where is my NP208 leaking from?

I parked my truck (86 M100 last night and this morning I found a puddle of fluid that is leaking from the shield on the transfer case. I cleaned it up, but it keeps leaking. This evening it is still leaking. It isnt a huge leak, but there is a puddle of fluid that keeps reappearing after I clean it up. The rear driveshaft seal is dry. The connection to the front drive shaft is wet, but I dont understand the spray pattern that I am seeing. It seems to be leaking higher up. Is it possible that the fluid is leaking out of the vent tube? I will check the fluid levels in the morning, but I am pretty sure it is coming from the transfer case. If it is the front driveshaft seal, is it not surprising that it is continuing to leak for a day after the vehicle was parked. Where else can these things leak?

They can leak anywhere. They leak at the seals as you mentioned and at the seal where the tail housing connects and the 2 halves are just sealed with Permatex. I hope you don't have a cracked transmission/transfer case. The tail section of the transmissions are notorious for cracking as is the case on the transfer case. Have you lubricated the front drive shaft C/V joint? I know if that dries up it can lock and push back against the transmission transfer case assembly and break things. But it is hard to diagnose a leak from afar. I seen them leak at the shifter seal, modulator seal, and blow out the vent tube on the transmission. I am sure there are many places the fluid can get out. But parked I am guessing a more serious issue. Find it and report back. Good Luck. Fingers crossed in PA for you.

I have a truck that has a decent leak from the governor cover (up high) on the transmission, which travels down the side of the case, down the adapter, and eventually drips from the very back of the transfer case skid plate.

Consider cleaning the underside and drivetrain, letting dry, and then reassessing what components show wetness/leaks.

The governor cover is an easy fix. remove and replace the gasket. Let it drip dry before you seal it.

I removed the filler cap on the transfer case, and the fluid came gushing out. A lot of fluid. What would cause this?

one more question. to lube the joint on the front drive shaft, I assume the drive shaft has to be removed? I dont see any grease fittings.

Oh it is in there. You need a special needle type tapered adapter. I will get some pictures for you. When I get home. And the transmission is leaking into the transfer case. I don't know exactly how to fix it but it has a seal between the 2. I removed the transmission and transfer case on a few and had them resealed entirely for this same issue. I tend to over do things. But it avoids me a lot of dead time along the road when a catastrophic failure could have taken place in stead of my over maintenance. I mean at 30+ years something's got to give. Good Luck. Do it right the first time and move on and forget about it.

As promised I took a few pictures of the grease gun adapter and the fitting in the CV joint that the adapter pumps the grease into the front drive shaft CV joint. This is the end that just snaps onto the grease gun. This is why I spend the time to remove the front drive shaft. The fitting is imbeded in the dirt. Many are neglected and have never been greased. After spraying the fitting with some WD40 and scrubbing it with a small brush it is ready to accept grease. With the front drive shaft removed you can get clean up the CV joint really well and get the grease worked in as you move the joint around. Don't get wild and over grease it. Grease attracts sand and dirt. Clean it all up after it is greased and give the entire drive shaft a good coat of paint. And while there change the pinion seal or clean the yoke and slip joint really well. be careful not to knock the front U joint caps off the U joint. That is always fun. I can take one of these front drive shafts off, grease it good and put it back on in about 20 minutes. 5/8" socket on a cordless impact to remove the flange mount from the transfer case and a 7/16" socket on the cordless for the front U joint strap bolts. I hope this helps clarify the procedure. And if you have never greased the CV joint. Now is the time to do it. if the shaft locks up it will push back and snap transfer case and possibly transmission. Have a Great Day.

I removed the transfer case and found the seal between the transmission and transfer case was the consistency of chalk. I replaced all the seals. For the record, the fluid leak was coming out of the vent tube on the transfer case. When I removed the fill plug, I got an unexpected heavy dousing with Dexron III. With these new seals, this should last me another 30 years. Thanks for the pics, and thanks for all of your help. You are a great resource.

TedO any time I can help fix/resolve a problem I am happy to do so. I should look closer at things so I can advise more accurately. When I do have to remove a leaking transmission or transfer case I just send it to the shop for overhaul or reseal. I don't like, have the know how or have the tools to do internal transmission repairs. And my experience is when 1 seal is bad there are 3 more that are not far behind that one. Yes the vent tube is the only exit for the excessive fluid. Good find. Have a Great Weekend. I will be doing some Mr Rusty diagnosis over the weekend. I will keep you posted as always.

I had the same problem on my M1008. The seal between the transmission and t-case was the cause. Along with a leaking front output shaft seal. New seals and everything is good to go. Same thing, seals were dry and cracked.

patracy said:

I had the same problem on my M1008. The seal between the transmission and t-case was the cause. Along with a leaking front output shaft seal. New seals and everything is good to go. Same thing, seals were dry and cracked.

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Reviving an old thread here - I've got the same issue as TedO. M1008 sitting for a few months, come back to a decent sized wet spot underneath my NP208.
Visible drop on the rear output shaft and skid plate underneath the t-case. I plan on cleaning up then reassessing the leaks, but I know I'm going to need seals changed. Figure I might want to tackle this job now since I have the front and rear driveshafts off the t-case.

What seals are everyone using between the transmission and t-case, output shafts, etc.? Would be useful part info for future problem solving