TJ 5.5 to 4.5 Drop - JeepForum.com

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post #1 of 22 Old 07-18-2016, 02:32 PM Thread Starter
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TJ 5.5 to 4.5 Drop

Considering moving to a set of 4.5 inch springs from my current 5.5 inch RE springs in hopes of finding a better ride, both on road and off.

I am curious as to what all will need to be changed when installing these new springs.

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post #2 of 22 Old 07-18-2016, 03:04 PM
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Springs, and likely shocks. Buy good shocks, they are going to be the biggest factor in how it rides aside from bad control arm bushings. Will probably need to look at bump stops too.


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post #3 of 22 Old 07-18-2016, 03:12 PM Thread Starter
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So aside from springs and shocks (maybe bumps), the control arms will be fine at the same length, driveshaft will work as is and track bars will be okay at the same length?
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post #4 of 22 Old 07-18-2016, 03:24 PM
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If they are adjustable it would be worth looking at, but I can't see it causing much issue. FWIW my jeep had a stock track bar on the front of it when I bought it with a 4" suspension lift.

What arms are on it now?


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post #5 of 22 Old 07-18-2016, 03:32 PM
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Quote:
Originally Posted by UNTJeep View Post
So aside from springs and shocks (maybe bumps), the control arms will be fine at the same length, driveshaft will work as is and track bars will be okay at the same length?
Control arms and track bar will likely require adjustment. Driveshafts probably OK, although that's assuming they were the right length before. If they were not the correct length before then hard to say.

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post #6 of 22 Old 07-18-2016, 03:35 PM
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Control arms and track bar will likely require adjustment. Driveshafts probably OK, although that's assuming they were the right length before. If they were not the correct length before then hard to say.
I'd think the rear pinion angle could only get better right? Unless it was cranked up so far that the shocks were binding or they had extension brackets on them.


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post #7 of 22 Old 07-18-2016, 03:36 PM Thread Starter
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If they are adjustable it would be worth looking at, but I can't see it causing much issue. FWIW my jeep had a stock track bar on the front of it when I bought it with a 4" suspension lift.

What arms are on it now?
I have the RE Long Arms (Adjustable) that came with my lift.

Driveshaft is correct length for current setup.
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post #8 of 22 Old 07-18-2016, 03:37 PM
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I'd think the rear pinion angle could only get better right? Unless it was cranked up so far that the shocks were binding or they had extension brackets on them.
Are you referring to my comment about the driveshaft? Angle and length are two different issues. Have to think about both. He could return it to stock and the angle would be wonderful, but the length would probably be way off.

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post #9 of 22 Old 07-18-2016, 03:39 PM Thread Starter
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Originally Posted by biffgnar View Post
Control arms and track bar will likely require adjustment. Driveshafts probably OK, although that's assuming they were the right length before. If they were not the correct length before then hard to say.
I'd think the rear pinion angle could only get better right? Unless it was cranked up so far that the shocks were binding or they had extension brackets on them.

I do run shock mount extensions as well as shaved coil buckets on my 44 that have resolved the issues you've touched on.
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post #10 of 22 Old 07-18-2016, 03:40 PM
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I have the RE Long Arms (Adjustable) that came with my lift.

Driveshaft is correct length for current setup.
The more I think about driveshaft the more I'd say it depends what springs you switch too. RE springs have some of the highest spring rates out there and I wouldn't be surprised if you are getting 6+" of lift out of them. If you go to RE 4.5s then you are dealing with the same high spring rate issue and so may really only lose 1". But if you went to springs that are more normal spring rate, you could end up giving up 1.5-2.0" of lift which will start to have a little more affect on the driveshaft length. You can play with a right triangle calculator if you want to see the difference the lift change makes in the driveshaft length.

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post #11 of 22 Old 07-18-2016, 03:45 PM
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Originally Posted by biffgnar View Post
Are you referring to my comment about the driveshaft? Angle and length are two different issues. Have to think about both. He could return it to stock and the angle would be wonderful, but the length would probably be way off.
I was thinking of rear arm length. Definitely changes the length of the hypotenuse of the triangle.


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post #12 of 22 Old 07-18-2016, 03:47 PM
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I was thinking of rear arm length. Definitely changes the length of the hypotenuse of the triangle.
Then I don't understand your comment. Yes, the angle would get better but the arms still need to be adjusted.

And as to the driveshaft length, yes it changes, but if the lift change is only 1" its probably still manageable with existing shaft. On the other hand if its let's say closer to 2" starts to become a more interesting question.

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post #13 of 22 Old 07-18-2016, 03:56 PM
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Originally Posted by biffgnar View Post
Then I don't understand your comment. Yes, the angle would get better but the arms still need to be adjusted.

And as to the driveshaft length, yes it changes, but if the lift change is only 1" its probably still manageable with existing shaft. On the other hand if its let's say closer to 2" starts to become a more interesting question.
I figured if he didn't have the extension brackets to keep the shocks from binding that the Jeep currently had a compromised pinion angle that would be improved by the drop. Although he confirmed that it does have the brackets and shaved buckets so my thought is null.


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post #14 of 22 Old 07-18-2016, 03:59 PM
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I figured if he didn't have the extension brackets to keep the shocks from binding that the Jeep currently had a compromised pinion angle that would be improved by the drop. Although he confirmed that it does have the brackets and shaved buckets so my thought is null.
Those aren't the only problems one can have with too high a pinion angle. Another one that it wouldn't surprise me if he had risk of, but might have been oblivious to was driveshaft bind at axle sag. So, you were correct that lowering will improve all of those things, but still will likely require readjustment of control arms and track bars.

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post #15 of 22 Old 07-18-2016, 04:03 PM
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Originally Posted by biffgnar View Post
Those aren't the only problems one can have with too high a pinion angle. Another one that it wouldn't surprise me if he had risk of, but might have been oblivious to was driveshaft bind at axle sag. So, you were correct that lowering will improve all of those things, but still will likely require readjustment of control arms and track bars.
Double adjustable arms FTW.


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