even though it only has 44,000 miles, that doesnt mean everything is good yet but in this case, everything is like new yet. Motor mounts are good. I was going to change the harmonic balancer just to satisfy my curiosity but it is a fluid balancer and I never heard of one of those going bad, Ever. The trans is quiet until it warms up, usually takes about 10 miles. The trans isnt overheating, it stays at about 220 degrees. I had it out twice and took the top plate off but everything looks like new and is tight. Nothing on the magnets inside the trans. I did install a new clutch (eaton fuller) and I had awful vibrations after that. Dealer Eaton wouldnt give me anew clutch, they said there is no way that little thing on the back of that big motor could cause that problem! What a bunch of morons those factory reps are, do they really drink their own Kool Aid? The dealer wouldnt exchange it either saying that Eaton wont reimbure them. Even though I didnt buy it from eaton, I bought it from the dealer, they still wouldnt stand behind it. Got to love JX Peterbilt? They told me to turn the clutch 180 degrees and try that. To my amazement it worked and the vibrations are minimal. I thought a clutch was suposto be balanced??? How can I explain flipping a clutch 180 degrees would make a difference? Anyway, the transmission still makes noise between 1400 and 1550 rpms. But it is only noticible on the high side of the trans. and really bad in 13th gear. But like I said if I run it above 1550 rpms it seems to be alot quieter but Im also running 72+ mph @ 1550. Should I get a thrid trans and see if that helps or do you guys think it is resignating from the engine? There is a slight engine vibration with truck stopped and clutched pushed in when I rev up to 1500 rpms. I looked at alot of 3126's and they all vibrate, mine really isnt any different.