), or improper clutching technique.

Suspension ride height is usually overlooked when transmission failures happen. If the ride height is OK then the driveline angle has to be off. Something is causing the failures you are having and angle/height is the most common issue.