I have a rattle that shows up (only) at about 70 in 5th, 55 in 4th, and maybe 32 in 3rd. The sound is similar to a loose shifter ****, but it's coming from down under. It might be a case of too much information because my shift boot has come loose, but if I lift the boot is loud. I would imagine that if I did the math I would find it is happening at a certain RPM because the spacing looks right.

Any ideas on this? It's worrying me.....

 

Have you checked valve lash recently.

 

I see you have replaced the Getrag with an NV4500, and if it is a 4X4 I would start looking at the linkage for the transfer case.

If it is a 2WD, then focus on the drivelines and the spline, the carrier bearing, and the universals.

If you have a lot of miles on the NV4500, it could be the syncros are developing a lot of slop. They will rattle pretty badly when they get loose.

Lastly, or maybe first, you list a Gear Vendors OD. They are well known for knocking out the planetaries, and will rattle badly from excessive end play.

 

I haven't run the valves in almost a year. Didn't seem like a lash problem because it's in such a narrow RPM band. Could be though. I have been running the engine hotter lately by virtue of my radiator block offs, maybe it's time to run them again.

I hope I can find it before the dyno run.....

 

I was putting pressure on the t-case sifter trying to get it to stop, but it still could be the linkage. I'm 99% sure it's engine or engine vibration harmonics related. The Gear Vendors is a new statue in my garage waiting for a rebuild. I like looking at it though, kinda shapey and industrial

 

Looks like I might have a shaft rattling in the t-case. If I put it in low range the rattle goes away completely. I don't have an exploded view of the NP205 so I'm not sure what shafts are in play in each range.

Any t-case experts out there?

I was afraid that the t-case was the next thing to go, I have blown up the rest of the running gear....

 

I asked Dan at QUAD4x4 who said he can't think of what would rattle like that in the t-case.

I'm having a hard time diagnosing this one. Not willing to hang from the bottom of the truck going down the freeway

 

The rattle is gone. I took out the carboard baffles I had in front of the radiator and no more rattle. The only thing I can figure out is at a certain RPM under a fairly light load the engine harmonics were causing a severe rattle between the cardboard and the radiator bailing wire straps. Sounds like bull even to me, but It's hard to argue with results. Once I got that resolved I re-mounted my shifter boots (both) and now am amazed at how quiet the truck is inside. Hopefully the mouse highway is now cut off too!

Dyno might be back on for the 4th if I can get it by my wife!