Can anyone help,I am now clueless what this could be? I have a 2001 Dodge 1500 Sport with the Off-Road package. I first noticed the real seal on the transmission started to leak between it and the tcase. I then began to notice a vibration at 68 MPH and over. The vibration always occurs at 68 MPH and over. I have checked in overdrive and out of overdrive and the vibration is there in both. It is definitely speed related and not RPM related. I will put the pickup in neutral and shut off the engine. The p/u will vibrate until 68 MPH and then quit. I put it up on jackstands and the the vibration seemed to be in the Tcase (NP231 d) I overhauled the T-case and the rear output bearing was bad. I then put it back in, and I have the same vibration. I have ruled out the driveshaft, ujoints, and rearend as it vibrates the same at 68 MPH and over with the drive shaft off. I replaced the tranny fluid and filter. The transmission seems fine. I replaced the rear seal and the output shaft is nice and tight with no play.

I am completey baffled by this. The only things I can come up with now is to replace the tranny mount, even though it looks good. If the vibration is still there I will pull the Tcase again. I would like to find someone that can speed test the case. Maybe the output shaft is not completely "true". When I overhauled the tcase it was in good shape except for the rear bearing.

Does anyone have any ideas or suggestions? I am damn near ready to take my 12 gauge to it I am so frustrated.

 

Bump.

 

I can't find anyone around that can speed test a tcase. I have come up with another idea based on the same principle. I am going to pull the tcase again and take it apart again. I will then put the output shaft on a lathe and see if it is true. I am really hoping that it won't be true, that way I will have found the problem. If the output shaft is good, I am going to be completely stumped.....

 

How about the midship bearing ?
Thats the thing, in case you don't know, that holds up the 1st part of the drivetrain before it connects to the second.
Those do get worn, and you will most definetly feel some bad vibes if it is going.
They can be tough to find too, not something auto zone is going to have, though they may be able to special order it.

Transmount, maybe, maybe not.
You should be able to tell with a visual inspection if it is Ok, I wouldn't replace it just for the hell of it if it looks good.

 

The midship bearing? Is that the bearing that is inside of the input gear that the output shaft goes into to? There are only three bearings on the inside of the case excluding the bearings for the front shaft. There is the input bearing, bearing in the input gear for the output shaft, and the rear output bearing. Some drive sprockets have bearings, but this one doesn't. It is very tight on the shaft, I am sure it is not it.

Anyway, all the bearings are now new and it didn't fix it. That is why I am leaning towards the output shaft not being true....though how it could have gotten bent is beyond me. Thanks for the advice, I will take any I can get at this point.........what a frustrating pain in the rear.

 

if you dont want to replace your transmission anytime soon then i suggest not shutting the engine off at 70mph ever again.

 

Why? It was in neutral.

 

I don't understand how you can get to 70mph in neutral? You have no gears, you have no speedo, your just reving? Your tach may tell you a certain RPM, but that's not the same as when the tranny is engaged. If you are engaging and then disengaging the tranny because you have it on jack stands, that is suicidal. If it falls off because of vibration all hell could break loose.

 

i think he was driving to 70 then taking it out of gear and coasting in neutral.

 

sorry, i assumed it was an automatic