Engine/Transmission (1998.5 - 2002) Weird vibration in 4th gear on '99

[DHarden]

I just got back from a trip to Texas from Ohio and I am puzzled at a vibration that I am getting in 4th gear. It happens exactly at 1500 rpm and then stops at 1600. When the truck is cold it isn't quite as noticable, probably because I'm not getting on the throttle as much. It is a higher pitch sound that my wife even picked up on. I can't really explain how it feels but it sorta feels weak and like I'm going to lose the gear. 5th gear has no problem. Also, this happens at all power setting on my comp and there are no changes in the guage reading during this short period.



Has anyone else experienced this or know what could be the problem?



Thanks

Derek Harden

 

[kdunham]

Is your fan clutch locked up?

 

[Halfbakediesel]

forth gear bearing is shot most likely had the same problem in both 5 and 6 speeds

 

[DHarden]

I was thinking that it could be the gear bearing as well. Does that go along with the off vibration that only occurs in 4th between 1500 and 1600? What do I need to do to check then fix the bearing? Thanks for the quality info guys.

 

[TowPro]

My 98 used to do the same thing (of course I have not heard your noise). Mine would do it under load (towing 10K) only in 4th around that same RPM. Threads back then said it was just gears vibrating on the shaft because 4th was 1:1. Never did have any problems with it in 100K miles, just always made the noise.