thrashingcows

I've read through a ton of "Vibration" issue threads and none seem to fit what's happening to old RAE.

Here is a break down of the vibration.

-Seems to happen only after the truck has warmed up.

-No vibration while driving, but come to a stop, in gear or out of gear, clutch in or out makes no change, and the truck will initially run down smooth, then the vibration will begin as the Pyro begins to drop.

-No it's not a steady vibration, it's more rhythmic. So it comes on, then almost goes away, then starts up again. And you can almost time the vibration. Feels like something is out of balance, or if it was a gas pot I'd say I had a miss fire on once of the cylinders. But you really can't feel the vibration through the motor.

-My IP is resealed, unknown timing bump..1/8-ish? I've since removed my 3200 spring and running the stocker. My fuel has 1oz 2 cycle oil for every gallon, and a couple ounces of Howes fuel conditioner.

-Another thing that might be relevant, or not, is my NV4500 sure makes a lot of growling noise in 4th, mainly between 35-40mph and around 1100-1500rpm. No noise when the fluid is cold in the morning, just once it warms up.

I've layed under the truck and watched things, and you can visibly see the tranny, and drive shaft shake in time with the vibration. You can feel the vibration run through to the oil pan as well with your hand. You can also feel the vibration through the cab and seats, front or rear.

I have a sneaky feeling it's my clutch? Supposed to be new, at least the PO said so. Maybe the pilot bearing/bushing is shot or going? Or the main input shaft bearing on NV4500 is on the way out? Or could a bad injector(s) cause symptoms like this?

Thoughts?

BILTIT

Do you know what kind of clutch it is?

G1625S

I would suspect the pump and/or injectors from what you describe. Lugging any tranny in direct will produce a fair bit of noise. Unrelated issue, IMO, but be careful with that. I split the aluminum part of my 4500 lugging it too much in 4th when I lost 3rd gear.

BigIron70

Did you check driveshaft ujoints and if two piece driveshaft check center suport bearing. Tires balanced and no flat spots on tires. Two piece driveshaft indexed properly do the ujoints line up? If truck is lifted is the rear axle shimed?

G1625S

No vibration while driving I think eliminates drivelines, et al.

BigIron70

I need eye exam

BigIron70

Out of balance clutch or flywheel Would give you vibration all the time not just when engine is warmed up. Set the timing back see if it changes any.

93flatbed

Whats your RPM set at after that pump rebuild?

tech-eh

I think its the tranny idler bearing on the idler shaft when the tranny is cold the oil takes up the slack when hot it doesn't it should be different vibration if put in reverse on blocks .the idler shaft may be bent which describes the growly forth gear .You didn't mention any stiffness in engaging or disengaging the clutch and putting it into gear so unless it lost a chunk out of it and its sitting in the bottom of the bell housing.which would give you the same vibration all the time not a variable . the variable vibration factor comes from the weights of the gears being different . its only my 2 cents worth

Mark Nixon

What you're describing is called "cycling".
Since it does NOT go away in gear, with the clutch in, it is likely NOT transmission related.

That leaves an imbalance of the rotating assembly, or fuel related issues.
Since it gets worse after it warms, the latter is what I would look into.

How many miles on the injectors and have you had them cleaned and popped?

{edit}
On thinking a bit more, you might also look into the clutch fan and front accessories, remove the drive belt temporarily after it's warmed up, fire it up and watch the harmonic balancer for "wobble" and see if it does the cycling.

Mark.

Kansascrewcab76

I have a similar vibration, but mine goes away when you push in the clutch pedal, so I'm thinking clutch/flywheel/idler cluster gear assembly.

thrashingcows

No idea, was installed by the owner before the guy I bough the truck from.

I just got my IP timing tool and plan on setting everything back to stock settings soon.

RPM is set at about 800 cold and then drops to about 750+ when warm.

I've serviced the tranny, new Syntorque, and I cleaned the case bottom out with rags and inspected things as well. There was no glaring problems that I could see. I also installed the Geno's oil filter at this time.

I assume the injectors are original, 156K miles? As for cleaning and popped, no idea, but I doubt it.

I just installed a new clutch fan, last week actually. But the truck did this with the old seized clutch as well. I was kind of hoping it was the clutch. But I'll take the belt off and watch the balancer.

Thanks for all the thoughts and ideas!!

brainfade

Usually when you have a cycling vibration it's due to two rotating assemblies going in and out of phase. I like the take the belt off idea, it may be that the fan is a little out of balance and interacting with the engine. The tranny idler would also fall into this catagory.

YOREL

What grade oil are you using in the tranny? maybe change to heaver grade to see if it is indeed the idler shafts.

thrashingcows

I believe the Castrol Syntorque only comes in one grade 75W90?