w250_93

It's been doing this for about a year now. It's kinda like transmission rattle when you lug it with just a tiny bit of a break between vibrations, it only does it between 55 and 62 mph while your building speed (it quits if you coast). I rebuilt the transmission about 7 months ago and found that fifth gear had wear marks on it so i just figured thats what it was and at the time i didn't have the money to replace it so i just put what was needed back in it and put it back in the truck. Now the other day the boss man gave me some scrap pieces of ibeams about 1500lb to 1800lb. I loaded them in the bed an noticed that the vibration was pretty much gone on my way home. I haven't unloaded it yet so i don't know if it going to start doing this again or not but why would weight in the bed make the vibration stop could it be rear wheel bearings or just the extra weight is keeping fifth from vibrating. I've replaced the u joints so thats not it. Also does it take an act of god to make the thermostat housing seal or just a cummins factory seal.

Thanks

Tron

Steady bearing??

Jim Lane

The thermostat doesn't take anything special to keep it from leaking, I got mine from my local Auto Parts and I have not had any sealing problems at all.

One thing to check is its mating surface on the block and make sure that is clean and is not pitted.
Jim

https://www.dieseltruckresource.com/...6&postcount=10

w250_93

i know the bearings don't make any sense, what else would be affected when the weight of the vehicle changes?
The thermostat housing won't seal i have cleaned everything down to bare metal and even put silicone on the housing, lifting eye and the head to try to make it seal but it just keeps seeping, i'll take it apart agian and check for pitting.

BearKiller

Make sure the small shoulder of the seal faces the thermostat; if it is in backwards it will not seal.

JQmile

That stuff is hard to track down. I have a vibration I am trying to "fix" by ignoring it, but so far no luck.

93flatbed

Drive line angle? Loose u bolts? Shifted blocks? Worn leaf busings/shackel bushings? Lots of stuff changes when you load the bed down, your taking up slack, if that makes sence? I know I loose some shimmies and shakes when I'm fat in the bed. Just my .02
Justin

w250_93

i did put new main springs in the rear before this vibration started i might have to look into that.