Anyone know how to verify if your car had 4 or 5 leaf Springs in rear?
I have a 68 400 HO coupe 4 Spd, and it appears to be the 5 leaf under it, the 5th being maybe a foot long? From the bracket back it looks like 3 springs on each side, but from the bracket forward you can count 5 on each side, and I have no idea if they’re original to car, the rear is not.
Would my PHS papers show somewhere?
Want to get a set ordered up for car and just curious what direction to go?

Thanks in Advance!

That may be hard to find out. Does the PHS send a build sheet when one gets info on their bird? the build sheet could have the spring code and I think Detroit Spring has a list of codes for GM springs.

I looked it up one time, the info is out there. Best thing to do is call Eating Spring, they have all the original info on spring specification for our cars.

I called Eaton and they said that the 68 Firebird 400’s came with either the 5 leaf 90lb springs or the 119lb 4 leaf but are not sure as to exactly what distinguished wether they got one vs the other?
Didn’t see any build sheet in the PHS pamphlet or anything that says anything about the leaf springs.

Try this:
https://firstgenfirebird.org/forums/ubbthreads.php?ubb=showflat&Number=261864

Thank you for the link to that thread!!

Although I’m a little more confused, lol! I’m not sure if Eaton came across some new information as of late or what, because nowadays if you call or just go on their site, they show the 90lb 5 leaf option or a 119lb 4 leaf option for a 68 Coupe 400 car?🤷🏼‍♂️ In that thread guys are talking about 103lb 4 or 5 leaf options and that doesn’t even come up nowadays!! I see that link is from quite a few years ago.

What can you guys tell me about U-Bolts and T-Bolts for my 68? I see kits from all sorts of companies that either include “4 U Bolts”, or “2 U Bolts and 4 T Bolts”? I see mine currently has 1 U-Bolt on each side, but I have no idea if that’s how it came originally, seeing there’s a 12 Bolt rear under there, it’s definitely been apart!!

Thanks in Advance!!

I'd say that you have two U-bolts and four T-bolts on your car. I tried to show the T-bolts with some blue lines in your photograph. There is also a good picture on page 295 in the Ames catalog.

From the Parts Illustration Book:

Ron's right, you only have one U-bolt and two T-bolts on that side. Since the rear axle assembly and traction bars are not original to the car, would it make any difference getting the exact same springs the car came with? Unless you plan on restoring the rear to original in the future? Looks to me you have five leaf springs, the bottom spring is always shorter on the one end than the other but yours looks like the second from the bottom is also shorter at the back, usually goes out past the spring clip. Maybe modified when the traction bars where added?

Some guys have a lot of trouble getting the stance they want when installing new springs, trial and error is a real pain when it takes so much work to remove and install. I did my front springs multiple times. I lucked out with the rears but I have the back a bit higher than others like.

Whichever spring you get, if you aren't worried about originality, I'd replace the T-bolts with U-bolts. I don't know why GM thought it was a good idea to use T-bolts but seems to me U-bolts would be a lot stronger. Maybe something to do with the brake lines, who knows, but bolting the springs to the perches instead of wrapping around the axle housing tube seems a bit lame to me. The weld attaching the perch to the axle tube on one side of mine was cracked, so I re-welded it and I replaced mine with 1/2" U-bolts.

Thanks for all the help and knowledge guys!!

Only reason I was leaning towards the springs from Eaton was figuring if by some chance down the road I stumble across a ZM coded BOP rear I’d have the correct springs already in, I know it’s a long shot. I do have a majority of the numbers matching items for car minus the rear if I were to ever want to try and get it back as close as possible to original. Prolly stupid though because I never plan on selling it so the point is moot anyways.

Does anyone have a ball park idea of measurements for a “stock” 68 with good springs, from like center of wheel to fender lip? I really like how mine sets with 60lbs of air in shocks. It’s about 16” from center of rear wheel to fender lip.

Bluebird offered a aftermarket part # 5 leaf that has his car sitting about like mine does, just wondering if I were to go with Eaton, what arch I should get, the lady I talked to at Eaton said they can do 1/2” increments also if I wanted, just really want to put these in and out as few times as possible, lol!

I’ll attach a pic or two of how my car currently sits with 60lbs of air, see what you guys think?

I like it, slightly higher at the back than the front. Opposite of stock, more muscle car look IMHO. What size rear tire are you running?
I just went out and measured mine and it is 17" from the center of the wheel to the bottom of the lip. About what I had with the awful air shocks I used to have on.

Thanks!! I know it’s not “original” looking, but mainly just wanted something different and cool looking to cruise around and always loved first gen Birds! Bought the thing literally in pieces and boxes.

Has 255/60-15’s on rear.

Anyone have a clue of what that measurement is on a original not worn out set of Springs?

So I found a few pics and specs looking around web in reference to measuring ride height to rocker panel, but not all the same, can anyone confirm what is correct, or maybe those specs on the one pic are measuring to a different point then where the pic is showing?

The 8” measurement on picture seem more realistic then the measurements given on the spec sheet??

Yep, that appears to be an inconsistency.

The Crash Sheets - Frame Dimensions seem to agree with the Service Manual dimensions. Although measured from different places it seems match. The Crash Sheet frame rail is 6 15/16" off the ground. Add the inch+ the rocker is higher than the frame rail and you're at the 8.1".

That said, when relatively new, these cars were very low to the ground. I know mine was.

I ended up ordering a 4 leaf set from Eaton Detroit, was torn between a 1” raise or a 2” raise, then when talking to them, they said they can also do .5” increments, so I split the difference and went with a 1.5” raise, hopefully it gets me close to how it’s sitting now.🤷🏼‍♂️ Have till Monday to change it, so I’m trying to figure out for sure this weekend if that’s what I want and if I need to change.

When looking through the 68 Brochure, they sure do seem low in the rear, has me wondering if I shouldn’t go with the full 2”??