My 68 400 is bottoming out and scraping bottom of mufflers and I am assuming that my 4 leaf springs are worn out and need to be replaced. I have found what appear to be decent replacement springs on Summit ($95 each), Classic ($125 each) and National Parts ($135 each) and I want to ensure that I am looking at the best performing lead springs. What lb rating should I be looking for - do I need HD or Regular? Also, should I also get new shackles, pads, etc. if I am replacing springs?
I will let others respond as to best source and spring rates, but I will say I bought mine as "HD" springs for a 400 convertible from JR Spring, and that purchase was made in 2001. I replaced my fronts at the same time. I don't know if they are still available, or if that company exists, and I don't know the rates of the springs. I also could not do a before-after comparo because one of my spring leafs was actually cracked in half and was therefore my bird was sagging lower on one rear side than the other so I had no baseline. I will say my replacements are very VERY STIFF, and they set the car so the rear is just a HAIR higher than the front. And that's even with my battery relocated to trunk.
I will address your other questions with my recent experience of actually installing them about 6-ish months ago:
1. Buy all new bushings (front and rear, although many new springs will already come with brand new rubber front bushings installed...so ask the spring supplier) I used Polyurethane, which are likely contributing greatly to my car's stiffness. But I'm building a bit of a rally racer type of setup here to I'm willing to trade no-slop performance for comfort. Many won't accept that trade for a driver and I believe most people would much prefer normal rubber bushings.
2. Buy 6 front spring pocket cage nuts. Yours will break upon removal, or will need to be torched off/destroyed.
3. Buy spring pads. When you see the originals removed from the car, you will consider them to not even be reusable. You'll see. Again I used Poly. Normal rubber will probably be better for most.
4. MAYBE buy: U-bolt and T-bolt kit. Totally depends on extent of rust and condition of yours. You're in CA...so if your car is relatively rust-free, no reason these can't be re-used. Also not terribly expensive and this is an ideal time to replace them. If you see anything bent or remotely questionable, just buy the kit.
5. DO NOT BUY: Repro shackles...unless your originals are physically damaged in some way. The original shackles are SOOOO much thicker/beefier/stronger/better than the thin-gauge repro shackles being sold by all the parts houses. When I saw them side-by-side I laughed out loud and tossed the repro shackles in my scrap metal pile. Take off your originals, blast/clean/repaint to bring them to your standards of appearance, and re-use, but you might need to buy new nuts & bolts depending on condition (I did). Cosmetically restore your front spring buckets and shock mount plates at the same time. Even though my car came from Chicago rust country and needed full replacement rear frame rails and floors, my original shackles were/are solid as a ROCK, and many times better/heavier than the repros. They're bullet-proof.
6. Use the torque specs and install procedures in the service manual. Don't just go by "feel" when tightening nuts and bolts.
7. No better time to service U-joints than when the driveshaft is already out of the car...and maybe a transmission output seal? Hard axle brake lines and hose, if you fully drop out the rear end while doing this? At least inspect this stuff and make your own call while it's apart.
And I'll close with a scary possibility that I do not wish on you. If yours happens to be a rust-belt car like mine was:
As stated, I bought my springs in 2001 and installed them in 2012. Why? When I removed one of my original spring front buckets, the entire frame rail/torque box section of the unibody came out with it as basically a pile of rust dust...so I needed far more than 6 cage nuts! So my planned weekend spring replacement project in 2001 became an unplanned 11 year full-frame-rail and almost-full-floor replacement project, that I have very recently wrapped up about 90%, and am FINALLY driving the car again but still working on full completion. That's one of the reasons I have become more active here lately...11 years of a disassembled car has led me to to FORGET a few things on how to rebuild it, and I needed some bits of advice from folks here who are familiar with it to help me over a few humps. I'm past most of them now, but always learning.
So those with rusty cars, BEWARE rear spring replacement. Never know what you might uncover. But mine was indeed a basket case and I somewhat knew of this risk going in.
I agree with everything Craze cars said, especially the part about the new cage nuts. Get the "new" design that is one piece instead of the prone to break clips with nut held in place. The multi-leaf rear springs have an advantage, they are the same dimesnions as the 2nd gen Trans Am. I used the highest rated spring at the time, an 81 WS-6 Trans am rear spring for my car and it works real well.
If you have a high horsepower car, I would also recommend using 4 U-bolts and eliminate the T-bolts on the axle to spring connection.
I used Eaton Springs (cheaper through NPD than Eaton) (how does that work??)
I purchased the 'install kit' for front and back. I rebuilt my entire front suspension at the same time I did the front springs. The install kits come with every stinking bolt and nut that you need to do the install, so well worth replacing everything at once. Spring rates go by engine size. Rear leafs for 400 coupes were 4 leaf, not 5 leaf as one might think.
I agree with the other comments above as well. You just have to decide how far to take it. But its easier to do it all at once rather than over the course of multiple repairs.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold
On the other side, my '67 is an original black plate California car. If your's is truely an original CA car, you most likely can remove all the fasteners after spraying them with PB Blaster and waiting a bit.
On my entire car, I sheared only ONE bolt, on the bottom of the drivers side fender, during dissasembly.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
One other item to be added to all of the comments above. You should wait to torque any of the suspension bolts until the weight is on the car. Maybe even bounce the rear end a couple of times, then torque them down. You don't want to get the suspension in a bind.
I know that washing and waxing my car with the present condtion of my paint is like polishing a turd.....but it's my turd and I want it polished!
Helpful feedback guys. I did find the right OE 4-leaf rear springs on NPD (Eaton), Classic (TBD) and Summit Racing - Summit's are $40 cheaper per leaf spring for some reason but htey have a decent rating?. NPD has the HD springs so I may go with these for s stiffer rear suspension and more longevity. Any good or bad experiences with the various brands? Car is truly CA car with little rust so I may get lucky removing fasteners, etc. Will purchase new pads and U/T bolts as well to be safe. Any other recomended modifications while I replace the leaf springs?
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
+1 for having them re-arched. I've also used Eaton and Spring n' Things parts with good luck. For that matter, I've used JC Whitney springs with good luck. I have their 4 leaf standard duty in my '68 Camaro with 6 years on them and no sag.
I got a 68 project that I knew going in needed considerable work, but like Salmon, discovered more and more I wanted done right. I will have had it 2 years next month. Worked on it almost daily and have been driving it for a month (still needs paint). PB Blaster with a good rapping and cold beer wait is key, and in all the work I have done on my Wisconsin car the only bolt I sheared was the same one as Salmon, bottom driver side fender.
My original 5 leaf springs seem ok, only 1/8" difference in fender height between them, ~30" off the ground and fairly stiff but I need the protection because I am running 295/50/15's (not tubbed). I am "stringing" the car today because my driver side axle slipped forward (yes it was fun, but now it crab crawls, vibrates at hwy speeds, and handles like sh!t). Having trouble finding a torque spec for the U bolts, and I think this is critical for anyone replacing springs.