Violent vibration

pinion bearing is possible. I had same type issue and turned out to be the pinion bearing. eventually it seemed to be worse when coasting.

 

Mud in the rims, U-joint, bent drive line.. Lots of supects ...

 

Re: Violent vibration update

Tackled a lot of scenarios this weekend. Unfortunately, I think it has something to do with the transfer case. Pulled the front driveline and took it down the highway at 50mph, vibration still there. Went home, put the front in a pulled out the rear, down the highway I went, vibration still there. Confirmed that in neutral at 50mph, the vibration was gone (or at least significantly reduced).

The next thing I came across has me puzzled. About a month or so ago, I changed the fluid in the trans and transfer case (point being, both fluids were at level). Upon inspecting the transfer case yesterday, it was almost completely out of fluid. Nothing is leaking leaving a spot on the ground or even fluid tossed under the tub. Just for my own sanity, I pulled the fill plug on the trans and gear oil came gushing out. Now I'm no rocket scientist but if container A and container B are at level and a month later container A is empty and container B is overflowing, that tells me fluid went from one to the other. What the heck would case this????

 

I have the SM-420 trans and the twin stick Dana 18 transfer case. I've heard of trans fluid filling the transfer case but never the other way around. My transfer case was almost empty yesterday when I opened it up. When I pulled the fill plug on the transmission, a good 2 quarts spilled out.

 

Check the vent in the transfer case. If it's plugged it can cause pressure to build in the transfer case and literally force the fluid into the transmission. I don't recall anyone's adapter sharing fluid for an 18 and SM-420.

 

Liquid sealant in the tires, I run a small amount in my tires but seldom get to 60 MPH.

 

Thank you nickmil, I appreciate it. I will check that tonight.

 

My thoughts were the same as Jasons-check the diff bearings, especially the pinion-shouldn't be any perceptible movement other than rotational. A failing transmission input shaft bearing might also cause those symptoms.

 

I looked at novak adapters and it show the sm420 to D18 and the sm420 output bearing is not sealed and the adapter is not drilled for cross-flow. Is it logical that the gear rotation of the D-18 throws the gear oil from the bottom up to the top gear and the oil is then allowed to flow through the open bearing into the tranny?

 

Those two adapters may be like the Novak adapter for the muncie car 4-speeds. It has a seal in the adapter that isolates the transmission from the transfer case, to keep the two separated.