Re-geared, now I have a vibration above 50 mph

[jeepndogs]

The only angle that matters is the one where it doesn't vibrate. So, I never give anyone an angle or much of anything except to start low in the back and move it up a 1/2 degree at a time until it changes and correlate the change with what you've done and keep messing with it until you get it as good as possible. Also, with problematic rigs, I remove the front shaft so I'm only working with one set of vibes.

So on a SYI with a CV joint what would be considered low to start at? 2 degrees? 3 Degrees? Ideally I have been told and have read that with a CV joint the pinion should point directly at the joint and that the rear can be below the driveshaft but not at all high, and the opposite would be true for the front.

So @mrblaine how low would you start at on the rear shaft with a SYI?

 

[bobthetj03]

Quick update. Forgot about this thread. Did the SYE and ordered a drive shaft. While I was waiting for the drive shaft to come in, I drove the jeep home in 4hi. No vibes. Installed the rear drive shaft when it arrived and vibes came back, but less intense, and it feels like the vibes are coming from the rear. My seat vibes above 55mph and gets more intense at 65 mph, but doesn't get any worse faster. I've adjusted the rear pinion angle a bunch of times with no change in vibes intensity. Something is acting like a tuning fork in the system and amplifying this vibe into the body of the jeep. It's hardly noticeable in the steering wheel now, but still get a good back and foot massage about 50 mph.

 

[jeepndogs]

Quick update. Forgot about this thread. Did the SYE and ordered a drive shaft. While I was waiting for the drive shaft to come in, I drove the jeep home in 4hi. No vibes. Installed the rear drive shaft when it arrived and vibes came back, but less intense, and it feels like the vibes are coming from the rear. My seat vibes above 55mph and gets more intense at 65 mph, but doesn't get any worse faster. I've adjusted the rear pinion angle a bunch of times with no change in vibes intensity. Something is acting like a tuning fork in the system and amplifying this vibe into the body of the jeep. It's hardly noticeable in the steering wheel now, but still get a good back and foot massage about 50 mph.

I have found the same thing. If only one shaft is in and spinning no vibration or very minor, with both in the vibration is back.

 

[bobthetj03]

I have found the same thing. If only one shaft is in and spinning no vibration or very minor, with both in the vibration is back.

I haven't tried pulling the front shaft since the SYE, but I'll gather I'll get similar results as you. Still doesn't explain the root cause of the vibes. Drives like a dream up to 50 mph. I've pulled the front drive shaft off and on so many times this past year, I really am tired of it all.

Do you still have factory control arms, or aftermarket?

 

[jeepndogs]

I have all 8 Metalcloak arms on mine. I'm right there with you on pulling the front shaft in and out. Taking everything I have not to trade it for a JK Lol!

My thoughts are but I have no way to confirm any of this is there could be two possibilities. One,the main shaft in the TC and the planetary gears have some slop designed into them. With both shafts spinning on either end it causes the vibration. My other theory is the shaft that extends and connects the trans to the TC case. That has some slop on the tail shaft of the trans and also some slop on the input shaft of the TC.

Again absolutely no way for me to test or prove either theory.

I have 99% of everything I need to do the lock outs on the front axel to stop the shaft from spinning. Doing a jeep jamboree up in the north woods in a week and after that I'm diving into the conversion.

 

[mtngoattj]

I jave the currie arms on mine i have a slight vibe still i just learnd to live with it. Mine is a dd to

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[bobthetj03]

I have all 8 Metalcloak arms on mine. I'm right there with you on pulling the front shaft in and out. Taking everything I have not to trade it for a JK Lol!

My thoughts are but I have no way to confirm any of this is there could be two possibilities. One,the main shaft in the TC and the planetary gears have some slop designed into them. With both shafts spinning on either end it causes the vibration. My other theory is the shaft that extends and connects the trans to the TC case. That has some slop on the tail shaft of the trans and also some slop on the input shaft of the TC.

Again absolutely no way for me to test or prove either theory.

I have 99% of everything I need to do the lock outs on the front axel to stop the shaft from spinning. Doing a jeep jamboree up in the north woods in a week and after that I'm diving into the conversion.

post your results when you do please.

 

[bobthetj03]

I jave the currie arms on mine i have a slight vibe still i just learnd to live with it. Mine is a dd to

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When you say vibes, what type of vibe? Not a tire balance vibe where your steering wheel wobbles back/forth, but more of a hum type of vibe that is felt and heard, with a sin wave cyclic flow, and not always consistant. Vibe does not change under load or coast or even with the clutch in and engine idling at freeway speeds.

 

[mtngoattj]

Not tire at all its like a sonic vibe

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[mtngoattj]

Hard to explain but sounds like the same vibe i have

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[bobthetj03]

Yep. It's not horrible with the top off, but when I put the hard top back on for winter it will likely drive me mad! Might be a legitimate excuse to bump to 35's and slow the spinning down a bit. Got the brakes for 35's, just not the height.

 

[jeepndogs]

I do know for sure if I still have the vibration after the hub conversion my next move is 5 gallons of gas and A highway flare.

 

[mtngoattj]

I am bumping up to 35s and droping the suspension down 1 inch in the winter

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[Jerry Bransford]

Bob can you take a really good well-lit (use a flash please) photo of the side of your rear drivetrain from at least half-way or 3/4 up the driveshaft to the rear of the rear pumpkin and post it here? It'd be good to see the angular relationship between the driveshaft and the pinion shaft. Please take the photo as parallel to the driveshaft/pinion shaft as possible. Really need to see as much of the pumpkin as possible too as that helps in placing the actual pinion angle.

 

[bobthetj03]

Bob can you take a really good well-lit (use a flash please) photo of the side of your rear drivetrain from at least half-way or 3/4 up the driveshaft to the rear of the rear pumpkin and post it here? It'd be good to see the angular relationship between the driveshaft and the pinion shaft. Please take the photo as parallel to the driveshaft/pinion shaft as possible. Really need to see as much of the pumpkin as possible too as that helps in placing the actual pinion angle.

Yes, I'll work on that tomorrow after work. I'll also include a pic of my digital angle finder on the drive shaft and the flat of the rear diff(the flat where a case spreader would go).

 

[lowranger]

I do know for sure if I still have the vibration after the hub conversion my next move is 5 gallons of gas and A highway flare.

Can I have the hub conversion before you throw the flare on it ??

 

[mtngoattj]

Hahaha i was gonna say the same thing low

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[bobthetj03]

Bob can you take a really good well-lit (use a flash please) photo of the side of your rear drivetrain from at least half-way or 3/4 up the driveshaft to the rear of the rear pumpkin and post it here? It'd be good to see the angular relationship between the driveshaft and the pinion shaft. Please take the photo as parallel to the driveshaft/pinion shaft as possible. Really need to see as much of the pumpkin as possible too as that helps in placing the actual pinion angle.

Ok Jerry, hope these pics will work. I also put my angle finder on there for reference. I also tried variations with the pinion angle 2* lower and 2* higher than the drive shaft angle with no change in vibes. I also put my 3/4" TC pucks back in to further lower the drive shaft angle and re-adjusted the pinion to where it is at now(11.5* DS, 11.3* pinion angle).

 

[bobthetj03]

Here is my chicken scratch trying different pinion angles. Each time taking it out on the freeway to see if I could feel a change in vibes.
Sorry for the upside down pics.

Thinking I was approaching the ujoint's working angles, I dropped my TC skid 3/4" and re-adjusted pinion to match.

 

[jeepndogs]

To me it looks like you are a little high with the pinion. Under a load the axel rotates up. I always went with the rear axel can be lower than the driveshaft under load but never higher. And the opposite for the front. You could be high but not lower.

I ended up with about 1.3 lower on my rear. I will be interested to see what Jerry has to say.