Basic jeep suspension rundown
dave92cherokee
11-16-2007, 09:00 PM
This is intended to be a basic guideline for all the newbie jeep owners or veteran owners who drive stock jeeps and wanted to lift but were unsure of what's involved. If anyone would like to add a little more depth please feel free to add it if you want, any questions feel free to send me a private message. This is not intended to insult anyone's intelligence just to shed some light on those that are unsure or simply curious.
Lift Basics
The best design of a suspension is obviously stock no matter who the manufacturer is. Every manufacturer thoroughly researches and designs the suspensions for their design car to give it the best performance and longest life possible. However most auto enthusiasts will not keep things stock for long as they feel the need to change and improve different characteristics.
Take the Jeep Cherokee for example at stock height the suspension, driveline, and steering is all properly centered and lined up (with the exception of death wobble) and will last a very long time. When you decide to lift a 4wd Cherokee is when a number of characteristics come into play, most of them can be lifted up to 3 inches without having to make any major mods to anything else and be very road worthy.
Driveline
Once you pass this invisible barrier of 3 inches is when other things start needing to be changed to accomodate steeper angles from being higher than before. From 3 inches and above the most common thing a Jeep needs is a SYE (slip yoke eliminator), which as it's name implies eliminates the factory slip yoke. The reason for this is that at higher lifts the rear driveshaft will pull the slip yoke off the transfer case output shaft and as you can guess cause alot of problems.
There are 2 basic designs and ways to accomplish this both with pro's and con's. The cheaper and often considered the "less prefered" way is the Hack-N-Tap which is available from Rubicon Express. This one entails removing the factory slip yoke and tail cone of the transfer case, then cutting off a certain amount of the output shaft, and then drilling and tapping threads into the center of the remaining shaft and bolting the new yoke and tail cone replacement in place. I have read MANY good and bad reviews about this option and is pretty equal with maybe a little more good luck than bad. One of the major influences of this method is the price as it can be done for around $100.
The other method of installing a sye is also considered the best and very few bad reviews have ever been head of about it. This one costs more money and takes more time and mechanical experience than the first but is widely viewed to be the strongest and best of the two methods. It entails installing an Advanced Adapters or equivalent sye mainly available from Rubicon Express and Rusty's Offroad websites.
To accomplish this second method you can either make it easy and completely remove the transfer case to have room to perform the work or leave it installed in the Jeep and do the work from underneath. In a quick rundown it involves completely dismantling the transfer case and replacing the rear output shaft, yoke, and tail cone assembly with what's provided with the kit.
Once the sye is installed, which ever method you choose to use, you will need a new cv driveshaft so when the suspension moves it adjusts it's length at the same time since the original solid shaft will not. Again with driveshaft's there are many types, models, prices, and makers but the most widely known and revered is Tom Wood's driveshafts.
Driveshaft Angle
Now having a tall lift above 5 inches will bring into account driveshaft angle also known as pinion angle. This is the angle from the yoke of the transfer case to the yoke of the axle differential, same goes for front and rear but rear is easier to adjust. The optimum angle is the axle yoke pointing 2-3 degrees below the transfer case yoke for proper alignment, and best ujoint angle scenario. This can be set with either putting in a shim between the rear leafs or completely cutting off the spring and shock mounting points and welding on new ones with the axle properly lined up.
As you guessed the latter is the best but more expensive and time consuming option, another way of accomplishing it is getting a new axle with a hi-pinion carrier which lifts the axle yoke from the bottom to the top and reduces the angle needed for alignment.
The same goes for the front but with a couple of differences, you cannot add a shim obviously to change the angle but instead can buy new adjustable control arms which allows some adjustment in the pinion angle. But beware tilt it too much and the front coil springs will not stay on and the steering will get kinked up on you. The best option for the front is a new hi-pinion axle and then setting the angles before welding on spring perches and steering components.
Steering
And the last major change that is made on the Cherokee when lifting is the steering components. The worst problem being the weak point is the steering box mounting. When you start using tires above 33" it causes alot of stress on the steering box mounts and have been known and seen to be ripped right through the frame. Thankfully there are many fixes for this, but all achieve the same outcome more strength.
When lifting the factory track bar will be too short and pull the front axle to one side so the higher the lift the more offset the axle will be. There are many adjustable track bar's available but most good one's will include a heavy duty track bar mount which also provides a stronger mount for the steering box helping to improve that problem.
After the track bar has been adressed then the steering linkage will need to be addressed. Usually, you will need a dropped pitman arm which lowers the steering linkage to help reduce the extreme angles on it. There is an abundance of information on doing an OTK (over the knuckle) steering flip to increase clearance and reduce steering angles as well. The main items for correcting steering system issues is a steering box brace, drop pitman arm, and adjustable track bar.
Those are some of the basics of lifting a Jeep XJ.
It doesn't stop there as it all depends on the person and what they want to do with it. Some simply want a few inches of lift for light occasional off roading and others want to go to the extremes for offroad only and heavy duty rock crawling and such. It all depends on what you want to do with it in the end as to how high to lift it.
Lift Basics
The best design of a suspension is obviously stock no matter who the manufacturer is. Every manufacturer thoroughly researches and designs the suspensions for their design car to give it the best performance and longest life possible. However most auto enthusiasts will not keep things stock for long as they feel the need to change and improve different characteristics.
Take the Jeep Cherokee for example at stock height the suspension, driveline, and steering is all properly centered and lined up (with the exception of death wobble) and will last a very long time. When you decide to lift a 4wd Cherokee is when a number of characteristics come into play, most of them can be lifted up to 3 inches without having to make any major mods to anything else and be very road worthy.
Driveline
Once you pass this invisible barrier of 3 inches is when other things start needing to be changed to accomodate steeper angles from being higher than before. From 3 inches and above the most common thing a Jeep needs is a SYE (slip yoke eliminator), which as it's name implies eliminates the factory slip yoke. The reason for this is that at higher lifts the rear driveshaft will pull the slip yoke off the transfer case output shaft and as you can guess cause alot of problems.
There are 2 basic designs and ways to accomplish this both with pro's and con's. The cheaper and often considered the "less prefered" way is the Hack-N-Tap which is available from Rubicon Express. This one entails removing the factory slip yoke and tail cone of the transfer case, then cutting off a certain amount of the output shaft, and then drilling and tapping threads into the center of the remaining shaft and bolting the new yoke and tail cone replacement in place. I have read MANY good and bad reviews about this option and is pretty equal with maybe a little more good luck than bad. One of the major influences of this method is the price as it can be done for around $100.
The other method of installing a sye is also considered the best and very few bad reviews have ever been head of about it. This one costs more money and takes more time and mechanical experience than the first but is widely viewed to be the strongest and best of the two methods. It entails installing an Advanced Adapters or equivalent sye mainly available from Rubicon Express and Rusty's Offroad websites.
To accomplish this second method you can either make it easy and completely remove the transfer case to have room to perform the work or leave it installed in the Jeep and do the work from underneath. In a quick rundown it involves completely dismantling the transfer case and replacing the rear output shaft, yoke, and tail cone assembly with what's provided with the kit.
Once the sye is installed, which ever method you choose to use, you will need a new cv driveshaft so when the suspension moves it adjusts it's length at the same time since the original solid shaft will not. Again with driveshaft's there are many types, models, prices, and makers but the most widely known and revered is Tom Wood's driveshafts.
Driveshaft Angle
Now having a tall lift above 5 inches will bring into account driveshaft angle also known as pinion angle. This is the angle from the yoke of the transfer case to the yoke of the axle differential, same goes for front and rear but rear is easier to adjust. The optimum angle is the axle yoke pointing 2-3 degrees below the transfer case yoke for proper alignment, and best ujoint angle scenario. This can be set with either putting in a shim between the rear leafs or completely cutting off the spring and shock mounting points and welding on new ones with the axle properly lined up.
As you guessed the latter is the best but more expensive and time consuming option, another way of accomplishing it is getting a new axle with a hi-pinion carrier which lifts the axle yoke from the bottom to the top and reduces the angle needed for alignment.
The same goes for the front but with a couple of differences, you cannot add a shim obviously to change the angle but instead can buy new adjustable control arms which allows some adjustment in the pinion angle. But beware tilt it too much and the front coil springs will not stay on and the steering will get kinked up on you. The best option for the front is a new hi-pinion axle and then setting the angles before welding on spring perches and steering components.
Steering
And the last major change that is made on the Cherokee when lifting is the steering components. The worst problem being the weak point is the steering box mounting. When you start using tires above 33" it causes alot of stress on the steering box mounts and have been known and seen to be ripped right through the frame. Thankfully there are many fixes for this, but all achieve the same outcome more strength.
When lifting the factory track bar will be too short and pull the front axle to one side so the higher the lift the more offset the axle will be. There are many adjustable track bar's available but most good one's will include a heavy duty track bar mount which also provides a stronger mount for the steering box helping to improve that problem.
After the track bar has been adressed then the steering linkage will need to be addressed. Usually, you will need a dropped pitman arm which lowers the steering linkage to help reduce the extreme angles on it. There is an abundance of information on doing an OTK (over the knuckle) steering flip to increase clearance and reduce steering angles as well. The main items for correcting steering system issues is a steering box brace, drop pitman arm, and adjustable track bar.
Those are some of the basics of lifting a Jeep XJ.
It doesn't stop there as it all depends on the person and what they want to do with it. Some simply want a few inches of lift for light occasional off roading and others want to go to the extremes for offroad only and heavy duty rock crawling and such. It all depends on what you want to do with it in the end as to how high to lift it.
AlohaBra
11-18-2007, 10:47 AM
Thanks Dave. (Hope it is OK...I made some edits to your fine writeup.)
I stickied this up here to help people who are interested in lifting a Jeep Cherokee (also know as an XJ). A lot of people don't realize that lifting a Cherokee requires more than just the lift kit.
I stickied this up here to help people who are interested in lifting a Jeep Cherokee (also know as an XJ). A lot of people don't realize that lifting a Cherokee requires more than just the lift kit.
dave92cherokee
11-18-2007, 01:20 PM
No problem like I said if there's anything I missed feel free to add it in so that people in the future will know all about how to do it and be better prepared to save up the money needed to do it.
citizen@large
11-29-2007, 01:16 PM
Sweet. Nice one Dave.
snobalz
05-18-2008, 12:14 PM
Great article. I have a few questions.
I recently acquired a 1986 XJ and the previous owner said that it has a 4" lift and that it was achieved by relocating the rear springs to the top of the drive shaft and putting larger springs on the front. If this is the case what potential problems should I check for on this type of lift? If this correct were the springs originally mounted on the underside of the rear axle?
Thanks for the help.
Snobalz
I recently acquired a 1986 XJ and the previous owner said that it has a 4" lift and that it was achieved by relocating the rear springs to the top of the drive shaft and putting larger springs on the front. If this is the case what potential problems should I check for on this type of lift? If this correct were the springs originally mounted on the underside of the rear axle?
Thanks for the help.
Snobalz
dave92cherokee
05-19-2008, 05:55 PM
All xj's are spring over axle design so that part was a lie. With 4" of lift you need to look at the length of your brake lines front and rear, your front lower control arms as they are probably close to hitting the spring mounting bracket, check and see if there is a SYE and double cardan rear shaft installed. From the way the previous owner told you about the lift I doubt any of that was done.
ironman2712
10-29-2008, 04:26 PM
yeah, tsis is what many of us 'undecided' needed, i love that forum, now i know where to start and whitch way to 'go', many thanks to the author-damn good job mate:popcorn:
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