Fresh 4.88 gear install, no I have issues

[midfat]

I need the help from some folks who know gears. Did a Nitro Gear install on my 1997 with a 3" Icon lift on 35s. I had a very reputable shop do it that's well respected for setting gears. I was told the backlash and coast were perfect, as was the mesh pattern. Issue is now, on my drive home, I have a buzzing vibe that's unmistakable between 50 and 75 miles an hour. It's powerful enough I can feel it in the driver's floorboard. On acceleration, all is good, the moment I lift or start to coast, it starts to roar.

This doesn't sound like gear whine as it's only present at specific speed, and under deceleration - or cost. But admittedly, I'm not sure.

Any thoughts before I start imagining the worst?

 

[chap79]

What are you using for caster correction? I would look at the u-joints. Pump them full of grease and see it that calms things down. If so replace them.

 

[midfat]

What are you using for caster correction? I would look at the u-joints. Pump them full of grease and see it that calms things down. If so replace them.

Running Icon's castor correction bushings on the front. I'm at just over 1* castor. I know that's a little less than ideal, but I'm okay with it. Doesn't hunt or dart.

You suggesting front ujoint?

 

[chap79]

I personally would replace all u-joints, front and rear. They've been operating at a static angle for the past 20 years. They're probably pissed off right now.

 

[midfat]

I personally would replace all u-joints, front and rear. They've been operating at a static angle for the past 20 years. They're probably pissed off right now.

The lift has been on the truck for a few months and everything has been running flawlessly. This new noise/vibration is related to some action during the Almost sounds like a worn bearing that starts howelling when it's unloaded and spinning. The moment I add throttle, is stops.

 

[scrowley]

take out the front drive shaft. lock center diff. drive. I bet the noise is gone. The lift throws off the drive shaft angle.

 

[chap79]

And the new gears will accentuate any vibration that may have existed before because everything is spinning faster now.

 

[LINUS]

Grease all the zerks - remember the driveshafts are a 2-3 pump max issue (till you see the splines move, then quit).

Flood the U-J's till you see new grease.

You are now effectively spinning the DS's faster, so it could be a driveshaft - if you planned on a DC DS up front, just buy one now rather than futz with your UJ's.

What kind of miles are on the rear DS? Enough to consider new UJ's.

If new UJ's come into play, I can say from experience the real Yota ones are worth the extra $8 over NAPA ones - I wasted time once over a 4th/July vacation fun run / poor planning on my part & it didn't last much too much longer.

Went in again with a real Yota (Koyo? -sorta sure) ---anyhow it's still in & I ordered it from @cruiserdan & seems like 2+ yrs since he pulled anchor & left port.

Or I just miss his ability to finish orders for us with parts we didn't know we needed

 

[richardlillard1]

Grease all the zerks - remember the driveshafts are a 2-3 pump max issue (till you see the splines move, then quit).

Why would you want the yoke to be so full of grease that it's forcing movement? Where is that grease going to go when the driveshaft needs to compress even a little bit?

Or did you want to turn it into a hydraulic ram capable of destroying things?

 

[richardlillard1]

I personally would replace all u-joints, front and rear. They've been operating at a static angle for the past 20 years. They're probably pissed off right now.

Then I bet mine are super pissed. I've had the stock ones for the last ~70,000 miles (they has 130k on them before the lift) and the truck has had J springs with spacers for most of that (I took the spacers out for a while).

How about greasing the joints and putting the drivetrain in neutral to check them for play before spending $200+ on replacing things that might not need it?

 

[bloc]

I wouldn't expect you to be able to "feel" a gear issue through the floorboard. But that's a classic symptom of problems at the frequency the driveshafts operate at. Other symptom is being able to feel it through the seat. Gear issues are usually a whine or howl. And as to a driveshaft acting up when you lift or coast.. it can happen. If the joins are sloppy angles change when you apply different forces to the drivelines which can quiet or make louder given problems.

Locking CDL and removing one shaft at a time can help you track down the issue.

 

[Proven]

In my experience gears are just noisy and only cause vibration just before failure. I believe that what has been said is the best course of checking your drive shafts.

When you put your foot on the throttle and increase speed there is rotational torque to the shaft which creates pressure to bind it in place and dampen the vibration. While coasting there isn't the same amount of rotational torque to apply pressure and thus it is free to wobble/hum/shake.

 

[landtank]

Why would you want the yoke to be so full of grease that it's forcing movement? Where is that grease going to go when the driveshaft needs to compress even a little bit?

Or did you want to turn it into a hydraulic ram capable of destroying things?

provided you regularly grease the shafts in this manner, the grease migrates down the splines and out the end of the shaft. With properly greased shafts there shoul be evidence of this under the truck. The rear driveshaft grease line is on the muffler and the front is on the oil pan.

 

[midfat]

Thanks for the fast advice. I'll pull one driveshaft at a time later today to try to localize the problem. I'll report back.

 

[LINUS]

Why would you want the yoke to be so full of grease that it's forcing movement? Where is that grease going to go when the driveshaft needs to compress even a little bit?

Or did you want to turn it into a hydraulic ram capable of destroying things?

2-3 pumps OR if you see it move, ever so slightly. Those splines need grease, but nobody is advocating greasebinding it.

Zerk is there for a reason.

 

[BILT4ME]

Why would you want the yoke to be so full of grease that it's forcing movement? Where is that grease going to go when the driveshaft needs to compress even a little bit?

Or did you want to turn it into a hydraulic ram capable of destroying things?

That's why he said only 2-3 pumps. So many folks don't think something is greased until it's puking grease out SOMEWHERE. By then, it has blown out the end of the dust cover or put it in a bind.

 

[ewillis]

Did you rebuild the knuckles within the past few months?

 

[midfat]

Did you rebuild the knuckles within the past few months?

Yes, rebuilt the entire front axle a few months ago. Then I decided to add a 3" Icon lift. And 35" tires. Then decided I needed to re-gear. Then the axle came back apart. (In hindsight, I should have re-geared when I rebuilt the axle the first time.) A benefit of rebuilding the axle is that I discovered one of the inner axle seals already failed. Must have been nicked or something as the birf was filled with gear oil. New seal went in when the axle was buttoned back up.

 

[ewillis]

Yes, rebuilt the entire front axle a few months ago. Then I decided to add a 3" Icon lift. And 35" tires. Then decided I needed to re-gear. Then the axle came back apart. (In hindsight, I should have re-geared when I rebuilt the axle the first time.) A benefit of rebuilding the axle is that I discovered one of the inner axle seals already failed. Must have been nicked or something as the birf was filled with gear oil. New seal went in when the axle was buttoned back up.

Might have a dry spindle bushing...happened to me last time I rebuilt. Made a grinding/whirring sound when I let off the accelerator and was coasting. There's a youtube vid someone attached to a thread I created about it. The sound was spot on. Might want to dig it up and confirm before tearing into it.

 

[Rifleman]

When the shop did the work, did they put witness marks on the drive shafts before they removed them??? If i remember right, there is something in the FSM about the drive shafts being in "phase" It says to mark them, before you remove them, so they can be put back in the same place. If not, it can cause strange noises, and vibrations.