Does Jacking Stress CV Axle?

[Chops]

the suspension sort of makes a 'triangle' with the frame, control arm/knuckle (whatever that's all called) and the suspension. Jacking it up lengthens the suspension but you're actually reducing stress on everything- watch the weight off the tire allow it to flex more (become more round instead of compressed at the bottom)

Thanks for your insight. I just learned a new automotive term - “Suspension Droop”. It is the max droop when vehicle is lifted off its wheels. Part of the vehicle suspension design. CV axles are designed to handle suspension droop.

Slowly but surely learning how to design a complete vehicle. Should take me about 900 years? AI is already doing it?

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[Howard]

I'd hope AI isn't doing it. There are enough problems when done by experienced engineers, don't need AI's imagined designs. AI used properly can help the engineers.

 

[Phimosis]

When I jack up my fx4 Mav, the cv’s are at enough angle that the rubber boots are visibly being pinched and deformed. If you drove like that for any period of time, it would for sure cause the boots to crack and let water and dirt in, which would then destroy the bearings.

But if the axles are jacked up and the boots are not rotating, it’s likely to make zero effect on the boots.

It’s hard to say if it’s the bearings failing and then the boots start leaking, or if it is leaking boots that are leading the bearings to fail.

 

[Timothyd]

Thanks for your insight. I just learned a new automotive term - “Suspension Droop”. It is the max droop when vehicle is lifted off its wheels. Part of the vehicle suspension design. CV axles are designed to handle suspension droop.

Slowly but surely learning how to design a complete vehicle. Should take me about 900 years? AI is already doing it?

Hell, AI is doing a new you. We are obsolete.

 

[kevinmccune]

It's only jacked up on each corner for 5 - 15 min so I doubt its a big deal.

the suspension sort of makes a 'triangle' with the frame, control arm/knuckle (whatever that's all called) and the suspension. Jacking it up lengthens the suspension but you're actually reducing stress on everything- watch the weight off the tire allow it to flex more (become more round instead of compressed at the bottom)

I don't rotate tires 20 k on my current tires no problem my big regret I didn't invest in better TPMS sensors nor about to break tires down to install new ones

 

[RoeB]

Does jacking a tire off the ground put stress on a CV axle? AI tells me “Yes” - especially on a compromised CV axle….

Maybe I should rotate my tires less often than Ford recommends?

Maybe the Tremor’s axles are designed differently to handle the droop of having a tire hanging off the ground while off-roading?

Edit…Grok AI

“When you jack up a car, the suspension droops, and the CV axle may extend to its maximum range of motion. This can place stress on the CV joints, especially if the car is lifted unevenly or excessively, causing the axle to angle sharply.

Lifting just one wheel (e.g., with a floor jack) can cause the CV axle on that side to extend more than usual, increasing stress on the joints. This is especially true for front-wheel-drive or all-wheel-drive vehicles where CV axles are critical components.

If the CV axle, joints, or boots are already worn or damaged, jacking the car may exacerbate existing issues, potentially leading to noise (clicking/popping), vibration, or failure.”

Would say if done with finesse would not effect but if you let Jack down with a thud. You might cause harm!

 

[Chops]

Only the CV boots. A CV axle has ball bearings inside sooo...there is basically zero stress on them when they are not under load (transferring motive power).

They are under a lot more stress when you, say, make a U-turn (full lock on the steering).



It could be jacked up for ten years and the worst that could happen is the CV boots tear.

The CV axle assembly is “stretched” a bit at maximum droop however? The distance between the PTU seal and the Hub seal is at the greatest distance? Unless the droop happens in a perfect circular motion…
But again I would think the “stretch”, if it even exists, would be incorporated into the design.

 

[ScottyC]

You think you are confused now...ask it about DAMB lifters in a hybrid motor.....lol

 

[Howard]

"Would say if done with finesse would not effect but if you let Jack down with a thud. You might cause harm!"

Any impact from dropping the jack no matter how hard would be minor compared to hitting a speed bump or a pot hole.

 

[Chops]

"Would say if done with finesse would not effect but if you let Jack down with a thud. You might cause harm!"

Any impact from dropping the jack no matter how hard would be minor compared to hitting a speed bump or a pot hole.

I think the worst would be launching off a hill in the road at speed - getting major air. Go from maximum droop to maximum squish in a matter of seconds. That’s gotta hurt a suspension/axles!

 

[jonshep]

Check your owners manual and you will find that Ford has engineered jack points where you place the little toy jack if you need to change a tire. The jack points are on the body not the suspension, so drooping the cv joints is engineered in the design. Normally you are not rotating the drive shafts while jacked up. The axles also have slip joints that allow the length to extend and shorten like when you hit a pothole. Old style U joints, Hoke and Cardan, must accelarate and slow down when they are not in straight alignment, thus vibraion and the bucking effect. You will not hurt or damage anything by jacking up your vehicle, just don't drive it jacked up.

 

[Chops]

…. You will not hurt or damage anything by jacking up your vehicle, just don't drive it jacked up.

The only “normal” situation to drive with a wheel off the ground is with a Tremor off-roading. Maybe that is why they have a different CV axle design.

For us other Maverick drivers - it would be best to lift off the throttle if you “get air” off a sweet jump!

 

[MaverickNoticer]

Stop using AI- its garbage and has no idea if the article it's robbing from is even a reliable source.

I second this. AI is garbage gobbledygook. Look to actual sources or experts

 

[notfast]

The CV axle assembly is “stretched” a bit at maximum droop however?

I'd be really surprised if the entire axle assembly stretches.

But again I would think the “stretch”, if it even exists, would be incorporated into the design.

I haven't looked at Maverick CV axles specifically, but typically the outer CV joint is fixed length and the inner CV is a tripod joint (three large ball bearings that ride on tracks that resemble a tulip flower). This allows the inner CV to extend and collapse by a small amount (maybe 20 mm) as the suspension cycles and the wheels are turned.

This is partly why altering a vehicle's ride height can prematurely wear the CV axles. It's not that they cannot handle the angle; after all, they are constant velocity, so they could ride at 45 degrees indefinitely with no issues if they could pivot that far.

But when the inner CV is at or repeatedly forced to maximum extension or retraction, the ball bearings in the inner CV are forced against those spiral tulip tracks rather than just riding in the tracks.

You could safely alter the ride height a little bit and have no issues. Think of it as a range. Let's say stock ride height means that the inner CV's total range is that it can extend 10mm and collapse 10mm, and the CV realistically only needs to extend 7mm and collapse 7mm before the suspension hits the bump stops and droop stops, respectively.

Now let's say you raised the ride height one inch, and that means the CV can now extend only 7mm but can collapse 13mm.

This setup is still acceptable, just we're now on one side of the range. Sort of like having a wheel alignment that is on one side of the "acceptable" range.

Now lets say you raised the ride height two inches, and that means the CV can only extend 4mm but can collapse 16mm. This means that every time the suspension is at full extension, the CV axle is now the limiting factor instead of the droop stops.

I think the worst would be launching off a hill in the road at speed - getting major air. Go from maximum droop to maximum squish in a matter of seconds. That’s gotta hurt a suspension/axles!

The cycling of the suspension isn't so much the issue. Again, with proper suspension geometry, it can be cycled repeatedly from full droop to full bump without issue because the droop and bump stops will prevent the suspension from cycling further than its design limitations.

It's more that there isn't enough suspension travel to decelerate the vehicle in its downward trajectory, hence the suspension "bottoms out" because the vehicle is still carrying momentum after the suspension reaches maximum compression.

However, cycling the suspension continuously from full droop to full bump can cause other issues, such as the oil in the shocks becoming hot or foaming ("shock fade") or the suspension bushings tearing or collapsing.

Much like the inner CV joints, the suspension has a typical range of travel and a maximum range of travel. Driving on the street, the suspension probably only cycles an inch or two in each direction when going over minor bumps or cornering. But when you hit a huge dip in the road, it'll cycle most or all of its travel. But since those dips are hopefully few and far between, the shocks have time to cool down and the bushings aren't repeatedly twisted to maximum.

 

[Chops]

I'd be really surprised if the entire axle assembly stretches.
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What a wonderfully articulate & educational post on this topic - thank you for your insights!

Btw, I meant the entire assembly “stretches” like my finger stretches when I pull on it. Sometimes I’ll get an audible “pop” when I pull & feel the give of the cartilage when pushing back into place. Probably the equivalent of a tulip shape in there somewhere. Man’s designs mimicking Nature’s.

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