2003 Duramax Transfer Case leak..

[Blang]

Leak doesn't appear to be coming from above... Leak from between the front and rear part of the case? Replace rear portion maybe and reseal?

 

[Rand]

Clean it so you can see what's going on?

 

[D60]

Mileage?

You're aware of the infamous pump rub, right?

If you find a pinhole in the bottom/side that's it.

I've installed the Merchant Auto kit in an '02 NP261, it's nice. But you'll need a new case half IF this is your problem, or JB Weld and hope and prayers.

 

[BrendanC]

i’ve rebuilt tons of these cases. get an aluminum rear housing from ebay and the cheapest drop in pump saver plate. get a seal kit. taking these units apart is super easy, just need a very good set of snap ring pliers. when you get done, fill with 0w-20 or 5w-30 motor oil instead of ATF.

 

[Blang]

Thanks for the tips! My concern is that it's the pump rub issue. Once it's cleaned up I'll keep an eye on it and see for for sure.
Why use engine oil instead of ATF?

 

[Nick1994]

Get a can of engine degreaser and let it soak, then pressure wash it off clean. Then you can monitor where it’s leaking from.

 

[350Rocket]

i’ve rebuilt tons of these cases. get an aluminum rear housing from ebay and the cheapest drop in pump saver plate. get a seal kit. taking these units apart is super easy, just need a very good set of snap ring pliers. when you get done, fill with 0w-20 or 5w-30 motor oil instead of ATF.

Is there a good resource I can find the difference between these cases? I have an 05 1500 and I thought it was a 261 but it's got auto mode and takes auto trak 2 fluid.....no issues with mine so far but it's got 270k miles on it. I now have 2 spares, one in a 02 1500.

 

[D60]

@BrendanC I meant to tell you when I was just into this BW4493 in an '06 H3 there's a sticker on the bottom specifically saying to add an additional 1/2 qt through the speed sensor hole.

I thought this was amusing as the aftermarket's been reco'ing it on the NP261 and 263 forever, as you know.

 

[D60]

Thanks for the tips! My concern is that it's the pump rub issue. Once it's cleaned up I'll keep an eye on it and see for for sure.
Why use engine oil instead of ATF?

Have you checked fluid level? Even with no leaks these things cook their ATF and it just vanishes.

I'd use a 5W20 or 5W30 full synthetic and forget it. I did this on our old '02 with zero ill effects.

I opted not to "overfill" but many do through the speed sensor hole.

Do not use motor oil on any "auto" or AWD case.

 

[BrendanC]

Is there a good resource I can find the difference between these cases? I have an 05 1500 and I thought it was a 261 but it's got auto mode and takes auto trak 2 fluid.....no issues with mine so far but it's got 270k miles on it. I now have 2 spares, one in a 02 1500.

i don’t quite know all the models in the half tons. for 99-02 silverado/gmc HD’s:
floor shift gasser is 261HD
electric shift gasser is 263HD
floor shift diesel is 261XHD
electric shift diesel is 263XHD.

XHD vs HD is different input splines and a wider chain in the XHD.

i also overfill with 0w-20 until it comes out the speed sensor hole and change annually.

 

[BrendanC]

i don’t quite know all the models in the half tons. for 99-02 silverado/gmc HD’s:
floor shift gasser is 261HD
electric shift gasser is 263HD
floor shift diesel is 261XHD
electric shift diesel is 263XHD.

XHD vs HD is different input splines and a wider chain in the XHD.

i also overfill with 0w-20 until it comes out the speed sensor hole and change annually.

sorry, 99-07 classic not 99-02

 

[D60]

i don’t quite know all the models in the half tons. for 99-02 silverado/gmc HD’s:
floor shift gasser is 261HD
electric shift gasser is 263HD
floor shift diesel is 261XHD
electric shift diesel is 263XHD.

XHD vs HD is different input splines and a wider chain in the XHD.

i also overfill with 0w-20 until it comes out the speed sensor hole and change annually.

I think half ton was just 261 and 263 -- no HD. The Auto-optional case was the NP246 but there was also a full-time ONLY option in the SUVs and it might have lacked low range, I can't remember. The 246 uses the same pump plate so pump rub can still be an issue, but not all cases experience it.

 

[c502cid]

i don’t quite know all the models in the half tons. for 99-02 silverado/gmc HD’s:
floor shift gasser is 261HD
electric shift gasser is 263HD
floor shift diesel is 261XHD
electric shift diesel is 263XHD.

XHD vs HD is different input splines and a wider chain in the XHD.

i also overfill with 0w-20 until it comes out the speed sensor hole and change annually.

My 2002 8.1 is most definitely a 263 XHD.

 

[clinebarger]

NV149 is the full time AWD unit....Silverado SS, Sierra C3, Cadillac Escalade, Yukon Denali mostly.

 

[D60]

NV149 is the full time AWD unit....Silverado SS, Sierra C3, Cadillac Escalade, Yukon Denali mostly.

I think I'm thinking of the BW4482 or 4481.

I saw one in an ~04 Tahoe and it caught my eye because the buttons have no letters ‐‐ just pictorial diagrams of all 4 wheels

 

[BrendanC]

My 2002 8.1 is most definitely a 263 XHD.

wasn’t accounting for the 8.1. should’ve said allison=XHD. 8.1 trucks are rare

 

[clinebarger]

I think I'm thinking of the BW4482 or 4481.

I saw one in an ~04 Tahoe and it caught my eye because the buttons have no letters ‐‐ just pictorial diagrams of all 4 wheels

Those require Stabilitrak (Vehicle Stability Enhancement System) to operate correctly as they have differential pinion gears.
The NV149 has a Viscous Coupler that doesn't require Stabilitrak/VSES.