'92 F150: Would a broken rear spring leaf cause a vibration at 43 mph?
 

Hi all,

A couple of days ago, my '92 F150 2WD 6-cyl E4OD (230,000 miles) started making a vibration/noise.
On a smooth road at around 43 mph when in 4th gear (OD), I can feel a vibration and hear a noise that sounds like when you run over those rumble strips on the side of an asphalt highway. It lasts about 2 seconds and goes away as I move up to higher speeds. Doesn't always do it but when it does, it's always around 43 mph in OD.
Hoping it might be the u-joints, I got under the truck tonite but the u-joints seem tight and I don't see any obvious looseness. I replaced them years ago at 80K but they're Spicers and get greased along with the front end every oil change by me.
This vibration/noise is bothering me because if it's transmission related (shudder-converter) I may have to send the ole gal to the salvage yard. Just not worth investing that much money in this old truck as it is rusty and is my winter driver. Damn shame too as it's been a great truck.
The only thing I found amiss under the truck is what leads to my question.
Last summer, a leaf of the passenger side rear axle spring broke. I replaced the spring with a junk yard spring. Tonite I found the driver's side rear axle spring with a broken leaf (see pics below).
My question is, is it possible for a broken leaf in my rear spring to cause the vibration/noise I described above? Currently the leaf shows no evidence as having rubbed against the tire side wall. A broken leaf in a spring defies logic in producing the vibration/noise I describe but I thought I would ask anyway. Any opinions out there?
Thanks guys.


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I am certainly not an expert but I would think someone would want to know if the vibration stays if you maintain 43MPH. Also, does it vibrate at 43mph when you are reducing speed. A broken leaf can cause noise, lean and an non centered axle. I doubt also that the leaf would only make a noise at a certain speed. Sandy

i would look at broken belts on the tires first

I have a 93 with broken leaf springs and its fine. Where do you feel the vibration the most?

Steering wheel? braking?

Does that have a two piece driveshaft, with the center support bearing? With the miles on that thing, it's a safe bet it's toast by now. It all adds up, add in out of balance tires/wheels, maybe weak shocks, and everything starts fighting each other and pretty soon it's like an out of balance washing machine. U-joints can be deceptive too, they can feel tight but are all wallered out.

Have the tires checked. I notice that tread pattern as the cheap Goodyear wrangler radial from Walmart.
​​Ive had to replace three of them on the wife's SUV because of bad belts, and one that caused a severe pull to where the steering wheel was turned to the ten o'clock position to drive straight.

Hey guys, I appreciate the replies.
Just for grins since I was under the truck last night, I greased the u-joints on the one piece driveshaft last night. I took it for a ride today and I was able to get it to do the vibration/noise only a couple of times, so probably not u-joint related. If I am in OD and vary it between 40-45, it will do it sometimes. Kinda hard to feel/hear where it is coming from esp with the roads around here. So it's hit or miss at this point. Yes, the tires are from Walmart and are nearing getting replaced.
You all have given me a number of things to consider. I am going to continue driving it and I am sure what ever is causing the vibration/noise will gradually manifest itself. On the bright side, I am glad nobody has said that this is the classic symptoms of torque converter/trans failure, LOL. I'd like to keep her.
Thanks for the replies and I'll update if I narrow it down. Regards. :-X22

If the next stop is the graveyard then I'd give her a real shot at letting me down before thinking about sending her away for good. Even still, someone would buy it for better than scrap value.

Like everyone said, the vibration probably isn't the spring but you should really deal with that broken leaf before it spits it out.

Well I found out what my vibration was. Torque Converter shudder.
I changed the fluid with Mercon V and a new filter and the shudder is gone.
Next stop is the junkyard, not to drop her off but to pick up a rear spring, lol.

when it comes to leaf springs ive been told you should always get them in pairs especially if used because no two springs break in the same

Yes, I agree. Last summer when the pass side broke, I found a lower mile truck in the boneyard and pulled the pass spring which was in pretty nice shape. I should have also pulled the driver's side as well. Anyway, hopefully I can find another low mile spring in the boneyard when it warms up around here. :-X22

You should look for a 4x4 f150 or any 250-350 and grab the springs, frame mounts, u-bolt top plates and hangers. That way you can convert to a 3 inch wide spring, I feel the 2.5" wide leaves aren't enough for a full size truck. That's what my old s10 had in it....

He'll need to swap hangers too. You offering to drill out all 16 rivets for him?

Pretty much everyone but Ford uses 2.5" for everything. IIRC some Dodges had 3" springs but I might be wrong on that. A lot of DRW trucks used 2-1/4" springs in order to buy a little more clearance for tires. The difference in performance from 2.5" to 3" isn't huge.

3" should be a little more resistant to sway when loaded (and more resistant to flexing off road) compared to an equivalent 2.5" spring. 2.5" stuff is easier and cheaper to source parts for and is easier to fine tune if you're making your own leaf pack (a small 3" leaf will affect the packs' behavior more than an equally thin 2.5" leaf) which is relevant to some people. Small, thin junkyard leafs are much more plentiful in 2.5" than 3" which is a big consideration for someone building their own pack.

I currently have 3" on my truck but only because I found a set of 66" Superduty leafs cheaper than I could find a set of 64" Chevy leafs at the time when I bought them. If you're putting on new hangers and the cost is the same, sure go with 3" for the added flexability but you don't gain enough to be worth to converting a working 2.5" setup to 3"