transfer case issue

[70stroker]

First of all i would like to thank anyone who helps me fix my issues with my trasfer case.

Alright guys the truck is a 86 chevy 1/2 ton 4x4, The previous owner swapped to a big block th350 and a transfer out of a 79 i believe he said. They transfer is gears and not the chain style. I plan on posting a pic for proper identification.

My 2 issues with it are as follows.

1) 4 high works great. 4 low on the other does not. It does one of two things when you engage four low. Either acts like its in neutral and just revs, or engages and then when you put a good load on it then it revs. Like the other night i was pulling a buddy out and it engaged and i go to pull on him and its just revs like its in netural.

2) Not 100% sure this is the transfer but for sure sounds like its around the transfer/ transmission area. Going down the road you hear a hmmming sound. to me its sounds like gears whining. Now this is the first truck i had without the chain type transfer case, So is this sound normal for geared transfers or do i have a problem?

I checked the fluid, it is gear oil and doesnt appear to have any metals in it.

Again thanks for any help guys.

[70stroker]

here is a pic of the transfer case

[Dieselwrencher]

That is a NP205 and is a gear drive unit. You could have a broken gear, some bad bearings, or a broken linkage rod at the shift levers. Have you checked to see if the rods both move when operating the shifter handle?

[48cj2a]

Looks like a NP205. Do you have a Chrome stick going staright up through the floor (no plastic covered console)

Did you try putting truck in neutral and then shifting into 4 low?

Operations manual says:

Shift Transfer Case from "2H" or "4H" to "4L" -

Shift transmission into Neutral, shift transfercase control firmly, but not forcefully, to 4L.

Reverse operation for back to 2H.

"2H" to "4H" can be in drive or appropriate forward gear.

[70stroker]

yes i forgot to mention that, I always put my truck in neutral before shifting my transfer case.

As far as checking things deiselwrencher, NO i havnt checked any of that, mainly because this is my first older 4x4, I have never had to dig into a transfer, so transfers are kinda my weak link in the car business, I have bebuilt motos and transmissions along wither diffs.

So Any advice on checking some of this stuff? Mainly step by step stuff. I would like to keep it in the truck to check as much as i can to have it still driveable.

Thanks

[Blazer1970]

4 low is both shift rails pushed all the way back into the case. If there is a bunch of crap stuck to the t-case in the area between the rails, it can block the shift rails from moving all the way back to the detents. Crawl under there and look.

[lurch115]

to check the linkage have someone sitting in the truck and have them move the lever from 4 high to 4 low. WITH the vehicle shut off and their foot on the brake with the transmission in neutral. i resently had a similar issue with an NP203 which is the chain drive version of your t-case and come to find out the shifter was actually the problem. also have to ask, as i know it can be easy to over look things. when you shift in to 4 Low have you tried pushing down on the shifter and then pushed it ahead more? i've seen the shifters "freeze up" before and not want to push down. in that case i usually take a dead blow hammer and give the shifter a few light taps straight down and that usually frees them up.

[MTCK]

So the gear whining noise, is that in 2wd with the hubs unlocked? I am also suspicious of the shifter. Make sure those rods are going all the way in.

[70stroker]

guys i think i have figured it out. It was hitting the floor just a little bit when tryin to go into 4lo I believe thats the reason as to why it sometimes would engage and others not depends how flexed my body was. I just notched the floor and have plans tonight to go test it out.

The whining gear sound noise is in 2 wheel drive and the hubs unlocked. Its for sure something in the powertrain, Its a nice steady humming while cruising and on throttle, you let out of throttle to return to coast/idle and it goes away, as soon as you give it gas again it comes back.

[Dieselwrencher]

Your humming noise sounds like it could be a ring and pinion/carrier issue in the rear diff. Or gear noise in the transfer case.

[white82]

Originally Posted by Dieselwrencher

Your humming noise sounds like it could be a ring and pinion/carrier issue in the rear diff. Or gear noise in the transfer case.

i agree about the noise.. might check .. change the fluids..

[70stroker]

Im gonna give it a try seeing as how i havent chaned the transfer or rear gear oil since i owned the vehicle.

What kind of oil goes in the np205 case, approximation on how much?

[Adams74Chevy]

Originally Posted by 70stroker

Im gonna give it a try seeing as how i havent chaned the transfer or rear gear oil since i owned the vehicle.

What kind of oil goes in the np205 case, approximation on how much?

I was under the impression it was 80w90 gear oil but doing a quick search on google it seems ATF is also used by some guys...guess I just muddied the water some.

http://coloradok5.com/forums/showthread.php?t=144480

[Redcap]

Originally Posted by Adams74Chevy

I was under the impression it was 80w90 gear oil but doing a quick search on google it seems ATF is also used by some guys...guess I just muddied the water some.

http://coloradok5.com/forums/showthread.php?t=144480

80w90 or ATF both work just fine.

70stroker, keep adding until it just starts to dribble out the fill hole. That is enough.