I have a bad vibration, in the truck when going down the freeway..
expecially at high speeds.
not as noticable at lower speeds..
but when traveling down the freeway, I am at 2500 RPMS.
when driving down the street I run the same RPM but it's not as bad..
so I dont think it is motor related..
any ideas on what else to check..
I was thinking possibly motor mounts, maybe u joints, or a bent drive shaft????

thanks
Daniel

 

I would think to check all the obvious first. Rotate/balance tires as much as possible. I know you are running a strange tire combo. I know you've done the drop, did you ever do a pinion shim kit? That could really effect the ride. Check u-joints, rear axle fluid change may be in order. Just do a general suspension check. Then go from there. I can't really think of anything else. You haven't hit any curbs or potholes lately have ya?

Where is the vibe coming from, front or rear, or can ya tell. My 04 GMC always had a bit of a vibe in the rear and got worse with the shackle drop, and even worse the more miles I put on it. If you haven't ever done the pinion shim kit, I think I'd start there.

 

did the shim kit when I put the drop on, also it is pretty much the whole truck vibrating..
I at first thought it to be the motor, but it doesnt vibrate when you run the RPMS up in park, only in drive, leading me to beleive I have a drive train problem.

 

yea.. i would say either tranmission related or driveshaft related... my whole truck will shake like your describing.. but only when im doing 120+ lol.

 

I had a worn pinion gear that would shake at 120 kph, or around 70 mph. It was worse when I let off the gas, 1 day when I accelerated to 130 kpf, the outputshaft and extension housing broke off the back of teh trans throwing my driveshaft. I replaced trans and got a custom driveshaft, got everything bolted in and took fr a test drive and whamm, another outputshaft and extyension housing, so another screwed 4l60e and bent shaft. So 1 more 4l60e and another custom shaft plus some exhust stuff this time, along with a new rear ring and pinion and everything was fine. This was a very expensive way to diagnose a worn pinion gear to say the least.

Lesson 1 here was that harmonics can travel from the rear end into the trans, causing havoc. Lesson 2 here is that driveshaft loops keep underbody carnage to a minimum when the driveshaft lets go. The driveshaft is spinning quite quickly with 4.10 gears, 130 kph and 28" tires.

Anything that spins can casue a vibration, if the vibe is still there after you shift into neutral and let the engine idle(while still at speed), you automatically know the flexplate, torque converter and engine are NOT the cause, the problem is then in the driveshaft, rearend, or in the tires. if swapping tires around doenst affect the vibrration only the driveshaft and rearend are involved. Borrow a driveshaft and install(out of a friends truck), if it is still there, the vibration has to be the rearend.

take care
peace
Hog

 

Mine vibrates a little but i think its cause of my balance on my rims and tires. Im running 22's so they are much harder to balance! Im sure thats my problem.

I would guess either you balance is off or its driveshaft related.

 

Here's my 2 cents. Possibly a fouled plug or 2. The engine will seem fine without any load on it. When load is applied, the spark plug is really put to work then. A weak plug will definately give you a dead cylinder. Check your plug wires for damage or burns as well.
Or is it possible your torque converted seen its better days? That will cause a vibration under load if it has gone south.
Final possibility, broken radial belt in one of your tires. Basically that would be a tire separation.
That's all from me.
Hope you find the problem.

Jim

 

drive shaft is bent or warped. get it fixed before the tail housing goes out on ya like mine did, it will pull the bushing right out and you will have to buy a new one. drive shaft balanceing is 50 bucks.

 

where at Kevin???

and I just changed out my spark plug wires yesterday
stock measured .47 ohms
new MSD measured .31 ohms
also brand new ac delco irridium spark plugs..

verter huh???
that could possibly still be under warranty
I will have to check that out, although I just had everything rebuilt about 3 months ago

 

I would say either u-joints, pinion gear/bearing, or converter. I had a u-joint do bad one time and I ran it kinda hard (15-80mph) and felt something funny, got back and checked it out and thats when i found the bad u-joint and obviously the vibration cracked the bellhousing on the tranny too.