Something abnormal after transmission rebuilt

I have a 92' Ford Ranger XLT with 2.9 V6. I just had the auto transmission rebuilt. I also had new trans mount, main seal, U-joints (with grease fittings) and driveshaft center bearing installed. Now the vehicle has a new sound (or sensation)that wasn't there before.

It is a low frequency vibration or humming above 40 mph. The transmission seems to shift very smoothly. The trans fluid is fine and they did grease the U-joints. And everything seems tight under there. This sensation definitely does not seem normal to me and it is quite noticeable. I was thinking maybe they didn't balance the driveshaft when they put it back on.

This old trans lasted almost 22 years, so I have little experience on what to expect with newly rebuilt transmissions.

 

Why not take it back to the trans rebuild shop and have them go for a test drive with you?

 

Yes, I am going to do that. But I want to be an informed consumer if he tries to talk it off as nothing. I am worried that this vibration might put stress on another part and cause damage elsewhere. This is too much aggravation. I was without my only vehicle for a whole week. I see so many errors and parts issues with auto repairs these days

 

Something like that can be difficult to diagnose without being there. I suppose you could take it to a different shop and get their opinion.

An unbalanced drive shaft would make a vibration. Drive shafts are balanced at the factory although you are supposed to mark them for orientation when you remove them.

 

I went to the transmission repair place today. They test drove it and put it on the rack where they discovered that a balance weight had fallen off the driveshaft. I also noticed a dent on the drive shaft I never saw before. They said they would have a driveshaft specialist correct it under warranty. I hope that is the end of that. Thanks