Grind at 45?

[theredmeadow]

Sorry, I tried searching for answers for this one.

I picked up my truck 3 weeks ago and I've noticed that when I get up to 45 and above the second I ease off the gas there's a grind noise. It'll happen when I'm coasting above 45 and I can feel it in the pedal. I don't feel it when I drive slower than that and it'll only happen when I ease off the pedal, goes away when I accelerate.

[Longhorn 70]

Hmmm.... Does it seem to come from the engine or tranny? Does it sound like a gear grind? Do you have a clutch fan? Does it do it in all gears?

[theredmeadow]

Originally Posted by Longhorn 70

Hmmm.... Does it seem to come from the engine or tranny? Does it sound like a gear grind? Do you have a clutch fan? Does it do it in all gears?

no it doesn't feel like it's coming from the engine. it's more felt under me. this is an automatic and only happens above 40ish.

[vectorit]

Tell us about your truck.
Suburban, Blazer, long bed, short bed, C10, or C20?

[theredmeadow]

It is a 1970 C10 longbed, 350 5.7

[zeldman]

Carrier bearing.... or the rubber around the carrier bearing? Just a quick SWAG.

[Longhorn 70]

carrier does sound like a suspect also look at the trans mount. Try this if you can but don't over do the engine...

See if you can hold it in a lower gear and test it at 45 again. IF it is the carrier it should do it at the same speed. If Mr. Transmission is unhappy it may do it at a lower speed. Without a lot more info, it's tough to guess at.

[theredmeadow]

How would I be able to tell if it's the carrier bearing? Should I be able to move it or in some way feel if its bad?

[c20pickup]

Originally Posted by theredmeadow

How would I be able to tell if it's the carrier bearing? Should I be able to move it or in some way feel if its bad?

the carrier bearing is shot on my 71 parts longhorn, im able to grab the driveshaft and move it atleast 1/2-3/4 of an inch. i doubt yours is that far gone, but try grabbing the drive shaft right infront or right behind the carrier bearing rock it up and down and side to side, there should be very little to no movement. if the carrier bearing is in good shape move onto u joints. i just had an intermittent shake and grind in my 99 yukon at various speeds, i crawled underneath the truck and shook the driveshaft and there was no play, i ended up pulling the driveshaft and pounding in new ujoint because they were bad, they had no play, but they would bind up if i flexed the yoke and the driveshaft. if all else fails have your driveshaft looked at, it could be bent or not balanced, this would cause more of a shake then a grind though, but ya never know. this is just where i would start, hope it helps.

[airdale94]

Originally Posted by theredmeadow

I've noticed that when I get up to 45 and above the second I ease off the gas there's a grind noise. It'll happen when I'm coasting above 45 and I can feel it in the pedal. I don't feel it when I drive slower than that and it'll only happen when I ease off the pedal, goes away when I accelerate.

That's classic symptoms of a pinion bearing going out in your rear end. Carier could be a posibility also. A pinion will have more of a hum sound. And I wouldn't think you would feel it on the gas pedal.

[Billett]

I know this is going to sound dumb, but it isn't an exhaust rumble is it? I know some of those glasspacks have a rumble when you let off the gas at higher speeds, hell my hookers do it to some extent.

[theredmeadow]

No its not so much a rumble but a grinding noise/feeling through the floor and gas pedal. I'm going to check the carrier bearing and if that's not it I'm going to check the balancing on my driveshaft.

[Zeke's Garage]

Don't overlook the suggestion of the pinion bearing on the rear-end. Especially if you're feeling it on 'coast' and not under acceleration. Could also be a carrier bearing, or broken tooth on the ring/pinion. You'll need to pull the diff cover to check it out.