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HOW TO: PML DIY - Fully Explained

31206 Views 67 Replies 27 Participants Last post by  Xterra3321
I know all of this information is covered around here, but I found that it was fragmented in different places. I am going to give a full explanation of all things PML and hopefully help a few people understand a torsion bar suspension system and the purpose of the bump stop gaps (two things I have found confuse a LOT of people). Read on, let me know if I missed something or if you have any questions. Really try to understand the mechanics of what is going on if you are new to this stuff because that makes the actual 'doing' a lot easier.

If you know nothing, start here:


PML = Poor Man's Lift = ~1.5" Suspension lift

Front: Stock torsion bar suspension is adjustable to an extent. This stock adjustment is used to gain an alleged 1.5". Free front end lift.

Rear: Shackles connect the leaf springs to the bottom of the frame. Longer shackles will add about 1.5"

Purchase rear shackles:

The typical ones are the 1.5" shackles:

Some people have complained about not getting enough lift in the front end, and so I decided to go with the adjustable shackles so I could use a lower lift setting in the rear if I needed to. I eventually plan to get upper control arms to add more lift to the front, and then can max out the adjustable shackle at 2 1/8":

If you are curious about how much lift you can get in the front end, place a jack under the front differential cross member, and raise both front wheels at the same time, watching the bump stop gap. Once you have between a ~0.5 inch gap between the upper control arm and the bump stop, you have reached PML ride height, and this will give you a good estimate of you front lift.

Further Explanation on the simulating a lift:

Lifting in the center, you will see how your control arms droop down. You know you have to stop lifting at ~0.5" bump stop raise the vehicle with a jack on that front subframe cross member until you see ~0.5" bump stop gap on each side.

Stop there and take a look...that is how high your front end will be when you are done.

Now is a good time to check your rake front to back. Do you still have a nose down rake? If so, you may want to just raise the front end, and leave the stock shackles on. if it is higher in the front, or perfectly level, you may want to go for the shackles. Or you may want to get the "Adjustable Shackes" that have multiple sets of holes in them, and dial them down a notch or two so you don't lift the rear as much. You will have shackle hanging off the end of the leaf spring, but you can cut the extra off if you really want.

The issue people seem to run into is that you don't get much lift out of the front suspension and still have an OK bump stop gap. The rear shackles will often raise the vehicle a full 1.5"...but the front will only adjust up 1" or so.

If you started with the nose down rake of 1.5" lower in the front...your ending rake will be 2" lower in the front, for example. Some people don't like the nose down rake, so they are tempted to over-adjust the front end, which can cause some problems. That is why I advise to check the front lift this way by "simulating" a lift in the front, THEN deciding what to do with the rear.

===========PREP WORK============

Prior to lifting anything, find a FLAT surface to work on (evenly laid garage floor is nice!). Ensure your tires are properly inflated. Ideally your tires should all be about the same tread height too.

Take preliminary measurements with a tape measure of your current ride height and write them down so you know where you are starting off at! Measure from the ground to the bottom of the doors right near each wheel well (not the wheel arches)

Measure the front:

Measure the rear:

Locate the rear shackles and the torsion bar adjuster bolts and nuts. Grab some PB Blaster or my favorite, Freeze Off! Drench all the hardware with some chemicals to keep them from being rust welded and breaking off. I started about a week before I was going to do the lift because mine looked really bad. I sprayed them all once, waited about 5 days, did them again, and sprayed them again on the day I did the lift. Maybe over board, but it definitely made things much easier.


Front torsion bar location and functional diagram:

Adjuster bolt, near mid section of truck. Spray bolt head, and both nuts above cross member.

On top of adjuster bolt, through cross member...two nut is just to lock the bottom nut so it doesn't rattle loose.

Rear shackle location:

Spray shackle hardware:
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===============LIFTING FRONT WITH TORSION BARS==================

Using a jack under the front cross member, raise the vehicle slightly, but leave both tires firmly on the ground. You are essentially letting the weight of the suspension and tires droop on the torsion bars some, and letting the jack hold the weight of the vehicle. This makes it easier to crank them so you don't have to overcome the entire truck weight.

Using an open end wrench (I think 3/4"), loosen the top nut, which is just a locking nut. Back it off the bottom nut a little bit.

Now, use the same wrench to hold the bottom nut in place. Use a socket wrench to turn the bolt head. Laying on your back under the car,the bolt head faces down at you, and the two nuts are above the cross member. Looking at it, turn it clockwise to tighten it. It can be useful to have two people for this! If you are holding the bottom nut, and tightening the bolt, the bolt will thread into the nut, raising the lever arm of the torsion bar towards the cross member. The bolt head should go higher into the cross member, and the gap between the two nuts should get larger, as the nut you are holding will thread down the bolt while the top nut stays in place:

Make some shims that are between 0.5" and 0.75". I used 3 paint stirring sticks taped together.

Look for the bump stop gap in the front of the wheel....Right inside here:

Use the shims to measure the gap. You need at least 0.5" gap between the upper control arm and the bump stop:

A better pic from RacerXXL...aftermarket UCAs and the bump stop gap:

As indicated in my picture captions, understand these bump stops. When people say there needs to be a 0.5" gap, it is not because there needs to be physical space between the UCA and bump stop. It is because that gap is the easiest way to measure the angle of the upper control arm. If the upper control arm droops too low, the camber will be way off, wearing the outer edge of your tires very fast, and the stock camber adjustments will not be able to compensate for it. If you have after market UCAs, crank away on the torsion bars with low profile bump stops and all. Lifting control arms don't actually lift the vehicle, they simply have modified geometry so that even with a higher lift, the camber can be corrected.

Repeat this process on the other side, and aim to have even bump stop gaps on each side. It requires some guessing and checking and raising and lowering. Once you think you have it where you want it, don't quite tighten the lock nuts just yet, as you may want to make adjustments after the shackles and when the suspension settles some. I did the front end lift first so I could max out my torsion bars, and then choose an appropriate height within the adjustable shackle.


A note on the infamous 're-indexing': Re-indexing does not offer more lift or better bump stop clearance. Re-indexing involves removing the torsion bar from the adjusting lever, and adjusting the initial position of the lever/adjuster arm. This is only done for two reasons:

1) There is no more room to adjust the lever upwards. As in you have room in the bump stop gaps to continue lifting, but the physical lever arm that the bolt goes through interferes with the cross member, or the bolt interferes with the body. When you re-index, it separates the torsion bar from the lever arm, allowing you to start the lever arm lower so you have a larger range of motion for the lever arm to raise into the cross member.

2) Your bump stop gaps are already at 0.5-0.75" but the lever arm and bolt head are below the cross member. You want the bolt head and lever arm to be inside the cross member to avoid having it snagged on terrain. Separating the torsion bar from the lever arm allows you to start the lever arm higher so that when you reach your desired lift height, the bolt and lever arm ends up inside the cross member.

I did not have to do this, but if you think you need to, check the DIY:


Another note on suspension lifts and the bump stops: A suspension lift does NOT add room for a larger tire. This only changes the ride height. The suspension system allows the tire to raise up when hitting a bump, but also droop lower. Adjusting the position for the tire to sit lower only trades up travel for down travel. Think of it like this: When you are jacking the front of the vehicle up to take a tire off...the tires do not immediately raise off the ground. The body and frame raises as the tire droops down. That magic point where the tires lift off the ground is the theoretical amount of maximum lift. You can have your vehicle ride that high, but now when raising the vehicle with a jack, the tire immediately raises off the ground, as it has no droop left. Of course, it can take a huge bump in the road as the tire has a lot of room to travel upwards. That point where the tires quit drooping is also when the UCA makes contact with the bump stop...IE the bump stop making contact with the UCA limits the droop of the front tire, so it can not droop any lower once it has made that contact.

Moral of the story: Regardless of your ride height due to a suspension lift, you can't fit larger tires than stock. You may have room for them while sitting in the drive way, but any amount of flex will cause them to rub whatever they would be rubbing if it was not lifted. If you want larger tires, the body lift is what you want as it raises the body (fenders) away from the frame, creating extra room regardless of suspension position. The suspension raises the frame (and body attached to frame), looking like there is more room, but once again, any flex in the suspension will quickly remove the extra room.
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===============REAR SHACKLES INSTALLED===================

Go to the rear of the car. Loosen those shackle nuts on both sides, but don't take them out yet.

You want to jack the rear end of the vehicle up, and support the frame rails on jack stands with both tires removed.

1. Chock front wheels so vehicle doesn't run away from you
2. Loosen lug nuts on both rear tires
3. Use scissor jack to raise drivers side frame rail
4. Remove drivers side tire
5. Place jack stand under drivers side frame rail
6. Lower jack
7. Repeat for passenger side

Go ahead and lower the spare tire by taking the T end of the jack bar with the scissor jack and putting it through the hole in the bumper by the license plate. Engage it with the chain mechanism to lower the spare tire from the vehicle.

You should now have your vehicle with wheels chocked, no rear tires, spare tire dropped down, and shackle nuts loose.

The rear axle weight is now supported by the suspension, making it difficult to remove the shackles. Take a jack and place it under the rear axle, right in the middle of the differential. Raise the differential just enough to relieve the weight from the shackles. The shackles should be a lot looser and easier to remove. I still had to give them a little tap with a hammer and a punch:

They come out in two pieces:

Remove both shackles. You now have the jack supporting the rear axle, jack stands supporting the frame on each side, and no shackles on! I had some issues getting the shackles out near the exhaust, but it was nothing a little pushing and pulling on the tail pipe didn't solve.

Go ahead and choose the setting in which you want to fasten the lower portion of the adjustable shackle (if applicable). I used jacks in the front and rear at the beggining to try and simulate the lift I could get, and my simulated measurements predicted about 1" in the front. I still did the 1.5" setting though...the front end looked much higher before the shackles. Plus my rake was a little low, so I figured I'd go for the high rear end. Based on the larger rake I have now, perhaps I should have stuck to the 1" setting.

Anyway, fasten the bolts through the bottom of the shackle on each side using the included hardware.

TJTJ recommends when installing all shackle hardware:

to clean up and then slather the threads/splines with anti-seize compound before reassembly would be nice too, as THAT makes the NEXT adjustments MUCH easier.
With both shackles connected to the leaf spring, you need to connect the top to the frame! However, with a longer shackle, you will realize they don't quite fit! You need to use the scissor jack (I had a second, hydraulic jack to support the differential) and place it in between the frame and leaf spring. Raise the jack, which flexes the leaf spring down, widening the gap with the frame. This gives you the extra room to attached the tops.

Drivers side scissor jack:

Passenger Side scissor jack:

Alternatively, to get the proper spacing for the longer shackles, TJTJ suggests:

When FIRST putting the rear on jack stands to REMOVE the shackles (Getting the tension off them so you can get them off easily), the trick is to find that magic height where the shackles are loose/ can rattle a bit...and then go HIGHER by the length of the added shackle lift.

IE: If your shackles will be give 1.5" of lift...raise the butt ANOTHER ~1.5", and THEN set it onto the jack stands.

Then use the floor jack, etc, to lift the axle BACK to the "Loose" height, and remove the OEM shackles...

..and then just LOWER it again to install the new longer shackles.

If you do the axle lifting from the diff, it lets you rock the axle left to right, etc...which makes lining up the holes for bolts easier as well.
Tap the top of the shackle in place:

Install the shackle hardware, tighten in place, and reassemble! With the longer shackle, the hub will sit lower, so you may need to use a jack to raise the differential some, or raise the frame rail higher to get the tires back on!

Beware of tire shops that over tighten tire will ruin the tire iron trying to get tires off!!!! That white line is an actual tear in the metal...

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Drive around some to settle the suspension, re-check the front torsion bars periodically to make sure the rake is even left to right, and about a 1-1.5 inch rake from front to back (front being lower). Get an alignment, but not to stock specification:

Quoting TJTJ

1. Set the Camber to 0°, or as close to it as

2. Try for getting the Caster to be between 0.3° and
0.6°, set differently between the right and left
side, with the left side being less than the right.

It doesn't matter what the Caster is, just as long as
you get the most Caster you can on the right
side, then set it so the left side is less by 0.3°
to 0.6°

Camber = 0.0°L.....0.0°R

Caster = 0.9°L.....1.2°R

Toe in = 0.08"L...0.08"R

Total toe = ...0.16"

I am still driving around some to settle the suspension and plan on making some more adjustments to the T-bars. However, it really does not look like I got much lift from the front T-bars. I know that the 'lift' is defined by the bump stop gap, and so by definition I have 1.5" over stock, but it makes me wonder how low was stock to begin with...because mine seemed low to begin with, and I barely got an inch in the front thus far. Looks like UCA's are in my future :)

Lastly, it appears that simulating the PML with jacks under the front differential and raising the rear frame/body was an accurate representation of my results...As the jack experiment predicted about 1 inch lift in the front...and that is what I was left with.

EDIT: Final Measurements and Reflection

Before I adjusted anything, the measurements I took were at the seam right below the doors:

Front Left: 19.5" Front Right: 18.5"
Rear Left: 21.5" Rear Right: 20.5"

After some final adjustments and negligence with the bump stop gaps (As I said, UCA's in the very near future, plus my tires are already I'll let the bad camber slide temporarily until I get both together) I got the ride height to:

Front Left: 20.5" Front Right: 20.25
Rear Left: 23.0" Rear Right: 22.5"

Interesting observations to note: The front to back rake was a bit large at 2 inches starting out. I should have gone with the 1 inch setting on the adjustable shackles. Oh well... I also began with a left to right rake of 1 inch. I tried to adjust the ride height to even it out. However, the front left tire, when maxed out at the bump stop gap, was much higher than the front right tire, when maxed out at the bump stop gap. I found it odd that the same ride height would have different bump stop gaps. I tried to even the front ride height to the same height the best I could (front right bump stop gap maybe 1/4 inch), which in turn brought the rear ride height closer from left to right, but not quite the same.

Lastly, using the jack under the front differential and raising the front end while monitoring the bump stop gaps gave me a predicted max front lift of:

Front Left: 20.5" Front Right: 19.5

This ride height was exactly what I had when maintaining the correct bump stop gaps.

So, in conclusion, if you are concerned about how much lift you can get from your stock torsion bars, raise the front differential and watch the bump stops. Measure before and after. You now know how high your front end will be after your PML.

After final adjustments and settling:

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I can't believe you did this all with hand tools. Ah, to be young..........

Nice write up! Approved!
This will be a Sticky!
NICE...My ultimate goal was achieved...a sticky thread and I don't even have 100 posts yet!!!!!


Hopefully this clears up some things people have been confused about :)

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NICE...My ultimate goal was achieved...a sticky thread and I don't even have 100 posts yet!!!!!


Hopefully this clears up some things people have been confused about :)

Your on your way kid! Keep up the good work. (and get some damn air tools) hahaha!
Pshhhh air tools. Real men use breaker bars and 1" pipe extensions.

(ehem... Secretly i need to invest in a 30gal tank and an impact gun)

Great job on the writeup. Looks like the formatting is just a tad off on the web side, but nothing that 'enter' cant fix!
Looks great, sweet write up.

Congrats on the Sticky!
Very nice job!


I would add a suggestion to address the part where you needed to re-adjust for the longer lift shackles:

When FIRST putting the rear on jack stands to REMOVE the shackles (Getting the tension off them so you can get them off easily), the trick is to find that magic height where the shackles are loose/ can rattle a bit...and then go HIGHER by the length of the added shackle lift.

IE: If your shackles will be give 1.5" of lift...raise the butt ANOTHER ~1.5", and THEN set it onto the jack stands.

Then use the floor jack, etc, to lift the axle BACK to the "Loose" height, and remove the OEM shackles...

..and then just LOWER it again to install the new longer shackles.

If you do the axle lifting from the diff, it lets you rock the axle left to right, etc...which makes lining up the holes for bolts easier as well.

Recommendations to clean up and then slather the threads/splines with anti-seize compound before reassembly would be nice too, as THAT makes the NEXT adjustments MUCH easier.
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Awesome write up!! Now it's time to remove that rear sway bar :) I feel your pain, I did my pml completely with hand tools also
Sway bar will probably come off in the near future.

TJTJ I saw a post you made about raising the vehicle the extra 3 inches to allow for the extra shackle length...but I saw it after I already did my lift and just kinda figured the shackles out on my own :D My jacks and jack stands didn't go much higher anyway :) I will make the note in the thread though.

Also, where are issues with formatting? Everything displayed as expected for me?
An excellent write-up, I just sat down on my break to do some research on the PML mod. Thanks especially for including the useful excerpts from TJTJ and the parts links :cool:
Awesome write up. Too bad it was too late for mine :D
Not to jack your thread, but here's another view of replacing the shackles.
This is a great write up have been wanting to do this but does any one know where to get shackles in Canada exchange and shipping is killer

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Well... I just ordered a set of Sway Away torsion bars. I have the shackles sitting on my front porch and started spraying all the necessary points with PB today. In 2 weeks I shall begin the PML!

I got underneath her yesterday and looked at the torsion bar adjusters and they will need to be (re) indexed. The driver side adjuster nut is stickling out anout 3/8 inch and the passenger side is buried and the arm has only about 1/2 inch that it can move up in the housing. I know that I could (re)index the stock bars, but for $185 more, I picked up the stiffer bars. Since I was cracking into the works anyway I figured I might as well do the upgrade.

I'll keep everyone posted when this jumps off!

It sounds like you will only need to re index the passenger side to move the adjuster out some (1-2 splines probably).

If the drivers side bolt head is about 3/8 below the cross member, you should have plenty of room to adjust it upwards.

Use anti seize on the torsion bar makes it much easier to remove them in the future...because most likely it will take a couple times to get the perfect position in the anchors.

Post here if you run into any questions!
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