Leaking Transfer Case - Best Kits for Repair

[BradL84D30M1008]

Si I've put enough miles on now on my recently acquired '84 M1008 to see that I have a nasty transfer case oil leak between the transmission and the transfer case, leaking gear oil down the along the frame crossmember supporting the transfer case.

I did a quick search here but didn't see anything recent for suggested kits/parts to address the oil leak at the front of transfer case.

What all is involved to repair the leak? Seal(s) for transmission output shaft into transfer case? Bearing(s) to replace?

Should I replace u-joints at the same time?

I'm a complete newb on transfer cases, never had to work on one till now!

Thanks in advance for any suggestions or recommendations.

 

[cucvrus]

If you are leaking gear oil out of the transfer case. You have serious issues. The transfer case and transmission have ATF in them. Or they are supposed to have ATF in them. Also the rear of the transmission has a seal in it to prevent the ATF from leaking back from the transmission into the transfer case. I would suggest you have the transfer case and transmission resealed. That means removed split and all new seals put in both of them. That is my opinion on this. But I do know as a fact that ATF is supposed to be in all the transfer cases. This is a bit of advise. I fix everything the right way the first time. It cost a bit more up front but out lasts a poor job by a long shot. Have a great day.

 

[The FLU farm]

If you are leaking gear oil out of the transfer case. You have serious issues. The transfer case and transmission have ATF in them. Or they are supposed to have ATF in them. Also the rear of the transmission has a seal in it to prevent the ATF from leaking back from the transmission into the transfer case. I would suggest you have the transfer case and transmission resealed. That means removed split and all new seals put in both of them. That is my opinion on this. But I do know as a fact that ATF is supposed to be in all the transfer cases. This is a bit of advise. I fix everything the right way the first time. It cost a bit more up front but out lasts a poor job by a long shot. Have a great day.

Off the subject, but imagine my surprise when checking the fluid level in an NP205 and found it filled with ATF.
It was in a '91 crew cab dually, and while I don't know when GM decided to switch to ATF - surely for mileage purposes - I filled it with normal gear oil. And it lived happily ever thereafter.
Obviously a 205 will work with ATF, too, or GM wouldn't have used it, but wouldn't gear oil be the preferred fluid?

 

[BradL84D30M1008]

Yep......I think I have gear oil leaking out of my transfer case......it's a light brown, clear, greasy fluid, not red, or with an odor, like ATF......so don't think it's the transmission leaking ATF, but I will certainly investigate further.....needs some serious attention for sure.

 

[The FLU farm]

Check the dipstick and find out what's in the transmission, then the level plug on the transfer case to see what's in there?

 

[rustystud]

Off the subject, but imagine my surprise when checking the fluid level in an NP205 and found it filled with ATF.
It was in a '91 crew cab dually, and while I don't know when GM decided to switch to ATF - surely for mileage purposes - I filled it with normal gear oil. And it lived happily ever thereafter.
Obviously a 205 will work with ATF, too, or GM wouldn't have used it, but wouldn't gear oil be the preferred fluid?

The NP205 is suppose to have gear oil period. The only NP205 that used ATF was the "Shift on the Fly" one that had a synchro shift on the front output shaft (1984 to 1986) . They where so bad and caused so much trouble that GM dropped them like a hot potato ! It was GM's idea in the first place and NP built them for them. The ATF in these units also caused a lot of trouble. More wear then you could imagine. Transfer-cases with solid steel gears like the NP205 make a lot of heat and the ATF would run like water at those temperatures. Now all the "chain drive" transfer cases (like the NP208 ) use ATF or Hydraulic oil. So the "rumor" started that all the NP205's was suppose to use ATF because of this stupid attempt of GM to have the NP205 shift on the fly.

 

[Kaiser67M715]

The NP205 is suppose to have gear oil period. The only NP205 that used ATF was the "Shift on the Fly" one that had a synchro shift on the front output shaft (1984 to 1986) . They where so bad and caused so much trouble that GM dropped them like a hot potato ! It was GM's idea in the first place and NP built them for them. The ATF in these units also caused a lot of trouble. More wear then you could imagine. Transfer-cases with solid steel gears like the NP205 make a lot of heat and the ATF would run like water at those temperatures. Now all the "chain drive" transfer cases (like the NP208 ) use ATF or Hydraulic oil. So the "rumor" started that all the NP205's was suppose to use ATF because of this stupid attempt of GM to have the NP205 shift on the fly.

GM specified ATF (per factory service manuals) in the 205 from 88 to 91, the 205 was rare to find in these years as the 208 and np241 came out(the 241 in right hand drop was just as rare).

But gear oil is the better choice IMHO.


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[The FLU farm]

Thanks for the info guys. I didn't know that GM switched to ATF as early as '88, and had never heard of the "Shift on the fly" 205 until Rustystud mentioned it a while back.

My ATF experience was after getting my first ever new car into the garage to look things over. First thing I do with any new-to-me vehicle is to check and/or change the fluids, and take a general creeper tour to find out what things look like.
A new vehicle shouldn't need to have anything checked, really, but part of the story is that it never went through dealer prep. Not wanting numerous cold starts by (presumably) uncaring mechanics, I arranged to take delivery in a shuttling yard instead of at the dealership.
Not taking anything for granted, I checked the levels in everything in the drivetrain (also a good time to install magnetic level plugs) and that's how I found out that the venerable NP205 had ATF in it.
Like mentioned above, for somewhat obvious reasons, gear oil used to be the lube of choice for gears so that's what went into the 205 before it left the garage.

I guess that the moral of the story is that I, too, would've been driving around with the wrong fluid in the transfer case had I not checked it as soon as possible after taking possession of the vehicle.
Whether it's worse to run ATF in a 205 or gear oil in a 208 I don't know. But probably the latter.

 

[Chaski]

One source for parts...
https://transpartswarehouse.com/

It isn't a hard to rebuild a 208. The only tricky part is removing the back bearing for the front output shaft. The bearing is in a blind hole so you have to make or buy a puller to remove it.

You can buy a bearing and seal kit from the vendor above, or from many other sources. Most kits do not come with a chain. Also buy some transmission assembly goop. You will need it since several of the bearings use loose rollers and you need assembly goop to hold them in place.

 

[glaser06]

One source for parts...
https://transpartswarehouse.com/

It isn't a hard to rebuild a 208. The only tricky part is removing the back bearing for the front output shaft. The bearing is in a blind hole so you have to make or buy a puller to remove it.

You can buy a bearing and seal kit from the vendor above, or from many other sources. Most kits do not come with a chain. Also buy some transmission assembly goop. You will need it since several of the bearings use loose rollers and you need assembly goop to hold them in place.

By "goop" do you mean like RTV for sealing the case or are you talking about a heavy grease to hold bearings in place during assembly?


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[Chaski]

http://www.lubegard.com/~/C-215/Dr.+Tranny+Assemblee+Goo


Good RTV is also needed to use on the case.

 

[rustystud]

GM specified ATF (per factory service manuals) in the 205 from 88 to 91, the 205 was rare to find in these years as the 208 and np241 came out(the 241 in right hand drop was just as rare).

But gear oil is the better choice IMHO.


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I'm totally aware of what the manuals say. They never changed them from the 1984 manual. How do I know this? I have all the Factory shop manuals from the 1970's to 2006. So since they didn't want to be bothered by changing it they just keep reprinting the same section over and over again.







Pictures 1 and 2 show my GM Component Repair Manuals from 1976 to 2006 .
Pictures 3 and 4 show my factory repair manual all the mechanics on the floor got to rebuild the NP205 transfer-case.
Pictures 5-9 show my "Motor" shop repair manuals from 1942 to 2010 .

 

[rustystud]

Picture 1 shows my "Motor" manuals going back to 1942. I have all the general vehicle manuals to 2010. Pictures 2,3 and 4 show my complete "Motor" Transmission manual collection. I also have about 20 of the Truck manuals and 30 Import repair manuals. This is just 1/4 of my shop manuals I own.

 

[Tinstar]

Imagine a PDF for all that?!!

Very nice collection!!

 

[doghead]

Clean and inspect closely.

You could have a cracked transmission housing.

Does your truck have the tell tale signs (body damage) that it's been moved with a forklift?

 

[rustystud]

Just like Doghead mentioned the transmissions cracking, I've also seen the aluminum housing of the NP208 crack. This can happen from many causes, like the chain going bad to twisting the frame severely. Take the transfer-case off and clean everything. After you fully inspect everything then you can make an informed decision on what to do.

 

[BradL84D30M1008]

Thanks rustystud and doghead......I will inspect the drive train thoroughly this weekend.....previous owner said he had dropped the transmission pan and replaced filter and ATF (Dexron III) with no issues, so this leads my initial focus to front of transfer case where I see lots of grime/seepage buildup over the years where transmission output shaft feeds into the transfer case.....I see all the references/specs for ATF in the NP 208, but drips I saw on crossmember still looked like gear oil, which is a bit perplexing.....I'll drain the transfer case and inspect the fluid......otherwise transfer case to front axle and transfer case to rear axle are dry and look fine.

I note that I get a bad vibration in the bed of truck even at idle.....not sure if transfer case issues are related to that.....and a good vibration at 35-45 mph speed.

My truck body has all kinds of dents/dings in it, but not noticing any wrinkles/scuffs on bottom of body or the frame.....I'll look closer for that, thanks for the tip.

 

[Recovry4x4]

Thanks rustystud and doghead......I will inspect the drive train thoroughly this weekend.....previous owner said he had dropped the transmission pan and replaced filter and ATF (Dexron III) with no issues, so this leads my initial focus to front of transfer case where I see lots of grime/seepage buildup over the years where transmission output shaft feeds into the transfer case.....I see all the references/specs for ATF in the NP 208, but drips I saw on crossmember still looked like gear oil, which is a bit perplexing.....I'll drain the transfer case and inspect the fluid......otherwise transfer case to front axle and transfer case to rear axle are dry and look fine.

I note that I get a bad vibration in the bed of truck even at idle.....not sure if transfer case issues are related to that.....and a good vibration at 35-45 mph speed.

My truck body has all kinds of dents/dings in it, but not noticing any wrinkles/scuffs on bottom of body or the frame.....I'll look closer for that, thanks for the tip.

Collapsed motor mounts send out all kinds of weird sounds and vibrations. Exhaust rattles too. I would suggest a kit to rebuild it. Gives you all new seals and plenty of peace of mind for a few hours work.

 

[BradL84D30M1008]

Any good suggestion to keep an eye on!

 

[BradL84D30M1008]

So I'll correct myself here......what I've got dripping off the crossmember is pretty red ATF.....after wiping down the frame crossmember last weekend I still have drips this weekend even while the truck is sitting for a week, so somewhat troubling to see ATF dripping off the crossmember with truck not even running for a week.....to be determined whether it is from transmission (my bet since it looks fresh) or from the transfer case (maybe)......but will get it into a shop for seal replacement in both in all likelihood......

Thanks rustystud and doghead......I will inspect the drive train thoroughly this weekend.....previous owner said he had dropped the transmission pan and replaced filter and ATF (Dexron III) with no issues, so this leads my initial focus to front of transfer case where I see lots of grime/seepage buildup over the years where transmission output shaft feeds into the transfer case.....I see all the references/specs for ATF in the NP 208, but drips I saw on crossmember still looked like gear oil, which is a bit perplexing.....I'll drain the transfer case and inspect the fluid......otherwise transfer case to front axle and transfer case to rear axle are dry and look fine.

I note that I get a bad vibration in the bed of truck even at idle.....not sure if transfer case issues are related to that.....and a good vibration at 35-45 mph speed.

My truck body has all kinds of dents/dings in it, but not noticing any wrinkles/scuffs on bottom of body or the frame.....I'll look closer for that, thanks for the tip.