Tranny fluid in Transfer case

[GI Blazer]

I've noticed for quite a while that my speedo output on the xfer case wet with tranny fluid, (never thought much about it as there was never more than a couple of drops under the truck) I was changing out the rear output yolk on the case a couple days ago and tranny fluid came out when I pulled the yoke out. I then drained the case and it was full of tranny fluid. I had this once before and the tranny was rebuilt since then and while the tranny was down a seal on the front of the xcase was changed as well. Is this common? Anybody have drawings or diagrams that show the seals in the tranny and the xcase. I would like to fix this permanently.

[lilred67]

what transfer case do you have?alot of them use atf for lubrication.

[mrein3]

What I know about transfer cases is limited to the NP205. This is the only transfer case I've dealt with.

The part between the tranny and the xfer is called the "adapter". Inside the adapter there is a drive sleeve. This drive sleeve slides over the output of the tranny and the input of the xfer. This couples the two together.

The drive sleeve comes in contact with a grease seal on the front and the back of the adapter. The front seal keeps tranny fluid in the tranny. The back one keeps xfer lube in the xfer. This is just like the front oil seal in your timing chain cover on the front of the engine or the rear axel seal on a 1/2 ton axel.

As you know you sometimes have to replace these oil seals. Sometimes the harmonic damper gets a groove cut in it so you need an offset seal or a new harmonic damper or that little ring you can hammer over the end of the damper.

It sounds like tranny fluid is getting by the seal in the adapter. If you ever worked on one of these you may seriously consider dealing with a slow leak verses trying to fix it.

[GI Blazer]

It would help if I was a little more specific. I have a Turbo 350 tranny and a NP205 xcase.

[krue]

I have the same problem. I'm gonna reseal everything (I have them out of the truck) and hope that fixes it. Makes me wonder what it would hurt to run atf in the xfer case, then I get to thinking about wear particles from the xfer case getting into the tranny thru the seal and not getting filter etc, etc, so I'm gonna try to fix it.

[krebsatm02]

From what I remember the 205 is just about speced for most types of lube, although the most popular is 80/90w. Maybe the person that rebuilt your 205 used ATF?

You could all solve this problem by running a SM465 and 205

My rock buggy will be a SM465 mated to the planetaries of a NP241, and then a Ford NP205 behind that all using the same 80/90w

[orange72blazer]

I have this problem also, th350 np205, I had everything all apart 2 years ago. I replaced the 2 seals in the adapter, and the big oring on the end of the transmission but it still leaks about a quart every 200 miles or so. I couldn't find any info or diagrams on the transfercase I'm not sure if I have all the oring and seals in it or if I may have missed something, I had a hard time even finding parts for it. Is ther any seals that I may have missed that would cause this? What keeps the tranny fluid from going thru the splines on the trans. and into the tcase?

[mrein3]

Originally Posted by orange72blazer

I have this problem also, th350 np205, I had everything all apart 2 years ago. I replaced the 2 seals in the adapter, and the big oring on the end of the transmission but it still leaks about a quart every 200 miles or so. I couldn't find any info or diagrams on the transfercase I'm not sure if I have all the oring and seals in it or if I may have missed something, I had a hard time even finding parts for it. Is ther any seals that I may have missed that would cause this? What keeps the tranny fluid from going thru the splines on the trans. and into the tcase?

I think you're screwed on that one. There is nothing to keep the fluid from going throught the splines through the drive sleeve. In fact it is probably designed that way so you get some lube in there.

Put the transfer case on your list of yearly maintenance items (change the gear oil), keep your tranny fluid up, and forget about it.

The only other way to get tranny fluid by is if you have a groove cut in the outside of the drive sleeve from the oil seal. I'm sure they don't make offset seals for this like they do for front engine oil seals. If this is the case you need a new $100 drive sleeve. Then of course while you are replacing that you may as well do the seals again because it is such a bear to get that far.

[jkade]

I been running atf in my 205 for years and no problems. I had it out a while back when I went to the 4 speed and I filled the 205 back with atf. I was told that is what to put in it.

[FRENCHBLUE72]

I have the same leak problem also I just deal with it.....

[1976K5CHALET]

Somewhere in the late 80's gm changed the spec on what fluid to use in the NP205..as far as what year i can not speak with certainty as my manuals are all boxed up until the new house is built. GM continued to run the 205 until the demise of the R/V series in mid 92...only in V30 models, 87 was the very last year of the K designation for pickups in our body style...except cab chassis...burbs...K5's...crew cabs which continued as the R/V series until mid 92 of course.

Pre 72 NP205's had side mounted torque mounts that bolted to the side of the frame...the other issue i am aware of is the early 205's had a bearing attached to the dry sleeve at the trans end...

An oddity i ran across years back was if you were to buy a 205 73-91 shifter it came with the pivot bolt which was machined for a grease zerk....this was in the early 90's if i can remember right. In the late 90's i bought another one and was surprised when no bolt fell out of the box...but the shifter had been slightly re-enginered to include a small spring eye looking bushing inserted to prevent rattleing of the shifter. It was odd as generally after the 10 years parts for a body line sease to be made...let alone re - engineered.

DW

[GI Blazer]

Seems this is a pretty common thing. I'm thinking of leaving it for now the way it is. I filled it back up with 80-90 gear oil. I'll watch the tranny fluid and see how much is disappearing. I appreciate all the help on this. I'm getting ready to move to Texas in a few months and once I get there I plan to redo my blazer anyway. Sounds like it can wait until then. Again thanks for the help.

[Critter]

I’m in the middle of changing the adapter seals on my TH350/NP205 right now. When I removed the old ones they were installed with the “cup” side of the seal facing outward. The flat side was facing inward where things, in theory, should be dry. For some reason I feel like I should have the flat side out. Which way is the proper way for these seals to be installed. I doubt that these are the originals so I am wondering if they are put in correctly. I don’t want to have to go through this again anytime soon so I thought I would get a second opinion. By the way, the seals that I pulled out were a National Seal # 480410-SS0 but apparently they have been replaced with National # 471424, which is what I am putting back in. The pics below show the seal in the two possible positions. Thanks.

[ecameron87]

I had replaced mine about 8 months ago when I noticed ATF leaking out of the transfer case vent hole. Now it is doing it again. I hope I didn't put the seals in wrong like Critter is talking about. I will have to check for grooves in the sleeve this time around. Where can I get one of these coupling sleeves?

[Critter]

After sleeping on it, I realized that the seals were installed correctly on mine. I put the new ones in last night. Cupped side to the outside. Fluid shouldn't be up against the flat side in most cases.

[ecameron87]

That makes sense. I believe that I installed mine like picture one - flat to the outside. I think I only have leaking problems after a long drive on the highway at high RPMs.

[Chris_T]

It's a very common problem with these. I've had it on mine - twice. The best indication is when you pull the fill plug on the NP205 and the level is higher than the plug - it obviously came from the transmission unless the ATF gremlins are sneaking in and overfilling your T-case.

Your T-case should be fine, but I've found that ATF will leak a bit more, or at least a bit more quickly, than gear oil just because it's thinner, so if you have a leaky T-case it makes matters worse. To keep it below the speedo gear (where mine also leaks from) you can pull the fill plug whenever you change your oil, see how much drains out, and make sure to keep an eye on the ATF level in case the seals deteriorate over time.

[mrein3]

Originally Posted by ecameron87

I had replaced mine about 8 months ago when I noticed ATF leaking out of the transfer case vent hole. Now it is doing it again. I hope I didn't put the seals in wrong like Critter is talking about. I will have to check for grooves in the sleeve this time around. Where can I get one of these coupling sleeves?

I bought a new "drive sleeve" at the dealer. I also bought a new NP205 to th350 adapter from a GM parts counter.

The down side is the sleeve was around $100 and the adapter around $250.

[Jason915]

you mean like this? It's also comming from where my spedo cable goes to and always drips right there

a little ATF mixed with your 90W will not hurt your T-Case, what wories me is 90W in my tranny

[Critter]

I'm afraid that I will forget to check the levels, or the leak will get worse overnight, and I'll run my TH350 dry!

[pound41]

I have had my blazer for 26 yrs and in that time I have had it happen twice for what ever the reason the transmission eventually failed and I had to have it rebuilt both times. Changing the seal only seemed to be a temperary fix. If a trans shop does something different I don't know. I kept the trans full of fluid. But reverse would start slipping and that was it.

[Green 1959]

So........ what should a 80 GMC use in the transfer case?

[87Skier]

I recently dealt with the same problem. Some 80's 205s did specify and use ATF, but for the most part use gear oil. Replace those seals mentioned above and put some rtv on the spines. That will keep the fluid from flowing into your transfer case. Good luck

[Big Block]

Mine has been doing this for over 10 year. Yes, I certainly need a transmission rebuild. That being sad the transmission works fine when full. Just leaks like crazy. I have a friend who is a mechanic in Denver. He said it isn't uncommon to fill transfer cases with atf. The cold weather is why. 90w thickens up in cold temperatures. Anyone who has every lived in a cold climate will know what I'm talking about. My transfer case is full of atf. It is as quite as a mouse. It makes no noise and I get no vibration driving at highway speeds. Don't think it's a problem other than the mess it makes.

[ballencd]

Is it OK to open this thread back up as it is related or should I start a new thread?
I have a 1991 Suburban, 350, 700R4, 241C and the vent on the transfer case looks to be leaking and when I opened the "fill" plug on the 241C I got all kinds of ATF out of it. The 241C runs with ATF which is not the issue but the excess fluid is. So....I pulled the 241C thinking I needed a front seal in it and maybe a rear seal in the 700R4 but the cavity in the adapter had only a tiny bit of oil in it. Can the trans lose oil to the transfer case and not fill the adapter with ATF at the same time? Confused....