Front Drive Shaft Update

[Dokatd]

I would also like to see a fresh one sliced in half. These are shaped in mold, and the if they wanted to control where the flex was occurring, the thickness would be tapered down in that area. Basically, I don't believe the thin part of the cross section is due to "wear". I don't believe material is just fluffing off, and it's not "extruding" as suggested because there wouldn't be molecular dislocation caused by elastic deformation. There's simply not enough heat being generated. I think its simply a case of the unit spends more time at an angle than the design allotted for, and the bonds are breaking causing a crack, and if there is any variability in the material that can cause a point of more focused elasticity, it's failing there, sooner.

You seem to know much more about material science than I do, so, how does that read as a simple explanation...

You're welcome to cut one up. But it will be a waste of money. As stated before, I have measured a new boot already. As well, the boots I have cut all have totally new features to them. These boots came from different vehicles with most boots being Tera but I have also looked at the stock boot post failure.

As for heat, sure the joint itself isn't heating up a ton, but that boot at the pinch location is certainly getting hot enough to allow the rubber to deform.

 

[Dokatd]

Actually Yes, because this could eliminate the boot pinching @Dokatd noted.

I think there is some misunderstanding here. You are correct Tom, if the metal flange was open more we would probably not be talking about this. But, the design is as such to allow installation and removal of the CV bolts. But there is some tolerance there that would allow a bit larger opening.

 

[ADVAW8S]

I would be surprised if the front geometry isn't exactly identical to the station wagon. So same problem .

It's exactly like the station wagon in the front. What I have noticed is the longer wheel base assist in keeping the truck tracking straight with a lower caster number. The lower caster number should based on what I have read here assist on longevity of the cv boot especially since I am running a zero lift and my rad flo shocks are OEM length.

 

[Tom109]

I think there is some misunderstanding here. You are correct Tom, if the metal flange was open more we would probably not be talking about this. But, the design is as such to allow installation and removal of the CV bolts. But there is some tolerance there that would allow a bit larger opening.

I may have to buy one and see how the boot’s flange is constructed. I’m wondering if it could be pressed a little wider without compromising the rubber adhesion.

 

[Clark Kent]

View attachment 7919700

I fixed my CV issue (with ChatGPT). Also lets the wife in easier without installing steps.

That looks like the daddy of a Rukus.

I was thinking something more subtle..

 

[Dokatd]

I may have to buy one and see how the boot’s flange is constructed. I’m wondering if it could be pressed a little wider without compromising the rubber adhesion.

You are on the right track. It can be done a bit for sure. But it will have to be done slowly and with plenty of lube. I'm going to regret that last sentence I'm sure.

The rubber is crimped not adhered.

Modifying the boots metal flange is plan B for me.

 

[Tenac]

That looks like the daddy of a Rukus.

I was thinking something more subtle..
View attachment 7919719

Put a standalone on that and 1000HP you got your self a real truck

 

[Zimm]

Ive only seen a pics of a few failed units, and the failures were at the radius'ed section of the boot. So... when people say "pinched" I'm picturing between two hard objects, such as tire pinch flat. Looking at the cv's, the only part that can get "pinched" is the neck of the boot, not the radius section, but I have not seen a failure in that area. If thats the case, lift install error never had anything to do with it.

 

[Dokatd]

The failure location changes relative to how far the neck of the boot was pulled when installed. This one just happened to be one we let more or less float where it wanted to be. So the damage is a bit higher on the neck than normal. Otherwise they pinch a bit farther back toward the radius. Failure occurs the same way though. I have since gone back to pulling the boot neck back up to the factory location and secured over the bead on the shaft. It's more consistent and doesn't seem to change outcome.

Damage can be caused by careless handling of the shaft for sure. But the failure is eminent regardless. How and where you drive will determine how quickly your boot fails. Best practice remains to remove the shaft from the pinion prior to lifting.

 

[Dokatd]

This is a previous one, you can see the failure is closer to the radius. You can also very clearly see the new feature in the rubber that was not there when the joint was installed. Heat and a gentle rolling/pinching motion takes its toll.

 

[Zimm]

View attachment 7919801The failure location changes relative to how far the neck of the boot was pulled when installed. This one just happened to be one we let more or less float where it wanted to be. So the damage is a bit higher on the neck than normal. Otherwise they pinch a bit farther back toward the radius. Failure occurs the same way though. I have since gone back to pulling the boot neck back up to the factory location and secured over the bead on the shaft. It's more consistent and doesn't seem to change outcome.

Damage can be caused by careless handling of the shaft for sure. But the failure is eminent regardless. How and where you drive will determine how quickly your boot fails. Best practice remains to remove the shaft from the pinion prior to lifting.

See, that cut looks like its too deep to be pinched against the outer rim anywhere.

 

[Zimm]

A kit with wider mouth opening, with studs and nuts?

 

[Dokatd]

See, that cut looks like its too deep to be pinched against the outer rim anywhere.

It's not the outer rim. You're not understanding the profile of the boots metal flange. The flange is like a trumpet. It necks down significantly

 

[Dokatd]

A kit with wider mouth opening, with studs and nuts?

This is possible and may solve everyone's problems. Again, this is my Plan B. I can modify the stock part with a mandrel and press. It's not hard, but it could result in failure of the boot for other reasons. The boot will be stretched a bit.

 

[Zimm]

It's not the outer rim. You're not understanding the profile of the boots metal flange. The flange is like a trumpet. It necks down significantly

No, when I say outer rim anywhere, I mean outer rim of the entire assembly anywhere until you see rubber. It appears too deep.

 

[Zimm]

This is possible and may solve everyone's problems. Again, this is my Plan B. I can modify the stock part with a mandrel and press. It's not hard, but it could result in failure of the boot for other reasons. The boot will be stretched a bit.

Don't stretch the boot. It will eventually tear at the point it's crimped.

 

[jvkintheusa]

No possible current solution. Needs a complete redesign. Until then, check weekly for tears, get a few extra CVs or a spare front drive shaft. The spare shaft is about $1k USD, but probably good to have on a remote trip.
If you desire more clearance, starting with a larger tire is probably your safest bet.

 

[agcheck]

Why is the Agile u-jointed front shaft not a reasonable solution for a modified vehicle?

 

[jvkintheusa]

Why is the Agile u-jointed front shaft not a reasonable solution for a modified vehicle?

From what I've read in this forum, the u-joint shaft tends to vibrate between ~ 55 and 70 mph. This vibration eventually could wear out the pinion bearings from what I understand.

 

[C-Mack]

Why is the Agile u-jointed front shaft not a reasonable solution for a modified vehicle?

Read through some of the threads on the Agile shafts but the quick answer is vibration/harmonics due to using single cardan u-joints and the diff and transfer case being at non-complimentary angles. For the current driveline angles on the Grenadier only Rzeppa style joints will run smooth at this time.

Note: The Agile shaft are tough but really only intended for off-road use as running at sustained high speeds the harmonics/vibrations will be transferred to other components in the front diff and transfer case possibly compromising their longevity which is something to be aware of.