[RUQWIKR]

Originally Posted by Ryephile

I'll put that on the to-do list. Thanks.

Take a look at the FEA knuckles you bought. You should see the same but two new PN's. Not very focused, but, you can see the mark next to the old FE4 (before commonization with FEA) PN.

[Ryephile]

I was able to use my phone to take a picture of the casting numbers. On the right I have 84089878, the "ZL1 series". Any idea what the difference is between that and the new 84258572? The latter # is in the FEA kit I have (for sale). They look identical in terms of bushings and ball-joints.

[RUQWIKR]

Originally Posted by Ryephile

I was able to use my phone to take a picture of the casting numbers. On the right I have 84089878, the "ZL1 series". Any idea what the difference is between that and the new 84258572? The latter # is in the FEA kit I have (for sale). They look identical in terms of bushings and ball-joints.

Higher rate bushings (I think it was in two positions) and casting beefed up. I bought a pair of the FEA ones and will put in when I rip the back end apart to put the solid cradle bushings in since many of the same things have to come off. The front FEA ride links were not bad to swap.

[sadpanda]

First, awesome work on getting P/N's pulled together. Very concise.

As an ATS owner I've been lurking for some time but I felt compelled to jump in on this one...

There have been many questions in the Caddie community about parts interchange between Camaro6 and ATS/CTS mainly because Camaro and the V-series cars get all of the aftermarket love.

Camaro6 seems to have many different part numbers for for all of the suspension variants but unless someone with SEMA Tech transfer access or a factory/GM rep chimes in we are not going to be able to verify any differences solely by catalog hunting. On the contrary I'm convinced there is actually almost NO variability in the entire Alpha lineup.

Case in point, I was pulling part numbers for all of the major components working from the CTS side of the catalog and found a number of interesting interchanges, many across the entire line...

http://www.cadillacforums.com/forums...l#post17321050

Highlights and deductions:

1. Alpha chassis (and pickup points) will be the same for all 15+ cars
2. Difference in track width between ATS/Camaro/CTS is all in wheel offset
3. Engine cradles are primarily tailored to engine package and somewhat to vehicle weight (SS same as CTS-V for example)
4. Rear cradles are tailored to power and vehicle weight. ie CTS-V is different then SS because of power, 1LE different then CTS-V because of weight, ATS-V is very close to SS in weight/power but only gets MRC and e-diff... There *may* be some tuning here in the pickup points with the cradles, however:
5. Most major hard parts are the same across the line with variants for MRC and brake packages (ie trailing arms, knuckles, tie rods, control arms etc)
6. Given the above, geometry is probably the same across the line and most of the setup variation comes from swaybars, shocks, springs, bushings, alignment, tires, stabilitrak tuning. Given the level of homogeny with the rest of the parts, *IF* any tuning does exist in the cradles it would have to be slight.

I'm not ruling out the possibility of ZL1 and 1LE getting some extra love over the CTS-V in the form of bespoke parts... However, development and tooling for something as large and complex as a rear cradle are enormous.

Just because the part numbers are different does not mean there is ACTUALLY a real or significant difference in the part. Identical parts are typically given different part numbers if they come from different suppliers.

There are other reasons for Camaro to have special part numbers:

The entire Alpha family is made at the Lansing Grand River plant. From what I've seen of modern assembly, parts are staged/binned away from the line and are delivered to plant JIT. Camaro has much more ordering flexibility with suspension options whereas Caddie ties the suspension variations to the trim level. Easier to bin parts for Caddie then Camaro.

Camaro offers post sale upgrade paths via GMPP, Caddie offers no post sale upgrades... Having catalog friendly 'package' part numbers for Camaro makes sense.

If someone has access to shop manuals, or a buddy that works at a dealer/alignment shop, the alignments specs for all the Alpha cars would be enlightening.

[Ryephile]

sadpanda: Very nice post and thank you for the information. Your post on the cadillacforum showing all the underbodies is excellent. I think we're on the same page regarding intra-Alpha platform parts interchange probability. It gets even more obvious seeing identical brake part numbers across both brands. (e.g. ATS-V and SS 1LE same rotors, CTS-V and ZL1 same rotors.

[sadpanda]

No don't! These are gold. Let me get them typed up tonight or tomorrow then you can remove. Any chance you can grab the CTS/ATS V and the ZL1/1LE (if they are different)

[sadpanda]

I've asked mods to enable [table] code... Until then, here is a JPG.

[cooper1965]

Thanks for the work @ sadpanda, much easier to view!

[Ryephile]

Originally Posted by sadpanda

I've asked mods to enable [table] code... Until then, here is a JPG.

Dropbox is kind of flaky. I added it to my attachments for those that can't see it.

Also, it's important to note that alignments are more or less a side-effect of the suspension, its inherent adjustability, and the calibrators choices and trade-offs. For example, more caster will give a stronger on-center feel but also makes steering effort off-center heavier, but also gives more dynamic camber. The decisions of the calibrators between Camaro and Cadillac intentionally choose how they want the "feel" of the car to be within the constraints of the hardware.

This alignment data also doesn't mention the FE4 or FEA "track" settings, which are much more aggressive in terms of static camber, yet can still be applied to all tuning levels as the driver sees fit. Moreover, GM's alignment recommendations aren't gospel for all drivers. Many of the 1LE guys are probing the alignment window to push the car to the maximum, street characteristics be damned.

[Dwille]

This is a great thread. Thanks for all the effort!

[sadpanda]

Although I agree with Fyephile I felt like the differences in the specs were less 'calibrator voodoo' and more logical requirement:

As the tire/rim width (and offset) increases more caster is required to maintain mechanical advantage over the tire (more contact patch/rolling resistance /weight) and more camber is required to maintain contact patch in corner (more offset/scrub radius)

[Ryephile]

I think we're getting at the same concepts. Trail has to be tailored based on rolling radius of the tire, and static camber adjusted based on the tire contact patch and subsequent dynamic camber at a specific g-loading.

e.g. running a smaller tire radius increases trail for a given caster, so to maintain the same trail, less caster is needed. That matches the Caddy tuning as they run smaller tires.

The outlier is the Camaro FEA setup, which runs a 26.3" diameter front tire (smallest of all the Camaro's but on par with the CTS-V) and the same caster as the FE4 Camaro. This likely results in the most trail of the group, and that's appropriate for a track car.

[EMTNLSS]

I got the FEA front ride links and am installing them today. I have a 2SS so FE3. I got the FE3 ones off and they look the exact same as the FEA. Wonder what the difference is since they don't have the same part numbers. I'm not seeing a difference. What's weird is the the FEA ones are the cheapest at about $60 and the FE4 are about $95 and FE3 are about $75. FEA are on the bottom in the pics.

[sadpanda]

If there is no difference in arm thickness then I'm going to guess there is no difference. Only possibility would be different durometer rubber bushing or briefer ball joint... But I doubt it.

As we've discussed, different part numbers ! = different parts