NP205 front seal keeps failing?

[rompinstompinmudmonkey]

I've got a dodge 205 behind a dodge NV4500 in my dually. For some reason I have to replace the front output seal every few months.
The case was rebuilt when I swapped the Cummins in.
I've got about 50k on it since then.


I've replaced the bearing, even though it wasn't loose.
I've even swapped the yoke of of the t case in my K5 [(no leaks on the k5)
I installed a new vent in case it was plugged.

The truck spends 95% of it'd time on the road in 2wd.
The front shafts is also balanced and tight.


I'm at a loss. I don't know what else to do. Changing front seals every few months is a pain. It's the only thing on the truck that leaks and if drives my nuts!

Anybody have any ideas?

 

[dremu]

I vaguely recall having immense trouble getting the right seal for my '205, as there are a couple that are very close in size. Maybe you're getting the slightly larger size, and it fits okay initial, but eventually settles in, shrinks a bit and leaks?

In my case, I think a CV yoke had a (slightly) different OD than the single U-joint variety.

Anyway, point being that maybe you're being given the wrong one? Maybe post up the part # you have?

-- A

 

[rompinstompinmudmonkey]

The dodge output uses a different seal (larger). Nobody stocks it and it's always a pain, so I swapped the output housing, seal, and yoke with a GM t case. I have no idea what year the case was that I robbed parts from. I always just order a seal for an 80's NP205

 

[sweetk30]

are you using a gasket for seal retainer to case ?

lots of times I see guys use rtv and plug the return hole off with it and build up extra oil in the seal retainer and push it past the seal .

also make sure the hole is not pluged in the case .

make sure the retainer is indexed to line up with the hole .

also on some there is room to add a second seal over top the first for a cheep double seal . and some also have a single seal with 2 lips on it .

pic little fussy sorry . but you see every part I am talking about.

also what lube are you using ? might try thicker if your doing atf or the special nv4500 lube . thicker gear oil might help a lot .

also new seals do NOT go in dry . always pre lube them with something . and check the seal riding surface .

I know prob beating a dead subject here for ya . just pointers for others later searching .

 

[Fordum]

If you still have one laying around, take a hard look at the old seal to see why it failed. Is the rubbber chewed up? Worn out? Torn?
When you replace it next time, lube the yoke, and then insert it into the seal with both off the truck.
Should be a nice tight fit. Spin the yoke a few times, then pull it out and look at the sealing lip.
Any marks after wiping it dry, means a problem with the yoke sealing surface.

If you have a micrometer or even a caliper, carefully measure the diameter of the yoke sealing surface at various places around its circumference.
It could be perfectly smooth, but slightly egg shaped which would beat out the seal rubber.

 

[miniwally]

Look at the depth the seal is getting installed at and make sure your on the seal surface of the yoke, sometimes the yoke and seal just don't line up correctly.

Also make sure your venting of the case is good, the front output may just be the weak spot when you build some heat and pressure in the case if the vent is not good.

 

[rompinstompinmudmonkey]

Hmmmmm... I put the front bearing retainer on with silicone. I'll have to pull it off and make sure the oil return isn't blocked.

I run 80-90 for oil. It really only seems to leak on hot days after driving, and more when I'm loaded and pulling a trailer. I have a small filter element for a vent. Like a small fuel filter for a lawn mower.

 

[Frscke1]

If your angle of the ft shaft is to great, you may have oblonged the seal seat. I have the same transfer case on my 1 ton. Make sure you run synthetics, that was the only thing that saved mine when I cracked the case out in the desert.
_________________________
PRESIDENT - SUNSHINE VANS - SAN DIEGO
ADRENALIN BY THE GALLON & CHASIN RACIN
ONE FOR THE DIRT & ONE FOR THE STREETS
'93 CHEVY G30 454 4X4 SPORTVAN EXT 146 WB
'92 CHEVY G30 454 BEAUVILLE EXT 146 WB

 

[rompinstompinmudmonkey]

Not much angle on the front shaft. Only lifted 4 or 5"

 

[sweetk30]

Hmmmmm... I put the front bearing retainer on with silicone. I'll have to pull it off and make sure the oil return isn't blocked. .

not to be rude but I have seen more people screw stuff up when not using the correct gasket and saying ahhh just rtv it and it will be fine.

as you said pull it and check it .

 

[miniwally]

Hmmmmm... I put the front bearing retainer on with silicone. I'll have to pull it off and make sure the oil return isn't blocked.

I run 80-90 for oil. It really only seems to leak on hot days after driving, and more when I'm loaded and pulling a trailer. I have a small filter element for a vent. Like a small fuel filter for a lawn mower.

Pull the filter off the vent, make sure you have a 3/8" + vent line, make the vent line kind of long and don't worry about a end cap deal for now.

what you just said tells me your not getting enough venting and pushing oil out of the seal.

 

[rompinstompinmudmonkey]

Wellllllll..... I needed to drive the truck today, so I pulled the vent off and pulled the fill plug so I could top off fluid. Oil came pouring out of the fill plug. The t case is way overfull. I must be building pressure in the transmission. I pulled the plug on the trans and the oil level is level with the fill plug. The last time I built the trans, I added PTO coolers that add an extra quart each of oil capacity, and I over filled the trans through the shifter hole. So the trans had 8 quarts in it vs the factory 5 quarts. Now I'm to the fill plug which should be right at 7 qts.
I wonder why the trans is building so much pressure? It has the factory vent installed on it. I'm going to remove both vents and see if my t case output seal stops leaking.

 

[sweetk30]

last I recall 1/2 qt over spec on nv4500 was recommended . plus any extra like your coolers .

but yes if 205 was way over and the super thin lube of 4500 in it I can see why it leaks from the seals . oil shouldn't make a difference tho on the seal side .

 

[chevyfumes]

That van is sick!

 

[rompinstompinmudmonkey]

Well.... I removed the vents and drove 70 miles tonight. Oil still streams out the front seal. I guess I'll swap the seal again , and inspect the flange really well. I can't decide if I want to drop the t case and replace the input seal, or just run the same Amsoil MTL in the t case that I run in the trans. The trans and t case sharing oil doesn't really bother me. I just want to get the leak stopped and find out why I'm pushing oil out the seal when I drive.

 

[sweetk30]

if your putting oil in the tcase its possible bad seal or in correctly installed seal .

I did that 1 time years ago . seal in the wrong way n th350/205 . dam thing had to be drained every week . went in to the tcase so fast .

I know it wasn't the tranny as it had the 1/8 pipe thread tap in the case breather hole and a barb fitting in it with 3/8 hose up to the fire wall for a breather.

 

[rompinstompinmudmonkey]

I'm sure the input seal is bad. I haven't had this issue until recently, so im certain that its not installed backwards. If I drop the t case to replace the input seal, I'll need 3 or 4 quarts of Amsoil to top off the trans again. If I just replace the output seal and drain the t case. I'll need 3 or 4 quarts of fluid to fill that back up. Is there any potential problems to come from just letting the trans and t case share the same oil?

 

[rompinstompinmudmonkey]

I still don't know why it's building pressure though, or how to stop that.

 

[sweetk30]

worst case if you ask me is low oil in 4500 and fry that sucker .

205 prob wont mind at all .

and might not be building pressure just bad seal letting oil in is all .

 

[rompinstompinmudmonkey]

I don't want to run the 4500 low. I've already wiped out an input bearing, broken an input shaft, and broken the counter shaft. I'm sick of rebuilding that trans.