Burning Rubber Smell (not joking)

[toddtheodd]

I have a 72 c10 lwb, and when I am doing about 60-70 I can start to smell what smells like burning rubber smell. Gets worse if I go faster.
I can smell it better if I ONLY have the wing window open partially.
I've checked my spark plug wires, and other wires under the hood, but they are all fine.
I have replaced the front calipers, pads, and rotors, but no change.
When changing the rotors, I replaced the bearings and grease, and packed the crap out of it, but no change.
Also, around 85ish, I get a hell of a vibration. I've checked the tire balance, and of course like I said I replaced the bearings, so I don't know where the vibration is coming from either.

What could be causing the burning rubber smell? At 70ish?

Could the u-joint bearings for my driveshaft maybe smell like that if they need more grease?

I am also suspicious of the transmission may be going out, though I am not having a problem with slipping or popping out of gear. I'm supposed to have a 2400 stall torque converter, but it is still the stock stall.

I'm at my wits end here.

[Sinister]

Belts?

[toddtheodd]

Originally Posted by Sinister

Belts?

Yeah... I checked those, and it's not them or the hoses.

[dmnall]

Tires?

Cheers,
Charlie

[toddtheodd]

Hardy Har Har...
I WISH I could roast the tires at 70...ish...

[oldblue1968chevy]

You cant roast tires at 70mph?!!!! I think you need to check your blinker fluid??



Honestly, good luck! plug wires melting or something???

[1971gmcshortbed]

Do you have a 2 piece driveshaft? If so i'll bet you a 12 pack that the carrier bearing is on its way out. Verify by driving it at speed then touching it. It will be hot,

[tim21391]

mine was ignition switch but smelled like electrcal and rubber

[screamin_c10]

Originally Posted by 1971gmcshortbed

Do you have a 2 piece driveshaft? If so i'll bet you a 12 pack that the carrier bearing is on its way out. Verify by driving it at speed then touching it. It will be hot,

^^^Beat me to it...the bearing gets red hot and the rubber around it starts to burn...I'd check it out quickly though, as enough heat and it will seize, or possibly ignite...either way its bad news....

[oldblue1968chevy]

my ignition switch went out and IT STUNK!! UHH NEVER SMELLED SUCH AN AWFUL SMELL.....but if its working then..lol

Carrier bearing sounds possible

[toddtheodd]

Originally Posted by screamin_c10

^^^Beat me to it...the bearing gets red hot and the rubber around it starts to burn...I'd check it out quickly though, as enough heat and it will seize, or possibly ignite...either way its bad news....

2 years ago I replaced the 2 piece drive shaft and carrier bearing with a 1 piece drive shaft.

[hayhauler71]

Check your starter wires and cable possibly to close to exhaust.

[vectorit]

Sometimes U joint grease or oil getting slung around and on the exhaust can smell like burning rubber.

Any mud or gunk on the drive shaft?
Lose a weight on the drive shaft?
Dented drive shaft?

How old are the tires? Could have a tread starting to separate.

[timski69gmc]

After I changed tires, they had a slight rub on the inside of the wheel well. But I could smell it driving around town. So it was quick to be fixed.

[dakman]

had the same smell, block huggers were contacting the rubber on the driverside motor mount.

[michael bustamante]

I was gonna say carrier bearing too, Also maybe the rear end is real low on fluid? and the residual is burning

[tim21391]

spark plug boot touching the header?

[Diablo de la Noche]

Troubleshooting. My favorite, next to root canal. If just your wing window is open, it may be causing low pressure in the cab, causing the air to be sucked in from other places, usually the AC/heater system, which gets the air from the cowl vent in front of the windscreen. That air comes from the front of the truck. At 70 mph, the air is moving pretty fast and probably can't be coming from anywhere aft of the cab.

So that leaves the engine compartment. What is rubber in there? Plenty. What smells (remotely) like rubber? Coolant may have a rubber smell if it is dirty or really thin (Heater core or hose forward of the firewall). ATF leak hitting hot parts? If automatic, it could be a leak in the trans cooling lines, and at speed the wind might blow it up to the headers, same with the power steering.

The only place rubber parts might hit hot parts would be the plug wires, or random hoses that are out of place. But you would smell it at slower speeds, too. Maybe look for burned stuff on the exhaust parts. Did you check for cupping or uneven wear on the front tires?

It sounds like you have checked all the obvous causes, but what about the odd ones? A front tire out of alignment or camber (maybe), or both so you don't feel a pull, might cause them to slightly slide, increasing some lateral friction. A slightly bent or warped (or loose) rim might not be noticable at low speeds but might cause the same lateral friction and maybe even a vibration at higher speeds (?). The fact of the matter is that the only things that really change at higher speeds is the speed at which the tires rotate. The engine is pretty much in the same operating parameters as at lower speeds, only the tires and wind speeds change (in the front half of the truck).

I don't know, but I'm leaning towards the odd, very odd, possibility that it is your front tires. Feel them after a drive and compare the heat to your rear tires. They should be the same.

I have the strangest luck when it comes to seemingly obvious symptoms. I once smelled burning rubber at speed and it turned out to be a rabbit stuck in my lower radiator mount area. You would think it would smell like chicken.

[LMN8UR]

I would look for the causes of the vibrations. . . You may have two unrelated issues. 70 and faster vibrations (You mean these things can go that fast?) Are there any unusual sounds that go with the vib? Have you put her in neutral during the vibs to isolate drive train? What was the last thing you messed with before it acted up?

[RustyParts]

Check the harmonic balancer, it could possibly be coming apart. Also a cause for vibration.

[toddtheodd]

Harmonic Balancer... wouldn't this smell at a specific engine speed?
I've put it in 2, and revved it up to 3500rpm, and no smell. Leads me to believe it isn't connected to the engine.

Could a bad brake hose cause the caliper to drag? Or... could a dragging brake smell like burning rubber?

The only burning stuff under the motor is an oil leak off of the back of the motor by the oil filter. But it doesn't smell when the engine is running in park with the hood popped...