TB EXT Lift Guidance

[80Flareside]

Hey all, pretty new member here, looking for some help and clarification on lift options. Ive read through many of the threads here, and at TrailVoy regarding lifts, but the more I read, the less I am sure how to go about what I am trying to achieve.

Im by no means a master mechanic, but Ive successfully (not always the first time, but eventually) rebuilt the C6 transmission, NP208 T-Case, and Dana 44 TTB on my truck, so I have the skills and background to accomplish this, I just cant figure out what I path I should take.

Scenario:
The TB is the wifes car, but its also what we use whenever we go anywhere as a family. It was bought used, and the dampening on the shocks is miserable (either worn out or way to soft for my liking - not sure which as I have nothing to compare it to), and she needs new tires. We plan to get a pop-up camper next year, somewhere around the 2,500 - 3,000 lb range, and this will be the vehicle we tow it with. 99% of what it will see is pavement, but there are some "4x4 - High Clearance" Class 4 roads in VT that we travel every so often.

Goals:
Increase the load handling ability of the vehicle
Improve dampening of compression and rebound of shocks
Improve clearance
Achieve slight rake from front to back (but less than factory) so it rides level with a moderate load

What Ive concluded so far:
Rear - Z71 springs, Bilstein 5100 Shocks, Bumped and Strapped
Front - Bilstein HD (Yellow Body) Shocks
Tire Preference - BFG Rugged Terrain T/A

Questions:
How much lift will the Z71's provide in an EXT? (assuming the figures I see here are for SWB)
How much lift can I give the front with out a UCA flip?
What is the largest tire I can run at that lift without a spacer?
What spring options are available for the front, and how do they affect ride height when combined with spacers?
What exactly are "86's", "87's", etc?

thanks in advance ~ matt

[06MidnightBlue]

The Z71's will give you about an inch of lift.

The most lift you should do in the front without flipping the UCA's, IMO, is 2.5 inches.

The largest tire you can run without spacers is 30.5.

There are a few spring options, with the stiffest option providing about 1.25 inches of lift in the front.

The "86's" and "87's" refer to the spring rate.

Most of this could have been found by searching.

[Gordinho80]

There are a few spring options, with the stiffest option providing about 1.25 inches of lift in the front.

The "86's" and "87's" refer to the spring rate.

Lift from stiffer front OEM springs is relative to the stiffness of the springs already on the vehicle. You will not get 1.25" of lift if you have 85's and go to 86's or 87's. Unless your springs are worn.

As far as the numbers, "86's, 87's, etc", we're referring to the OEM part #s, not the spring rate. The stiffest OEM front springs found are the 89's. If you're running 83's and you go to 89's, expect lots of lift and a stiff front end.

But like Jeff said, search, read... lots of questions will be answered.

[06MidnightBlue]

Thanks for the clarification Mario. Not quite awake yet

[The Roadie]

One question you asked I don't remember ever seeing before was about the UCA flip. Pretty much only the max lifts *require* the frip to allow the alignment shop to come closer (or to achieve) an in-spec camber adjustment. But flipping the UCA with ANY amount of lift can only help reduce stress on the upper ball joint because it puts the ball shaft closer to being centered. I don't think there's any downside, and if you're in there with the struts removed, all it takes is a short amount of time to flip them. You need an alignment anyway after the lift, so it's good to do it all at the same time.

[06MidnightBlue]

Roadie does make a good point.

[80Flareside]

The Z71's will give you about an inch of lift.

Thanks, wasn’t able to find anything stating how the extra weight of the LWB would impact this.

There are a few spring options, with the stiffest option providing about 1.25 inches of lift in the front.
The "86's" and "87's" refer to the spring rate.
Most of this could have been found by searching.

I would never choose a spring based on the amount of lift it provided without knowing the rate. I choose spring rates by use and ride - soft for off road, stiff for on road. I know I want something stiffer than what I have, but without knowing the rates Im left to trial and error to get the right one, and then as mentioned the ride height changes.

Looking at the figures I have been able to find puts spring rates somewhere in the 65 – 80 n/mm range which roughly converts to 372 – 458 pounds per inch of compression. I am having trouble with these numbers given that Im currently running 295 lbs per inch of compression on my ½ ton, stockers rate at 320 lbs, and my old lift coils rate around 425 (poor substitute for not having a anti-sway bar to limit roll under load).

Knowing how the truck rode before I got my Deaver coils, if I went and put 400 lb springs on that car my wife would kill me. What I'm trying to accomplish is approximate the ride height of the desired spring. From there I can then figure out my spacer options to get the height to where I want it. Not knowing the rates makes that near impossible, and unfortunately I don't have the time or money to experiment.

As far as the numbers, "86's, 87's, etc", we're referring to the OEM part #s, not the spring rate.

Has anyone measured the free length of any of these, thrown 500 lbs on, and re-measured?

flipping the UCA with ANY amount of lift can only help reduce stress on the upper ball joint.

Noted. I am also considering replacing the ball joints with quality greasable ones to prolong life.

The largest tire you can run without spacers is 30.5.

Stock 245/65-17's are 29.5" in dia and 9.6" wide. That means there is currently less than 3/4" clearance somewhere (which given how small those tires look in the wheel-well is absurd). I would prefer to keep the offset as it is. Where would it rub first with a 255/70-17 (31.1" x 10")?

[Trail X]

It was bought used, and the dampening on the shocks is miserable (either worn out or way to soft for my liking - not sure which as I have nothing to compare it to), and she needs new tires. We plan to get a pop-up camper next year, somewhere around the 2,500 - 3,000 lb range, and this will be the vehicle we tow it with.

Check on your diff gear ratio. If you're wanting to tow and have 3.41s, you probably won't want to get larger tires. On the other hand, if you have 4.10s you can probably go up to 33s and still tow pretty well. I'd also suggest putting a trans cooler in there before you tow anything. A shift kit that replaces the torque converter lockoff clutch PWM valve with an on-off valve can also greatly reduce your trans temps.

[fishsticks]

I would never choose a spring based on the amount of lift it provided without knowing the rate. I choose spring rates by use and ride - soft for off road, stiff for on road. I know I want something stiffer than what I have, but without knowing the rates Im left to trial and error to get the right one, and then as mentioned the ride height changes.

Looking at the figures I have been able to find puts spring rates somewhere in the 65 – 80 n/mm range which roughly converts to 372 – 458 pounds per inch of compression. I am having trouble with these numbers given that Im currently running 295 lbs per inch of compression on my ½ ton, stockers rate at 320 lbs, and my old lift coils rate around 425 (poor substitute for not having a anti-sway bar to limit roll under load).

Knowing how the truck rode before I got my Deaver coils, if I went and put 400 lb springs on that car my wife would kill me. What I'm trying to accomplish is approximate the ride height of the desired spring. From there I can then figure out my spacer options to get the height to where I want it. Not knowing the rates makes that near impossible, and unfortunately I don't have the time or money to experiment.

The angle of the coilover unit on our trucks is not vertical. The bottom of the unit mounts approximately 11.5" away from the fulcrum of the LCA and the knuckle attaches at about 16" out. The top coilover mount is roughly in line with the LCA fulcrum. Higher rate springs are needed to compensate for the added mechanical advantage the LCA has. I would look at stiffer front coils for load handling of armor/winch. The extra possible lift is more of a "bonus" IMO. Also, GM undersprung these vehicles from the factory. Even with sway bars, the body roll is unacceptable. Z71 rears and 87/88/89 fronts help shore things up.

We have a member running RadFlo front coilovers with 600# springs IIRC. He's very happy with the ride quality. I'm looking at the possibility of FOA coilovers with similar spring rates. He and I both have 300+lbs extra on our front ends though.

Has anyone measured the free length of any of these, thrown 500 lbs on, and re-measured?

Approx 18" free length for all factory front springs. You should be able to calculate compression distance based on the rate of the spring in question. Or are you asking about rears?

Noted. I am also considering replacing the ball joints with quality greasable ones to prolong life.

I would leave them unless they show signs of wear. I'm at 115K on my original uppers with lots of abuse and they are solid. My LCA bushings wore out before my lower ball joints did.

Stock 245/65-17's are 29.5" in dia and 9.6" wide. That means there is currently less than 3/4" clearance somewhere (which given how small those tires look in the wheel-well is absurd). I would prefer to keep the offset as it is. Where would it rub first with a 255/70-17 (31.1" x 10")?

The clearance issue is between the top inner shoulder of the tire and the knuckle where the upper ball joint sits. Options are different offset wheels (25mm works well for most sizes), spacers/adapters, or (ick) grinding the knuckle.

[fishsticks]

Also, I think your cooling post merited it's own topic, so I split it off for you. Found here now.

[Trail X]

There are a few spring options, with the stiffest option providing about 1.25 inches of lift in the front.
The "86's" and "87's" refer to the spring rate.
Most of this could have been found by searching.

I would never choose a spring based on the amount of lift it provided without knowing the rate. I choose spring rates by use and ride - soft for off road, stiff for on road. I know I want something stiffer than what I have, but without knowing the rates Im left to trial and error to get the right one, and then as mentioned the ride height changes.

Looking at the figures I have been able to find puts spring rates somewhere in the 65 – 80 n/mm range which roughly converts to 372 – 458 pounds per inch of compression. I am having trouble with these numbers given that Im currently running 295 lbs per inch of compression on my ½ ton, stockers rate at 320 lbs, and my old lift coils rate around 425 (poor substitute for not having a anti-sway bar to limit roll under load).

Knowing how the truck rode before I got my Deaver coils, if I went and put 400 lb springs on that car my wife would kill me. What I'm trying to accomplish is approximate the ride height of the desired spring. From there I can then figure out my spacer options to get the height to where I want it. Not knowing the rates makes that near impossible, and unfortunately I don't have the time or money to experiment.

As far as the numbers, "86's, 87's, etc", we're referring to the OEM part #s, not the spring rate.

Has anyone measured the free length of any of these, thrown 500 lbs on, and re-measured?

viewtopic.php?f=15&t=158

Post #3 has the spring rates for comparison. Note that 87s and 88s are apparently sold out nationwide, never to be replenished.

Oh, and good luck loading these with 500 lbs... they aren't flat ground, so would have to be loaded while in the strut assembly.

[80Flareside]

Oh, and good luck loading these with 500 lbs... they aren't flat ground, so would have to be loaded while in the strut assembly.

HS shop class we had a rack with 4 vertical posts welded to the corners of a 3x3 ft piece of 1" steel plate. A fifth post was welded in the center which the spring would be slid over and and free length measured. We would then hoist a 150 lb plate with the 5 hole pattern over, and down on top of the spring. We would measure the compression for the first 150 lbs, getting the initial rate, and then start stacking 45 lb free-weights on measuring the compressed length 45 lbs at a time.

We were able to measure exact rates on new springs and then check them every so often after installation. It was a great way for the instructor to demonstrate linear rates, progressive rates and fatigue over time.

If I had the kind of shop at home I really wanted something like that would be sitting right next to a Bridgeport and CNC plasma table.

[80Flareside]

The angle of the coilover unit on our trucks is not vertical. The bottom of the unit mounts approximately 11.5" away from the fulcrum of the LCA and the knuckle attaches at about 16" out. The top coilover mount is roughly in line with the LCA fulcrum. Higher rate springs are needed to compensate for the added mechanical advantage the LCA has. I would look at stiffer front coils for load handling of armor/winch. The extra possible lift is more of a "bonus" IMO. Also, GM undersprung these vehicles from the factory. Even with sway bars, the body roll is unacceptable. Z71 rears and 87/88/89 fronts help shore things up.

We have a member running RadFlo front coilovers with 600# springs IIRC. He's very happy with the ride quality. I'm looking at the possibility of FOA coilovers with similar spring rates. He and I both have 300+lbs extra on our front ends though.

OK, that make sense. I appreciate the patience. It took me 3 years to understand how the Twin Traction Beam on my truck worked, and thats barely a step up from a solid live axle.

Are there any off the shelf truck shocks with the correct or close open and closed lengths that could be easily adapted on top, and bushed at the bottom to fit? Many modern truck suspensions have a similar coil on shock design.

Approx 18" free length for all factory front springs

So therefore there is not really any option to select the rate you want, and then select a longer spring to level. For example. If I had the ride dialed in, but then added a 300# plate bumper, winch, etc, my front end would drop. I wouldn't want to increase the rate to compensate, as I would loose the handling and articulation I worked so hard to get right. Ideally I would either increase the pre-load, or get a longer spring of the same rate. Has anyone looked into custom length & rate coils to fit the oem style shocks? I would be surprised if they weren't more than $200-$300 a set. You might even be able to get progressive rates for that price.

Other option I mentioned was to increase the pre-load - which is what the spanner nuts do on a threaded body coil-over. Is it possible to insert a spacer either directly beneath or on top of the springs in the OEM shock to add that additional pre-load?

The clearance issue is between the top inner shoulder of the tire and the knuckle where the upper ball joint sits.

I really need to stop being baffled by the short-sightedness of automotive engineers.

[The Roadie]

Are there any off the shelf truck shocks with the correct or close open and closed lengths that could be easily adapted on top, and bushed at the bottom to fit? Many modern truck suspensions have a similar coil on shock design.

Excellent thought. The top threaded shaft isn't a huge problem. The bottom might be able to be adapted, and keep the overall length the same for inner CV joint safety. But the problem is the lower spring perch on the body of the shock. The formed sheet metal perch is retained on the shock body by a circlip set into a very shallow groove machined into the body. To put that perch onto a new shock body (presumably larger diameter to get more shock function) involves machining that most backyard mechanics don't have access to. And making a product out of them might mean you have to charge $300-400, and that's a tall enough barrier that the market shrinks even more. Full-up coilovers were going to be in the $1000-1200/pair range, and you should have HEARD the howls of outrage and frustration at what top-end products need to cost.

My attitude is that if you're going to wheel it hard, and have the trails to challenge the suspension (as I'm lucky enough to live next to), it's an expensive hobby. Safety doesn't come cheap either, for self-recovery gear and spares.

I really need to stop being baffled by the short-sightedness of automotive engineers.

It was only after I discovered what my low range transfer case could do, that I realized they had bolted the front diff to the SIDE of the oil pan and that was a major reason there were no diff drop lift kits available. And I started talking to the lift companies and NONE of them wanted to touch the platform except for spacer style lifts.

[Trail X]

Are there any off the shelf truck shocks with the correct or close open and closed lengths that could be easily adapted on top, and bushed at the bottom to fit? Many modern truck suspensions have a similar coil on shock design.

For the front shocks? Not that we've yet found. The big issue is the lower mount, as it's a squeeze mount that connects to an offset yolk. Seems a lot of truck IFS designs just offsets the strut from the CV, but not on these trucks. The strut is centered on the CV, using a dog leg lower yolk. Bayonet style shocks aren't rare, but pinch-style bottom mounts seem to be. At least, ones that can take the bending moment from the dog-leg are. Although, I don't think anyone's been that unhappy with Bilstein HDs to ever put a lot of effort into it. But I guess you really enjoy redesigning the wheel eh? That's good, we need options.

Other option I mentioned was to increase the pre-load - which is what the spanner nuts do on a threaded body coil-over. Is it possible to insert a spacer either directly beneath or on top of the springs in the OEM shock to add that additional pre-load?

Pre-load is a misnomer. Sorry, just annoys me when people call it that. It's just "lift that does not affect the down-stop of the suspension".

Most of the lifts on the market provide a mix between inside and outside shock lift. You can't do it all outside the shock because the CV shaft can get over extended if you go beyond ~1.5" of outside-shock lift. It varies between vehicles though.

The clearance issue is between the top inner shoulder of the tire and the knuckle where the upper ball joint sits.

I really need to stop being baffled by the short-sightedness of automotive engineers.

I'm not sure it's short-sightedness. There are a few things that leave us off roaders scratching our heads. However you can understand the reasoning behind most of them. The ball joint being so close to the wheel's center plane helps contribute to that amazingly small turning radius.

Just wait till you take a look at the front diff... that should give you another good baffle.

EDIT: I should stop taking 20 minutes to draft emails... that way Bill can't beat me to the punch!

[navigator]

EDIT: I should stop taking 20 minutes to draft emails... that way Bill can't beat me to the punch!

I do that all the time, start a response, get distracted with work or looking up something, post and someone else has said what I was thinking!

[v7guy]

I've wondered for about 6 months now if it would be feasible to make a sleeve to fit around the lower tube of an exsisting shock with the groove for the bolt/pinch part of the dogleg. Could probably incorporate a lower spring mount so we could just use whatever shock we wanted. Maybe it would be fine, or maybe it would bend the shock tube. I dunno.
It would be relatively simple to turn on a lathe. Bet somebody could market them for relatively cheap if it was without a lower spring mount.
It's the only way I can think of to open up the shock options for the front.

[The Roadie]

I've wondered for about 6 months now if it would be feasible to make a sleeve to fit around the lower tube of an exsisting shock with the groove for the bolt/pinch part of the dogleg.

It would indeed have to handle the spring, but you'd need to choose a short shock. The alternative shocks you want to pick from would all have a larger diameter, so the machined adapter would make the shock significantly longer.

[Trail X]

How would it hold on to the shock alternative? Just clamp force? That spring is so strong that it could pull your shock out of the hold.

[chevycrew]

you could have the new shock slide into the sleeve/lower mount, then once fully seated a bolt would be placed through the lower shock eye to lock it into place.