4wd problem please help

Yes I bought this truck this past October and put maybe 1500 miles on it since. I bought it with 138,000 so I have no idea when they were last done if ever. I am going to change all the fluids anyway being this is what I have to get to work in bad weather I have a county job that has no snow days so up keep on this truck is very important to me. I just like to get a lot of input before I dive into a project. I was also talking to my father about it and he brought seething up I never even thought of maybe it could have been a hub.

 

Locking hubs?

 

They are the stock auto ones

 

Not sure it'd be a hub but wouldn't rule it out. You have the ADD which means the hubs and the CVs are spinning all the time. I'd expect to feel something wrong with the hub whether you're in 4WD or 2WD. As I said earlier, wouldn't rule it out but I'd move it down the list of suspects. I'd go after the easy ones first like the diff and transfer case fluids. Sounds like they should be done anyways.

 

That is going to be this weekends project. Thank you for all your input. I might have a lot of overtime this weekend though with the snow we are supposed to be getting here in ny so I might have to load the back of the truck this weekend if I can't get to it

 

I was thinking I'm not 100 percent sure how it works but as you said if the cv's are always spinning while driving wouldn't the differential be in motion aswell while in 2wd. Might be a stupid question I'm am just unsure how it works

 

I'd really find a way to check fluid levels and top off if needed on the front diff and transfer case in a hurry if it was me.

 

I am hoping tomorrow I will be able to. I am working a double shift today started 7 thismorning get out 11:30 tonight. It's like everything always happens all at once the day before I started having the issues with the truck my clutch master cylinder went out on my commuter hyundai accent. So that's in my garage taken apart because my local store had to order it, then this happens with the truck then I get slammed with overtime this weekend when I was planning to get everything fixed. What is a good recommended oil to replace it with?

 

I don't recall what the owner's manual specifies for viscosity so you'll want to check, but I use Mobil-1

$28 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 in the front diff and transfer case. Rear diff called for heavier viscosity if I recall right, I went with Lucas and change it every 3 years.

 

In 2wd with ADD, both CVs are always spinning. The pass side CV is completely disconnected from the differential. The driver side CV is permanently connected to the differential but only spins both side gears and the spiders. The side gears spin in opposite directions and the carrier, R+P gears and drive shaft do not spin. They may rotate a bit in sympathy with sloshing oil but they are not driven.

 

Update: I just changed the fluid in the transfercase and the front diff. Transfer case looked like it was brand new golden color. The front diff on the other hand was black and felt thin. The drain plug had a buildup on it that I can only discribe as a magnetic clay. It had the consistency of clay and covered the whole area of the plug maybe 1/16" thick. I'm sure that is not a good sign. I refilled both with 75/90 and took it for a ride. I don't know if my mind is playing tricks on me or not but I think it may have been a little quieter and been a little smoother. I guess all I can hope is for the best now and hope it holds up

 

Here's hoping that was all that was needed.

 

Final update: today it was put to the test I did my 40 mile commute but the roads were completely snow covered except for maybe the last 10 miles and I put it back in to 2wd. My top speed in 4wd this time was probably 45 mph and there were absolutely no issues for the 30 miles I was in it. So thank you to everyone's input, advice and knowledge and I lucked out