Replaced rear coils - can they be installed upside down?

Chickenhawk

Original poster
Member
Dec 6, 2011
779
I noticed the rake on my 04 is much less than my wife's 07, and I wanted to try changing rear coils. I often drive many miles over bumpy northern roads with 600 pounds of shotgun targets in the rear, so it wouldn't surprise me if the rear coils were starting to sag a bit.

I pretty much gave up on trying to read my OEM spring rates as nothing in any of the many helpful tables seemed to match up. The tag says YEX 15097377 and YEW 15097376. I assume GM changed those part numbers over the years.

I replaced them with AC Delco 45H2133 (19261981) from Rock Auto. The length was about the same, but the diameter is slightly larger. They also weigh just under 1 pound more, so I assume they are a slightly higher spring rate.

I followed instruction on this site. I jacked up the rear axle, put jackstands under the frame, lowered the diff a bit and unbolted the bottom shock bolt and then lowered the diff until the bolt slid out freely. I then lowered the diff all the way. The OEM springs pried out fairly easily with a big screwdriver and I managed to force the new springs on with a pry bar.

I am now sitting here admiring my work, but then it suddenly struck me. (Not the springs - that would hurt - but the thought.) I never bothered to check to see if there was a difference between right and left, or even top and bottom. They looked the same to me so I just fired them up there.

Can you install the rear coils upside down or on the wrong side? Once installed, is there a preferred alignment for placing the coil ends? They seem to fit just fine any way and there doesn't seem to be any ridges or stops on the bottom spring perch but I am the guy who always gets the toast landing on the floor butter side down 90% of the time.

Thanks for the help from folks who have done this.
 

IllogicTC

Member
Dec 30, 2013
3,452
As far as I'm aware there's no up and down to them, unless marked or have some special design on one end compared to the other, etc.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The Avalanche Z71 springs some use for upgrades are progressive, and have a tag that says this side up. That side is the section where the coils are closer together and it comes with a plastic cover to muffle the clanking that might happen as the coils collapse under load and touch each other (the way progressive springs work).

I haven't seen any directionality that will matter on the OEM springs. If they fit on the perches, don't worry.
 

Chickenhawk

Original poster
Member
Dec 6, 2011
779
Interesting. Thanks for the input!

Just for fun, I measured the I.D. of the OEM coils at their smallest point. One end IS slightly smaller (by about 1/4 inch) than the other. The other interesting part is the fact that the smaller end was installed at the bottom.

So basically, as Roadie says, they fit in the rubber bushing on the top; they fit into the perch at the bottom, so they really can't be installed upside down. I am certainly not going to go through the entire exercise again to match half an inch difference in inside diameter, especially when GM seems to have designed them for people like me who forget to check BEFORE they slap on the new ones.
 
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Chickenhawk

Original poster
Member
Dec 6, 2011
779
Oops, had to correct my post. The smaller end was at the BOTTOM on the OEM springs, at least according to my calipers.
 

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