What do you mean? An African or European swallow?

 

is there a spot on the jeep, say the frame, that you can check the angle of the jeep itself with the plumb type angle finder?

 

It all depends on what he is using to measure castor.

 

Just put the Jeep on a level surface and it won't matter. There will be no math to do. Caster illustrations all show degrees from vertical, so start from a level surface. KISS works.

 

Update! I pulled the Jeep onto a level spot in the driveway (zero degrees with angle finder on pavement). The castor read 5 degrees. In that I still have a mild pulsating vibration between 50-55 mph, I decided to turn in the castor to 4 degrees (shortened the lowers by two full turns).

With only one degree difference, most of the vibration is gone (it's there slightly, but for a narrower speed window). However, the one degree makes a big difference in steering stability - very twitchy - much like the feeling when it was stock. I will not be going any lower than 4 degrees!

The real test will be on the commute to work tomorrow. It's getting way to cold to be working under the Jeep!

 

I talked with Gokracer1 this evening about this - he and I both have the 4" TF lift as you know.

I pointed out to him that if you can find the sweet spot - that's great - but if you can't definitely take it in to a shop. I found that while my angle finder was telling me 5, the laser finder at the alignment shop was telling me 3. Just goes to show you how inaccurate those angle finders can be.

Bottom line is you can give it a best guess with an angle finder and if you find it - great. But if you can't, don't hesitate to take it to someone who can really get you a good reading.

FYI, the 4" lift instructions call for caster to be set at 3.5. WOL says 6-7 from his experience installing the lift. Just goes to show you imperfect this process can sometimes be.

 

Thanks for all the input. I still do have vibration between 50-55mph and only on accel. My next step would be to pull the front driveshaft to see if it is indeed there or the rear. If its the rear, then perhaps a rebalance is in order.

One last question for everyone. Is the brief vibration something that most with aftermarket shafts deal with. Is there anyone with a completely smooth ride. My other lifted trucks have all had ride issues that are just secondary to being lifted, so I assume the Jeeps may as well.

 

That's exactly right. But modern alignment machines just measure including the Jeep's angle right off the bat. I say modern...those type machines have been out about 25 or more years now.

 

All this is fun, but the OP doesnt have an alignment machine, and he is probably thoroughly confused now.

 

It's probably your rear drivesahft (I say that because at 50-55 I assume you're on the street in 2WD and your front axle is not being powered). There is a rule of thumb that says if you experience vibration on acceleration you either have too much pinion angle or not enough. And if you expereince it on deceleration it is the opposite. For the life of me I can't remember which it is; maybe somebody who rememebers can pitch in. Or you could call a driveline shop and ask them as it is not a Jeep specific thing. Or you could go 1 degree in one direction or the other. If it's better you're going in the right direction. If it's worse go back 2 degrees so you're 1 degree in the other direction. That's what I did with mine rear and front shafts to get them to smooth out.

Having said all that Jeep did put those funky driveshafts in because they are smooth. Going to something else will give up some of that smoothness. Buth then if smoothness were the over-riding issue we'd all have bought Grand Cherokees or Commanders.