Squeaking when 40+ mph and accelerating?
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Cross-Country
Joined: Nov 2020
Posts: 50
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Squeaking when 40+ mph and accelerating?
I have a 1978 f250 with a 460 and 4wd, auto trans (c6). This weird thing started happening when I hit 40-45 mph. The truck starts squeaking from what sounds like the passenger side towards the front. I can't for the life of me figure out what it is. It's a pretty soft squeaking, but enough for me to notice it (and know that it's a new sound and not normal).
Only happens when accelerating and over 40mph. The second I take my foot off the gas, it stops. Doesn't seem to be an rpm thing either because the sound doesn't happen when parked and revving the engine. Any ideas?
Only happens when accelerating and over 40mph. The second I take my foot off the gas, it stops. Doesn't seem to be an rpm thing either because the sound doesn't happen when parked and revving the engine. Any ideas?
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,251
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From: S/W Missouri, Polk county
X3 front axle passenger side steering knuckle u-joint, or wheel bearing. I would give the front and rear d/s u -joints a good service of grease and then take it for a spin. Make sure it is not a rock in the disk brake rotor stuck behind the dust shield. If still there, time to take the long route and pull the passenger side brake caliper/hub/rotor /spindle and short and long axle shaft. Replace that sealed style u joint between them and hope that is it.
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Cross-Country
Joined: Nov 2020
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So I greased up the u-joints, and it's still making the noise. Now that I've been listening more closely, I don't think "squeak" is the right way to describe the noise. It almost sounds like a "sucking air" sound...like from a vacuum line. The sound seems like it's coming from the vicinity of the heater assembly on the passenger side under the dash. But it's weird that it only makes the noise when accelerating over 40 mph, not when I take my foot off the gas or when accelerating any slower. Also, it's pretty subtle at 40mph--sounds like a leaky weatherstrip...but then when I really step on the accelerator, The sound is a very noticeable "sucking" sound. Is there a vacuum line back there or something I'm missing? No A/C in the truck, so I was pretty sure the 78 heat system was all mechanical, so no vacuum ports.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,251
Likes: 5,815
From: S/W Missouri, Polk county
Well a/c truck or none a/c? If a/c you have a large vacuum module connection 9 lines (attached to the lever/switch behind the face plate) to select the direction (vent, defrost, floor) right behind the environmental control panel. AND you have another one that is for selecting the temp. The bottom one is prone to breaking after years of use. The plastic stud the 2 part vacuum switch attaches too, snaps off.
How are the power brakes? You could have a power brake booster going bad?
How are your vent wing seals? Take some blue painters tape and do some masking off and test driving research. Same for the cab and door glass seal.
Does it start and idle good?
How are the power brakes? You could have a power brake booster going bad?
How are your vent wing seals? Take some blue painters tape and do some masking off and test driving research. Same for the cab and door glass seal.
Does it start and idle good?
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