Transfer case & manual hub questions

[85burb4x4]

I have an 85 K20 diesel Suburban, and the transfer case (NP-208) in my Burb is stuck in 4wd for the 2nd time in less than 2 weeks. I figured the 1st time was because I didn't check the linkage adjusment after I converted over to an SM-465. That time the chain snapped and took out part of the case with it. I found a replacement and got that installed and readjusted the linkage according to the Haynes manual. This morning, on my way home from work, I noticed it was stuck in 4wd again. Fortunately, I got home before the chain snapped, but I think there might be some internal damage...there were 3 sharp jolts while I was driving. Anyways, I am totally confused as to why this is happening. I know my tires are out of balance (can really feel it at 65 mph) and I was planning on replacing them tomorrow. That now will wait until I get the t-case figured out, but I will have the newer tires put on before I drive it again. Could the out of balance tires be the cause of my transfer case problems? I haven't pulled the t-case yet so I'm not sure what the damage really is. Any other ideas or things I should check?

Also, my friend gave me the old manual hubs from his K5 Blazer...he upgraded to Warn Hubs. Can I use those hubs on my Suburban even though my Burb is 3/4 ton and the Blazer is 1/2 ton? Do I have to worry about a spindle nut conversion kit? I really want to get rid of the autolocking hubs.

Any help will be greatly appreciated. Thanks!!!

 

[bronc3buster842001]

the hubs will interchange between 1/ and 3/4 tons

 

[85burb4x4]

Thanks!!! I ordered a set of Warn Premium Hubs yesterday.

Any ideas on my transfercase problem? I should have it apart Friday.

Thanks!

 

[randy88k5]

Usually the pads on the mode fork, when they wear and dissappear, allow enough movement in the fork from vibrations and such that it will kick it in and out of gear. They are 3 little plastic pads that go on the fork (one one each and and in the middle). I'd check their condition when you have the case apart. They should come in a rebuild kit.

 

[Avery4jc]

This morning, on my way home from work, I noticed it was stuck in 4wd again.

Wait...I'm confused as to how its getting stuck while you're gone...so you come out and start the truck up and you just don't notice that its in 4wd? So it falls into 4wd while you're gone or you were playing in 4wd and forgot to put it back and when you realized it was in 4wd and tried to put it back then it was stuck?

-Avery

 

[85burb4x4]

The shifter is in 2HI, but the front driveshaft is turing. The 1st time this happened a gear broke apart and I'm thinking those pieces jammed it in 4wd. I'm not sure what cause the gear to break. I think part of that may be because I didn't check the linkage adjustment after I converted it to an SM-465. I checked and readjusted the linkage on the 2nd transfer case.

I haven't done any serious 4x4ing with either t-case. Both problems happened shortly after a 4 hour drive home...drove from Winthrop to Gold Bar. When I was in Winthrop I had it in 4wd a couple times when I was on a dirt road.

That's a good idea, I'll check the pads when I have it apart. I'm hoping they are the cause of my transfer case issues. At least this t-case didn't blow apart like the 1st one.

Thanks!!!!

 

[resurrected_jimmy]

Usually the pads on the mode fork, when they wear and dissappear, allow enough movement in the fork from vibrations and such that it will kick it in and out of gear. They are 3 little plastic pads that go on the fork (one one each and and in the middle). I'd check their condition when you have the case apart. They should come in a rebuild kit.

X2 .my 02

 

[85burb4x4]

Update

Now I'm really confused. I got it all apart and didn't see anything obvious. The pads on the shift forks seem good to me. Just to be sure, I will be taking everything to a local shop Monday and see what they say. I think the t-case is in good shape and I can put it back together....just have to wait for the hubs to arrive.

 

[jk3078]

Are all your tires the same size? If your front and rear tires are differant, even the differance between bald and new tires,it might be enough to cause some gear bind on the highway and either your tires will slip or your t-case will blow. The sharp jolts may have been something inside popping in and out to relieve the pressure. This would also explain not being able to shift it out of 4 wheel drive. J

 

[dremu]

The shifter is in 2HI, but the front driveshaft is turing.

Dumb question ... your hubs ARE unlocked, right? The front shaft would turn -- regardless of the t-case setting -- if the hubs were locked.

-- A

 

[85burb4x4]

The tires are pretty much the same, the tread depth looks like it is the same on all 4 tires. When I took them in to get balanced the first time, the guy said they will need to be replaced soon. I mainly was after the wheels, but figured I woud use the tires for a little while.

I was using the stock autolocking hubs, and I didn't think to jack up the front wheels to see if they were actually locking. The last time I pt it in 4wd, I made sure to back up a bit to unlock the hubs.

Hopefully, sometime next week the manual hubs will arrive and I can take it in to get the tires replaced.

Thanks!

 

[85burb4x4]

Update....back on the road again!!!

Thursday was a productive day. I took the back wheels in to get the tires replaced and when I got home the manual hubs had arrived. I got it all back together and the hubs installed. When I had the hubs out I noticed the spindle nuts on both sides were extremely loose so I tightened & torqued them down.

There is a little vibration at freeway speeds, but I still need to replace the front tires. I will go in Monday and get that done and have them check the balance on the rear tires, and hope that will eliminate the vibrations. Hopefully, now I won'y have any more problems with my driveline. Next on the list is a set of new injectors. Thanks!

 

[diesel4me]

"stuck" in 4wd huh??..me too!

My 82 K20 refuses to come out of 4wd too--has a NP208 T-case..I tried adjusting the linkage,but to no avail--all the ranges work ,4 lo,4hi,but when I shift it into 2wd,it feels like nothing in the case moves,and the front drive shaft still recieves power..so I've had to drive it with the hubs unlocked most of the time.. --shifter feels tight,no slop,and the case is quiet when driven--no pops or strange noises..

I bought a "spare" transfer case for it,but decided not to install it unless I absolutely have too..truck sees little use other than dump runs or plowing my yard,but I would like to know what the problem is with this T-case..I'd like to be able to trust the truck on a long trip,but am reluctant too with it being like this..did you figure out why yours wont come out of 4WD?..

Someone told me the rear output shaft bearing can lose a snap ring and cause this problem,but I've never "split" a transfer case and rebuilt one,and am not looking forward to doing that (the reason I bought the spare one!)..also,others have said I could "flip my truck right over" if the hubs ever decided to lock themselves at highway speeds,and to NEVER use 4wd above 30 mph!..I say its BS,I've driven my other part time 4wd's on long drives during snowstorms at up to 55 mph in 4wd,with 0 troubles!..anyone else heard that??..

 

[85burb4x4]

I really haven't found anything that I could say is the main cause. I think it was a few problems combined that caused my 4wd issues. My tires really needed balancing and I found the spindle nuts extremely loose. I'm thinking those were the main problems. The plastic pads on the shift forks looked good too. I also assumed it was the transfer case that was causing my problems because I had to pull it apart to change out the input gear when I converted over to an SM-465. I didn't check to see if the stock auto-locking hubs were the problem.

Pulling apart the NP-208 is very easy. I've had one apart and back together in a little over an hour. There are some spring loaded pieces on the inside that can be a PITA to assemble. They are on the gear that the shift fork assembly that actually puts it in 4wd slides on....if that make any sense.

So far I've put close to 200 miles on it without any problems.