Drivetrain vibration / rumble
 

Ok, I've searched and not found anything that seems to help me so I'll post this up and see if anyone has any other suggestions that might help out.

About a year ago bought a 94 Dak 3.9 AT ext cabn 4x2, 167k miles, had been sitting for a couple years next to a guys garage, he hadn't been able to get it running. A friend and I came in on Saturday morning and by noon had determined it was the CPS and with a little crude rewiring we had it running and drove it out of his back yard. He was glad to see it go although he said he'd owned it since it was new. I'm not sure that's true or not but whatever.

After getting it back home and doing oil change on it proceeded to find out that it needed a bunch of work, as anything this old parked on dirt is likely to need, so I set it aside for a while and finally this fall decided I needed this truck for the winter. I originally bought it because although it had sat and had not run it hadn't been messed with other than what the mice had done (wasn't all that much).

The trip to get it home to my house wasn't a big ordeal, it ran ok, not great, and it might have stalled once or twice on low idle. At any rate the following has been done to it in the recent past:

1. all new brake lines / hoses except on the rear axle hard lines.
2. drill out and replace broken exh mani studs / bolts (3) and new bolts/nuts at Y pipe flanges.
3. new front rotors / pads and full system bleed.
4. replacement drums (new shoes will come later when cables are done)
5. plugs / wires / cap / rotor.
6. new pcv valve and crankcase vent
7. soldered up some chewed wiring under the hood.
8. replacement radiator, water pump, temp sensors (both) and new coolant.
9. timing chain / tensioner / crank seal.

So she's now running great, starts a little hard I still have to remove and clean the TB but that's ok. It still also has a idle issue where it will drop some and possible die when going in gear but I cleaned the IAC and it's better. I'm hoping the TB clean will help or I may try replacing the IAC and see what happens. I also now have no dash lights on at all, which is great! Before had ABS / Brake lights on and a CEL for something I don't recall.

So here's the problem, at around 28 mph I get this annoying drive line vibration and I cannot track it down. I have drained the rear axle, because it needs to be changed, and there's nothing bad inside there, it looks good. I have put it up on jack stands and run it and even with tires off (and drums bolted down) it still comes on. I have pulled the rear driveshaft and it's better but still there, and I have no reason to think that the driveshaft is bad and the u-joints don't seem to be bad on the rear shaft.

What I have noticed is that the transmission tail vibrates at speed (around 30 mph) and I've witnessed this while under the truck with it on stands. Trying to capture video of this event is hard because the frame rate is not as good as the eye, but it's there. While it's diminished with the rear driveshaft off it's not completely gone and so I'm left wondering if it's the trans, the driveshaft(s) the CSB, or maybe even the torque converter? I don't think it's the rear axle, I drained that tonight and don't see anything suspect in there. I will also say that while I can feel the truck go into OD I can't swear that the TC is locking up properly.

I need to get this resolved, it's really annoying to try and drive it this way. Also additionally, the PO told me that the transmission had been overhauled by AAMCO although he didn't say when that was and I got zero receipts with the truck when I bought it. I will say if they did overhaul it they were idiots when they reinstalled the dipstick tube and bolted it down. The tube was compressed enough that when you bolted it down through the bracket that it pulled out of the trans case enough to reveal the o-ring so in essence the thing leaked like a sieve. I still need to fix it properly but for now at least it's inserted into the trans enough to keep from leaking fluid.

Anyway, this is where it's at right now. I have told a friend that if in fact it's the TC that it will likely mean that the truck gets converted to MT because I'm not dealing with an AT overhaul on this thing and I'm not springing for a TC when I can probably buy 75% of the crap needed to convert to MT for that same money, maybe less, who knows.

So anyone with any suggestions let me know.

Thanks
Steve A

Since I don't think I've ever posted up a pic of it I'll do that here since the 'roll call post up pics' thread is locked down.

http://i258.photobucket.com/albums/h...ps5vpzwebe.jpg

Hope this works, I know PB has been kinda butt heads about allowing this.

Steve

Wow. That's in nice shape......

How is the rear trans mount?

Dat's PURDY!

RwP

your winter must be alot different than mine. that 2x4 truck wouldnt make it to the end of the street around here :icon_biggrin:. i was thinking bad tailshaft bearing but maybe its something else in the trans. ax15 is a good trans if you decide to swap. 160k on mine and still shifts like new. throw a new clutch kit in before install and youll be set for 100k+
just put on some new tires

https://cimg2.ibsrv.net/gimg/dodgefo...09b02d3d54.jpg
new tires

It looks nicer than it actually is. There's rust holes under the wheel flares, the fenders are crap and the box is not great. It looks decent from 20'.

Living in town I really didn't want the complexity of a 4x4, I've had one before and I just didn't want another one. I don't need to get out in the winter and I don't try if the snow is too bad but they're reasonable about plowing so I think it'll be ok for what I need. Like my dad I'll put some weight in the back end and that will help. He farmed for 50 years and never had a 4x4 and never got stuck because he was smart enough to not go into places where he would get into trouble.

As for trans mount it seems fine to me, it doesn't have any torn rubber, it's just doing it's job but with this kind of vibration it just can only do so much.

I was thinking if I had to do the conversion I would get as new a transmission as possible, so something besides the AX15 might be in order. I was reading someone upgraded to the NV3500 from 03 Dak, thought that might be a good thing.

Steve

Id replace the U joints 1st.... probably one binding up. Dodge U joints.... common as dirt and cheap. being a cab and 1/2 it probably has a 2 pc driveshaft, replace carrier bearing too.

That's what I'm ordering up right now, and it is a 2-piece driveshaft.

Steve

Don't have any advice on the trans that hasn't already been given. U joints are a good place to start.
however I can give some input on the rough/low idle and stalling.
There's a good chance that the gasket to the belly pan on the bottom of the intake manifold has a hole in it. It's not a hard fix, manifold gasket set and a couple hours of work, no biggie. Have that issue on my 93but mines bad enough that it's actually sucking in some oil from the lifter valley and burning it. But it causes enough of a vacuum leak to mess with your idle and cause you to stall. Be a good chance to clean out your intake manifold too.

Be sure to use shorter bolts on the belly pan. Stock were too long, which is the whole problem.