Bump in the night, drivetrain binding??

[NC_Mule]

So I've put about 5,000 miles on my 70 11A since I picked it up in Feb 2010. This summer I used the 4x4 on a limited bases never for more then 10-15 miles at a time. Now that snow has hit the mountains of NC I have been using the 4x4 20-30 miles a day over the past 2 weeks.
In my 25 mile round trip commute the noise pops up 3-4 times.

I've heard the noise in 3rd and 4th gear, I'm going between 20 and 30 mph on a flat road, wheels are straight and the road is smooth. I've never heard the noise in 2wd. It lasts less then a second. I use 2nd gear low range 4x4 to get up my drive (2/10th of a mile) have not heard/felt the noise in that short amount of time.

It sounds and feels like something is binding for a split second. You feel the noise in your seat and is sound like it might be coming from the transfer case but I'm not sure it could be from the ft. end. I assume it's one of those areas because it's never happened in 2 wd.

I pulled the ft drive shaft off and checked the torque on the ft. output shaft nut, greased the U joints and checked the torque on the drive shaft bolts. Checked all fluids, tranny, X-fer case, swivel balls and ft/rear diff oil. Had no effect still hear/fell is 3-4 times per commute.

Anyone have some ideas for me? I'm afraid something is going to have to get worse before I can figure it out. My thought is may be someone else had a problem that started this way and ended up being....???

I tried to include as much detail as possible but feel free to ask questions.
Thanks pb

[Cutter]

Check the hand brake shoes, they may be too tight and catching. It doesn't sound that simple in your case, but mine had a similar sound - I adjusted according to the bible instructions and it went away. Its at least a place to start, not sure how it would relate to 4wd only though.

[NickDawson]

does it happen when you go from costing and begin to apply some gas?

[siii8873]

Are you driving with the front wheels locked in and the transfer case in 4WD? If so and you have the slighest difference in wheel size from wear, turns on road it sounds like the drive train is binding and releasing. My first rover would do this if I had it in 4wd and front hubs locked and driving over 10 miles or so. It would sound like a little pop in the rear and then sound fine.

[NC_Mule]

does it happen when you go from costing and begin to apply some gas?

It happens with steady throttle.

Cuttet, good idea on the hand brake..I'll check that tomorrow.

siii8873
Yes I'm in 4x4 with the ft. hubs locked. Sounds like you've heard the same "pop" that I'm having. Good info about the differnt wheel size. I had a tire patched this summer, so I installed the spare. Both the spare and the patched tire had "about" the same tread so I just left the spare on and made the other my new spare. They have "about" the same tread but from what you are saying a little difference can cause a problem

I also phoned a friend who suggested to check my wheels bearings, he said I might have one binding and when it does it might send a shock thru the drive train when it catches and then releases.

I'm going to check the e-brake and wheel bearings tomorrow...while I have the ft. end up I'll swap the spare back. Will report back tomorrow.

Thanks, I'm optimistic one of these will lead me to the solution.
pb

[Tim Smith]

Sounds like I went through the same thing at, wow, post 817!

http://www.roversnorth.com/forums/showthread.php?t=817

I turned out to be wrong about the rear and front being different ratio's. In the end I think it was just wind up from turns or crowning in the road. The only thing I would advise you check is that your spider gears are in working order. Even if you are driving on a straight road, eventually they will make a full rotation and you could get that thunk if they are damaged.

Really though, I'm betting it's tire pressure or road surfaces not being as straight and perfect as you think. Nothing to worry about so long as the pavement will allow the drive line to relieve pressure.

[KevinNY]

These are old school part time 4wd systems and really should not be used in 4wd on the pavement unless it is snow covered, not just wet. I agree with the others that you experienceing driveline bind.

[siii8873]

I also think this is just a binding from very slight differences in wheel/tires, road conditions / turns causing the binding / releasing. I only run my TCase engaged under road conditions that allow some slipping.
IIRC the spec for newer 4WD is that the circumfence of all tires have to be within 1/8" . That is VERY tight and it is for this very reason.

[NC_Mule]

Just to clarify, the roads were snow covered when the noise occured.

So I pulled the mismatched spare tire off the left front (same size tire but different brand) measured the rolling radius on the garage floor and it's 3/4" longer then the right ft tire. I installed the correct matching size/brand tire on the ft. As a double check I pulled the front rt. tire off and it's rolling radius is exactly the same as the ft. left. Long story short I have two ft. tires with matching rolling radii.

When placing my hands on the road wheel at 12 and 6 I had slight movement, both sides had the same movement. Is it normal on these trucks to have slight play?

I also checked for wheel bearing noise, both sides felt/sounded smooth. In fixed mode.
For fun I moved the hub to free and when I spun the left wheel I heard a slight knocking/ticking coming from inside the hub. Did the same to the rt. wheel and it was smooth, no knocking/ticking.

Local weather man is calling for a white Christmas so I'll have some snow covered roads to see if changing that mis matched tire had an effect. I'll report my findings.
In the mean time I'm going to search this forum and read my manuals on what exactly goes on when you move the hub from free to fixed.

Hopefully the mismatched tires were causing my noise.

Thanks for everyones input
pb

[Tim Smith]

Slight movement is kind of tough to say. There should be some movement but the culprit for that is at the wheel bearings. If you are worried about it then you will need to check them properly.

However, I don't think this is related. I'm betting it's just your tires producing different turning speeds.

[NC_Mule]

Are you driving with the front wheels locked in and the transfer case in 4WD? If so and you have the slighest difference in wheel size from wear, turns on road it sounds like the drive train is binding and releasing. My first rover would do this if I had it in 4wd and front hubs locked and driving over 10 miles or so. It would sound like a little pop in the rear and then sound fine.

siii8873 wins the prize!! Come down to NC and collect your free all you can drink home brew ticket. I've been driving my route back and forth in snow the past few days and I haven't heard that pop since swapping the tire. Visions of the front axle locking up have passed and I'm a much happier motorist. Note to all, as little as 3/4" of rolling radii can cause some nasty drivetrain sounds. Thanks again!!
pb

[siii8873]

Great glad you resolved this. I have a daughter in Charlotte so I do get down that way. Where are you located?

[NC_Mule]

Great glad you resolved this. I have a daughter in Charlotte so I do get down that way. Where are you located?

Were close to Charlotte, 2 hours from the airport. I'm in Boone, in the mountains in the north west part of the state, 3,000-6,000 elevation. Not sure if you've been to Boone or not but it's very pretty worth making the drive from Charlotte. Let me know if you make it up my way.
Thanks again for the help.
pb