F100 suspension rebuild thoughts

Jesse73

Well-known member
Hey guys,

I have been working on rebuilding our '73 F100 over a number of years. Up until this point I have just sort of been driving it and fixing what crops up. Last year I added power steering as it was too difficult for my wife to drive in town. Unfortunately for me, the box leaks like a banshee and caused more headaches then help. I think it is time to finally dig in to the whole front suspension and renew as much as possible. I would really like this truck to be a nice driver. Right now I have a few thoughts on what to do. Feel free to offer any advice on these bullet points

1. Redhead power steering box. Mixed reviews, but from what I can tell old truck owners are happy with them. They have new bearings that should help the seals last. The original Ford box has had about 5 seal replacements, its not going to magically heal up and stop leaking.

2. King pin replacement. I have a set of steel/bronze kingpins to install. Mine are currently shot and there is too much play in them. I'm thinking I will pull out the axles and have a local machinist press out the old and fit the new? Does anyone have the service manual section that covers this? Might be nice to hand the guy the tech specs on how to properly ream the bushings etc. I'm guessing no one around here is going to remember king pin service off the top of their head.

3. All new rubber bushings. I have the I-beam pivot bushings as well as the trailing arm bushings. Those could be replaced when I take the axles out for kingpins.

4. New coil springs. I'm thinking about the Moog progressive springs? Any thoughts there? Might ride a little nicer?

5. Shocks are set, I have all new Gas magnum shocks already installed

6. Sway bar. This truck is terrible to drive on a windy freeway day. A lot of it has to do with everything else being worn, but I'm thinking a swaybar might help the truck feel more planted/modern? We don't tow huge trailers, but I don't want to have to avoid doing so if its called for. Maybe also add a rear swaybar.

7. Steering dampener. This would not have been a stock item but they exist on modern vehicles for a reason. As a bandaid I think they are not smart, but maybe adding a dampener to the tie rod might add to a stable driving experience hitting pot holes etc.

8. Possible bonus. Chevy long leaf rear springs. If everything works out this summer, I should have a better condition bed available to me. I was thinking at that time it might be cool to take off the spring hangers and move them to accommodate the longer new chevy truck springs. I see they are available in the same width but a few inches longer. Worth it for a better ride or simply use stock replacement rear springs? Truck already has airbags so I'm not too worried about the rear being too soft with a payload.

9. Brakes. I feel that the brakes are pretty decent as they are. I could maybe look at better quality rotors and pads for the front, I don't think it really warrants a big caliper swap etc for how we use the truck.

It would be an expense, but I'm thinking that it would be a good idea to take the axles out for a kingpin replacement and do everything else while its apart. Then it would all be done properly instead of mickey mouse piecemeal like I have been doing. Any thoughts feel free to throw your hat in the ring. Thanks guys!

-Jesse
 

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Frank

Famous Member
Supporter 2022
Supporter 2021
Hey Jesse- I fully rebuilt the front end on a 79 f100.
I was able to get all NOS parts from Rock Auto. Moog and Federal Mogal. Nice USA original equipment stock. I recommend staying clear of the cheap China stuff. And yes- do it all while you're in there. The original stuff lasted 49 years, do it right once, and it's good for another 49. My machine shop did the king pins, he knew what to do. (He's been in business almost 50 years).
I did all the bushings also. The toughest ones were the I beam to frame, really tight fit in the chassis, and the bushings press into the axles very snugly. I wish I had let the machine shop do those two bushings as well, but I managed. If they put up a fight, it may be worth the few $ to let them do those axle bushings. All the rest is real straightforward.
Front coil springs, I got stock replacement and the ride is nice- firm and sure-footed. They also restored the proper stance** of the truck, bet it brought the frontend up 1 1/2". A lot of the sway and drift in curves, wind or undulating roads is the coil springs. Worn king pins and bushings cause the steering to wonder, obviously, but the "unpredictable steering drift" is compounded by the springs letting the body weight shift. I say, try the new springs and if it's still too soggy for you, then get the sway bar. I predict the gas shocks (which I also have) combined with new coil springs, plus the K pins and bushings, you'll be satisfied with the ride and cornering stability. The rear end is stock springs and Monroe air shocks. I don't recommend the air shocks due to the steep angle they mount on the Ford, it puts uneven torque on the springs, trying to twist the front of the diff downward.
Front brakes were redone, also with USA factory parts. The stock brake package is more than sufficient for my driving needs, including pulling a 3500 lb trailer, and that's manual master cylinder, no vacuum assist. I like the brake pedal feel, actually better than the vacuum brakes on my '90 F150. For me, a brake upgrade would be an unnecessary use of $
My steering is still manual, with a rebuilt factory box installed, so I can't address the power steering question.
In conclusion, I am very happy with the ride, cornering, hitting potholes, etc with the new factory parts and gas shocks. The sway bar and the steering dampener, add later if you think they're still necessary. (Especially if your budget is like mine! lol) The difference in drivability, ride quality and control is night and day over the worn out original parts with new USA NOS factory parts. Truth-to-tell, I was on the verge of selling this truck, now it's my daily driver.
Frank
** EDIT- As can be seen from the following posts, ,the new springs exceeded the proper ride-height, and modifications need to be made.
 

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Blairsville Ed

Famous Member
Hey guys,

I have been working on rebuilding our '73 F100 over a number of years. Up until this point I have just sort of been driving it and fixing what crops up. Last year I added power steering as it was too difficult for my wife to drive in town. Unfortunately for me, the box leaks like a banshee and caused more headaches then help. I think it is time to finally dig in to the whole front suspension and renew as much as possible. I would really like this truck to be a nice driver. Right now I have a few thoughts on what to do. Feel free to offer any advice on these bullet points

1. Redhead power steering box. Mixed reviews, but from what I can tell old truck owners are happy with them. They have new bearings that should help the seals last. The original Ford box has had about 5 seal replacements, its not going to magically heal up and stop leaking.

2. King pin replacement. I have a set of steel/bronze kingpins to install. Mine are currently shot and there is too much play in them. I'm thinking I will pull out the axles and have a local machinist press out the old and fit the new? Does anyone have the service manual section that covers this? Might be nice to hand the guy the tech specs on how to properly ream the bushings etc. I'm guessing no one around here is going to remember king pin service off the top of their head.

3. All new rubber bushings. I have the I-beam pivot bushings as well as the trailing arm bushings. Those could be replaced when I take the axles out for kingpins.

4. New coil springs. I'm thinking about the Moog progressive springs? Any thoughts there? Might ride a little nicer?

5. Shocks are set, I have all new Gas magnum shocks already installed

6. Sway bar. This truck is terrible to drive on a windy freeway day. A lot of it has to do with everything else being worn, but I'm thinking a swaybar might help the truck feel more planted/modern? We don't tow huge trailers, but I don't want to have to avoid doing so if its called for. Maybe also add a rear swaybar.

7. Steering dampener. This would not have been a stock item but they exist on modern vehicles for a reason. As a bandaid I think they are not smart, but maybe adding a dampener to the tie rod might add to a stable driving experience hitting pot holes etc.

8. Possible bonus. Chevy long leaf rear springs. If everything works out this summer, I should have a better condition bed available to me. I was thinking at that time it might be cool to take off the spring hangers and move them to accommodate the longer new chevy truck springs. I see they are available in the same width but a few inches longer. Worth it for a better ride or simply use stock replacement rear springs? Truck already has airbags so I'm not too worried about the rear being too soft with a payload.

9. Brakes. I feel that the brakes are pretty decent as they are. I could maybe look at better quality rotors and pads for the front, I don't think it really warrants a big caliper swap etc for how we use the truck.

It would be an expense, but I'm thinking that it would be a good idea to take the axles out for a kingpin replacement and do everything else while its apart. Then it would all be done properly instead of mickey mouse piecemeal like I have been doing. Any thoughts feel free to throw your hat in the ring. Thanks guys!

-Jesse
I re-did my 1968 F100 front end.
king pins require the proper reamer. If your shop has the reamer they will do it correctly.

The springs are interesting. Apparently, Ford had several front coil springs that they used depending on which motor the truck came with. It comes down to proper ride height. The new springs are a “one size fits all” and will most likely be to tall for a Six cylinder truck. This creates an overly positive camber. There appears to be some adjustability in the ride height by turning the spring into the groove in the upper perch. The more the spring is turn into the upper concave form the lower the truck will sit. The upper strap locks the spring position in place. Although this is a limited adjustment. I struggled with mine and drove it but everything works correctly when the ride height is correct. The shop manual gives a good picture of wear to measure this. In my case, I actually needed to use a cut off wheel on my angle grinder and cut the top coil of the springs.
I started by removing 1/4 of a turn off the top end. Then you reinstall and measure ride height. As you get closer to the 4 inch ride height measurement you reduce your cuts to 1/8 of a turn. It‘s best to do this with the normal load in the truck. This is done after all the bushings, king pins, and shocks are replaced.
Correct ride height is the secret to get the I beam trucks to drive well.
 

Frank

Famous Member
Supporter 2022
Supporter 2021
I re-did my 1968 F100 front end.
king pins require the proper reamer. If your shop has the reamer they will do it correctly.

The springs are interesting. Apparently, Ford had several front coil springs that they used depending on which motor the truck came with. It comes down to proper ride height. The new springs are a “one size fits all” and will most likely be to tall for a Six cylinder truck. This creates an overly positive camber. There appears to be some adjustability in the ride height by turning the spring into the groove in the upper perch. The more the spring is turn into the upper concave form the lower the truck will sit. The upper strap locks the spring position in place. Although this is a limited adjustment. I struggled with mine and drove it but everything works correctly when the ride height is correct. The shop manual gives a good picture of wear to measure this. In my case, I actually needed to use a cut off wheel on my angle grinder and cut the top coil of the springs.
I started by removing 1/4 of a turn off the top end. Then you reinstall and measure ride height. As you get closer to the 4 inch ride height measurement you reduce your cuts to 1/8 of a turn. It‘s best to do this with the normal load in the truck. This is done after all the bushings, king pins, and shocks are replaced.
Correct ride height is the secret to get the I beam trucks to drive well.
thanks for this Ed- I've learned something. Where is this 4" ride height measured from, point to point?
 

Blairsville Ed

Famous Member
It would be best to take a pic of the shop manual and I’m at work at the moment.
Also, 1973 was the first year of the sixth generation. The frame changed a bit and the I beams are slightly different from the fifth generation. The best way is to get a shop manual on a cd disc from eBay. I think there around $30
The measurement was a part of the chassis that is adjacent to the I beam pivot point.
I‘ll take a pic from the shop manual tonight.
 

Blairsville Ed

Famous Member
Here a pic from the Fordification web site. The pic shows a 4inch block placed in this spot with all of the front end alignment specs checked with this block in place. However, this is the fifth generation. It may be different for the sixth generation.BA3BD813-4072-4AB5-8955-34066AE10E4C.jpeg
 

Frank

Famous Member
Supporter 2022
Supporter 2021
i have a shop manual for a 1977. It shows a slightly different process. Notice in the chart that if the ride height exceeds 4.50 inches there’s no alignment specs.
Apologies to the OP, not attempting to sideline the thread, but this is very helpful Ed. My '79 is too high, at 4.75". What is the ideal height in your estimation, from the specs in the manual?
 

Blairsville Ed

Famous Member
Great question!
What I didn’t mention is the text in the manual indicates that the ibeams are NOT to be bent to correct the alignment but rather replaced. The 5th generation trucks used a 20 ton ram to bend the ibeams If the alignment was out.
Remember, all alignment specs are checked assuming the ibeam bushings ,radius arm bushings, shocks and king pin bushings, wheel bearings are in good condition.
Notice how the camber goes less positive as the ride height lowers. Use that as a guide. Do you use the truck with a heavy load or a trailer. That would lower the rear and raise the front. If that was the case, you would want a lower ride height when the truck was empty. Do you normally have a heavy load in the cab. That would lower the ride height.
To summarize, consider the load you normally have in the truck.
if it’s a minimal load, use the 3-1/2 inch block of wood as shown as a good point of reference that Ford used. My fifth generation F100 shows a 4 inch block. That is what I used and the truck handles nicely at 4 inches. It tracks straight with no abnormal tire wear. Before I shortened the springs my ride height was 4-3/4 and my tires were wearing on the outside edge due to excessive positive camber.
 

Frank

Famous Member
Supporter 2022
Supporter 2021
Remember, all alignment specs are checked assuming the ibeam bushings ,radius arm bushings, shocks and king pin bushings, wheel bearings are in good condition.
Everything is new (and correct), per post #2.
Before I shortened the springs my ride height was 4-3/4 and my tires were wearing on the outside edge due to excessive positive camber.
Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
 

Jesse73

Well-known member
Everything is new (and correct), per post #2. Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
Everything is new (and correct), per post #2. Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
Everything is new (and correct), per post #2. Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
Everything is new (and correct), per post #2. Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
Everything is new (and correct), per post #2. Yes, sir the same here. Upon close inspection. the outside 1/3 of the tread is wearing slightly more than the rest. And the + camber is visible to the eye, when looking for it. Interesting, the 4 3/4" must be the new norm with the generic spring. . I may have some adjustability left in the upper perch, don't remember where I set it. The truck drives really well for what it is, with manual steering. Tracks straight and doesn't wonder. Thanks again for this valuable input.
 

Jesse73

Well-known member
Sorry, having technical difficulties over here. Certainly a lot to chew on. I think to proceed with all of the work, I need to first find a decent machine shop to do the kingpins. I don't see why I couldn't do the rest of the work myself. Maybe take it in for an alignment when finished replacing all of the bushings.
 

Frank

Famous Member
Supporter 2022
Supporter 2021
Sorry, having technical difficulties over here. Certainly a lot to chew on. I think to proceed with all of the work, I need to first find a decent machine shop to do the kingpins. I don't see why I couldn't do the rest of the work myself. Maybe take it in for an alignment when finished replacing all of the bushings.
Sounds good Jesse73. Yes, I got an alignment after the install, since replacing the steering box and all that linkage the toe-in would need to be reset. Now you are fore-armed about the generic springs likely being too tall. Other than possible spring mods to assure the correct ride height, and professional pressing of the kingpins, this project is very straightforward. As is everything on the old vehicles, it's why they are all I own. Best of luck on the project, keep us posted.
 

Wesman07

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Supporter 2020
Good stuff. I would like to add one thing regarding cutting coil springs. The more you cut, the stiffer the spring gets. The stiffness of a spring can mathematically be determined by wire diameter, overall diameter and number of active coils. This calculator is pretty useful.


If you have the ability to measure the sprung corner weight of your truck (chassis, engine, body), you can pretty much nail it first shot.
 

hodaka100

Well-known member
Good stuff. I would like to add one thing regarding cutting coil springs. The more you cut, the stiffer the spring gets. The stiffness of a spring can mathematically be determined by wire diameter, overall diameter and number of active coils. This calculator is pretty useful.


If you have the ability to measure the sprung corner weight of your truck (chassis, engine, body), you can pretty much nail it first shot.
You can use a torch to cut half a circle off or however much you think you need off the spring and then heat up the remaining half red hot. Turn the spring upside down and push it on the floor to get the same shape it was before you cut it.
 

Wesman07

1K+
VIP
Supporter 2020
You can use a torch to cut half a circle off or however much you think you need off the spring and then heat up the remaining half red hot. Turn the spring upside down and push it on the floor to get the same shape it was before you cut

You still decrease the number of active coils. Heating spring steel also reduces the memory of the spring. I’m not saying that these practices won’t work, you’ll just better results taking a few measurements and using a calculator to find the correct spring. There are ways to weigh your vehicle with a typical bathroom scale, or measure the sag of a spring of a known rate.
 
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