1968 F41 rear coil spring installation - Impala Tech
Brakes & Suspension Conversion Questions & more

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post #1 of 24 (permalink) Old 02-22-2020, 01:26 PM Thread Starter
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1968 F41 rear coil spring installation

I have put in many coil springs over the years but for some reason these rear coils are kicking my ***.
On the Impala the bottom of the spring rides on the lower control arm and not on the rear.
I originally got moog springs but they were way different, so I called Detroit spring and spoke to them and
had the correct spring delivered. Even with the spring compressed I am having a hard time fighting them
into place.
Anybody out there with some advice to help me out.
Thanks guys
Tberg.
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post #2 of 24 (permalink) Old 02-22-2020, 03:07 PM
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You are going to have to use a lift and a tall tranny jack or get it two feet in the air with HD (I use six ton Hein-Wierner) jack stands I bought from NAPA and a floor jack. The HD jack stands will hold your car and an APC up; and they won't wobble around. They are also tall enough fully extended to get the room you need to work.

Then disconnect the drive shaft (it will bottom out if you don't), then the shocks to let the rear end drop down supported by your floor jack. You should then be able to wrestle the springs in place and reconnect everything.


Big Dave
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post #3 of 24 (permalink) Old 02-22-2020, 03:09 PM
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Some pictures would probably help us diagnose the problem.


Once car is in air (on hoist or jack stands on frame), support rear end (stands or floor jack), disconnect lower shock bolts, raise car (hoist) or lower floor jack, pull old springs. Then insert new springs, correctly indexed (see FSM) raise rear with floor jack (or lower hoist, bolt shocks back in. Sometimes you need to raise one side to droop the opposite side to give you more room. Sometimes a ratchet strap around the spring and arm will hold it in place while you raise rear end (or drop car on hoist).

Two doors, four doors, wagons, and ragtops.
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post #4 of 24 (permalink) Old 02-22-2020, 08:39 PM
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I had to do this again recently on my '68, and I will tell you there is NOTHING I hate more than messing with coil springs, front or rear. Here is what I did.

First, as others have said, getting the car as far off the ground as possible so you can drop the axle way down after shocks, panhard bar, upper control arms, driveshaft, etc. are all disconnected is key.

I placed the springs in the pockets in the frame and used a heavy duty ratchet strap over the frame to hold the springs firmly in place, NOT compress them. Then I used my coil spring compressors on the front of the springs (on either side of the lower control arms) to compress them on one side - if you've ever looked at them installed you know they are not straight, but are curved since the lower control arms are not parallel with the top surface of the frame pockets.

The curve in the springs allowed me to then use a floor jack to lift the axle up, place the spring cups in the bottom of the springs, align the holes between the spring cups and lower control arms, and then run the fasteners through the holes. It was then just a matter of alternating between lifting the axle up with the floor jack and torqueing the fasteners to secure the springs to the lower control arms.

Sorry for the long description. This worked for me and was the least amount of trouble I've had putting them in. I still cursed PLENTY and was amazed at how high I got a wrench to bounce off a concrete floor.
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post #5 of 24 (permalink) Old 02-23-2020, 10:09 AM Thread Starter
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Thanks for all the feedback, but after trying everything i put the new springs and the old springs next to each other
and they are slightly different on the bottom. The old spring has much more room between the bottom ring and the next ring up.
Right now the spring touches the lower trailing arm bracket when put in place, the spring needs more of a gap between the bootm and
first ring. I went back to the build sheet and just like I thought, the F41 suspension option is taking its toll. I think
the spring is still wrong. I have a message in at Eaton/Detroit spring and I will speak to them on Monday.
I'll keep you in the loop.
Thanks again.
Tberg
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post #6 of 24 (permalink) Old 02-23-2020, 12:11 PM
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The new springs are probably progressive rate (compared to constant). Post the Moog PNs you are trying to use, please.

Two doors, four doors, wagons, and ragtops.
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post #7 of 24 (permalink) Old 02-24-2020, 06:52 AM Thread Starter
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The Moog springs aren't close to fitting. I am hopeful to get it right with Eaton Spring.
Thanks
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post #8 of 24 (permalink) Old 02-24-2020, 10:25 AM
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Moog made the springs originally for your car (OEM vendor). They still make them today for a service part. I have heard a number of complaints about Eaton Spring, but I have no personal experience because of the negative complaints on many automotive boards had me buying Moog springs for my cars.

A variable rate coil spring has a noticeable decrease in the gap between the coils from the bottom up. It offers a smoother ride but has issues with rough roads as the suspension will frequently bottom out transmitting a jolt to the occupants. They are never used on a race car because it makes handling too unpredictable to maintain control while driving (you have to slow down to stay on the track).

Big Dave
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post #9 of 24 (permalink) Old 02-24-2020, 04:50 PM
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Sorry if some of this is redundant, you never know what someone has already tried or maybe overlooked.

I removed variable rate springs that I had previously replaced. They tend to bulge and rub the suspension. They just weren't right for the car. The right spring came from a Viking vendor, the left spring came from Eaton Detroit. The Eaton springs ride better in spite of being the heavy duty version.


You are taking the shocks off in order to do this? That is several more inches of drop. Do not take off the panhard bar, it won't line back up when you're done.

Also, if you jack up the opposite side of the axle from where you're working, it will force some more articulation and push the other side down. Take the wheels off to give yourself room to work. I also recall using a bottle jack between a couple of hard points to spread things open a little more.
I did this job on my 69 about 8 months ago.

1969 Impala convertible build thread here:
https://www.pro-touring.com/threads/...ghlight=impala
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post #10 of 24 (permalink) Old 02-24-2020, 04:51 PM
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Quote:
Originally Posted by tberg View Post
The Moog springs aren't close to fitting. I am hopeful to get it right with Eaton Spring.
Thanks

I realize that you are having problems with them. Please post that part number so we can try and figure out if it is the correct spring. Moog has thousands of numbers, and lots of people have used Moogs on Impalas. Strange things happen, box falls off shelf, wrong springs go in, etc.



Post the part number. Part number and a photo of the springs you are trying to install would be much better. Help us help you.

Two doors, four doors, wagons, and ragtops.
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post #11 of 24 (permalink) Old 02-26-2020, 07:46 AM Thread Starter
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The moog spring number is CC601.
Looking at justjohn's picture his Eaton spring looks like what I need. If you could tell me the Eaton Spring
number I will forward it to them.
Thanks Guys
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post #12 of 24 (permalink) Old 02-26-2020, 05:19 PM
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Is your car a four door? If not, the 601 is the incorrect spring.

Two doors, four doors, wagons, and ragtops.
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post #13 of 24 (permalink) Old 02-27-2020, 09:59 AM
 
 
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Have you considered an external coil spring compressor?? you do not need to collapse them very much. I also use a longer bolt in the lower pocket to make lineup easier.
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post #14 of 24 (permalink) Old 02-28-2020, 06:07 PM
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Make sure you use only a grade 8 bolt in the lower pocket. Ask me how I know. Don S
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post #15 of 24 (permalink) Old 02-28-2020, 07:30 PM
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And the fasteners you buy in the big box stores are not grade eight. They are made in China and testing proves that they are about half of what they claim as to hardness or strength.

Big Dave.
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post #16 of 24 (permalink) Old 02-29-2020, 08:52 AM Thread Starter
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Thanks for all the input, Mike at Eaton/Detroit spring says the heavy duty version spring is
what I need. When I get them installed I will let you guys know how it worked out.
Thanks again
Tberg
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post #17 of 24 (permalink) Old 02-29-2020, 11:14 AM
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Still need to know if your car is a four door or a coupe.

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post #18 of 24 (permalink) Old 03-01-2020, 09:03 AM Thread Starter
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The car is a two door custom coupe.
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post #19 of 24 (permalink) Old 03-01-2020, 10:56 AM
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Well, that would explain some of your issues. You bought Moog 601 progressive rate springs for a four door sedan. You have the wrong springs, as I pointed out in post #12.


Moog 6187 (constant rate) or 609 (variable) are the correct rear springs for your car.

Two doors, four doors, wagons, and ragtops.
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post #20 of 24 (permalink) Old 03-28-2020, 08:45 AM Thread Starter
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F41 Springs

Finally got notice that my springs from Eaton/Detroit are being shipped. I looked around for any definitive model number
for a 68 Impala with the F41 option and nobody could definetly say that it would fit.
Went to Moog and they do not say anything about F41.
Im keeping my fingers crossed that Mike at Eaton said these will fit.
I will let you know how it works out.
Thanks for all your help.
Tom B.
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post #21 of 24 (permalink) Old 03-28-2020, 08:00 PM
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I don't think the F41 was ever offered as a suspension package on the full size car to the public. Only the F40 HD suspension was an option. The F41 was the spring and shock combination used on the police package (9C1) that were not available new to the public. If you wanted one you bought it at public auction used. This is why you can not find info for a F41 in a passenger car. Look in the catalog under police and station wagon.

Big Dave
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post #22 of 24 (permalink) Old 03-28-2020, 08:05 PM
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Police package wasn't RPO 9C1 until the 70s.

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post #23 of 24 (permalink) Old 03-28-2020, 08:32 PM Thread Starter
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F41

Hey Dave, I have the build sheet sheet for the car and it is on it.
Tberg
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post #24 of 24 (permalink) Old 04-01-2020, 11:01 AM Thread Starter
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F41

Update, just installed the springs from Eaton/Detroit. It was a battle but installed.
The new heavy duty spring weight wise was much heavier but not as tall mas the regular spring. Will let you
know about the ride height soon.
Thanks Guys
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