I have searched the site a lot and came across some spring codes but not the follwing ones:

Front:
BUN, BUM
BUK, BUJ
BUH, BUF

Rear:
NWA, NUZ
NUY, NUX

I got these codes from GM who says they were the ones available to my car (85 fb V6 with F41/Y99 perf suspension). They for some reason couldn't tell me the spring rates. I am trying to figure out what rates these are so I can get a good match as the handling is great and I definitely don't want weaker ones (or radically stiffer like a lot of the drop springs).

Can anyone help out here? I am lost.....

thanks.

 

If you go to the moog website you can find out what the spring rates are. You may need to measure the diameter of your current springs with calipers. I think that someone posted a chart with all of the info on this forum about 6 weeks ago.

 

Well, that's the thing, I don't think the aftermarket ones are necessarily exact replacements. They seem to have only about 3 different rates for fbody's (347, 421 and 707) whereas there are a couple dozen of these 3 letter spring codes from GM (i have seen a couple lists posted on this site but none of them include the ones I listed above). I also read multiple times in searches that irocs have 550's up front and GTA 500's, but MOOG says the replacement is 707.......so i don't know??

 

The number of springs will depend on the year of the car. For my car there are 4 rates and two of the rates have 2 different free heights. That is a total of 6 part numbers for the front and there are two for the back so that makes 12 possible combinations of springs for my car. If you have a different engine or year there will be different options. There are several things that caused GM to use different spring rates.
Federal-Mogul Aftermarket USA & Canada - Moog - Chassis Parts
click on catalouges then make/model look up and go from there.

 

yeah, that is the site I was looking at. I looked up 89 too just now and I saw 5 different front spring #'s (5598, 5600, 5602, 5604, and 5662). The first 4 are all variations of the 347 rate and the last is the 707 rate (although the site says 748, i heard that is a mistake???). I don't know, maybe I am missing something though . That's what I mean though, all those options are just whether you have ac or auto and it is only 2 rates. I looked through most of the other years and a 421 is added and thats it.

Also, the only option for any 3rd gen on that site for rears is the 5665 (or cc635 which is variable rate and not stock anyway). So that definitly can't be accurate for direct replacements since GM listed 2 options for 85 alone (see my list above).

One other thing that I noticed was that for 85 (my year) they listed the 5608 as the heavy duty option for the V6. Well they also list 5608 in subsequent years for the V8. That doesn't make much sense as there is definitely a bigger weight difference then just whether or not you have ac.


Do you see what I mean though? I am very confused......

 

any minor variation was a different part number. 2 heights for one springrate is two numbers. Even if it was only 1/4" difference. 5 front and 4 rear is 20 codes. Do you really want stock replacements? You can do so much better.