I run the teraflex 4 inch lift, and love the quality of the kit. It is very comfortable, and behaves well on and off road. To create a less light around centre driving experience, I changed the castor to 6 degrees. The stock drive shaft does not like this too much, with a vibration at around 50 mph. It seems to be since I changed the castor (which was a good thing because it has less bumpsteer and goes down the road as straight as an arrow!)

I think I need to change the front drive shaft, and was wondering what was the most economical and practical out there.

Many thanks

Paul

 

Hi Paul, if you are still running a factory drive shaft, you really shouldn't be having any vibrations as it uses CV joints and they are made to be run at high angles. Are you absolutely sure that you have your caster set at +6° and not a lot more? Where are you taking you taking your measurement from? Whatever the case might be, if you install an aftermarket u-joint style double cardin drive shaft, you will have even more vibes at pretty much anything more than stock.

BTW, how big are your tires, did you adjust your toe at all and did you install a dropped pitman arm and track bar relocation bracket up front with your lift?

 

Thanks for the quick reply WOL.

I am running the stock front driveshaft , so now am indeed wondering.................. I was considering buying the Skyjacker dropped pitman arm, a really cheap fix, but was concerned about added stress on the steering box. I am now going to trade the front track bar that teraflex provided, for their new HD version. I believe this comes with a bracket as required for the 4 inch lift. With that, I will probably not need 6 degrees of castor. As for measuring it, I am going to buy an angle finder, as the alignment shop may have put more than 6 degrees castor. They did seem to understand what I was asking them to do though.

It has 1/8 of an inch toe in, on 35 inch tires as you recommended. With that and 4 degrees (measured by alignment machine) it would wonder around a bit. Hence 6 degrees....

Thanks for a great site and the energy behind it.

Paul

 

Hmmm, that is odd but I suppose not impossible. Based on what you've said, I would probably recommend installing the dropped pitman arm and new track bar with drop bracket and that should allow you to eliminate some of your + caster. It's tough because the added caster as you know will make your Jeep drive/handle a lot better but vibes can be quite annoying.

 

As I've said before I don't always agree with all of this caster stuff. But I think you adjusted your caster for the right reason. Are you sure the vibes you are getting are drive shaft related? The best diagnosis step is to pull the front shaft and go for a ride.

Also is there a compromise in the setting your have achieved and the vibes? Can you go part way back and see if your "near center at speed" wheel behaviour and vibes are under control? You can use your angle finder to restore the alignment settings in case this does not pan out.

I have the same concern WOL has. The factory shafts don't vibe much until they are operated at angles that start to destroy them.

Light "around center" steering behaviour can also be caused by riding on the center of the tread. One of the best indicator of this is "light near center steering" at single digit speeds as well as highway speeds. Although increased scrub radius will cover it up at very slow speeds somewhat. This is easy to do with street pressures in bigger meats. Search for "chalk test" for a easy way to check.

 

Don't change to an aftermarket front shaft like the JE Reel to get rid of a vibration, it will make it worse. They are great shafts just a matter of design that you will have to run with less castor. I'm fighting the vibes with that setup now and I can't get rid of them unless it's at 2 degrees of castor.

 

It is impossible to measure caster correctly with an angle finder. Caster is measured as an arc. In other words, the "swing" of the front spindle. Whether you use an old bubble style manual caster gauge, or get a professional alignment, the measurement is taken basically the same way. There are many other factors that will throw off a measurement of an angle finder trying to measure caster, not the least of which is S.A.I., (steering axis inclination), which is also impossible to measure with just an angle finder. Caster must be measured in this way, because of S.A.I. S.A.I. causes the spindle to be non-perpendicular to the steering axis, resulting in the need to measure the created arc, and not just the bare caster angle of the steering axis. Without compensating for S.A.I., all bets are off for an accurate measurement with an angle finder. It won't happen. My advice is to go have a professional alignment done. You may well have way more caster dialed in than you realize. This would point the pinion angle down toward the ground and indeed result in driveline vibration whether you have a CV joint driveshaft or not.

 

I running the TF 4"" suspension kit with Tom Woods drive shafts. The maximum castor that I can achieve is 5.0* anything more and I have drive shaft vibes. When you get a chance crawl under your Jeep and look at front drive shaft. Paying attention to the CV joint at the transfer case, you can visibly see that the drive shaft is near its maximum operating angle at static height. This is why I changed my front dive shaft. Even before I replaced my front drive shaft the maximum amount of castor I could achieve was 5* without vibes occurring. I am running Rock Krawlers front track bar relocation kit and I am very happy with it. Before installing the kit the steering gear was not able to hit the steering stops on the knuckles due to it internal limits being maxed out. With the Rock Krawler kit installed I have the full factory range of steering back and I eliminated all my bump steer.

 

Thanks so much for the very good info provided. I have only got back late from flying clients around today, and have time tomorrow to investigate further.

I appreciate the experience and depth of knowledge shared no end. I will let you know what transpires.

Paul

 

I am running teraflex 4" kit as well,no vibes,stock shaft ,4.5 caster was going to get front shaft and am changing to lowered,stronger front track arm+high steer draglink(rubi express)and probably their driveshaft,was hoping to increase caster to 6 as i'm reading on this site,but is this gonna cause me vibration issues with aftermarket front driveshaft,i agree just looking at it (at 4.5deg)I do not want to increase the working angle.will the geometry change with lowered track+highsteer (did u change drag link or pitman with R.C.kit?)improve the "flightyness",was hoping to increase caster but now doesn't sound like good idea,also looking for good recomendations for rear track bar relocation bracket+adjustable bar combo for 4 lift