Lift problems

[mineral co]

Sides shots with the wheels pointed straight ahead. Doesn't look quite right does it, though the wheels are offset to the rear rather than the front. The front is obviously not sitting level either.

IMG_0554_mid.jpg

IMG_0555_mid.jpg

[will e]

Something looks weird to me. Almost like it is too high. Here is Drew's rig, he just put a Rusty 4" lift on his. His looks like it didn't get a high and his wheel seems more centered. I really wonder if your springs are on 'backwards':


Before rusty's 4" lift:


After lift:





Hey Drew, post up some side shots of your 4". Maybe some close ups of the front springs.

[mineral co]

Something looks weird to me. Almost like it is too high. Here is Drew's rig, he just put a Rusty 4" lift on his. His looks like it didn't get a high and his wheel seems more centered. I really wonder if your springs are on 'backwards':

Judging from the rear wheels, his looks like it might be a bit higher than my truck. I have 31" tires on mine, perhaps that would account for the visual difference?

I'm open to all ideas. Going from the size of the spring eyes, the front springs are installed correctly (the larger eye in the rear). Also, as the front axle is not centered on the spring (offset to the rear by one inch if I remember correctly), I have that as a reference and, as you can see, the axle is definitely offset to the rear on these springs.

Please, if I've got any of this confused, please say so. This whole thing has been a mess and I'm so fed up with it all that I'm willing to go lay in the snow to start working on a front D60 swap with custom springs.

Thanks,

Chris

[will e]

Drew is a good guy and will post some pics.

Is it possible you over torqued the bolts? Do the front shackles compress some if you jump up and down on the bumper?

[mineral co]

Drew is a good guy and will post some pics.

Is it possible you over torqued the bolts? Do the front shackles compress some if you jump up and down on the bumper?

It took me a minute to figure out what you meant or, at least, I think I understand. You are refering to the shackle bolts at the front. (?) If so, no they are not over-torqued. What I did was get the truck sitting level with all the nuts loose so that none of the rubber parts would be under any stress and then hold the bolt heads steady with one wrench and turn only the nuts down to torque with a second wrench.

However, I like your thinking. I had not considered the possibility that the shackles might be in an incorrect static position. Even though I think everything is okay in that respect, I will check it to confirm.

[TUDrewser]

I'm running 31s too. Will grab some pics shortly.

[TUDrewser]

[TUDrewser]

None of those showed the spring angle well. Here is another.



This is Rusty's 4" left with 31" tires.

[mineral co]

Thanks for posting those pictures!

If I compare our two trucks' height using body lines, they look very similar. But your front wheels look like they are centered in the wheel wells a lot better than mine. And the slope of your front springs doesn't look nearly as steep as mine but that must be an illusion.

Chris

[TUDrewser]

I was thinking the same thing about the "slope". I think my wheels may be a little higher into the wheel well judging by lines...maybe an inch or so? But your spring looks like it bows a lot more than mine. I have no idea how that could be, as the mounting points and height are basically the same...

For what it's worth, I measured ground to top of tire and it's 29" (I'm probably a little low on air too...it's cold outside, but tires are def 31's), and ground to bottom of frame/panel is 17.5".

As a side note, I'm curious for someone with a stock ride to measure so I can know what my actual lift is...I forgot to measure before

[will e]

Good luck finding someone with a 'stock ride'. They are all saggy by now.
Yeah, his looks more sloped than yours for sure.

[BigJ200]

Hi mineral co,

I have read your entire thread and it appears that you are working through the issues. Good to see that you are learning as you go. You have received some very good advise.

BTW, most of these issues are very common when suspension mods are made. Especially with older rigs that have worn out parts.

A couple of thoughts...

You mentioned installing a double cardan on your front driveline to help with the vibration. However, it won't help anyway unless your front pinion angle is inline with the driveline. And that won't happen without the cut and turn resulting in knuckles back at 4-6* caster and pinion pointing up. Both have to be done at the same time to attain the correct geometry. A double cardan on both ends will only mask the problem.

One other thing... It is quite strange and problematic to have an engine/trans/t-case sitting at 6* down relative to the frame. It makes the rear driveline angles easier to deal with many times. But it causes massive vibration issues with the front d-line. This is because your front t-case yoke is pointing up at 6* creating an excessive u-joint angle, even worse with a lift. Then consider that to make the angle of your front pinion the same as the t-case, you would have to point the pinion 6* down, which is not going to work. Does that make sense? So, check your engine angle again, making sure your frame is level or take the difference. The drivetrain should be ideally at 1* down for correct geometry. If it is truly 6* then it will be a huge problem with a lift. Hope that helps.

I have been building custom Jeeps for 25+ years and I've seen this kind of thing over and over. It's like a chain reaction that continues from one problem and component to another. And it's often exacerbated by one or more mistakes, bad decisions, bad advise along the way. Ultimately, leading to unsolvable issues. The info you are receiving from this site will hopefully keep you from that particularly unpleasant kind of hell.

Oh and I hope ya don't hate poly bushings now.

And you may have received a bigger lift spring than what you ordered, or Drew's is not 4" or it is settled down after use. Tough to tell, but yours definitely has a bigger arch. Sumptin' ain't right...

MB

[will e]

That's interesting, until you pointed it out it didn't occur to me that the front of the tcase is pointed 'up' at the same angle the rear is pointed 'down'. It's less of a problem for me, I only run the front at slow speeds.

I get a vibration under certain acelleratin/decelleration conditions after swapping in an Atlas 4spd but I think my problem is my cheezy exhaust repair.

[mineral co]

BigJ200, thank you for the comments.

I was wondering if somebody would comment on the downward angle of the TC. I didn't say it, but that was a measurement that I got with the truck sitting in my back driveway which has a bit of a slope to it. What I was after at the time was the difference between the TC, the driveshaft, and the rear pinion. I did not take a measurement of the frame at that time as I knew the truck wasn't sitting level, and it would likely be different every time I moved the truck. The number I posted for the TC and the pinion are relative to a horizontal line, but not to the frame. Removing the BDS rear shims was an effort to get the TC and rear pinion closer to being in the same plane, and it did greatly reduce the vibration coming from the rear.

I would like to have some measurements with the truck sitting flat on perfectly level ground, but I don't think there is any such thing as a truely flat spot any where in town! I had hoped to be able to do this when the truck was on the alignment rack, but the shop operator refused to allow me to be near the truck while it was on his rack. Unfortunate, but understandable.

I had thought that a double-ended double-Cardan front shaft would be a workable solution to the front vibration problem, but then I talked to a couple manufacturers. Hmm! The number I had in my head was only about half of the quoted prices! At $600, I'll reconsider the other options. I am planning a Ford HP D60 swap in the spring, and I now intend to make sure that axle is set up as "right" as possible to deal with the pinion angle issues while maintaining caster so that the need for the special driveshaft is avoided, even if it means cutting both knuckles off and turning them. For $600, I can make all the necessary driveshaft changes and axle changes to do it right.

I should clarify that the truck has a stock single-ended double-Cardan front shaft. Before the lift, the front pinion did point directly at the TC, and there was zero vibration from it. Assuming that any front spring was designed to maintain the pinion angle (and caster angle) after a lift, the angle would still be in the same plain, but the pinion would be pointing four inches below the TC, and could cause a vibration as the angle through the lower U-joint would no longer be zero. If I were a spring manufacturer, I suppose I would try to balance caster vs. pinion angle so that neither was too adversly effected (split the difference). And, the more I think about all this, the more convinced I become that the "front" problem is nothing more than the axle is not sitting at the right position (fore and aft) on the springs. Those side view photos make it clear that the axle should be furthur forward.

I really wish I had thought to check the front pinion angle before doing the lift (and, now, I would encourage anybody to do this before doing the lift). Ryan at BJ's has asked me to get the current pinion angle (along with some photos) as part of satisfying himself that he understands what is going on, but the snow is deep enought that it would require digging down through it to be able to get that number. Once conditions permit, I will get it. Knowing if the angle is the same now as it was before the lift would be revealing.

Looking at the photos I posted above (the side view shots), I am now of the opinion that the axle is sitting further rearward than it should. Considering the arc on the springs, this may well be the explaination for why the caster after the lift was so far out. Moving the axle forward to the center of the wheel wells might make up the entire 6 degree caster error, and would effectively make the front driveshaft a bit longer, and that might mitigate the amount of vibration from it.

I am of the opinion that something is not right with the front springs but I would like very much to understand the problem and fix it correctly. Unfortunately, winter is conspiring to slow this exercise down considerably.

[will e]

I am going to go search the web a little but what is the correct method for measuring/calculating TC and pinion angle?

[BigJ200]

Actually, if you have no way to get your frame level, you can simply check it where it currently sits. Then check the TC, pinions and caster. Then just figure the difference between them.

So, say your frame is currently sitting lower in the back...

Say down 5*

Then say your angle on the rear of the TC is 6.5* (the engine,transmission,t-case)

So 6.5* down.

The actual resultant angle is 1.5* down. That's the angle of your drivetrain if your frame were level. And that's within acceptable tolerance.

Now if your rear axle is pointing up at 11.5*, you subtract 5*, which comes to 6.5* up. That's the resultant angle of your rear pinion if your frame were level. The difference between 6.5* up and 1.5* down is 4*. That's how much you need to rotate the rear pinion down so both angles match. This is assuming you have standard u-joints on the rear driveshaft. No CV.
Make sense?

Now on the front your TC is 6.5* up. The rear is down so the front is up. 6.5*- 5* (again the current frame angle is 5*) the difference is 1.5* up. The resultant front TC output yoke is 1.5* up. Exact opposite of the rear TC yoke.

And say your front pinion (right on the flat surface of the pinion yoke) is 8* down. Again subtract 5* and the resultant front pinion yoke is only 3* down if the frame were level. However, now your front TC yoke is 1.5* up and your front pinion is 3* down. That's a difference of 4.5*. That will vibrate with standard u-joints or a double cardan. The lift has put you in no mans land. And honestly, with a CV on the front TC, any lift will change the geometry and cause vibrations. There is no way to correct it unless you tip the front axle forward (which destroys caster) or you can cut and turn the knuckles.

Do the same math for figuring current caster. Just take the difference between the frame and knuckle.

I really hope this makes sense.

MB

[BigJ200]

One other thing you mentioned... And you are right. It is possible to have all angles correct within the Spicer specifications and still have vibrations and premature u-joint wear if the u-joint angles themselves are too severe. There is a complex set of rules for that too. Solve the first issues of overall geometry and see how it works. You should be fine with only a 4" lift.

[serehill]

Sounds like the slip joints are shot.

[rocklaurence]

Your rear diff should have the same angle as the t-case. Put your magnetic angle finder on the t-case out put, then on your rear axle. They should not be more then 1-2* difference. The closer to the same, the smoother they run and the joints last longer.

Actually, they need to be equal but opposite. For example: Tcase +2, axle-2 degrees. Normally the Tcase is pointing down and the axle is pointing up.

[jaber]

http://4xshaft.com/driveline101.html

This is what helped me understand it, even if I cant describe it correctly.