I have a 97 Ram 1500 with the 5.9magnum engine with 96,000 miles. I just had the transmission rebuilt (twice but that is a story in itself). I have noticed since the rebuild that it makes a clacking noise when there is a load on the engine. The noise gets louder the faster you drive it(the more load on the engine) but goes away when it hits the last gear. It does not make any noise at idle or if I rev the engine in neutral. It also does not make any noise in reverse gear. It has been a long time since I have heard the sound of bad lifters in a car so I can't figure out what the noise is.
If it were lifters, wouldn't it make noise all of the time?
If it were a U joint wouldn't I hear the noise more on the outer side of the truck by the wheels?
I even thought it could be a Cat Converter problem but I can see that it has been replaced before I bought the truck (it still has no rust on it and shines and the welds look clean)
Any Ideas out there folks. I hate to have to get rid of a self destructing truck since it is only a second owner truck and was ordered from the factory by the first owner.

 

I also wondered if this could be another transmission problem since they did something wrong on the first rebuild. They told me it had something to do with not removing a plastic check valve in the transmission line that was restricting fluid movement to the transmission.

 

I just though I would add that the noise doesn't get faster with the rpm's. The rpm's can be high when going uphill but the noise is consistent with the speed of the truck.

 

My first thought was that it is something in the transmission, but if the sound only changes speed as the vehicle speed is changed, it would seem to me that there is something going on with the drive line between the tranny and the rear end. You say the clacking doesn't change speed with engine rpms, even when it downshifts under load going up a hill, then it has to be something after the tranny.

I would first check the U-joints. they may be only slightly going bad and not too obvious upon inspection, but look at them a little closer. There should be NO play in them. Even a slight amount will make noise.

Also check to make sure the rubber transmission mount on the cross member isn't deteriorated, or loose. If it is, it will allow things to shift position and possibly cause the noise you hear. This is a bad thing, and this should have been changed with the transmission rebuild anyway as preventive maintenance. It's not that expensive a part, and it has to handle quite a bit of stress, so changing it is a must when the tranny is removed for a rebuild / replacement, in my opinion.

These are my best guesses for now.

 

Thanks for the response. I have to bring it back to the transmission shop this week to have them check it out.
The dangdest thing is that it sounds like someone put a playing card in the spokes of a 10 speed bike. No matter how fast you pedal the bike(rev the engine) the noise only goes as fast as the wheels spin.