'04 rearend - finned diff vs. new axle

shaffer · 03-06-2006, 11:22 AM

Looks like I'm the lucky recipient of a dying rear end. My '04 Titan just turned 30,000 miles. While changing a flat tire the other week I noticed the diff cover was completely rusted form top to bottom and the paint was gone. The diff was also leaking. I took it into the dealership last week to look at a couple of items which included the rearend. When I went to Sutherlin Nissan I honestly expected them to tell me this is normal and just deal with it (they like to tell me that). When they called to tell me the that the entire rearend has to be replaced and they ordered a new axle seembly I was impressed. I was glad to hear the axle will be replaced, but surprised it has lasted 30,000 miles. I do a fair amount of towing with my truck, pulling a CJ-7 to places like North Carolina and Alabama from Atlanta. You'd think it would of died out log before now.

I read another thread on this site that talks about Titan owners having their rusted diff covers replaced by Nissan dealerships, switching them to the finned version found on '05s and up (not switching out the entire axle). Is this just the dealership putting a band-aid on a bigger issue? After reading all of the stories about rearends blowing up, I would not be comfortable with just a new diff cover to solve the problem. When so much heat is generated by the R&P that the paint peels of the diff cover, a finned cover isn't going to fix the damage already done internally.

I looked over the Dana 44 yesterday and was unable to find a vent hose on the pumpkin. Surely I just overlooked it and Nissan is intelligent enough to properly vent their axles - otherwise just about every Titan out there that pulls in the 5,000 - 6,000 lb range will eventually lose their rearend to heat!

What's my point? I hope those people who are getting their diff covers replaced aren't getting the smoke and mirrors treatment from Nissan.

bestatchess · 03-06-2006, 11:33 AM

The vent is a check valve that sticks up on the right side of the rear axle assembly (not on the pumpkin or close to the pumpkin).

**helomech** · 03-06-2006, 11:40 AM

Maybe when they were trying to seal the rearend they may have noticed some broken gears, and aren't telling you. I doubt they would have change the rear if they didn't have to. If it wasn't broken the dealer would have to eat the cost because nissan would not reimburse them. I just posted some pics of the diff vent in the thread below this one.

shaffer · 03-06-2006, 02:00 PM

Why would the vent not be on the pumpkin since that is where a majority of the heat is generated? That doesn't make sense. The seals to the left and right of the carrier prevent the heat from exiting the pumpkin. The heat does not escape left and right down the axle tubes. Maybe that's the problem - the vent is not properly located.

Sammy Sandbag · 03-06-2006, 02:03 PM

Quote:

Originally Posted by shaffer

Why would the vent not be on the pumpkin since that is where a majority of the heat is generated? That doesn't make sense. The seals to the left and right of the carrier prevent the heat from exiting the pumpkin. The heat does not escape left and right down the axle tubes. Maybe that's the problem - the vent is not properly located.

Vents aren't for heat, they are for the pressure that builds as a result of the heat. The axles are sealed at the ends of the tubes, not inside the carrier. There's nothing really wrong with their placement, as long as they are working properly.

shaffer · 03-06-2006, 02:34 PM

I believe they are sealed at the chunk as well. Otherwise your diff fluid would run into the axle tubes during any off camber run. If you look at any other dana 44/60/70 they are vented at the pumpkin.

Is the pressure not generated from heat buildup?

Sammy Sandbag · 03-06-2006, 02:42 PM

Quote:

Originally Posted by shaffer

I believe they are sealed at the chunk as well. Otherwise your diff fluid would run into the axle tubes during any off camber run. If you look at any other dana 44/60/70 they are vented at the pumpkin.

I see what you're saying, but I've also seen axles that carry fluid in the tubes. Seems sorta pointless to have a vent there otherwise and seals at the ends as well. Now front axles are usually the way way you describe.

Quote:

Is the pressure not generated from heat buildup?

Symantics. The vent isn't there to release "heat" but air pressure as a direct result of heat.

shaffer · 03-06-2006, 02:43 PM

Disregard the heat/pressure question. You won't have one without the other. The vent allows the heat to escape, thus keeping the pressure in check.

I'm not trying to be difficult with this. I just have a hard time understanding why the vent isn't in the more logical location - on the pumpkin.

Sammy Sandbag · 03-06-2006, 02:51 PM

Quote:

Originally Posted by shaffer

Disregard the heat/pressure question. You won't have one without the other. The vent allows the heat to escape, thus keeping the pressure in check.

Well except the heat is still present. The heat is created by the friction between the gears, not the friction between air molecules.

Quote:

I'm not trying to be difficult with this. I just have a hard time understanding why the vent isn't in the more logical location - on the pumpkin.

Your guess is as good as mine.

ptgarcia · 03-06-2006, 06:02 PM

Quote:

Originally Posted by shaffer

Disregard the heat/pressure question. You won't have one without the other. The vent allows the heat to escape, thus keeping the pressure in check.

The vent is there to bleed pressure, not release heat.

Quote:

Originally Posted by shaffer

I'm not trying to be difficult with this. I just have a hard time understanding why the vent isn't in the more logical location - on the pumpkin.

If the axle is pressurized it doesn't matter where the vent is placed because all points inside the axle will have equal pressure.

shaffer · 03-15-2006, 02:17 PM

I just spoke with my Nissan dealer. Looks like it is going to be a couple more weeks before my new Dana 44 arrives. According to the service rep the axles assemblies are on "national backorder." Apparently the problem is big enough to drain Nissan's supply!

RB's Titan · 03-15-2006, 03:05 PM

Quote:

Originally Posted by shaffer

I just spoke with my Nissan dealer. Looks like it is going to be a couple more weeks before my new Dana 44 arrives. According to the service rep the axles assemblies are on "national backorder." Apparently the problem is big enough to drain Nissan's supply!

Part of the problem maybe that Dana has filed for bankruptcy.

http://www.detnews.com/apps/pbcs.dll...603040330/1148

autotech · 03-15-2006, 11:40 PM

the rear end not properly vented would cause leaks the problem with our diffs at these low mileages you see posted is the fact that the spider gears are made out of a composite metal instead of solid steal bad idea i have a 65 dodge dart gt put a big block in it the first time i jumped on it i did the same thing that happened to the diff in my truck known problem with the 7and3/4 inch chrysler diff of the past COMPOSITE GEARS

Smoke05 · 03-17-2006, 08:25 PM

Quote:

Originally Posted by autotech

the rear end not properly vented would cause leaks the problem with our diffs at these low mileages you see posted is the fact that the spider gears are made out of a composite metal instead of solid steal bad idea i have a 65 dodge dart gt put a big block in it the first time i jumped on it i did the same thing that happened to the diff in my truck known problem with the 7and3/4 inch chrysler diff of the past COMPOSITE GEARS

Leaks lead to low fluid levels, which leads to higher heat in the diff, which can contribute to weakening the spider gears. I'm sure the powdered metal process and it's apparent lack of QC consistency from Dana isn't helping either.