Ok, problems again...

My truck shakes pretty bad accelerating from a stop.

Now for the details :

It's a full body shake. Not from the front end (steering doesn't go wonky). It started a day or two after I gave it a tune-up. My tune-up involved plugs, wires, cap/rotor, ICM, coil, and fuel filter (didn't need it but meh what the heck). For the first day it was beautiful, shortly after it started this.

Now I don't think it's a missfire, I tried out swart's misting thing and no sparks flying. Tried going from the ac delco plugs to iridium plugs, no difference.

I can't hear if it is the engine missing, the vibration actually resonates through the truck. It sounds like I have a KILLER sub setup LOL, but the acceleration is there... It's not slouching on pick up one bit, at least not to what it was before... It could possibly be slower than "normal"...

Now, checking up on things, my tranny fluid was a little low, so I topped it off, no difference. I noticed that my front differential is leaking fluid. I'm pretty sure it's the differential. It smells like gear oil (I despise the smell, so I remember it well), and the front cv's are joined to it. I haven't checked the rear end fluid, but had no reason to because the only leak is the front. The truck leaks nothing else at all...

So the shaking only happens on acceleration, it gets worse with more throttle applied, and the vibration noise changes with engine rpms. Doesn't do it in neutral, and I tried holding the brake and giving it gas while in gear to see if it was a miss, and it didn't shake. Once I hit 3rd gear and close to cruising speed, it rides nice. It shakes very little if you have to give it some more gas to go up a hill or pass, almost unnoticeable.

I'm going crazy with this... I really hope it's not a drivetrain issue... That would suck considering I'm virtually broke for the next couple months...

Hope someone can help me out...

 

This may seem stupid but have you had an alignment done recently? becuase it could cause it to shake a bit if you camber is off or something.

 

Done a few months ago when I replaced all the steering components. Drives straight as an arrow, and the steering wheel doesn't turn or wiggle at all when it does happen...

If I can't find the issue, I'm gonna bite the bullet and take it into the stealership...

 

Could be u-joints. my rear joint is getting bad, can hear it when I put it in gear, and it vibrates a bit from a stand still under mid to hard acceleration.

 

It Could be that you have a Torque Converter Shudder. There are additive on the market that fix this problem like


DR. TRANNY LUBEGARD TRANSMISSION INSTANT SHUDDER FIX. Hope this helps? T.J.

 

I would have the suspension checked out. If your bearings are bad enough or if the races are chipped, you will get a low pitch grind noise along with a bad shake. Also like stated above, check the drive shaft and u joints. The drive shaft should have a balance weight on it.

 

You may want to look for a broken motor mount.

 

I'll check all this stuff this weekend... I'm still leaning towards an ignition problem though. If I press on the gas really lightly, it will get up to speed without shaking. It may be torque converter shudder as well... I'll find out soon enough, just have no time around my work schedule right now...

 

So I had some time to screw around with it today.

I figured I would try the 4x4 to see if anything changes. I pulled out onto the road, and put it in 4 high, took off like a bat outta hell, and not one little shake or shimmy... I got to the end and made a left turn nice and wide (don't want it to bind up lol) and it started shaking even though I wasn't on the throttle, I was just coasting. After I made this turn, it was shaking when accelerating again. I came to a stop and changed to 4 low, and drove, again no shaking. Made another turn, and the shaking comes back.

When its in 2wd, it shakes on acceleration, but not on turns (unless I was at a stop and starting out with a turn).

So ignition is out of the question I would think because it runs like a champ.

The 4x4 still engages/disengages nice, so I'm thinking it's not the transfer case. Now I'm starting to wonder if that front diff leak is causing this?? It is leaking pretty bad, and I would assume that if it's dropping one or two drops when it's parked in the driveway, its probably leaking a heck of alot more while its actually driving.

So let's hear what the 4x4 gurus have to say... This is my first 4wd vehicle, so I'm pretty well lost when it comes to this...

EDIT : Forgot to add that when I hit a dip in the road (smooth one), I hear a humming noise. Sounds like a wheel bearing going out, but it doesn't do it when the road is flat, or while turning... It only happens when the suspension is compressed from the dip, when the truck rebounds to normal height, it stops.

 

I think I have narrowed it down... I'm almost positive it's the u-joint(s) going bad.

Took it to my mechanic buddy (an actual mechanic I went to school with) and he put it up on the hoist and looked at it. He said the rear joint was looking like utter crap LOL, and was well on it's way out. He also said looks might be deceiving because he didn't pull the shaft out because he had (paying) cars waiting to get in... I takes what I gets for free LOL

So I figure at $20 a pop, I might as well replace the 2 rear shaft joints to eliminate it, and at least not have to worry about them.

I have another question about this though... Are the splines on the shaft keyed? As in do they only fit one way? Or is it trial and error until you get them perfectly lined up again to do up the 4 bolts on the rear end?

Obviously I am going to mark the shaft, but is there a bit of play that may mess me up?

Thanks.