View Full Version : Lifting a JK - introduction
Kerry and I have spent some time working through what a lift does - very often learning the hard way. It's a topic that ask 10 Jeeper and you'll get 20 different answers - so go easy on me. Just my thoughts.
First, let's start with a pretty decent introduction to the components and key issues when modifying your Jeep.
https://www.youtube.com/watch?v=ZttaTkR2OLk
(https://www.youtube.com/watch?v=ZttaTkR2OLk)
Then we can talk about how the typical lift systems in Australia relate.
Note that
a) the this does not at all apply to the IFS/IRS Jeeps: WK2, Trailhawk etc.
b) but the themes completely apply to all live axle jeeps, TJ and probably the JL too.
Dru'n'Kerry
OK summarising what happens when we lift a Jeep:
1. Because the jeep is higher off the ground the wheels, and with the wheels the axle drops lower away from the Jeep chassis. Because the live axle does not travel straight up and down, but rotates around the control arms (forward and back), as the axle drops the front goes backwards a bit, and the rear goes forward a bit.
2. Not only the wheel base is shorter, but the angles of everything that controls or attaches to the axle just changed. As that geometry was optimised by Jeep for ride control in the factory and before you started mucking around with it, your Jeep is no longer optimal! The bigger the lift, the more extreme the issue. Two keys for the front end: caster angle and pinion angle.
3. Caster angle: Take the front wheel off a push bike with the forks and handle bars. Now position it so that the forks are totally vertical. It is easy to see a vehicle engineered like that is going to be really manouverable, but any road input or bump/bounce will also turn the wheel. So easy to turn but not easy to keep going straight. Now set it up like easy rider with the wheel way out in front on a long angle. Engineered like this the vehicle will stay straight, isnt going to get off line _ _ _ AND wont go around corners.
That is caster angle. In a JK lift kit, the caster is either a) not adjusted and you get what you get; b) has brackets that are designed to adjust in the factory but have no further adjustment; c) are fully adjustable, and (if you know what you are doing) should be really good. Once you lift the Jeep it changes the caster so the steering is flighty and wont stay straight and cruisey like easy rider. We want to shift the angle forward for better handling.
The problem is, with limited adjustment depending on your kit and how good the guy setting it up is - as you make improve the caster - YOU STUFF UP THE PINION ANGLE. They kind of go together.
4 Pinion angle: Draw a line through your axle out through the uni joint and along the drive shaft up to the transfer case. Obviously in the perfect world to reduce wear and tear (in the worst case, vibration, whine and heat build up) you want that line to be perfectly straight. But if you increase the caster the line is bent at the uni joint. If your are really pushing your lift, say 6" - the only way to solve it is a new axle that is manufactured with a different pinion angle!
Here are another two matters to keep an eye on: track bar and drag link.
1. Track bar: As earlier, when you lift, the axle drops lower (and rotates so that the Jeep track is shorter). But look at things from the front of the Jeep. As the axle is lower, it is held side to side by the track bar. The track bar has to be long enough to allow the axle to travel up and down. So it is NOT mounted onto the jeep in the middle. So it is another suspension component that does NOT travel straight up and down but rotates around a centre point. The effect is the axle is no longer sitting in the middle of the jeep but has become offset to one side.
So you will want to adjust the new position of the axle.
3. Drag link: This connects the steering to the front wheels. Set up in the factory, the drag link is parallel to the axle and moves up and down with it. With the lift, it is no longer parallel so as the axle ides up and down, the drag link changes from not parallel in one direction, through parallel to not parallel in the other direction. This has the effect that the steering is not in harmony and going straight - over a bump - the steering will lurch in your hands. So you want the drag link adjust to be parallel with the axle and all working together.
So what does it mean with the lift kits common here in Sydney?
MINOR LIFT
First let's take a minimal approach. Just see what we can get away with no attempt to make geometry correction. YES, these sort of lift is not uncommon in Australia! Not to be fair too much with Wranglers.
Probably this would be done with either spacers (between the coils and the chassis). Typically you would only go 1 inch more than that is asking for trouble. In theory the geometry changes might be minor and you might get away with it. Cost is low, sometimes the dealer may offer something like this. If you are going through a cheaper lift from an Aussie brand just check out what they do for the geometry.
Avoid these lift kits if you can. Not recommended.
STANDARD 2' OR 2 1/2' LIFT.
Available from pretty much all Jeep mod manufacturers but the big three are probably AEV (American Expedition Vehicles), Terraflex, Synergy.
What these kits do is try to keep the cost down by lifting as much as they can withOUT needing adjustable everything. Adjustable stuff is expensive to manufacture. Typically it invloves beefed up brackets that are pre-drilled to ensure that the geometry correction is sorted out automatically. There is some adjustment eg the track rod but on the whole the kit should be "set and forget".
As it so happens, these kits will let you install 33" on the 2' lift so that you are at the legal limit and do not need to get certification and engineering in NSW.
Another advantage is that, other than bolting it all together, there is nothing to adjust, no fine tuning knowledge required - bolt it together and go wheeling!
You can see why this lift system is considered something of a "go to" at the SJC. Very effective, sensible, and with an experienced driver a huge step up from stock. And the Jeep was good stock anyway!
Highly recommended.
3" 3.5" 4" Lift - typically AEV, Terraflex, Synergy.
This stuff is NOT "plug and play". Everything needs adjusting and there is more than enough room to build in strife - or to really fine tune things. The kit is a lot more expensive and takes a lot more time to build.
You need it for 37's, I'd recommend it for 35's though plenty of Jeepers disagree.
I don't think it's enough to leave this with the mod shop - you are on a journey here and will want to be directing how you want it looked after. Quite likely that it is not perfect the first time - these systems need fine tuning. Sensational ability off road, should be great on road. Just more work.
Recommended? Yes but expect to need to work it through.
Other advancements?
Off set to new wheels - in essence making the Jeep track wider so that it is less tippy after lifting. A great improvement for road handling, but resolving clearances to rubbing tyres can be painful and new mud guards may be required.
Want to go extreme? It's a Jeep there is ALWAYS more you can do if you insist.
Long Arms: Longer control arms which means that the radius the axle uses is longer - much more straight up and down. Also more movement available. Problems? More movement the suspension just has a little more "slop" so engineering is a little tougher, road handling not quite as tight.
4 Link rear: I mention it in passing but it removes off centre with the rear track bar so the axle stays centred. Jose has this on his TJ. I suspect it
will challenge road handling though Jose's TJ seems wonderful!
Coil Over: The shock absorbers are inside the coils. Allows longer travel but shock maintenance is more involved.
If you are considering any of this then you will know what is going on and will be running with your own recommendations. :highly_amused:
Great summary Dru
Our newer members will be looking for more tips and advice I believe.....thanks for sharing!
Sent from my iPhone using Tapatalk
Great summary Dru
Our newer members will be looking for more tips and advice I believe.....thanks for sharing!
Sent from my iPhone using Tapatalk
Yeah, I';m not sure it's very organised, more "stream of consciousness:" but I did promise to nail our experiences, lol.
Compare the kits. Personal opinion and for 10 Jeepers there will be 20 thoughts that do not perfectly align (partners get involved too).
The Aussies - look , I am not a fan. They just cant match the R&D investment in USA and Aus equipment lifts I have seen had little to no geometry adjustment. No doubt this will have us called out, fine. We're sticking with the US mod kits and go local for various bits and accessories only.
Terraflex - Really strong and tough, Personality of the company really fits the Jeep culture, impressive gear. BUT they can do silly things and installation is often complicated.
Take a look at their install video for front sway bar disconnect - grinders, blow torch, etc. Overkill for home handyman.
Consider the Falcon shocks - cornered the market in Aus. For good reason. The beefiest solid effective shock available and not much more than half the cost of the competition. What's not to like? Cool video on the upside down install method "proving" they are tough enough to put the most vulnerable part of the shock in the most exposed location. This is the secret of their cheaper manufacture as they don't need gas reservoirs. Didn't work too well so now people add solid skid plates under the shocks - another thing to hang up the under-body on. We happily paid the additional money for the opposition, but I really get why people choose them.
The adjustable Control Arms have a fantastic reputation and are favoured by plenty of Jeep shops. But if installing yourself, remember that they have to be removed to be adjusted. Think that through before you dismiss it as unimportant. Adjust, not right, adjust again, almost, adjust. Dis-assemble and re-assemble the suspension every single time. Guarantee you will lose your sense of humour well before it is done.
The Terraflex diffs are awesome kit, but you have to buy the components and build the diff yourself. Ok for home build, but the mechanic hours will cost you plenty. We went G2 which are pre-built to spec.
Summary: Terraflex is "close, but no cigar". We do however check Terraflex components against every single thing we purchase, and our hybrid build does include plenty of Terraflex. More and more as we get new parts.
Synergy - super install friendly, rarely as robust as Terraflex or AEV.
Adjustable control arms can be adjusted on the vehicle. Pretty much as close to "bolt on" application as you can get. For everything. You wont see axle grinders and blow torches in many of their install vids. The CA "johnny joints" mean that when installing you do not have the get things perfectly aligned before bolting home, much easier. BUT they need maintenance. No scratch that. They wear out. Much sooner than the opposition and the bushes/joints need replacing at that point. You can get the bushes pressed out and replaced (these days), but maintenance is the price you pay for ease.
Compare the the track bar bracket - looks beefy compared to OEM, in fact you install it over the OEM bracket to double strength. Cute. Then sit it next to the same Terraflex component. Turns out that actually Synergy is the skinny guy who gets sand kicked in his face by the Terraflex bully at the beach. In the mean time the AEV part just looks right.
Our build started life as Synergy but over time is increasingly a hybrid as we find weak points. Exaggeration? I guess this is Jeep life, but you get the point I hope.
Summary: If you are lifting beyond a bracket correction system and need adjustable everything, and you are doing the build at home yourself - this is your kit. Period. Otherwise think about it.
AEV: Robust. Conservative. (Boring?)
It's hard to find problems other than the conservative design - which of course is why there are no problems. Still if you want to push the limits probably Terraflex and Synergy will appeal more.
I don't like their wheels - we have had to replace more Pintels than I care to think about, and the off set isn't compatible with some Terraflex components. The spare wheel carrier is a nightmare if not installed properly and a sweet gem if it is. Get it right, or consider Uneek.
Summary: Does everything right, understated, over-engineered (as if that is a bad thing) does not push the limits.
Others
I don't know anything about Rubicon Express and there are plenty of other US manufacturer's that turn up every now and then. These are the most common in Aus though.
Recommendation
There is no straight answer.
The "go to" lift in a club Jeep is a 2" lift on 33"s using pre-drilled correction brackets, no adjustment necessary, doesn't require engineering. For this it is AEV all the way for me. Add the drop brackets for road handling.
If you want more than this then you hit a world of opinion. Listen to your Jeep shop and make sure they will treat you as warmly after the big money lift for tuning and maintenance. Shop attitude and availability is probably more important than the kit choice. If your chosen shop turns out not to be all that you expected and you have to resolve tune and problem solving yourself, you are going to rue the day that you ruled out Synergy CAs.
Personally by going higher than 2" you are looking to push limits and I am far more inclined to the quirky thinking of Terraflex than AEV. Even though they design themselves into corners on occasion. If you are going 3" and doing it yourself - save yourself a headache and put Synergy on your shopping list. Some Jeepers will be giggling that we mark down AEV for being boring. It works so you call it boring?!? To each his own.
Spooky action will follow the Mud Magnet with a Synergy base. Because we already have the components from the old Jeep.
If we were starting with a truly clean slate I'd be going full on custom. Which is not the purpose of this post. Though I will add one last note. Seven Slot can source Genright Off Road fabricated CAs with Curry joints. Serious Jeep porn for comp trucks, off road racers, and of course general Jeep lunatics. Green with envy. :kiwi-fruit: :kiwi-fruit: :kiwi-fruit:
SnakeDoctor
11-03-20, 12:45 PM
Great intel here Dru, thanks.
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