My 85 IROC/Z has rear spring codes 8NN and 9NN. I have seen other IROCs with 8NL and 9NL. I thought the difference was because I didn't have T-Tops and they did. Here I find an IROC without T-Tops and it has the 8NL & 9NL spring codes. anybody know why the difference?

 

Wish I could answer your question. My '85 has 8NL & 9NL, and it is a hardtop. I'm sure someone will shed some light for you.

 

I looked at my spring codes on my 1985 1C5 Iroc-z and they were the 9NL and 8NL. I also checked the RPO codes on two other 1985 1C5 Iroc-z that I have copies of and they were the same. My car was made in the 2nd or 3rd week of May, I then looked at the "black 1990 1LE 5.7 #25"RPO codes that are on Third Gen and noticed that they were like yours the 8NN and 9NN. Maybe, late 1985 through 1990 had the 8NN and 9NN. I don't have any other RPO codes to look at. If that's not the case yours has the same as the 1990 1LE.

 

If it helps, i have a 92 RS with a 305 that has 9NL and 8NL.

 

Your RPO code information on your 92 RS springs tells us there wasn't a change of springs in late 1985 to 1992. If that's the case, mr396's 1985 Iroc-Z has springs with the same 8NN and 9NN code as the 1990 #25 1LE. It looks like we should check to see if all 1LE Camaros have that code and if anyone else has them on their Camaros. They might be a stronger rated spring?

 

The springs were computer selected based on the weight of the options. I did not compare all of the options on these labels but I'd bet that there are total vehicle weight differences that required different spring rates. I would also bet that the minimal differences in the spring rates are why there are only one rating for aftermarket replacements.

 

Here is, I think yo soy el warg cool california IROC. Both are cars have just about the same options except his has the T-Tops and my IROC has G80 posi. yo soy el warg I noticed on your 1C5 it has the D88 option, decal stripe. I thought 1C5's were decal delete?

 

I've also noticed that before on mine and also on two other 1985 1C5 California Iroc-Z RPOs that I've got pictures of and will try to post. In fact there is another 1C5 identical to mine with all the same options and it has the D88 listed. Mine was built 91 units after this one according to the vin #s. I've also got one Rpo picture of a red 1C5 hardtop that has the D88 listed. I'll try to post it also. Another person we might ask is Calroc to see if his black 1C5 has the D88 also listed, but not on the car? I'm thinking that maybe the Z5V RPO I've been trying to figure out deletes the stripe, rear spoiler, hood louvers, and some emblems on the rear bumper, since all 1C5s have the Z5V listed.

 

Here's the pictures of the two SPIDs

 

Mine also has the D88. No definitive explaination. It came off the truck as all the 1C5's I saw back then without decals/stripes.

 

I just looked at the RPO codes in a 1989 Iroc-Z with the G92 performance axle and it had the same springs that you have on yours. They only put that in 1426 cars in 1989. They apparently put those springs in if you ordered the G92 performance axle.

 

You mite be on to something.

 

Here is a cool thread on the subject. https://www.thirdgen.org/forums/hist...ur-spring.html