NP205 to SM465 Adapter Crack - Not just an oil leak

[jeffahart]

I recently had my SM465 and NP205 rebuilt. I had a leak at the bottom of the adapter on the transmission side. I figured it was the gasket or one of the through bolts. I pulled the transfer Saturday and replaced the gasket. It's a full day project for me to pull everything off, including the hump, drop the transfer and stick the thing back in and reassemble everything. At the end of the day a bead of oil appeared in the same location. The gasket looked fully dry. What a pisser. I got under the truck this morning with an ultraviolet light. You don't need dye, you can see the oil with a real ultraviolet.

Attached picture, you can see the oil seeping from the crack. Ordered a new adapter.

Looks like I'll be pulling the 205 for the third time in an month.

Sucks, but glad I know it's cracked, I have freshly rebuilt gear boxes and a new drive shaft.



j

[GSP7]

Is that a advance adaptor? Or is there a OEM factory type cast iron adaptor?

https://www.polyperformance.com/adva...SABEgIz_PD_BwE



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[jeffahart]

The one in the picture is an OEM iron. I ordered an Advanced Adapter replacement(shown in your link) from Offroad design, which is aluminum.



j

[sweetk30]

sorry to here this one . lots of guys break them and or 205 t-cases from no gasket . they were designed for specific gasket thickness NOT rtv only .

but like you said yours was gasketed . . . must have been somthing else .

to bad you didnt post a wanted ad . i have a good clean used gm unit sitting here .

but ord are good people and will get you covered and rollin again . then know there gm trucks .

[jeffahart]

Originally Posted by sweetk30

sorry to here this one . lots of guys break them and or 205 t-cases from no gasket . they were designed for specific gasket thickness NOT rtv only .

but like you said yours was gasketed . . . must have been somthing else .

to bad you didnt post a wanted ad . i have a good clean used gm unit sitting here .

but ord are good people and will get you covered and rollin again . then know there gm trucks .

Yep, and you need the big fat gasket to maintain tolerances. I only have a few miles on the new trans and transfer. Just wanted to get the leak solved and call it done. I hate rebuilt stuff that leaks, ain't right.

Thanks on the adapter, I just ponied up the bucks for new. They say it's stronger. My t-case had the frame mount for years. That probably didn't help anything, as I've read on this site they discontinued it because it was cracking adapters.

I really hate how long that adapter is, it just want's to crack!


j

[Blazerowner]

My original is cracked and repaired. Seemed to work fine until I replaced it with an adapter for my 4l80e.

[jeffahart]

Originally Posted by Blazerowner

My original is cracked and repaired. Seemed to work fine until I replaced it with an adapter for my 4l80e.

Yeah I thought about trying to get it repaired but decided just to get a new one. They're a bit pricey. But I'm starting to get a lot of new parts I want to protect. Getting the trans and transfer rebuilt is really starting to turn into the domino effect.

[SunSoaked]

Can you guys elaborate a little? I'm about to install a 205 round pattern behind my 4500. I can't tell from the picture what exactly your talking about. Just curious and like to be educated.
Thx

[jeffahart]

Originally Posted by SunSoaked

Can you guys elaborate a little? I'm about to install a 205 round pattern behind my 4500. I can't tell from the picture what exactly your talking about. Just curious and like to be educated.
Thx

Sure. I annotated the pic. We're talking about my np205 to SM465 adapter has a hairline crack at the bottom on the transmission side.

First, everything glowing is the oil viewed in the complete dark with a true ultraviolet light, that's why it's glowing. The thin sheen of oil can not otherwise be seen. And, it's actually hard to feel. It is a very thin wall of oil seeping out the crack.

See the short red line with the arrow above it? that very thin glowing line is the hairline crack.
See the green curved line with the arrow below it? It's the more severe crack with more oil seeping. I cannot see this with the naked eye.

I visually inspected the adapter and it looked good to me. Go figure.

My transmission and transfer have been leaking for years. Just figured good old leaks. NOT... it's the sinister dreaded cracked adapter.


Hope this helps. Let me know!


j

[sweetk30]

Originally Posted by SunSoaked

Can you guys elaborate a little? I'm about to install a 205 round pattern behind my 4500. I can't tell from the picture what exactly your talking about. Just curious and like to be educated.
Thx

your style dont crack like the fig 8 style adaptors tend to do .

[jeffahart]

Installed the new Advance Adapters 'Adapter' Saturday. Took the better part of the day. But it's in and no more leaks. I examined the old adapter and the crack is not visible from the outside, and you can barely make it out looking at it from the inside. It is very annoying, after spending time and money seeing a big obvious crack would make me feel a bit better about the whole fiasco.

Here's the adapter. Nice piece. The boss is bored for the 9/16 pivot bolt, so I will switch over to a the bigger threaded bolt. Right now I'm using a straight 9/16 bolt with stacked bronze sleeves.

Here's some pics of the new adapter.


j


New Advance Adapters 205/465 Adapter



New Advance Adapters 205/465 Adapter



New Advance Adapters 205/465 Adapter

[GSP7]

My t-case had the frame mount for years.

Are there two different mount systems? Any pictures of the two type mountings?

Is this the frame mount? No crosss member ?



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[jeffahart]

Originally Posted by GSP7

Are there two different mount systems? Any pictures of the two type mountings?

Is this the frame mount? No crosss member ?



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All have the cross member. The side mount to the frame, shown in your pic, was an early model extra. But it looks like it ended up doing more damage than good, so they discontinued it. That's from what I read on this forum. You can dig around and find the thread.

It has me scratching my head, because I love to strap the crap out of things. But I guess it's too rigid of a system when the side mount is combined.

Also, see the bracket at top next to the exhaust? That's the top part of the cross member. The rear cross member is very similar to the one under the engine.



j

[Mendo70C20]

I'm in the process of resealing my transfer case as well, and we noticed hair line cracks in the sunflower cover. So i ordered a MUCH beefier, and prettier billet aluminum one from Northwest Fabs. Thing looks amazing. I'll be using a new Advanced Adapters, adapter as well, but i'll mating it all up to a new Tremec 4050.

[Richard]

Myself, and others think adapter failures are due to the side mount on the NP205. Will not be reusing it in my 650hp build with low gears and big tires. GM stopped using this mount after 72 I believe. The mount does not allow the transfercase to move the same as the engine and transmission, causing undue stress on the fixed trans/t-case adapter. A divorced t-case can use the mount with no problem. Simply using poly bushings on the engine and a rubber mount on the trans mount can cause problems as well. My two cents.

[Orange Crate]

I really like your trans jack to 205 cradle, I need to make one of those. I have a trans jack and the 205 will skate around on the flat platform (as you already know). Nice work there to have a leak free overhauled drive train now....