Pulled my '99 Velocity 320 with T-7.4 to Fl from NC last weekend with my 03 chevy avalanche 1500 4wd. Pulled great all the way. After dropping off boat the rearend starts to "roar". Have rear end looked at and ALL the bearings in the rearend are GONE!!! Races seized to surrounding parts--WTF??? The truck is rated to pull the boat and trailer weight. I was worried about the tranny so I ordered a large capacity pan and tranny cooler and was going to upgrade some internals. What the hell should I do to the rearend? Let me guess, new Eaton or Strange differential?

Rearends are relatively cheap. Put a Meritor in. Look at their website. Ford uses them for the majority of their 650 and 750's. They can be put in relatively small banjo's and fit on light duty trucks

A Velocity 320 with twin big blocks being pulled by a half-ton truck is your problem.

A 7.4 in a 1500? I thought they were 2500's

I'm with Chris

The T-7.4's are in the boat.

Your truck is not rated to tow that boat. That's the problem.

It's not surprising that the rear gave up- although the trans they put in those trucks isn't known for durability.

The 1500's are made for intermittent use when carrying/pulling load. This is best evidenced in the rear end. Unlike larger trucks, the small one's use a non-floating rear axle. If you're unfamiliar with this, I'll explain. A car axle has bearings that the end of the axle ride upon and the wheel bolts to the end of the axle at the flange. A full floating axle is entirely different. The wheel bolts to a hub which rides on a pair of bearings that mate to the housing stub at the end of the axle tube. This bears all the vehicle's weight and forces. The axle engages a spline in the differential and another one in the hub. It only bears the torsional load from the vehicle's drive force.This is why they're called "floating"- they bear no vehicle load. This is primarily a safety factor- if the axle breaks the tires are still retained. It's a not too infrequent occurence for a non-floating rear to break an axle and lose the tire and the outboard section of the axle. Not good while towing a big boat.

Keep this in mind- the axle in that truck is constructed commensurately with all the other structural and load-bearing componentry on the vehicle. The frame, brakes, driveline including driveshaft and so on are all made for tossing less that 1,000 lbs in the back on infrequent occasions and moving them about.

Boat is rated at 6900, truck is rated at 7900 Ain't dis a beatch, just bought the damn truck--time to trade up.

Boat is rated at 6900 dry maybe.. You have the trailer weight, fuel, and cargo etc.etc. I personally recommend serviceing front and rear differentials and transfer cases every 10-15k miles with full synthetic gear lube. I know I am overkill on maintanence but knock on wood I have never had a major failure. Here is what your avy is rated at.
Vehicle
Axle Ratio
*Maximum Trailer Weight
**GCWR

C-1500 (2WD)
5300 V8
3.73
7,200 lbs. (3 266 kg)
13,000 lbs. (5 897 kg)

4.10
8,200 lbs. (3 719 kg)
14,000 lbs. (6 350 kg)

K-1500 (4WD)
5300 V8
3.73
7,000 lbs. (3 175 kg)
13,000 lbs. (5 897 kg)

4.10
7,900 lbs. (3 583 kg)
14,000 lbs. (6 350 kg)