1973 K10 Differential and transfer case fluid

[mjb73k10]

Ok I finally got the truck i've wanted for years its a 73 k-10 its bone stock I want to Service the differentials and transfer case but im not sure which weight gear oil to run in them. And does the tranfer case run transmission fluid or gear oil? Ive read people saying both. Also do the differential need any additive? Thanks for the help.

 

[crazy4offroad]

Which t-case do you have? If you're not sure post a pic. Also do you know if the rear end has a factory limited slip? If not sure remove the cover, take a pic and post it up. Lastly, is this an auto trans or standard? You left out a lot of important details.

 

[mjb73k10]

Its the np205 its an automatic turbo 350 trans. Not sure if its Limited slip ill pull the cover and post a pic as soon as possible thanks

 

[crazy4offroad]

90w gear oil in the t-case.

 

[mjb73k10]

ok finally got the truck back in the garage here the rear diff

 

[crazy4offroad]

Not the greatest pic but just going by what I can see of that spring in the middle I would say you have a limited slip and should use the additive.

 

[bucket]

Hey, look at that HRPC, a '73 with auto and np205 like you said!

Out of curiosity, the truck is a V8 right?

 

[75Beast]

Hey I need similar advice but can't post yet. I have a 75 k10 that has been worked on in the past. It's a auto 3 speed on the floor. To my information the tranny is a 350 turbo. What fluids do I need and how much for t case, transmission and differential
Front and rear ? Thanks

 

[crazy4offroad]

Hey I need similar advice but can't post yet. I have a 75 k10 that has been worked on in the past. It's a auto 3 speed on the floor. To my information the tranny is a 350 turbo. What fluids do I need and how much for t case, transmission and differential
Front and rear ? Thanks

TH350 needs Dextron II or III auto trans fluid. A 75 K10 should have an NP203 chain drive t-case so it can take 10w30 (recommended more for a 203 behind a SM465 4-speed) or Dextron II or III auto trans fluid. The rear diff may need gear oil with limited slip additive, either way I think it's 80W90, same for the front but it will more than likely be an open diff which will take straight 80W90.