1997 - 2002 Express / Savana coil springs

[markopolo]

Here's what I found for replacement coil springs for 1997 - 2002 Chevy Express 3500 / GMC Savana 3500 vans:

Dayton 350-1205SD: 1.000" diameter bar, 15.250" free height.

Supersprings Supercoils SSC-13: 1.000" diameter bar, 15.30" free height.
Tuftruck TTC-1616: 1.000" diameter bar, 15.375" free height.

Moog 81012: 1.031" diameter bar, 15.535" free height.

The Moog 81012 with greater diameter bar and more free height would give the most lift.

I found these interchange numbers for the Moog 81012 coil spring:

Moog 81012
ACDelco 45H0344
Napa 277-3439
Husky SC20476
Raybestos 585-1344

------------------------------------

I've decided to try a taller spring than those but am not sure if will work without modification. My van is heavy and has the 6.5l diesel engine. I'll have Airbags in the rear to lift that so the van is level. The coil I'll try is:

Moog 81008: 1.031" diameter bar, 16.657" free height. It's more than an inch taller than the coil springs mentioned previously. Booster has helped me a lot with all the calculations needed and I'm prepared to cut this spring if necessary. It'll be a few weeks before the springs get delivered but I'll start this project as soon as they arrive and post info.

Interchange numbers I found for the Moog 81008:

Moog 81008
ACDelco 45H0342
Napa 277-3437
Husky SC20472
Raybestos 585-1342

You'd have to verify all the above info for yourself as this is not something I got to know much about until about a week ago so I still have a lot to learn.

-----------------------------

Just a final note about 1996 vans. A lot of sites list some of the part numbers noted as fitting 1996 vans. You really have to triple check that if you have a 1996 van. From GM:

NEW FOR 1997:

* Vehicle completely re-engineered with body-on-frame construction (became available as a 1996 model in the latter part of '96 model year)

[markopolo]

I may refer to this as a lift but really all I want to do is restore the heavily loaded van to GM's specified trim height. Most of the added weight on our Class B Vans is permanent.

I found the following Front Trim Height (Z) Specifications for 1997 - 2002 vans:

Application: All Vehicles
Service Checking: 3.74 in
Service Setting: 3.74 in ± 0.236 in
Side to Side Tolerance: 0.5 in

How to determine the Z Height Measurement:

1. Lift the front bumper of the vehicle up about 38 mm (1.5 in).
2. Gently remove your hands. Let the vehicle settle.
3. Repeat this operation for a total of 3 times.
4. For all vehicles, measure from the pivot bolt center line (2) down to the lower corner (5) of the steering knuckle (1) in order to obtain the Z height measurement (4).
5. Push the front bumper of the vehicle down about 38 mm (1.5 in).
6. Gently remove your hands.
7. Allow the vehicle to rise.
8. Repeat the operation for a total of 3 times.
9. Measure the Z dimension.
10. The true Z dimension number is the average of the high and the low measurements.

z trim height.jpg

The average Z Height Measurement for my van was 1.46" - that's 2.28" below specified. Restoring the van to the full Z height trim measurement plus the 0.236" tolerance would increase the measurement from the wheel well to the ground by 3 inches.

I want to limit the height increase at the wheel well to 3" or less to remain within the specifications. Every 1 inch increase in the compressed coil height looks to add 2 inches to the wheel well height. It looks like I'll need 1.5" increased compressed coil height.

Here's a calculator to help find out what the load on your springs will be: Automotive Spring Rate Calculator

from the site:

*Note: If you are running reverse offset wheels, then measure to the center of the wheel.

You need to know the weight of the front of your van. Most of the front end weight is sprung, maybe 5% unsprung and even less partially sprung - just guesses on my part. Spring angle is a factor also. The coils in my van look to be close to 90 degrees, or not much less than that.

I calculated a range of weight load on the spring ranging from 4,000lbs to 4,800lbs depending on if I choose low or high inputs. That's a range of 0.5" 0n the Moog coil springs. That 0.5" would equal 1.0" at the wheel well. The numbers kept indicating that I would need a coil spring in between the 15.535" 81012 and the 16.657" 81008.

I chose the taller spring because it looks to me that series of coil spring are all the same basic spring with additional bar length to make them taller so cutting to get the exact height I want would appear to be an option. The plan is to try the taller spring and see if it settles in at all.

Moog 81004 to 81012.JPG

[booster]

Marko makes a very good point about calling what he is doing, and what others have done, a lift. Technically, it isn't a lift, as all it is doing is restoring the van to where it should have been in the first place, or some amount less than all the way to stock height, that is higher than before the change.

A true lift goes above factory desired ride height, and I think only Photog has done that much height increase. Several of us got back to the factory desired height, and some went up some but not all the way to factory height.

I think the main thing is the that a true lift can have negative suspension consequences, but getting closer to original recommended specs usually will be an improvement.

[markopolo]

The Moog coil springs were delivered yesterday. They are heavy! I'll slowly get going on this project.

Here are photos of the difference in how the ends are finished:

coil other end.JPG

coil flatter end.JPG

One end is a bit flatter and I'll use that as the top of the coil.

I have the OTC 7045B Front Coil Spring Compressor so hopefully that helps.

OTC 7045B Front Coil Spring Compressor.jpg

[booster]

Originally Posted by markopolo

The Moog coil springs were delivered yesterday. They are heavy! I'll slowly get going on this project.

Here are photos of the difference in how the ends are finished:

Attachment 3181

Attachment 3180

One end is a bit flatter and I'll use that as the top of the coil.

I have the OTC 7045B Front Coil Spring Compressor so hopefully that helps.

Attachment 3179

Did your springs come with a paint mark on them to identify the ends? The ones I just got for my Buick Roadmaster have a white paint mark, and have the ends similar to what you got. I do think the flat end goes up. I think I remember seeing something about the paint mark in the factory service manual, so I will look for sure.

[markopolo]

No paint mark that I can see on the coils. I'll see what the coils that are on the van look like when they come out. The shop manual says taper goes up. Not much of a taper on these coils but one end is clearly more tapered than the other.

I'll try to use the 2003 & newer front coil springs replacement & installation procedure. Those instructions show the use of the OTC 7045B compressor & say flat end of the coil up.

[markopolo]

Mini update:

The OTC compressor works great. I managed to get a plate stuck in the coil but that was user error as I had positioned the plate too low. It got pinched on one corner and wouldn't let go. I've used it to remove and install a coil now and it does the job.

It's really looking like the 81008 coils are too tall. If ordering again I'd get the 81012. I'll go ahead & install the second coil to confirm & get measurements but will probably end up having to remove them.

The 19 year old OEM coil I removed from the van is 0.9375" diameter bar, 15.25" free height.

[markopolo]

Update - It's looking like the 81008 coils will be fine. I'm surprised but happy. There's more at play here than just the coils. Front and rear sway bars, rear air bags, the stiff van frame all factor in.

I will take a drive tomorrow to let it all settle in and then measure the Z trim height to see how it compares to the shop manual specifications. My guess is that lift in the front will be 2.75". I already installed the Air Lift bags for the rear so I'll be able to set them so that the van floor is level.

I don't know if they'll work for all 1997 - 2002 Chevy Express 3500 / GMC Savana 3500 Class B vans as mine has the 8 cyl diesel up front. I have the equivalent of 5 batteries forward of the midpoint of the coach also.

Those two upgrades will let the suspension work better and should result in a more comfortable ride. The rear leaf springs are well up off the overload leaf and the front is well up off the bump stop.

[markopolo]

The front end lift settled in at 2.25" after a long test drive on rough country roads. The Moog 81008 coils turned out to a great choice.

The Z Trim Height setting specified in the manual is: 3.74" in +/- 0.236". I measured it to be 3.8125" so it is nicely within spec.

Leveling the van requires approx 60 psi passenger side and 70 psi drivers side. If the front settles a bit more over time then I'll be able to reduce those pressures. The rear air bags are really fun. An on-board and plumbed-in compressor would be handy as the relatively small volume of air in the bags makes precise control difficult. Just checking the pressure with a gauge can cause a 1 psi drop.

Some photos:

Old & new coil springs:

new and old coil.JPG

Front bump stop before:

bump stop old coil.JPG

Front bump stop after:

bump stop with new coil.JPG

You can see how much more suspension travel is available before any "bottoming out" could occur.

Rear leaf springs are up off the overload spring now:

rear off overload with air bags.JPG

rear off overload with air bags 2.JPG

[markopolo]

Two views of the van:

It'll turn 20 years old next January and is still is good condition. An interior reno might be a way to celebrate the milestone.

lift front view.JPG

lift from distance.JPG

[booster]

Very nice results, and a very nice looking van, especially for it's age.

Marko will be the first one here to use a spring made with 1.03 wire, so it will be interesting to see his impressions.

Although his van has a slightly different lever ratio on the spring, it is close to the later Chevies, and on those many think the stock and replacement springs with 1.0" diameter wire are too soft and prone to "porpoising" or "wallowing" depending on your terminology. Some, definitely not all, think the aftermarket springs with the 1.05/1.06" diameter wire are too stiff, giving good control but uncomfortable ride.

Perhaps a longer spring like Photog used (his is 1.0" wire and is said to wallow some) but with the 1.03" wire might give a good middle ground of lift and comfort and the later, low riding Chevies.

[markopolo]

Just a few test drives so far. It absorbs oncoming bumps much better. What I'm describing here is when you see a bump in your travel path ahead and then impact with it - it's a much more minimalized event. The rebound seems sharper. I guess the stronger coils are able to lift the van quicker. There's no porpoising.

There's one road we sometimes take that is very bumpy - I'd describe the impacts as "bang" previously. Driving on that road is much improved. It's not car like - you still know you're in a cargo van - but definitely an improvement. If there was an indicator scale between the previous suspension in the van and our Ford Escape SUV on rough roads I'd say it has easily moved half way between the two.

I will experiment with tire pressures and air lift bag pressures.

Disregarding lift for the moment; what would the ideal gap between the rear leaf spring pack and the overload leaf be?

[booster]

Originally Posted by markopolo

Disregarding lift for the moment; what would the ideal gap between the rear leaf spring pack and the overload leaf be?

On your setup you probably wouldn't even need the overload at all, because you have the beehive overload inside the airbag (wish we had that) which should pick up any really big bumps.

I haven't looked really closely at ours since we got back from the first long trip after the re-arch of the overload, but it was in the 1/4" range of clearance when first done. The van is back on the ground so I will look today. It does hit the overload on ours before the airbag bottoms out, which I think is important. Having the extra clearance to the overload really smoothed out the small/medium bumps and noise which would still cause the overload to hit when only 1/8" of gap, and also allowed a bit lower bag pressures.

[markopolo]

Using spacers and blocks for lift is probably worth mentioning here. I think you can get up to about 2" lift using them.

I first thought of using them; quicker, cheaper & I'd get some lift. The primary deciding factor for me was looking at the leaf spring pack of the rear suspension on my van. They were pretty much flat and the van was riding on the overload leaf all of the time. It just all looked stressed. Adding blocks would not help either of those two problems. The second deciding factor was the adjust-ability of lift from air springs. I could adjust the height of the rear up to around 3 inches.

I also considered spacers for the front coils. I got some advice from Booster and did a bunch of Googling. The spacers would give some lift but would permit the coils to be compressed more than the original suspension design allowed for. By the time the bump stop started to protect the coil it would compressed more than it could have been prior to installing the spacer. The risks could be breakage of the coil or increased likelihood of the coil sagging further.

[markopolo]

Just a note about possible added expense when making a major change in ride height. I got the alignment done and it cost more because additional labor/time was need to to punch-out the camber/caster knock-outs to allow greater adjustments.

I don't know if that could have been DIY or not but worth looking into when doing this work.

[etbike]

Sorry I'm stealing this thread. Just signed on to the forum, can't find how to create a new topic?
I recently bought a 05 1500 high top conversion. I then sold my 00 standard conversion that I had owned for 8 years.
I have found the 05 to ride like a marsmellow, porposing in the front a lot. The van only has 59k on it. Also, I nearly sold the thing after I brought it back to Wisconsin from Florida. All over the road in the wind! I've never had to fight something like that in my life.
So I set about to make changes. Michelin tires, defefenders. Allignment. Kyb gas matic shocks, bilsteins were not available for this year. Poly bushings on the front sway bar. And I installed a hell wig bar on the back. Have made improvements but after I installed the rear bar I became very aware that the front was the real problem even with the new shocks. When I back out of my driveway I can just feel the bounce in the front, and it's the main concern in body roll when cornering. So, my next thought is springs. I've read this post and looked in the moog catalog and see my springs are .93 dia. They may a 3500 spring that is 1.03. The load rating is nearly 1800lbs heavier for those springs. Is that too much?

[markopolo]

Just a note: Great topic here: http://www.classbforum.com/forums/f8...190v-1552.html for vans newer than 2002.

etbike - they could be too stiff. I'm finding mine to be on the firm side as I get to drive it more and will try lowering the front tire pressure to see if that's better. On good roads they're great but somewhat harsh on bad roads. The van is empty right now, no gear, no water, no cargo box etc.

Have you tried increasing the front tire pressure? On the 3500 vans the door sticker on RV conversions often show 50psi front and 80psi rear. Lots of folks run up to 65psi front. I don't know what the recommended pressures are for the 1500 vans. Load range E tire on the 3500 vans.

[booster]

As Marko and many others have seen, taller, higher rate, springs are going to firm up the ride. How that increased firmness is perceived is all over the map do to individual ideas of ride quality. On the same setup, some will say it is horrible and others will think it is just right. It may depend on what folks drive for daily drivers and how mushy the van was before the changes.

As is shown in the the referenced handling thread, there is a very fine line between trying to get as soft a ride as possible while still gaining height and staying away from too soft bouncing and porpoising.

It will be interesting to see how the perceived harshness changes on Mark's van once he puts the cargo box and loads back on the van, as that will change his front wheel weights quite a bit, I think. I don't know which way it will go, but he also may get a bit higher in the front which also will change the geometry a bit.

In our 07 Chevy based Roadtrek, I wondered how much noise contributed to the perception of rough ride, and how much was the actual rougher ride. The trucks have much less rubber between the road and body so a lot of noise comes through the spring to frame and body. Add to that the fact that our Roadtrek generates some loud booming sounds (maybe from the tanks hitting the floor?) on very big bumps and it can get a bit scary loud sometimes. Bottom line was that I drove the same route around a variety of roads around our home, from 30-70mph, twice. Once just normally, and again with earplugs in. I perceived the van to be substantially smoother with the ear plugs in. I thought that might happen, but I was surprised by how much it was. I got into looking at that when I got my old Buick Roadmaster, that has the same body on frame build as the van, but is very quiet. After I replaced all the front suspension and steering parts, including springs and A arms, it got a lot quieter do to getting rid of looseness and old hardened rubber bushing noise. It also seemed to ride smoother, but there is no reason to believe it did, as it should have gotten stiffer with new springs instead of 20 year old saggy ones. Very interesting.

[markopolo]

Great point about noise affecting perceptions. That's what got me started thinking ride harshness. I've been getting a loud bang inside the van on big bumps and it is startling.

I think it could be a recently modified bathroom door swinging open then slamming closed. If the noise isn't from the door then it could be from the rear dinette table. The rear edge table rests in a track and one fold down table leg supports it. It's very stable but only gravity holds it down so it could bounce. We used to leave the rear set up as a bed but now leave it set up as a dinette.

[WJones]

Regarding the noise vs perception ... very interesting indeed!
How we feel the handling of our vehicles is subjective and I'm starting to think noise is a bigger factor than what we might think. I have - or perceive having - minor handling problems with my Roadtrek 200 Popular with strong crosswinds. I've started to notice how loud the wind noise is when this occurs. I feel the van move to the side very slightly, but I'm pretty sure that the howling I hear at the same time tricks me into thinking the problem is worse that it is in reality. When driving my car in even stronger crosswinds, it will react like the RT, but without the noise ... and it doesn't bother me at all.
I'm tempted to try your ear plug idea, just to confirm this.

William