Lil’ Help - Question About ZW7 Code and Suspension Upgrade

[Scott in AZ]

I’m doing homework on suspension for my 2001 GMC Yukon SLT 4WD. I’m leaning towards Bilstein B6-4600 front and rear, because seems like can’t go wrong with this choice. The spec for my front shocks are Bilstein PN 24-065009. My rear shocks are Bilstein PN 24-143806.

On Bilstein’s webpage there is a note stating “If vehicle is equipped with ZW7 Premium Smooth Rode Nivomat Suspension you must purchase Bilstein spring PN 199021 in addition to the damper.”

My original window sticker has a bullet that states "SELF-LEVELING REAR SHOCKS". I have RPO code ZW7 and G65 on the decal in my glove box. Does this mean that I have ZW7 Premium Smooth Ride Nivomat suspension and will need to replace the big rear springs when I replace the rear shocks?

Edit / Update - Yes, I am almost sure I have Nivomats, but would realy appreciate any input on which rear shock/dampener/spring to use.

Is there another “go to” front and rear shock combination that will offer equivalent good performance, and keep the old OEM springs? Or should I replace the springs regardless ? This SUV is not my daily driver but I still put 3-4K miles per year, mostly road driving with some forest service double-track mountain bike access, but no rough off-road and no heavy trailering.

Thanks!

 

[mattbta]

If you’re not replacing the rears with Nivomats, you must change the springs, too, as they mention. Other members have said it gets pretty squirrely on the highway without stiffer springs when changing to a standard shock with G65 & ZW7. Keep in mind that the rear height will raise, too. My original Nivomats are still doing their job well in my 2004.

I do have 5100’s up front and they’re pretty stiff. Considering the 4600’s.

 

[Doubeleive]

leave the nivomats alone, change the front to bilsteins
nothing on the market will do a better job than the nivomats
if you decide to do it anyway I highly recomend not gretting rid of the nivomats because you will want to put them back on after you figure out the line I just wrote above this one.
besides if you get rid of them you will wish you had not, they are not cheap they used to be $500-600 (each) last time I checked, if they are even available anymore.
anyway just my .02 cents worth of advice

 

[Fless]

The Nivomats are fairly fat (girthy, LOL) compared to a conventional shock; here's a pic of mine on my '04. Same experience as @mattbta, mine are still doing great and re-level after adding weight and driving a block or two.



The G65 code is for the Nivo shock, and the ZW7 springs are softer than Z71 or standard springs.

I replaced my front shocks to the specified Gas-A-Just model (KG5040) from KYB and haven't really noticed a difference. Stay away from the cheaper KYB Excel-G; they don't have very good reviews. Check the catalog for model numbers if you're interested. https://www.kyb.com/

EDIT: you can test your rear shocks by measuring the bumper height, then adding 200-400 lbs of whatever to the rear. Measure the sag, then drive a few blocks to let the Nivomats adjust. Then re-measure the height at the same place on the bumper to see if they came back up to your liking. They are manual adjusting so they take a little "work" to recover.

 

[Scott in AZ]

You guys rock. This is all great information. Thanks Matt, Wes, and Fless.

Yep, I have Nivomats in the rear. Mine look like those above. I guess I will leave them in place, keep the self-leveling feature save some $. Replace the front, probably with Bilstein. But I wonder about wear and tear on the OEM Nivomats. How long do they last? I've got 170,000 miles on my 2001.

In doing some homework on this I learned that both Bilstein (B4600 line, about $500 for the kit) and Monroe (OESpectrum line, about $250 for the kit) offer a replacement "kit" that features springs and shock/dampeners, with the same caution that you mention that the OEM springs that come with self-leveling Nivomat are too soft for standard suspension. I would lose the self-leveling feature, but I would gain zero-time on the suspension.... maybe I'll look around for Nivomat replacements.

 

[Tonyrodz]

Those Nivomats last a long time. I replaced mine years ago, had maybe 250k(?) On them. Still worked great too. I'd say yours still have lots of life left.

 

[TahoeRestore]

Coincidently I just finished my parts order ($2K) for a complete steering & suspension rebuild on my 2003 Tahoe with 160K miles and a G65/ZW7 suspension. I had loose steering from an aging steering gear & other worn parts. I also has a leaking Nivomat. After a good bit of research, I decided to stay with the Nivomats. I loved the original smooth ride and occasionally trailer a 5,000 lb boat with a hefty tounge weight adding value to the self leveling feature. The best deal I found was at Rock Auto for $280 each. Part number - SACHS 030239.

FYI - My plan is to keep this truck. This work follows a complete paint job with all new exterior lighting. You can find that post on this forum. Next, will be the sound system and a few interior improvements. I will even renew the power train should it ever have an expensive failure.

 

[Hops4Pops]

I agree on sticking with the Nivomats. I just looked up the SACHS 030239 part on RockAuto. It shows 1 remaining. Perhaps you already purchased yours. If so, great! If not, here are the ones I put on my 03 Yukon:
GM Genuine 580354
Hope it helps you or someone else if needed.

 

[TahoeRestore]

I agree on sticking with the Nivomats. I just looked up the SACHS 030239 part on RockAuto. It shows 1 remaining. Perhaps you already purchased yours. If so, great! If not, here are the ones I put on my 03 Yukon:
GM Genuine 580354
Hope it helps you or someone else if needed.

Thanks for the heads-up. I ordered mine when when there were 3 in stock so there's 1 left.

 

[clandr1]

One of my Nivomats started leaking around 2017, so I replaced the rear shocks and springs with the Bilstein parts you referenced above. I've been totally happy.