Situation: I am getting an OME HD lift with JEReel shafts (I know I dont need them, I want them and I want to get this done now). I was told by someone very knowledgeable that I need adjustable upper control arms with these shafts.

My understanding is that you tend to shorten upper CAs to improve caster and lengthen them to improve drive line (drive shaft) angle. So what is the optimum compromise, in CA length, between these two with the OME lift (right at 3 inches)?

edited to say:
If my understanding is incorrect, please enlighten me.

 

With 3 inches of loft, you probally will not need driveshafts and uca. I'd spend the money else where.

 

I've never heard of needing adjustable control arms because of driveshafts. the thought might be to adjust castor to help with driveline angles, but its more important to adjust castor for alignment reasons. I personally wouldn't bother with the control arms right away, run it how it is and see if you need it. Good luck

 

For the rear, you will need adjustable upper control arms so that you can set your pinion angle to being parallel to the drive shaft. Up front, you will need them to set your caster but if you set it too high, you will end up with vibrations. Pretty much, you're kind of stuck with keeping your caster at stock or close to it with double cardin u-joint style shafts.

 

Wayolife, I've read many threads on the topic and all they do is make me more confused (cause it seems like no 2 people say the same thing). I am doing 3.5 RE lift soon and heres my current understanding of pinion angle/caster settings. In the rear you set it so the pinion points at the output shaft of the transfer case. That I understand. The front is what gets me. Some people say with the after market drive shaft you have to do the same in the front. Others say to set it to the stock caster setting witch as I understand it is going to have the pinion pointed too low and will not be the correct angle for the drive shaft. If I point the pinion at the transfer case then my alignment will be way off. So I compromise and put it somewhere in the middle. I don't want my alignment to be WAY off and I don't want to worry about vibes and u-joint failure going down the road. PLEASE HELP.

Ty

P.S. Thanks for the awesome site. I really enjoy it. The reason I ask you is you have had more parts on your JK&TJ than most on this site I'm sure.

 

WOL, or anyone, Can you recommend a good book for information on suspensions and drivelines? I'm looking for something with diagrams and terminology. Entry level is ok, but technical would be even better. Thanks!

 

Ty, the front drive shaft is long enough that you should not feel vibes even if your front pinion angle is not set exactly in line with it. At +4.2° of caster (factory specs), you should be just fine and you most likely will be fine with a little bit more as well. This is also true of the rear shaft on a 4-door as it is quite long (it is more forgiving) but on a 2-door with it's short rear shaft, it is important that it is set correctly to prevent vibrations.

 

Honestly, the best book you can own is the Factory Service Manual. It's expensive but worth every penny. Granted, the new JK FSM isn't as good as the old TJ one but it's still better than anything else out there.

 

I have the same lift as you, and just ordered front upper Currie CA's. My caster is currently around 3.5*, but I am going to try to shorten the new arms around 3/8" to achieve 6* and see if it improves the roadability. I do currently have a very slight amount of bumpsteer and wandering, so hopefully this will cure it.

 

Do you have a suggestion what length (both front and rear) would be good to start with?