14ff corporate vs AAM 10.5- parts compatibility

454cid said:

The newer axles got synthetic gear oil, but I wouldn't hesitate to run regular 80w90, if you've already got it.

You should be able to ID the gasket you need just by looking at the cover, while on the truck. As far as swapping covers, if they fit, they fit. I think they will. Looking at Rockauto's offerings, the fitment guides look incomplete, to me. If I look up a 73, the fewer parts they list often go up to the 2000s, but'll skip 87. If I look under 2005 they only go back to the 80's. I think it's just screwy listings. Covers don't really need to change to accommodate a new vehicle platform. Maaaybe the accommodation for the brake lines changed?

As I mentioned elsewhere, the gaskets I've used for the axle shafts were a funny paper. As long as there isn't a significant thickness difference, I'd think either would work. Some people skip the gasket and go straight to RTV.

New GM covers are available, too. I think I remember someone in the last few months buying a new GM cover that was cheap/crappy, Though. I got mine several years ago on ebay as a kit.... cover/gasket/bolts.

Bolts.... my 99 still uses SAE cover bolts. I'd guess your 2005 does too, but I'd suspect you could get something functional from Menard's or TSC, either way, if you needed to.

A wire wheel on a angle grinder makes quick work of old gasket material, just don't get any stray wires stuck in you, or inside the differential. I haven't been able to find a wire wheel that doesn't throw wire.

What made you decide to pull your axle shafts? That oil looks really brown.

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The part number is now 88900401

because I live in northern wi i think i want to make sure i keep the synthetic 75w-90

AuroraGirl said:

I did take a look, gm of course said that they returned to rear drums in 2004, but it appears only in light duty 1500? But light duty 2500 maybe also got drums? but i assume LD 2500 wouldnt get a full floater, but i have no idea.
I have a 2005 hd so makes sense i have the disc

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Read drums yes on the 10 bolt and 14b SF, just not on the FF as far as I know.

454cid said:

I don't even like using the year range because GM overlaps platforms. Our trucks are 88-98, but there were still Squarebodies being built through 91, and GMT-400s were still being built through 2000, and even later if you want to include the 3500HD that went through 2002 in the US.

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Very good point

AuroraGirl said:

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The part number is now 88900401

because I live in northern wi i think i want to make sure i keep the synthetic 75w-90

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I would do the same in your climate. I'm in the deep south so I wouldn't have any qualms about using thicker conventional gear oil here

glock20 said:

Read drums yes on the 10 bolt and 14b SF, just not on the FF as far as I know.

Very good point

I would do the same in your climate. I'm in the deep south so I wouldn't have any qualms about using thicker conventional gear oil here

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I think GM had a TSB about g80 functionality in colder climates when they had changed to that synthetic, or im misremembering another TSB lol

AuroraGirl said:

I think GM had a TSB about g80 functionality in colder climates when they had changed to that synthetic, or im misremembering another TSB lol

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If so, I've not heard of it. The one I've heard a million times is about not putting a limited slip additive in the oil, for the G80 locker.

80w90 was used for years before the switch to synthetic. You mentioned funds being tight, so not having to buy something, is why I'd suggest using the dino-oil.

454cid said:

If so, I've not heard of it. The one I've heard a million times is about not putting a limited slip additive in the oil, for the G80 locker.

80w90 was used for years before the switch to synthetic. You mentioned funds being tight, so not having to buy something, is why I'd suggest using the dino-oil.

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I looked into it more, the gm fluid speced comes with friction modifier in it. you arent to add any extra . Eaton says the same thing about the texaco fluids they recommend (likely the gm ones in original packaging)

But eaton maintains you can use any synthetic or conventional and any weight. i suppose for gm its the all-round and the additive situation built in they say you must only use that one.

454cid said:

The newer axles got synthetic gear oil, but I wouldn't hesitate to run regular 80w90, if you've already got it.

You should be able to ID the gasket you need just by looking at the cover, while on the truck. As far as swapping covers, if they fit, they fit. I think they will. Looking at Rockauto's offerings, the fitment guides look incomplete, to me. If I look up a 73, the fewer parts they list often go up to the 2000s, but'll skip 87. If I look under 2005 they only go back to the 80's. I think it's just screwy listings. Covers don't really need to change to accommodate a new vehicle platform. Maaaybe the accommodation for the brake lines changed?

As I mentioned elsewhere, the gaskets I've used for the axle shafts were a funny paper. As long as there isn't a significant thickness difference, I'd think either would work. Some people skip the gasket and go straight to RTV.

New GM covers are available, too. I think I remember someone in the last few months buying a new GM cover that was cheap/crappy, Though. I got mine several years ago on ebay as a kit.... cover/gasket/bolts.

Bolts.... my 99 still uses SAE cover bolts. I'd guess your 2005 does too, but I'd suspect you could get something functional from Menard's or TSC, either way, if you needed to.

A wire wheel on a angle grinder makes quick work of old gasket material, just don't get any stray wires stuck in you, or inside the differential. I haven't been able to find a wire wheel that doesn't throw wire.

What made you decide to pull your axle shafts? That oil looks really brown.

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Lol. The vent on the axle was bad (it still is)( and the trailer was used to move firewood from outback with a tractor, it got muddy, and took on water and mud.
The poo that came out was definitely contamination. The vent is still bad, but its now not hanging low and I am aware of it, i checked the fluid 2 years ago and its still clean so i think its taking on so little dust now its not as bad. still need to get a vent on cap on the line, i just need to cut it shorter and stick one in. no need for it to be on the bottom of the bed like OE mounting was.
The axle shafts were removed and replaced with snowmobile stop sign caps to hold fluid in. The fluid is there to lubricate the bearings. But with no axle shafts to distribute the oil down the tube, I have submerged them by jacking up the axle after capping one side and pumping that puppy pretty full.
Dont mind the mess, I got excited with the pump wand and kinda kept pumping while removing the end of the wand /nozzle in an oopsie event lol.


Fun fact I did try to source new bolts from menards because I had exactly 2 missing bolts on one side which were replaced with normal bolts (non flanged) by either my gpa or the original owner of the 76 c20 thats been a trailer longer than it was a truck lol, and it was shorter too. I couldnt find any at menards that were flange that were the right length, id have to cut some down. for the time i just lived with the odd bolts, but the washers prevented the easy removal and install of the wheels.. so I found my spare squarebody parts coffin in the back of a 1980 cutlass outback and there was a mostly full set of bolts and two shafts, but one shaft had spline damage so i wouldnt ever want to install it lol.


another fun fact, ididnt know what i was doing then but I used Red RTV on both sides of the metal gasket (cringe, I know) it didnt leak but when I removed the caps to inspect the fluid and stuff I removed the gaskets and put new ones on (they are one time use but im sure i could have reused since my cover is signage aluminum not a flange of hardened steel)