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[1978k10Petty]

I have a 1978 GMC sierra grande short bed 4x4. I was wondering what type lubricant everyone recommends for the transfer case. Synthetic/conventional etc...

 

[Dan Miller]

Welcome. I've been using Valvoline high performance SAE 80W-90 Gear oil in mine for 15+years with no issues . You have any pics ? Mine is also a 78 Sierra Grande, My son uses syn 75w90 in his 80 K35. Sorry bout the mis info earlier

 

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[Doppleganger]

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[Old77]

 

[1973c10]

Welcome aboard

 

[Shorty81]

Welcome from the Buckeye State

 

[Preston]

Welcome to GMSB from Virginia

 

[Charlie]

 

[Rusty Nail]

In original 30 + year old state?

Conventional GL-5

 

[TerryRH]

Welcome from Misery

 

[82sbshortbed]

Welcome from Texas

 

[Goldie Driver]

In original 30 + year old state?

Conventional GL-5

I like this answer, but it also depends on whether or not it was ( is ? ) full time. NP203 full time is 10W30 motor oil, IIRC.

I can tell you I put syn tranny fluid in my '80 NP205 ( I had a '81 Factory Service Manual that recommended tranny fluid the syn was just what I grabbed) - umm, not a good plan. Leak city.

Went back in w/ conventional 80W90, IIRC.

 

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