Front Drive Shaft Update

[Dokatd]

Per the photos there are single cardan u-joints on both ends of the front and rear drive shafts. For this to run smoothly the angle of the joints at the pinion and the transfer case must match in order to cancel out the oscillation. If the angles do not match then vibrations are inevitable at certain speeds. Dialing in this angle on the rear shaft using adjustable control arms (Metalcloak potentially) should be relatively straight forward. But on the front this is likely impossible because of the need to maintain an already minimal caster angle.

This is correct if you are not phasing the joints. It's possible to phase the joints to cancel each other. Land Rover did this on the Defender and the Discovery series I. It however was not 100% ideal and they eventually went double Cardan at the T-Case.

A front shaft with a Rzeppa at the pinion and a double cardan u-joint at the transfer case is the type mostly likely to run without vibration while eliminating the problem Rzeppa at the transfer case. This type of shaft is angle agnostic. I have yet to see this configuration implemented on the Grenadier. I have a long standing relationship with a custom driveshaft builder in my local area and might have to contact him about building a shaft of this type for the Grenadier.

This is the direction I was trying to go. But several extremely big name drivers shaft shops here in the US pointed out that the Double Cardan joints in the correct size could not handle the angle. It would work on a part time vehicle but not a full time 4wd. The Rzeppa joint has a higher published angle limit than the Double Cardan. It's just that we are running at max of what the boot can tolerate, not what the joint can tolerate.

Currently the best option is to reduce your caster to the minimum you can and still be comfortable with the driving characteristics. This will likely spare your front drive shaft, at least for a long time anyways. People running long distances at high speeds will be more at risk of losing a boot due to heat.

Cross your fingers that a solution to mod or replace your axle housing comes along as that's debatably the only real solution to save the front drive shaft and make these things drive correctly at the same time.

 

[Tinerfeño]

No U-Joints, they are using CV/Rzeppa joints

I misunderstood these images being from front, according to the topic ...

 

[derek0343]

No U-Joints, they are using CV/Rzeppa joints

All my new drive shaft are using U joint.

 

[derek0343]

Hi Derek. Did you need to chop out some of the rear skid plate to gain access to the valves? I was wondering if they were going to bring this out for the grenadier as it looked a little awkward to get access to disconnects in the rear.

Cheers
Clint

Yes, the rear skip plate need to chop in the corner to fit this set up. There will be no actual disconnection on this sep up. You will able to lower it to 0 psi to get the max travel from the link.

 

[derek0343]

This is correct if you are not phasing the joints. It's possible to phase the joints to cancel each other. Land Rover did this on the Defender and the Discovery series I. It however was not 100% ideal and they eventually went double Cardan at the T-Case.

This is the direction I was trying to go. But several extremely big name drivers shaft shops here in the US pointed out that the Double Cardan joints in the correct size could not handle the angle. It would work on a part time vehicle but not a full time 4wd. The Rzeppa joint has a higher published angle limit than the Double Cardan. It's just that we are running at max of what the boot can tolerate, not what the joint can tolerate.

Currently the best option is to reduce your caster to the minimum you can and still be comfortable with the driving characteristics. This will likely spare your front drive shaft, at least for a long time anyways. People running long distances at high speeds will be more at risk of losing a boot due to heat.

Cross your fingers that a solution to mod or replace your axle housing comes along as that's debatably the only real solution to save the front drive shaft and make these things drive correctly at the same time.

Totally agree your point. I saw some people adding the metalcloak extension link to the Grenadier which will get you even bigger caster, I think the will get even worse result on this drive shaft issue.

 

[derek0343]

I misunderstood these images being from front, according to the topic ...

The second and third picture showing it's a U joint on the front axel.

 

[Tinerfeño]

And how does that work?
And is it normal ot phased?

 

[TCMColorado]

And how does that work?
And is it normal ot phased?

Ideally the u-joints should be phased at 90° to each other. Derek0343 can confirm if this is the case for his drive shafts. The angle of the joints at the pinion and the transfer case should also match each other. But that is basically impossible on the front axle while preserving the caster angle.

 

[IslandFalconer]

All my new drive shaft are using U joint.

I was speaking to the original shaft and not yours. Also u joints in this setup must be introducing some oscillation

 

[Dokatd]

Ideally the u-joints should be phased at 90° to each other. Derek0343 can confirm if this is the case for his drive shafts. The angle of the joints at the pinion and the transfer case should also match each other. But that is basically impossible on the front axle while preserving the caster angle.

Ideally the joint angles should be the same, but they are not as you know. So you must phase the joints say 5° or 10° off 90° or whatever is required to compensate. But the angles are bad on the Gren so it might take more than that. It's not the same situation as Land Rover where they were able to
Phase the joints such that they work smoothly.

 

[TCMColorado]

Ideally the joint angles should be the same, but they are not as you know. So you must phase the joints say 5° or 10° off 90° or whatever is required to compensate. But the angles are bad on the Gren so it might take more than that. It's not the same situation as Land Rover where they were able to
Phase the joints such that they work smoothly.

Unless I am misinformed about u-joints, changing the phasing from the ideal 90° will not entirely compensate for dissimilar joint angles at the transfer case and the pinon. The result will be harmonics/vibration at certain prop shaft velocities. The lack of longitudinal alignment between the transfer case and pinion (the two are offset from each other when viewed along the length of the vehicle) further complicates the issue. Will it be good enough that is worth the additional strength as a sacrifice for the greatest possible smoothness, maybe.

 

[Commodore]

I am currently of the opinion that the best all around solution is to find a different style high speed rated boot design or boot material. We aren't binding up the Rzappa but rather ripping the rubber boot which leads to contamination, lack of lubrication, and failure. As we know this is the same CV that is used in the Jeep JL/JT platform. I'll bet that the CV is something off the self and there might even be different options for the boots that already exist.

 

[Dokatd]

Unless I am misinformed about u-joints, changing the phasing from the ideal 90° will not entirely compensate for dissimilar joint angles at the transfer case and the pinon. The result will be harmonics/vibration at certain prop shaft velocities. The lack of longitudinal alignment between the transfer case and pinion (the two are offset from each other when viewed along the length of the vehicle) further complicates the issue. Will it be good enough that is worth the additional strength as a sacrifice for the great possible smoothness, possibly yes.

Setting the joints out of phase to adjust for irregular joint angles can run perfectly smooth in the speed ranges drive shafts operate at in vehicles. Again, Land Rover did exactly this on the front drive shaft of every Defender and Discovery pre 1999 give or take. But they also suffered when you lifted these trucks as well. The phasing was no longer appropriate and joints would tend to fail.

I am currently of the opinion that the best all around solution is to find a different style high speed rated boot design or boot material. We aren't binding up the Rzappa but rather ripping the rubber boot which leads to contamination, lack of lubrication, and failure. As we know this is the same CV that is used in the Jeep JL/JT platform. I'll bet that the CV is something off the self and there might even be different options for the boots that already exist.

This is 100% my thought as well. Many of us are already using an aftermarket joint with a seemingly better boot compound. I believe I have round about 5k miles on my Terra flex joint. But there is at least one report of a Terra joint boot failure. But that could have been an outlier.

 

[TCMColorado]

I am currently of the opinion that the best all around solution is to find a different style high speed rated boot design or boot material. We aren't binding up the Rzappa but rather ripping the rubber boot which leads to contamination, lack of lubrication, and failure. As we know this is the same CV that is used in the Jeep JL/JT platform. I'll bet that the CV is something off the self and there might even be different options for the boots that already exist.

This is spot on.

 

[Commodore]

This is the front driveshaft from an 06-10 Jeep Commander / Grand Cherokee. Why can’t we run a CV boot like this? Clearly this is a “plunge” style CV but it has the added benefit of a much more flexible boot. Really all we need is a plunge style boot that fits our existing CV and driveshaft that will accept it.

 

[TCMColorado]

A custom driveshaft builder would easily be able to fabricate a shaft for the Grenadier that uses a "plunge" style accordion boot.