Leaking CV joint?

[2KWIK2C]

With that BDS 6 inch kit, didn't that include lowering the front differential?

Yes all of it to keep factory alignment.

 

[Cabin 4]

Yes all of it to keep factory alignment.

Makes sense.

 

[Transient]

The GM lift is a not a spacer lift, its just a longer shock. The longer CV's are so that the CV doesn't pull out, or cause damage to the transfer case, when the suspension is at maximum articulation.

That being said, I have yet to see a Z71, even with 4"+ of lift, break a CV. I have seen busted UCA's, but I have yet to see a single broken CV on non TB Z71's, leaving me wondering if the TB CV is really necessary at all.

That part that I'm not understanding is the correlation between the leveling kits and the vibration in 4 Auto. Why is there a vibration? Is it because the cv axles aren't long enough and causing tension on components in the diff? Based on the info I've found 3rd party, the Trail Boss cv axles are slightly shorter (24.69" vs 24.84" = 3.81mm) than non-Trail Boss cv axles. Did GM possibly experience the same vibration when testing the Trail Boss with the axles all other trucks come with from the factory? NAPA's supplier seems to be a company called Trakmotive. They provided all the same specs the NAPA posted on its website. Not only are they making the OE replacement axles, but also those "lifted truck axles" I shared previously. I might be reaching out to them.

Update: No point reaching out to them, imo. Trakmotive is a US distribution company in California owned by Wonh Industries in China for the sole purpose of selling Chinese made automotive products like cv axles. Basically, if I want answers I need to look elsewhere.

 

[Jmzvet]

Here’s what I know. I have a 2in ReadyLift kit with 34in tires. I have used 4wd auto up to 50 mph in snow/ice conditions only with zero problems.

 

[Transient]

Here’s what I know. I have a 2in ReadyLift kit with 34in tires. I have used 4wd auto up to 50 mph in snow/ice conditions only with zero problems.

With 35s I'm still spinning tires under light acceleration on wet roads. I don't have a lift. Just want to make sure I'm not damaging my truck if I install the ReadyLift 2" SST kit and choose to use 4 auto because of wet roads. It rains quite a bit in Florida compared to San Diego, CA.

 

[Cabin 4]

This AWD auto issue is the only reason I've not put a front level up on my truck. I don't want to lose that function or risk damage to drive from using the AWD mode.

I had the dealer install the GM factory 2 inch lift on my 2022 SLT so its the same exact set up as the AT4/TB. I do have the replaced CVs and the rest of the replaced parts. They put all those in a box for me when I took delivery of the truck. I'm thinking of going with the Cognito kit that comes with the new UCAs and Elka coilovers up front and Elka rear shocks. So I suppose I could have the original CVs reinstalled if that addresses this AWD issue. What might work to get a good answer on this is talking to an engineer at Congnito, BDS or Icon on this if you can get to the right person. They design these kits and test them out. They also give out the AWD warning so they know the issues at hand.

 

[Gangly]

The whole 4Auto issue has nothing to do with the reliability of the CV's. The two are unrelated, and just an assumed correlation between the two. There were issues with balance and harmonics in 4Auto for some reason and the drivability issues were noted while in 4Auto, but not 4Hi. The only difference between 4Auto and 4Hi is the automatic, and potentially constantly adjusting percentages of power transfer between the front and rear differentials as you drive over varied terrain. Again, not the CV's, or differentials at issue.

There is no difference in the function of the CV's or differentials when in 4Auto vs 4Hi vs 4Lo, they transfer forces from the transfer case into forward and rear motion, and that's it. Again, they perform no difference in function whether 4Lo, 4Hi, or 4Auto. Furthermore, although its obvious, your vehicle suspension dynamics DO NOT CHANGE based on the selection of 4Hi, 4Lo, or 4Auto, so there are no geometry changes and no functional changes occurring to the front end of the truck.

The only functional difference between 4Hi and 4Auto in our trucks occurs in the transfer case whiles it's distributing constantly variable drive force percentages to the front and rear differentials while in 4Auto.

 

[Gangly]

Why is there a vibration? Is it because the cv axles aren't long enough and causing tension on components in the diff?

The CV length is constant regardless of 4WD mode, so if it were a CV length issue, it would be present in all modes. Since the issue is only present in 4Auto, then by default, that eliminates CV length as being the issue.

 

[Cabin 4]

The whole 4Auto issue has nothing to do with the reliability of the CV's. The two are unrelated, and just an assumed correlation between the two. There were issues with balance and harmonics in 4Auto for some reason and the drivability issues were noted while in 4Auto, but not 4Hi. The only difference between 4Auto and 4Hi is the automatic, and potentially constantly adjusting percentages of power transfer between the front and rear differentials as you drive over varied terrain. Again, not the CV's, or differentials at issue.

There is no difference in the function of the CV's or differentials when in 4Auto vs 4Hi vs 4Lo, they transfer forces from the transfer case into forward and rear motion, and that's it. Again, they perform no difference in function whether 4Lo, 4Hi, or 4Auto. Furthermore, although its obvious, your vehicle suspension dynamics DO NOT CHANGE based on the selection of 4Hi, 4Lo, or 4Auto, so there are no geometry changes and no functional changes occurring to the front end of the truck.

The only functional difference between 4Hi and 4Auto in our trucks occurs in the transfer case whiles it's distributing constantly variable drive force percentages to the front and rear differentials while in 4Auto.

So I agree. What I was told is it's with the torque management that's with the AWD mode. As we know, in AWD mode the system is distributing torque based on a predetermined/programmed criteria between the 4 wheels. Its my understanding that the change in CV angles from leveling up the front beyond EO spec is causing just enough mild binding. That mild binding apparently is enough to "throw a curve ball" with the AWD modes ability to transfer torque. It thinks the front wheels have more traction, but as the truck rolls down the road and the suspension is flexing, that binding is quickly being relieved and then back out of spec/binding.

 

[Gangly]

So I agree. What I was told is it's with the torque management that's with the AWD mode. As we know, in AWD mode the system is distributing torque based on a predetermined/programmed criteria between the 4 wheels. Its my understanding that the change in CV angles from leveling up the front beyond EO spec is causing just enough mild binding. That mild binding apparently is enough to "throw a curve ball" with the AWD modes ability to transfer torque. It thinks the front wheels have more traction, but as the truck rolls down the road and the suspension is flexing, that binding is quickly being relieved and then back out of spec/binding.

The constant binding and relinquishment cycle would explain the presence of vibrations, or "out of balance/harmonics" issues that were reported. Thanks for the insight.

 

[Transient]

The constant binding and relinquishment cycle would explain the presence of vibrations, or "out of balance/harmonics" issues that were reported. Thanks for the insight.

So, theoretically, why wouldn't the CV axles NAPA sells for "lifted trucks" that I posted earlier not work? Their advertisement says cv axles are made to flex ~23°. These "lifted truck" axles flex ~46°. Seems like the binding issue may be alleviated?

 

[Gangly]

So, theoretically, why wouldn't the CV axles NAPA sells for "lifted trucks" that I posted earlier not work? Their advertisement says cv axles are made to flex ~23°. These "lifted truck" axles flex ~46°. Seems like the binding issue may be alleviated?

I'm not sure to be honest

 

[Grey]

I know this thread has taken a few different paths, but I completed the job today and swapped the axle.

Getting the axle out was my biggest question going in, and it turned out to be cake. I rented a slide hammer from autozone and it popped out in two pulls. Hardest part by far was getting the upper ball joint for the control arm loose. Odd, because it gave me no issues installing the lift, but had to get a torch out on this. Between lost tools, watching tv in the garage and that ball joint, total install time was about 2 hours.

I’m sure there will be a few more board members that do this as these trucks age. Total cost for me was about $220 for a GM shaft delivered plus a can of brake cleaner and some shop rags to clean up the old cv grease. Rent the slide hammer and don’t look back.

 

[Alamorepairman]

Just researching this problem I found today and decided to chime in. Wondering if this problem is more common. I purchased GMC Sierra x31 a couple of weeks ago. Compared to my father in laws trail boss it seems identical. I was doing a break in oil change at 500 miles and found this on passenger side. Took it to the dealer and they immediately said they will replace the entire axle next week. I can’t see the hole but they are convinced. Could be a one off defect but I don’t seem to be the only one. Truck is new so it’s never left the pavement or even driven hard yet. Truck totally stock.
Curious to say the least.

 

[Bcmountainman]

Mine had a pinhole on the drivers side within 18k. They wouldn't warranty it.
So I put electrical tape over it. Been good since. Now at 86k