What do driveline vibrations feel like?

andyj

andyj

TJ Enthusiast
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I got my 35mm (1.38 in) spring lift installed recently and didn't expect any problems. My understanding is that lifts up to 2 in don't cause any driveline issues but it appears that all TJ's are a bit different. My TJ feels a bit rough now and I don't know if it is coming from the driveline or maybe it's just because the springs are a bit harder that I feel something. I certainly get some vibrations at some speeds but the frequency is matching the revs of the engine, not the drive train that rotates a lot slower.

So, what do drivetrain vibrations actually feel like?

Cheers,
Andy
 
andyj said:
I got my 35mm (1.38 in) spring lift installed recently and didn't expect any problems. My understanding is that lifts up to 2 in don't cause any driveline issues but it appears that all TJ's are a bit different. My TJ feels a bit rough now and I don't know if it is coming from the driveline or maybe it's just because the springs are a bit harder that I feel something. I certainly get some vibrations at some speeds but the frequency is matching the revs of the engine, not the drive train that rotates a lot slower.

So, what do drivetrain vibrations actually feel like?

Cheers,
Andy
Click to expand...

It’s not the springs.

Driveline vibes increase with rotational velocity. Not sure how to describe them, but you feel them through your seat, steering wheel, shifter.
 
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andyj said:
I got my 35mm (1.38 in) spring lift installed recently and didn't expect any problems. My understanding is that lifts up to 2 in don't cause any driveline issues but it appears that all TJ's are a bit different. My TJ feels a bit rough now and I don't know if it is coming from the driveline or maybe it's just because the springs are a bit harder that I feel something. I certainly get some vibrations at some speeds but the frequency is matching the revs of the engine, not the drive train that rotates a lot slower.

So, what do drivetrain vibrations actually feel like?

Cheers,
Andy
Click to expand...

Did you change anything else when you changed the springs? Shocks and/or tires can affect ride quality.
 
TheBoogieman said:
That's not driveline vibes with that tiny lift.
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Maybe I'm just a bit paranoid. I guess it's best to measure it, so I ordered an angle finder yesterday. Just from looking at it, it doesn't look excessive. The drivetrain was almost a straight line before the lift, probably because the old springs have been worn out.


drivetrain.jpg


So far I changed only the suspension and the tyres. The suspension is a complete kit from dobinsons https://www.dobinsons.com/

The shocks are quite tough as well but I like the ride quality. It sits on the road like on rails.
 
Quick thoughts:

If it were me, I'd probably have the tire shop rebalance the wheels/tires. If they ask "why?" then tell them you have vibrations at certain speeds.

Regarding the rough ride, you may want to check your tire pressure. It's possible that you want your pressure at around 25-26 psi, and tire shops are known to overfill tires. That might solve or reduce the rougher ride you've noticed. I'd have the rebalancing done first since they will likely just hike the pressure up again when you have them rebalanced.
 
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I don't think it's the tyres, I know what it feels like if they are not properly balanced. I got new rims and tyres, got them balanced and I got a wheel alignment done (the wheel alignment after the lift). The tyres are not very coarse either, just simple A/T that I run at 28 psi. I got those wheels two weeks before the lift and didn't have any problems with them. But thanks for your advice, it helps to narrow down the problem.
 
Even though the driveline angles aren't excessive, you did change them.
An older ujoint may now be operating out of its (normal) worn position.
This could apply to the slip yoke position too.
Try pulling the driveshafts to verify if the vibe is in the front or back.
 
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LONGJP2 said:
Even though the driveline angles aren't excessive, you did change them.
An older ujoint may now be operating out of its (normal) worn position.
This could apply to the slip yoke position too.
Try pulling the driveshafts to verify if the vibe is in the front or back.
Click to expand...

That's what I was thinking as well if OP knows the wheels/tires are good.

Could also do a dry steering test to ensure things are tight up front, and you can jack up the front axle and check for wheel play.

Have you double-checked every fastener that's been recently turned including the wheel nuts?

This seems odd and why I'd consider throwing on your older wheels/tires so you for sure know it's not them. It's all a game of probabilities so just check what you can to eliminate them rather than assume (you'll spend more time not getting answers by assuming). For example, what if the wheels were balanced/installed by little Jimmy on his first day working at the shop). Discount tire damaged one of my wheels because it was a dude's first day on the balancer. Don't underestimate others' ability to fuck up in improbable ways.

You didn't do a ton of mods so it shouldn't be too difficult to double-check and this is all assuming things were good to go before the mods were done.

Best of luck man
 
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The most tell tale feeling for me when I develop a drive shaft vibration is in the small of my back. It does kinda feel like a “massager,” But it’s usually cyclical. Like the vibration comes and goes. The vibration is a much higher frequency and lower amplitude than a tire vibration.
 
Mike_H said:
The most tell tale feeling for me when I develop a drive shaft vibration is in the small of my back. It does kinda feel like a “massager,” But it’s usually cyclical. Like the vibration comes and goes. The vibration is a much higher frequency and lower amplitude than a tire vibration.
Click to expand...

That's a very good description, that's what I noticed too. I ordered the UCF Deep-Cover Skid Plate System yesterday that comes with a "LOPRO". If I got it right, this allows me to lower the transfercase by 25mm. I'd be almost back to what it was before. At least it may reduce wear and tear (and I get rid of the shovel).

"Try pulling the driveshafts to verify if the vibe is in the front or back."

I'm not sure what I should do here. Just try to move the driveshafts to see if they have play somewhere?
 
andyj said:
"Try pulling the driveshafts to verify if the vibe is in the front or back."

I'm not sure what I should do here. Just try to move the driveshafts to see if they have play somewhere?
Click to expand...

It's a troubleshooting method for determining if the vibes are coming from the front DS or rear DS by doing the following:

Remove the rear DS, then drive in 4wd to see if the vibes are gone.

If you still have vibes, then drive with the front DS removed and the rear DS installed. Edit: You might even want to do both tests regardless of the first test's result just to ensure it's not only occurring when both are hooked up.
 
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JMT said:
It’s not the springs.

Driveline vibes increase with rotational velocity. Not sure how to describe them, but you feel them through your seat, steering wheel, shifter.
Click to expand...

Well said.

To me they have sort of rough grinding feel- its not a soft pulse usually- and you will often noticeably hear them as you accel/decel or feel them, and maybe even a clunk as it tries to get the driveline going that almost wants to be at different speeds.
 
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AndyG said:
Well said.

To me they have sort of rough grinding feel- its not a soft pulse usually- and you will often noticeably hear them as you accel/decel or feel them, and maybe even a clunk as it tries to get the driveline going that almost wants to be at different speeds.
Click to expand...

Since the regear, my front end has a slight oscillation/shimmy that gradually increases with speed if I forget to unlock the front end. It’s clean once I unlock the hubs.

I noticed a vibration in my last rig in idle that was due to a bad transmission mount. It seemed fine while driving.

OP’s got a vibration while driving and said it doesn’t feel like a balancing issue.

So odd.

How are your shock bushings and are your shocks all properly torqued down? If so, and steering dry tests well, I’d check wheel bearings and then confirm it’s not your driveshafts.
 
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You can almost be like you’re getting onto the rumble strip on the highway just a little bit at times

When you get into the ones that only show up at higher speed they almost sound like a bass speaker rattle
 
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andyj said:
That's a very good description, that's what I noticed too. I ordered the UCF Deep-Cover Skid Plate System yesterday that comes with a "LOPRO". If I got it right, this allows me to lower the transfercase by 25mm. I'd be almost back to what it was before. At least it may reduce wear and tear (and I get rid of the shovel).

"Try pulling the driveshafts to verify if the vibe is in the front or back."

I'm not sure what I should do here. Just try to move the driveshafts to see if they have play somewhere?
Click to expand...

The LOPRO transmission mount has less rubber to isolate vibrations than the stock mount. It is known for increasing vibes at idle.
 
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