2" lift - Driveline Angle PoV

First off, I've read all the 2" lift threads - very helpful so far. What I'd like to know is which lift is better from a driveline angle point of view: the full length AAL or the shackle. Does one lift change the angle more than the other? It seems to me that the shackle would rotate the axle slightly since it drops just the rear of the leaf. Maybe I should have payed more attention to my geometry teacher, oh well.

Thanks,
Dave D.
2001 XJ Sport 4wd - bone stock

It kind of depends on what kind of driveshaft you are using. With a standard two U-Joint shaft you want both the T-Case output and pinion on the same plane. If you are using a CV shaft you want the pinion to be pointing at the T-Case output. This will give you the least vibrations.
With this said, if you are using a stock shaft I would suggest the full length AAL.

DaveD912 said:

First off, I've read all the 2" lift threads - very helpful so far. What I'd like to know is which lift is better from a driveline angle point of view: the full length AAL or the shackle. Does one lift change the angle more than the other? It seems to me that the shackle would rotate the axle slightly since it drops just the rear of the leaf. Maybe I should have payed more attention to my geometry teacher, oh well.Thanks,Dave D.2001 XJ Sport 4wd - bone stock

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My experiences tell me the full length AAL will not result in angle change, but the longer shackle will. However, it seems that around here, everyone's experiences are different. If you are running a stock t-case output and driveshaft (which i assume you are as it says bone stock) the less you mess with the angles, the better. It saves you from having to shim your axle.
Buck :canada:

I would go with the AAL because over time the shackle will sag your rear springs. :wave1:

At 2 inches your driveline angle is inconsequential. I'm running 3" and have done nothing to either d-line.

well, shackle will allow for a smother ride, less bumpy. AAL's are known to make suspentions stiff...

annothe option is blocks (i know, dreaded axle wrap) but you can buy/make blocks with the shim built in to make up for the change in angle...

just something to think about...

Shackles are super easy to put in and I didn't shim a thing and I still have no vibes at 80 MPH+

Thanks for all the input. After reading all the saggy leaf spring threads, I'm leaning towards a full length AAL.

i'll suggest superlifts, i think its a 2.5 inch, but it actually rides great.

Adding a leaf strengthens the whole spring pack. Especially the full-length ones. A shackle places more stress on the spring, it is longer than a stock one obviously, and therefore when it flexes it places the stress on the spring instead of on, say, an add a leaf.

I have the add-a-leaf in my 3" lift and it has sagged. I dont think it is a full length. I was thinking of adding a bracket to bring it back & cause more sag.. Then I will finally get a full leaf pack. :looney:

jeepguy97 said:

Adding a leaf strengthens the whole spring pack. Especially the full-length ones. A shackle places more stress on the spring, it is longer than a stock one obviously, and therefore when it flexes it places the stress on the spring instead of on, say, an add a leaf.

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Of course adding more leafs will increase the spring rate and therefore the load carrying capacity of the spring.

I'd like to hear why a longer shackle places more stress on the spring than a short or stock length shackle. I think the devil made you say this.

jeepguy97 said:

Adding a leaf strengthens the whole spring pack. Especially the full-length ones. A shackle places more stress on the spring, it is longer than a stock one obviously, and therefore when it flexes it places the stress on the spring instead of on, say, an add a leaf.

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I'm afraid you have made an error here. A longer shackle will not "place more stress on the spring" as you have said. Springs don't know how long their shackles are, and continue to function almost exactly the same with a short shackle as with a long shackle. The only thing that might become affected is that the longer shackle may create a slight change in shackle angle which in turn can minorly affect installed spring rate (no effect on free rate of course), however with a simple extension of 3" on the shackle, the shackle angle is not affected enough in order to effect a change in the overall installed spring rate. You would need to be changing the shackle angle by probably about 25 degrees or more in order to see a change in the spring rate (something you cannot even do only by changing to a longer shackle). And it is only negligibly arguable that a changed spring rate will cause "sagging springs". This type of spring rate consideration is usually only made when you are tweaking the spring rates of leaf springs on oval track race cars and such, and is not at all related to sagging springs. So to summarize all of this mumbo jumbo, in an application such as the XJ, longer shackles will have NO adverse effects on the springs. How it affects your pinion angle is a whole other ball of wax, but then again, simple angled shims take care of those problems.
Buck :canada:

Ok why do we hear over and over again that shackle lifts cause the springs to sag. Do a search you will come up with many many people whom agree that when they used a shackle lift their springs did indeed sag.

jeepguy97 said:

Ok why do we hear over and over again that shackle lifts cause the springs to sag. Do a search you will come up with many many people whom agree that when they used a shackle lift their springs did indeed sag.

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That was not just my opinion, it was a detailed explication of why longer shackles have no impact on loss of spring flex. I'm afraid that 100+ armchair offroader's opinions do not overwrite reality. Simply put, if someone attributes their sagging springs to longer shackles, they are incorrect. Their springs may indeed have sagged, but it had nothing to do with their longer shackles. If you still don't believe me do a little internet research or talk to a spring shop, they will explain the same thing I did. Look, its not that I'm trying to be an a$$ here, its just that I know that what I have explained here is not incorrect, and I am always concerned when I see someone give faulty advice. We all learn from each other here, and I don't want some poor soul avoiding a simple mod because someone suggested something that was incorrect.
Buck :canada:

I'm afraid that 100+ armchair offroader's opinions do not overwrite reality

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Yea none of us ever actually hit the trails. :sure: Sometimes authority (spring shops,etc.) doesn't out weigh experience and I know many people who never had a sagging problem until they installed a shackle lift. To me thats more of a fact than any scientific evidence.

jeepguy97 said:

Yea none of us ever actually hit the trails. :sure: Sometimes authority (spring shops,etc.) doesn't out weigh experience and I know many people who never had a sagging problem until they installed a shackle lift. To me thats more of a fact than any scientific evidence.

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Okay this is just getting irritating. I know you are probably trying to make a valid point here, but back up your statements with evidence my friend. I don't care how many people "think" their sagging springs are due to their shackles, they are all wrong, or are the victims of coincidence. I said it before, do your research first! In your next post, explain HOW do leaf springs sag from longer shackles? Explain it to me, and to all of us. If you can put together a coherent convincing argument, then I will absolutely consider it, but don't just tell me joe blow said so, so it must be true. My son came home from school one day and told me that his entire class believes that you can get pregnant from kissing. Should I believe them too, or should I correct his faulty information? Funny thing is, despite the fact that he is eight, once I explained to him the way it works, he was able to accept it without presenting the same argument a second time. Just look it up and study it until you understand why leaf springs cannot sag due to longer shackles, when you are done, no apology is necessary, just don't disseminate disinformation....
Buck :canada:

I'm done arguing. I was simply stating what I've observed in the real world so he would know. I'm not saying I'm wrong or running away with my head down, I'm just saying I'm through.

jeepguy97 said:

I'm done arguing. I was simply stating what I've observed in the real world so he would know. I'm not saying I'm wrong or running away with my head down, I'm just saying I'm through.

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I already know the answer. I posed the question to spur on a debate. This statement is often made on this and other sites, but is not supported by a valid explanation, only anecdotal evidence.