Double cardan front shaft with stock upper CA

[Bingobelle]

Hi

Do you need adjustable upper front CA to run a aftermarket double cardan style drive shaft? I have heard that otherwise you will get vibration if you do not adjust, is that correct?

I´ve installed a AEV 3.5 inch liftkit and to be honest regardless to the AEV instructions I do not see how that r-zeppa joint at the transfercase will handle that steep angle.

I´m not even sure that the big rubber bot will clear the exhaust y-pipe. I installed a exhaust spacer kit but even then the driveshaft rested on the y-pipe but at that time I had not yet installed the geometyry brackets. I did that the next day but I have not been able to lift up the jeep yet after that to have a full drop on both wheels but that geometric brackets will have to do some major magic if the driveshaft is going to clear the y-pipe. I´, not convinced but will see on monday when I can get a car lift to see.

Anyway, any problem to install a aftermarket driveshaft with stock dana30 front axle and the aev geometry brackets?

Thanks

 

[wayoflife]

Up front, caster angle needs to take priority over pinion angle and assuming you're still running factory gears, you should be fine without making any adjustment. Just install and go.

 

[bmkrinne]

The geo brackets will allow you to change the caster angle to one of three settings. 3.5” should be the middle adjustment hole on the upper control arm. As Eddie said above, pinion angle is secondary to caster. The rzeppa joint will do ok at the extreme angle at the transfer case and should not cause additional driveline vibrations, but the rzeppa joint and boot at the tx case will fail soon. Swapping to a double carden drive shaft will likely cause more driveline vibrations due to the poor pinion angle and high misalignment between the driveshaft and pinion. It’s a give and take relationship. In the end, I replaced my front axle housing with a Dynatrac PR44 Unlimited housing to correct the pinion angle and get rid of my driveline vibrations.

 

[Bingobelle]

Thx for input.
Eddie, I'm not sure if I follow you about factory gears. Do you mean that because of the 3.73 ratio the driveshaft will turn less rpm then a 4.56 for example and because of that vibration should not be a problem?

In future I will regear to 4.56 but I will proberly buy a whole new axle. I know dynatrax are the best but since I'm in sweden it is proberly more easy for me to buy a ultimate dana44 axle as a bolt on solution from quadratec. But will have to look into that closer. Maybe a second hand Rubicon axle also would do.

But my thoughts where that a aftermarket axle have more caster build in and a better pinion angle from start and that the geometry brackets could work with that?

 

[bmkrinne]

Yes, the lower the gear ratio, the faster the pinion and driveshaft spins. So with 4.56 gears, your driveshaft will spin faster and have higher vibration when misaligned.
I went from 3.73 gears to 5.13 and 4” of lift and had quite a bit of driveline vibes due to the higher driveshaft speed.

Whichever aftermarket front axle you buy, just make sure it has a larger pinion offset.
No on the used Rubicon axle, as you’ll have the same pinion angle problems as your D30.

 

[wayoflife]

Thx for input.
Eddie, I'm not sure if I follow you about factory gears. Do you mean that because of the 3.73 ratio the driveshaft will turn less rpm then a 4.56 for example and because of that vibration should not be a problem?

In future I will regear to 4.56 but I will proberly buy a whole new axle. I know dynatrax are the best but since I'm in sweden it is proberly more easy for me to buy a ultimate dana44 axle as a bolt on solution from quadratec. But will have to look into that closer. Maybe a second hand Rubicon axle also would do.

But my thoughts where that a aftermarket axle have more caster build in and a better pinion angle from start and that the geometry brackets could work with that?

Yes, however, 4.56 is still a pretty low ratio and really, I should clarify that the vibrations is really only an issue IF your driveshaft isn't balanced well. The higher the ratio, the greater the chance that you will feel vibrations as the shaft spins faster. For the most part, I find that up to a 4.88, you can get by so long as your caster isn't set more than 4° which is factory. At 5.13 or more and IF your caster is set at a higher angle, the odds of you feeling an unbalanced shaft will be that much greater.

I personally like the UD44 and would highly recommend it.

 

[Bingobelle]

Thx for the good explanation. But I feel I have to ask one more thing. It says that the UD44 has more caster than stock and also better pinion angles for lifted jeeps. I understand what that means and that is a good thing since the pinion angle is far from great right now. But it does not say how much mnore caster it gives so my concern is, can I get to much caster if I keep the geometry brackets, and if so, will it proberly just be enough to move the upper CA to the most upper hole that is for 2.5 inch of lift or will I proberly need adjustable upper CA? Or is it a shitty idea to run the geo brackets with the UD44? I do like how the jeep runs on the road now.

as a sidenote I took the jeep on a carlift today and even though the geo brackets and exhaust spacers are mounted the rubber boot makes some real good contact with the y-pipe so how AEV can claim it vworks with stock shaft is not something I understand. Maybee I need even longer exhaust spacers.

Sure, to make that happens both front wheel must be of the ground but after all it is a 4x4 and getting high centered is something that I consider can happens.

 

[wayoflife]

Thx for the good explanation. But I feel I have to ask one more thing. It says that the UD44 has more caster than stock and also better pinion angles for lifted jeeps. I understand what that means and that is a good thing since the pinion angle is far from great right now. But it does not say how much mnore caster it gives so my concern is, can I get to much caster if I keep the geometry brackets, and if so, will it proberly just be enough to move the upper CA to the most upper hole that is for 2.5 inch of lift or will I proberly need adjustable upper CA? Or is it a shitty idea to run the geo brackets with the UD44? I do like how the jeep runs on the road now.

as a sidenote I took the jeep on a carlift today and even though the geo brackets and exhaust spacers are mounted the rubber boot makes some real good contact with the y-pipe so how AEV can claim it vworks with stock shaft is not something I understand. Maybee I need even longer exhaust spacers.

Sure, to make that happens both front wheel must be of the ground but after all it is a 4x4 and getting high centered is something that I consider can happens.

I can't remember for sure but I'm pretty sure the UD44 comes with 6° of caster just like a PR44. That will give you more room to work with IF you have driveline vibrations. Of course, if you don't, you can leave it all there and your steering will feel nice and tight.

As far as what AEV says about running a factory shaft, clearly, they are wrong on that.

 

[Bingobelle]

I can't remember for sure but I'm pretty sure the UD44 comes with 6° of caster just like a PR44. That will give you more room to work with IF you have driveline vibrations. Of course, if you don't, you can leave it all there and your steering will feel nice and tight.

As far as what AEV says about running a factory shaft, clearly, they are wrong on that.

Thx for your quick response!

 

[ScottofKSU]

I can't remember for sure but I'm pretty sure the UD44 comes with 6° of caster just like a PR44. That will give you more room to work with IF you have driveline vibrations. Of course, if you don't, you can leave it all there and your steering will feel nice and tight.

As far as what AEV says about running a factory shaft, clearly, they are wrong on that.

Starting by recognizing that you have forgotten more about Jeeps than I even know...

I thought the stock driveshaft had 6 degrees built in and the UD44 came with 10 degrees built in...

 

[ScottofKSU]

Starting by recognizing that you have forgotten more about Jeeps than I even know...

I thought the stock driveshaft had 6 degrees built in and the UD44 came with 10 degrees built in...

Wait. I think I am thinking of the PR44 Unlimited... I have only been heavily investingating the fine offerings from Dynatrac after reading cautionary posts about other companies offerings (e.g., UD44). My apologies!

 

[wayoflife]

Factory JK front axles come with +4.2° of caster. ProRock 44's come with +6°

 

[Bingobelle]

Ordered a spicer driveshaft. It has two options on lift heights. one is for 0-2 inch of lift and one is for 2-4 inch of lift. Since I have a aev 3.5 lift kit I ordered the 2-4 version which seems obvious to me but, can the geo brackets somehow change this since that aev use and therefore the 0-2 inch version is to prefer?

Thanks

 

[wayoflife]

Ordered a spicer driveshaft. It has two options on lift heights. one is for 0-2 inch of lift and one is for 2-4 inch of lift. Since I have a aev 3.5 lift kit I ordered the 2-4 version which seems obvious to me but, can the geo brackets somehow change this since that aev use and therefore the 0-2 inch version is to prefer?

Thanks

No, what you ordered is right. Good choice too.

 

[Bingobelle]

I´ve now been driving with the new spicer driveshaft for some weeks and it works very well. Can not feel any vibration so I´m happy. Also no worries about the rubber boot to get torn up on the exhaust pipe.

There is still a very light contact between the driveshaft and exhaustpipe but only with both frontwheel of the ground and it is not worse than you can turn the shaft by hand with no problem. only some scraping of the paint.

With a new front axle with bigger castor/angle pinion seperation I guess that will go away.