Knocking axle

[1984Silverado4x4]

I can hear a knock coming from the rear axle of my truck when I slow down to come to a stop or when the engine is off and I just let it roll.
It seems to drive just fine though.
Anyone know what this might be?

[Corts60]

Is your axle full floating or semi-floating?

[1984Silverado4x4]

Not sure

Whats semi and full floating axles

[1969K10]

Originally Posted by 1984Silverado4x4

I can hear a knock coming from the rear axle of my truck when I slow down to come to a stop or when the engine is off and I just let it roll.
It seems to drive just fine though.
Anyone know what this might be?

Have you taken your U-joints out and checked them yet? If not, I'd start there.

[1984Silverado4x4]

I replaced the rear U joint

[Corts60]

If its full floating it will have an 8 bolt hub in the middle that sticks out of the center of the wheel, if not it will just be flush.

[BFRO$TY]

it may be your carrier bearing, i had to replace mine because of the same reason. they are pretty cheap a new one from carquest is only $25.99

[Corts60]

Originally Posted by 1984Silverado4x4

Not sure

Whats semi and full floating axles

This quote is from off-roadweb.com. They can explain it better than me:

SEMI-FLOATER vs. FULL-FLOATERThere are two types of rear axles found on light-duty 4x4s: semi-floating and full-floating. Each has its advantages and disadvantages.

A semi-floating axle is very common on the rear of most 4x4s. It consists of an axleshaft on each side that is splined on the inner end where it mates to the differential and has a wheel flange where the wheel studs mount at the other end. This assembly typically mates to the end of the axlehousing using some type of flange arrangement. The axleshaft also rides on a large roller or ball bearing out at the end of the axlehousing.



1. This Dana 35C semi-floater rear axle from a late-model Jeep TJ uses a flanged outer axle housing (brake backing plate and components removed). The shaft and flange that holds the wheel studs are all one piece.
The axleshaft in a semi-floating assembly serves two purposes. First, it attaches to the wheel and is used to support the weight of the vehicle and its cargo. Second, the axleshaft must transmit the rotational torque from the differential out to the wheel.

A full-floating axle can be found on the rear of some 4x4s, but it is generally reserved for vehicles that are designed for severe duty, or are intended to carry heavy loads. This type of axle uses an axleshaft on each side that is simply splined at both ends or splined on the inner end and has a drive flange on the outer end. The shaft mates to the differential in the same way as a semi-floater. However, the outer end of the shaft differs. Here, the splined end of the shaft slides into a locking hub or an internal splined steel drive plate that bolts to a hub cap, similar to what is found on a front axle. In some cases, the drive flange may be part of the shaft itself. In either case, the axleshaft is allowed to float in the system.

For a full-floater system, the axleshaft only serves to transmit the rotational torque from the differential out to the wheel. It does not carry the weight of the vehicle like a semi-floater does. On a full floater, a spindle is attached to the outer end of the axlehousing. The hub's cap is attached to this spindle and rides on tapered roller bearings. It is this assembly that carries the vehicle weight. As such, a full-floating axle system is considerably stronger than an equivalently sized semi-floating system.



2. A full-floater axle is easily recognized externally by the drive flange or locking hub that is evident in the center hole of the wheel.
For those of you who carry heavy loads, this means your axle load capacity is greatly increased with a full-floater. Load ratings for similar vehicles with the two different axles are usually significantly different. If you do hard-core 'wheeling on big tires, a full-floater means that your axleshafts can also handle much more loading than a similar semi-floater could because it now must only handle torque loading.

Further advantages of a full-floater include being able to remove a broken axleshaft, yet still have the ability to keep a functional rolling tire on that corner of the vehicle. This can be done since the wheel actually bolts to the hub that rides on the spindle attached to the axlehousing. If the axle has manual locking hubs, it may be possible to unlock the rear hubs for towing a disabled vehicle on the trail or for flat towing over the road.

[1984Silverado4x4]

Originally Posted by Corts60

If its full floating it will have an 8 bolt hub in the middle that sticks out of the center of the wheel, if not it will just be flush.

Its semi floating then

[Hoods69BadBowTie]

I was wondering about carrier bearing as well. Did you pull the rear diff cover off yet?

[1984Silverado4x4]

No I havent done that.

Wheres the carrier bearing?

[BFRO$TY]

is your truck a long bed, cause if so those are the only models with a carrier bearing in them?

[1984Silverado4x4]

Nope mines a short bed

[Albatrossian]

Could be just a brake problem.. have you done a brake job lately?

[1984Silverado4x4]

No have done anything to the brakes

[Albatrossian]

A knock is usually caused by something hitting something else or something binding up then letting go. I'd get the rear of the truck off the ground and move the back tires(by hand)back and forth and try to find the noise. Safety first.

[BFRO$TY]

if its a shortbed then it doesnt have a carrier bearing, im not sure what the noise is.

[1984Silverado4x4]

Well I jacked up the back of the truck this morning and turned the wheels by hand. Didnt hear anything so I started it up and put it in gear and sure enough it was going clunk, clunk, clunk,clunk. I saw the driveshaft was moving kinda funny so I turned it off and turned the drive shaft by hand

The little strap clamps holding the U joint at the axle end of the driveshaft werent loose but they werent holding the U joint in place tightly enough allowing it to slide back and forth when it was turned making it go clunk.

So some new clamps for the U joint or make the old ones work somehow.

[Albatrossian]

Check and see if the u-joint caps the clamps are holding aren't grooved. You might just need a u-joint.

[80SPORT]

short bed trucks with the 454 and/or th400 trans use a 2 pc driveshaft with a carrier brg and a special angled hangar ....

[1984Silverado4x4]

Originally Posted by Albatrossian

Check and see if the u-joint caps the clamps are holding aren't grooved. You might just need a u-joint.

Its got a new U joint so the caps shouldnt be grooved. I kinda think the clamps are bad but well see.