'87 F350 4X4 460 5 speed. I just recently began getting vibration while in a nuetral power. What I mean is if I let off the gas, I get vibration between the time I let off and the time the engine begins to hold back the truck. The same with coasting. It seems that if no power is applied, it vibrates like I'm going over some catepillar tracks in the road. It also happens when I push in the clutch and coast. Not getting any better either. Anyone experienced this identical problem. I'm concerned that it might be front end bearing on the tranny, but I dont' feel vibration through the stickshift. I've heard about checking weights on the drivelines and checking universals..which I've checked out a little. It isn't in 4 wheel drive, but could this be front axle universals anyhow? Thanks in advance.
Tony G

 

Tony ,
Its possible you have a Release , Throw Out Bearing that is bad ? Do you have the Mazda M5OD Trans ? They have a lot of gear roll over noise . How many miles on your truck ? Do you have the integrated Slave valve / Release Bearing combo ? If its the Release Bearing , If you sit idling and shove the clutch pedal in , the noise should become more noticeable . My experience is that those Slave Valves / Release bearings will die anytime after 130 K miles . When I did the Clutch R&R on my M5OD , I pulled the trans front bearing cover off and resealed it ...It uses the FIP / Black Silicone sealant . The cover has a passage for the trans fluid to lubricate the input shaft bearing and what I found was some of the original silicone gasket material partially blocking that passage . You really have to be careful not to use a lot of that stuff to reseal the cover otherwise it will block lubrication to that bearing . Also , if you get into replacing the clutch etc , don t overlook the pilot shaft bearing mounted in the end of the crank . Its possible this bearing if failing will cause some vibration . Hope this helps you out a little .
Paul

 

After lifting my vehicle (89 F150) I had a custom rear driveshaft manufactured. This resulted in the exact same low frequency vibration you are experiencing. It is felt in the floor and is noticable when you "unload" the driveshaft between coast and drive mode. I took it back twice for rebalancing but the vibration still existed. I am trying to balance it myself using the "hose clamp method" and trial and error. It is now very hard to detect and feel if I get energetic I could eliminate it all together. Try installing a hose clamp at each end of the shaft one end at a time moving the clamp at 90 degree intervals and note the difference, if you find a "good spot" try adding another clamp, etc. Check shaft 1st for damage and bad u joints. Good luck
Mark

 

Well, after further investigation and taking the transmission out of gear, I've found that my front universal on the rear shaft is shot. This is the one close to the slip joint on the driveshaft and is allowing the joint to flex causing even more vibration than if it would be the universal at the rear end. Thanks for the suggestions and I hope replacing this universal clears things up for me.
Tony G