Re: Rear vibration 65-70mph+ Reply #50 – August 28, 2014, 08:37:00 pm To keep updated from the beginning of this thread: My 1998 u270 has about 75,000 miles on it. I have no slop or play at all in the output shaft of the transmission or retarder damper.Doing some thinking and talking with people, it is obvious there was an application and/or design error. In our case, I really think it is an application error as the coach has very low rear end gears with 5.13:1. For now, I just stay slow at 60mph or so. But, in the next few months I'm going to change gears to 4.33 or 4.63....probably 4.33, but I need to do some analysis.Experience and gut tells me that the p3 problem appears to happen on vehicles that do lots of highway driving. Trashtrucks and city busses likely don't have the problem. Quote Selected
Re: Rear vibration 65-70mph+ Reply #51 – September 07, 2015, 02:35:21 pm To follow up on this thread, I did the rear end swap from 5.13 to 4.33. I have about 13,000 miles on it with mostly 70-75mph cruising.The vibration is gone at 70-75mph.It does come back up around 80-85. But I don't drive that fast, so it doesn't matter. However, this proves to me that the vibration is from the driveshaft. How do I know? The 80 mph is about 3000rpm in the driveshaft with 4.33 gears. 68mph was 3000rpm for the driveshaft with 5.13.Remember, in 1999 or 2000, foretravel started putting in 4.65 gears.See this thread for more details and analysis on the gear change: Rear end gear change from 5.13 to 4.33 on 8.3 Cummins u270 Quote Selected
Topic: Rear vibration 65-70mph+