Need help on NP205 Lubrication - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70Chevy4x4Nut · 08-02-2003, 07:51 PM

I'm working on a 70 chevy 4x4 1/2 ton. It had a 3 speed manual with a NP205. I am going to go back automatic so I acquired a TH350 and NP205 from a 71 blazer.

I drained the oil from the NP205 that is with the Automatic transmission and it is Automatic transmission fluid and the other NP205 has gear oil. Which one is correct or are they both correct?

It seems like the bearings in the adapter for the TH350/NP205 are lubricated from the transmission, but I thought the NP205 itself would be sealed off from the tranny and take gear oil. Does anyone know what I need to put back in the NP205 when I go back with? I thought that ATF would be too thin an oil for lubricating the NP205.

Thanks

JimKshortstep4x4 · 08-02-2003, 09:05 PM

The NP 205 should have gear oil in it. Some times the automatics
leak into the transfer cas and dilute the gear oil or replace it over time. We use a 90 weight gear oil, same as for the differentials.

Jim

70Chevy4x4Nut · 08-02-2003, 09:36 PM

Thanks Jim,
Was wondering if having the transmission oil in there might have wore it a little. I was either going to use the one that is already setup for the automatic or change out the input gear on my original one and use it. They both feel smooth, but my original one feels a bit smoother. That may just be because of the heavier oil that was in it. When I drained the ATF I didn't see or feel any shavings. What might be the best thing to do? I will at the very least install a gasket kit, but I may want to tear one down and inspect it real good.
What would you do?

JimKshortstep4x4 · 08-03-2003, 06:19 AM

More than likely the transfer case is good as they are well made and heavy duty. If you did not see any unusal debris then I don't believe you have any damage to the unit. I would just put the gear oil in it and use it after replacing the seals

If there were any gear spalling or bearing deterioration, then it would show up in the oil.

Transmission fluid works pretty well in gear boxes and is used in lots of applications. For example, my 95 Escort uses Dexron III in the manual box and it has 258,000 miles on the transmission with only one changeout at 250,000 miles.

The gear oil is heavy duty and provides more protection under
heavy loading.

Jim

**kwmech** · 08-03-2003, 12:18 PM

Been working on trucks and 4xs now for just about 25 years and have seen all kinds of fluid in these t-cases. I think the most important thing is the fact that there is oil in it no matter what it may be. Advance adaptors reccommends using the NV 4500 fluid when doing a 5 speed conversion just in case there is a seal breech between the 2. This is so the 90 wt. won't destroy the trans. But I have seen trans fluid, motor oil {all kinds of different weight} and of course 90 without a hint of any kind of damage.

DrMaserati · 08-03-2003, 03:32 PM

The current trend is to using heavy motor oil in t-cases and manual transmissions. Generally 30w to 50w. Seems to work as well as 90w gear oil and makes for easier shifting. And I believe some chain drive cases specify auto trans fluid. I think there is a common misconception that auto trans fluid doesn't lubricate well, but keep in mind it is the sole lubricant in an automatic transmission and works very well for that purpose.

The exception would be a differential, where it is still necessary to have an oil with EP additives.

JP

08-02-2003, 07:51 PM	#1
70Chevy4x4Nut Registered User Join Date: Dec 2002 Location: TX Posts: 311	Need help on NP205 Lubrication I'm working on a 70 chevy 4x4 1/2 ton. It had a 3 speed manual with a NP205. I am going to go back automatic so I acquired a TH350 and NP205 from a 71 blazer. I drained the oil from the NP205 that is with the Automatic transmission and it is Automatic transmission fluid and the other NP205 has gear oil. Which one is correct or are they both correct? It seems like the bearings in the adapter for the TH350/NP205 are lubricated from the transmission, but I thought the NP205 itself would be sealed off from the tranny and take gear oil. Does anyone know what I need to put back in the NP205 when I go back with? I thought that ATF would be too thin an oil for lubricating the NP205. Thanks

08-03-2003, 03:32 PM	#6
DrMaserati Village Curmudgeon Join Date: May 2003 Location: Salem, OR Posts: 75	The current trend is to using heavy motor oil in t-cases and manual transmissions. Generally 30w to 50w. Seems to work as well as 90w gear oil and makes for easier shifting. And I believe some chain drive cases specify auto trans fluid. I think there is a common misconception that auto trans fluid doesn't lubricate well, but keep in mind it is the sole lubricant in an automatic transmission and works very well for that purpose. The exception would be a differential, where it is still necessary to have an oil with EP additives. JP __________________ 78 Chevy K30 duallie, 454, TH400 78 IH Scout II, 4X4, 345, 727TF 76 IH Scout II, 4X4, 345, 727TF 65 IH 1200C pickup, 4X4, 345, 4 spd 48 IH KB-8-F, RD-450, 5 spd, 35,000 GVW (a REAL truck) "Life is too short to drink cheap beer." Harry S. Truman

08-02-2003, 09:05 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The NP 205 should have gear oil in it. Some times the automatics leak into the transfer cas and dilute the gear oil or replace it over time. We use a 90 weight gear oil, same as for the differentials. Jim

08-02-2003, 09:36 PM	#3
70Chevy4x4Nut Registered User Join Date: Dec 2002 Location: TX Posts: 311	Thanks Jim, Was wondering if having the transmission oil in there might have wore it a little. I was either going to use the one that is already setup for the automatic or change out the input gear on my original one and use it. They both feel smooth, but my original one feels a bit smoother. That may just be because of the heavier oil that was in it. When I drained the ATF I didn't see or feel any shavings. What might be the best thing to do? I will at the very least install a gasket kit, but I may want to tear one down and inspect it real good. What would you do?

08-03-2003, 06:19 AM	#4
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	More than likely the transfer case is good as they are well made and heavy duty. If you did not see any unusal debris then I don't believe you have any damage to the unit. I would just put the gear oil in it and use it after replacing the seals If there were any gear spalling or bearing deterioration, then it would show up in the oil. Transmission fluid works pretty well in gear boxes and is used in lots of applications. For example, my 95 Escort uses Dexron III in the manual box and it has 258,000 miles on the transmission with only one changeout at 250,000 miles. The gear oil is heavy duty and provides more protection under heavy loading. Jim

08-03-2003, 12:18 PM	#5
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,650	Been working on trucks and 4xs now for just about 25 years and have seen all kinds of fluid in these t-cases. I think the most important thing is the fact that there is oil in it no matter what it may be. Advance adaptors reccommends using the NV 4500 fluid when doing a 5 speed conversion just in case there is a seal breech between the 2. This is so the 90 wt. won't destroy the trans. But I have seen trans fluid, motor oil {all kinds of different weight} and of course 90 without a hint of any kind of damage.



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