Author Topic: Unexpected leaking  (Read 5134 times)

Offline Jon87V20

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Unexpected leaking
« on: December 08, 2016, 06:06:15 PM »
I'm in the process of removing the transfer case from my '87 Suburban V20. It's an NP208 I believe with a TH400 in front of it.

I started loosening the lower three of the six bolts that attach the t-case to the tranny and some transmission fluid started steadily dripping from around the screws.

I'm not sure if I'm being stupid, but I didn't think there should be fluid draining from the transmission if they're separated from each other (the transfer case has already been drained but not the tranny).

Is this normal? Am I un-bolting the wrong bolts? Could this be a bad seal on the transmission's output shaft?

I'm working towards getting the tranny out because it failed so I wouldn't be surprised that a bad seal would be another thing wrong with it. I just wanted to make sure I'm not doing something wrong.

Thanks!


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1987 Chevrolet Suburban V20 Silverado
350ci TBI TH400 NP208

Offline hatzie

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Re: Unexpected leaking
« Reply #1 on: December 08, 2016, 07:33:29 PM »
I'm in the process of removing the transfer case from my '87 Suburban V20. It's an NP208 I believe with a TH400 in front of it.

I started loosening the lower three of the six bolts that attach the t-case to the tranny and some transmission fluid started steadily dripping from around the screws.

I'm not sure if I'm being stupid, but I didn't think there should be fluid draining from the transmission if they're separated from each other (the transfer case has already been drained but not the tranny).

Is this normal? Am I un-bolting the wrong bolts? Could this be a bad seal on the transmission's output shaft?

I'm working towards getting the tranny out because it failed so I wouldn't be surprised that a bad seal would be another thing wrong with it. I just wanted to make sure I'm not doing something wrong.

Thanks!


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There are only six bolts that hold it to the transmission adapter.
Sounds like you started to split the transfer case open. 
Pull em both as a unit then separate em once they are on the garage floor.

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Offline Jon87V20

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Re: Unexpected leaking
« Reply #2 on: December 08, 2016, 07:37:54 PM »
Thanks, Hatzie. Bringing them down together sounds like a good idea.

Do you think I could have messed anything up in the transfer case by doing that? I only got a few turns out.


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350ci TBI TH400 NP208

Offline Irish_Alley

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Re: Unexpected leaking
« Reply #3 on: December 09, 2016, 01:58:27 AM »
no, youre ok. trans fluid does make its way back to the adapter plate and theres a drain hole on the transmission side to allow it to drain back to the trans pan. nothing is wrong but you have to make sure you use a gasket or gasket maker when you mate the pieces back together. think of it like this also on a 4x2 trans you need a seal around the driveshaft yoke to prevent fluid from coming out. so fluid has to make it way back on the splines to lube the slip yoke and theres pretty much no difference in a 2wd trans vs 4wd except the lack of output shaft housing and the output shaft itself. i dont know how it the fluid gets back there if its slung or of theres some sort of weep hole but it does make it back there for lube
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Offline hatzie

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Re: Unexpected leaking
« Reply #4 on: December 09, 2016, 06:58:58 AM »
You broke the gasket seal on the transfer case chain housing halves so you may need to replace the gasket.  OTOH you may just need to re-torque the bolts to stop the leak.

I'd replace the fluid while you're in there especially since you drained some of it out.

The NP208 used Dexron III when Dexron III actually existed. Dexron III ceased to exist as a licensed by GM transmission fluid in December 2006 and has been superseded by Dexron VI but only for automatic transmissions. Any transmission fluid labeled Dexron III is not monitored by GM so you're on your own as far as the formula meeting the original specs from GM.
GM states you should use 88861800 Manual Transmission and Transfer Case Fluid in TSB 04-07-30-037E.  It says... "The content of this bulletin does not apply to manual transmissions or transfer cases. Any vehicle that previously required DEXRONģ-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Some manual transmissions and transfer cases require a different fluid. Appropriate references should be checked when servicing any of these components."

Valvoline Synchromesh MTF and Mobil 1 112980 Synthetic Automatic Transmission Fluid state that they meet 88861800 right on the bottle.

The transfer case doesn't share fluid with the transmission.  There's a seal in the adapter to keep this from happening. 


« Last Edit: December 09, 2016, 07:01:44 AM by hatzie »
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Offline Jon87V20

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Re: Unexpected leaking
« Reply #5 on: December 09, 2016, 02:09:51 PM »
Great thanks for that info. I probably would have put the wrong fluid in there.


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350ci TBI TH400 NP208

Offline Irish_Alley

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Re: Unexpected leaking
« Reply #6 on: December 09, 2016, 07:12:28 PM »
Hatzie, i lost he said he started to remove 3 of the 6 bolts and it started to leak.

jon take a picture please
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Offline 1967KaiserM715

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Re: Unexpected leaking
« Reply #7 on: December 09, 2016, 07:47:04 PM »
Hatzie, i lost he said he started to remove 3 of the 6 bolts and it started to leak.

jon take a picture please

Yeah, I don't think he was seperating transfer case halves, all auto 4x4 transmissions are open in the rear, there is a gasket between the adapter and transfer, and a seal on transfer input. All he saw was a little fluid from transmission, it,s how I drain all transmissions I'm removing, drop the rear end and let the fluid pour out, easier to control over removing the pan.




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Offline hatzie

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Re: Unexpected leaking
« Reply #8 on: December 10, 2016, 01:07:21 PM »
Hatzie, i lost he said he started to remove 3 of the 6 bolts and it started to leak.

jon take a picture please

Yeah, I don't think he was seperating transfer case halves, all auto 4x4 transmissions are open in the rear, there is a gasket between the adapter and transfer, and a seal on transfer input. All he saw was a little fluid from transmission, it,s how I drain all transmissions I'm removing, drop the rear end and let the fluid pour out, easier to control over removing the pan.


I misread it as "he removed six bolts and it started to leak". 
I think I'd still pull the trans & xfer case as a unit.  I usually weld drain plug bungs onto the pan on my AT vehicles.  Much easier to control where the oil splashes.

Pictures are worth 10,000 words.
« Last Edit: December 10, 2016, 01:10:41 PM by hatzie »
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
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Offline Irish_Alley

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Re: Unexpected leaking
« Reply #9 on: December 10, 2016, 02:57:04 PM »
i do hear to pull them as a unit all the time and not to pull them separate. get them on the ground then start messing with the bolts. but draining them on the ground is going to be a pain so do that while theyre still in the truck
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Offline Jon87V20

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Re: Unexpected leaking
« Reply #10 on: December 10, 2016, 03:05:20 PM »
Ok will do. I have to bring these down by myself with no help. Do you think an average guy could do that with them together safely with a jack to help?


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Offline Irish_Alley

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Re: Unexpected leaking
« Reply #11 on: December 10, 2016, 03:18:06 PM »
is it safe? no. will someone else being there make it safer? no. i would take a couple straps to help out. take the torque converter bolts out. take the top four bolts out of the trans to the engine. put a strap on the tail end of the trans put the other. take the cross member out. put the other strap on the motor to hold it up and away from the firewall. put the jack under the trans careful not to damage the pan. if you use wood make sure it doesnt slip off. this is where a good jack helps out. take the strap off the trans tail and lower it down. there may be a better way but this is how i would do it
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When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes