More troubles..."popping or banging in 4wd"..

[diesel4me]

Truck is putting me thru hell lately..

Had to plow with my truck yesterday--and to my chagrin,it is still having a loud "bang" or "pop",mostly while backing up in 4wd,but it has done it a few times going forward too..

Truck drives fine in 2wd,no noises,no other issues..

I had replaced two rear tires Sunday so all 4 are equal diameter,I assumed because the tires on it previously were slightly larger in the rear than the front,that was causing a driveline bind up situation..(but last winter I plowed with zero issues with tires that were equally or worse mis-matched ,with no noises or binding at all.)..unfortunately it made zero difference,it still feeling like something "catches" and goes "pow" when it releases,mostly while backing up with the plow raised..

The only things different than last winter,is I replaced the u-joint on the front drive shaft at the diff,it was shot,no needles left in all 4 cups,this past summer.

I just unbolted the shaft at the diff,slid off the sliding yoke,put the new U-joint in it,and slid it back on,and I was careful to make sure it went back exactly as it was,on the same splines,I marked the shaft & yoke before I removed the yoke,and the truck was not moved while it was not connected--so the "phasing" should be correct..

The CV portion of the front shaft had no play,so I assume the u-joints in it and the ball seats are OK...

I also replaced the passenger side axle U-joint,as it also was shot..
You cant really screw that up..
I replaced the drivers side axle U-joint about 2 years ago,its had little use since and is still like new..

The only thing I may have screwed up was the hubs,the first time I put one together,they refused to lock--took them back apart,flipped one of the gears around,then they would lock & unlock properly..this was on the drivers side,and it worked OK all last winter that way..the passenger side I just removed and replaced without letting the parts separate, and was careful to put everything back in the right order..so they "should" be assembled correctly..

One thing I haven't yet checked,is to see if the front drive shaft is hitting anything--the front springs are sagged bad on this truck,they touch the rubber bump stops with the plow raised up,so it might be possible it is rubbing the CV joint yoke against a cross member or something..

The front drive shaft yoke looks to be completely bottomed out on its splines with the plow up too,and even with the plow off,I can hear something feel like it bottoms out when I hit a bump up the road sometimes...so I know the saggy springs might be allowing the shaft to fully collapse at the splines..and maybe trying to bash the front output of the T-case in....?..but there are no cracks,leaks or weird noises coming from the t-case in 2wd..
I would think the bump stops would prevent the shaft from collapsing enough to cause damage that way ?..

One thing about the NP-208 though--ever since I've owned this truck (16+ years),is the front drive shaft always has power to it,even in 2WD--so I've had to leave the hubs unlocked in 2WD and I just made sure the front diff was full of lube,and let the axles and u-joints spin..didn't seem to harm anything,but I know it isn't "right" either..I made sure the shift linkage was adjusted right and it was,and it shifts into 4 low and 4 hi no problem,so I think the shift forks and pads are OK..

I'm at a loss how to diagnose this issue--seeing it only seems to do it with the plow on in 4wd,I guess I would have to jack up all 4 wheels and put both diffs on jack stands,with the plow on it and raised,and try running it in reverse in 4wd ,and jump on the plow to see if it makes the drive shaft contact something ?..
Could it be something crapped out in the front diff ?...chain "skipping" in the transfer case ?...seems unlikely to me seeing it plowed OK last winter..

I have a spare NP-208 that is supposedly "good" ,that I picked up cheap years ago,but I'd hate to have that put in if it isn't the problem..seems weird its fine in 2wd and it makes no noises with the front shaft spinning in 2wd,I would think it would be popping or banging in both 2 and 4wd if the front shaft had CV issues ?..

Right now I'm close to vomiting thanks to a miserable cold or maybe the flu,I'm in bad shape and cant be screwing around outside in 20 degree weather--just would like some advice from you guys,if you have any ideas what's causing this..and how to diagnose it..

 

[6.2Blazer]

My first suspect would the locking hub you mention and having to flip a gear around. I have seen issues in which the gears were on wrong and therefore make very little contact with the splines and can skip, and eventually will completely strip out the small portion of splines they are contacting. For all the u-joints, especially the front axle shaft ones, make sure one of the caps has not worked its way out of the yoke some and is catching lightly on something. Also, the description of your transfer case shifting worries me some also. So if you shift the t-case into the 2wd position it is still in 4wd? Meaning if you try to spin the tires on dirt or gravel all 4 tires will spin? Reason I ask is that it's not uncommon for the front driveshaft to still spin some while driving down the road in 2wd because of the internal fluid friction in the case. But if the t-case is not shifting properly you may be only getting partial engagement of the gear which could cause it to slip teeth every once in awhile.

 

[diesel4me]

Yes,I've been able to plow with it in the 2WD position provided I lock the hubs in--yesterday I put it in 4WD to see if it made any difference,it didn't,it still makes the "bang" and you can feel something like it binds up for a second,then releases..it sounds more like it is coming from the middle of the truck or the front drive shaft area,than the front end..but it is hard to tell for sure..

I did peek at the axle u-joints,I had also thought maybe a cap came out and was getting caught on the "C" knuckle area,but they looked like they are all seated OK,the clips are intact..

I was worried that the axle shaft or stub shaft might have failed,because they were pretty thin from rust when I replaced the axle U-joints,and I've babied it ever since to avoid them breaking..but driving in 2wd with the hubs unlocked,the axles still spin also,and they would have made noises during normal driving on the street too,if the caps had wormed their way out..(and possibly locked up the steering!)..nothing like that has happened..

The hubs on this truck are not the same as the older Dana 44 ones I'm used too,I think they are either Warn hubs or maybe OEM Ford ones ,they have only one big circlip holding them in to the hub casting on the rotor,and a phillips screw you take off,to get the gears out (which I was told you dont even need to do,just removing that big circlip lets the whole unit pop out into your hand)--there is no smaller snap ring on the axle shaft on these hubs..
But since I did have them apart,it is possible I didn't put something back in facing the right way--but I cant recall if I plowed with it after I had them apart last year or not-I think I did,and it worked fine..

I'm thinking the hubs are OK,it might be the drive shaft hitting something,or maybe the CV joints are shot,but just feel "tight",or it may be the T-case...weird it drives fine in 2wd though,I'd think if something failed in it,it would make noises in both 2WD and 4WD..

I try not to whale on the truck while plowing,knowing the items listed above could fail pretty easily --its had some whippings in the past though..

Been searching online for an exploded view of those style hubs,haven't found a good one yet..

 

[Bent77]

With that known issue on the hub Bob, I’d start there if you have another

 

[Recon 78]

Any chance you can get a helper to stand near each wheel as you try to recreate the issue?
Sometimes easier to locate from outside the truck

 

[6.2Blazer]

When you say it drives fine in 2wd, do you mean if you shift into 2wd and unlock the hubs? Or if you just shift into 2wd and leave the hubs unlocked the noise goes away? If it is this last one something is definitely weird as you said it doesn't actually shift out of 4wd.

FYI, if a front axle shaft or stub shaft failed you would have no four wheel drive. On a regular open front diff if you break the shaft on one side it is the same as if that tire is in the air with zero traction....it will only try to spin that side and will not give any power to the side that is not broken which essentially is the same as being in 2wd.

 

[Fordum]

The symptoms sound darn familiar, but I can't figure out why it would do it while backing up.
My '79 F150 was the worst. I would be driving along, come to a stop at a light or stop sign, and all would be well. Then I would take my foot off the brake to pull off, and there would be a loud bang and the whole truck would shake.
It felt like I had been hit by a truck.
Turned out the splines in the rear driveshaft were worn in one place. Under load, they would twist slightly and become misaligned with the rest. When I pulled up to stop, they would lock in place and not let the shaft adjust when the rear axle shifted.
When I released the brakes, the twist load came off, and the shaft released the strain it was in.
Greasing the splines through the zerk would stop it for a while, but it always came back until I replaced the spline.

Sure sounds like your drive shaft if binding somehow, but not sure how

 

[euzoa]

I would bet on the CV in the front driveline has gone out. If you pull it out it should have some tension in it, not flop free. There may be other issues, easiest way to check to see if your front driveline is staying engaged is to put it in 2wd, unlock the hubs and spin the front driveline. If it wont spin there is something wrong in the case. Good luck man

 

[imiceman44]

Yes,I've been able to plow with it in the 2WD position provided I lock the hubs in--yesterday I put it in 4WD to see if it made any difference,it didn't,it still makes the "bang" and you can feel something like it binds up for a second,then releases..it sounds more like it is coming from the middle of the truck or the front drive shaft area,than the front end..but it is hard to tell for sure..

I did peek at the axle u-joints,I had also thought maybe a cap came out and was getting caught on the "C" knuckle area,but they looked like they are all seated OK,the clips are intact..

I was worried that the axle shaft or stub shaft might have failed,because they were pretty thin from rust when I replaced the axle U-joints,and I've babied it ever since to avoid them breaking..but driving in 2wd with the hubs unlocked,the axles still spin also,and they would have made noises during normal driving on the street too,if the caps had wormed their way out..(and possibly locked up the steering!)..nothing like that has happened..

The hubs on this truck are not the same as the older Dana 44 ones I'm used too,I think they are either Warn hubs or maybe OEM Ford ones ,they have only one big circlip holding them in to the hub casting on the rotor,and a phillips screw you take off,to get the gears out (which I was told you dont even need to do,just removing that big circlip lets the whole unit pop out into your hand)--there is no smaller snap ring on the axle shaft on these hubs..
But since I did have them apart,it is possible I didn't put something back in facing the right way--but I cant recall if I plowed with it after I had them apart last year or not-I think I did,and it worked fine..

I'm thinking the hubs are OK,it might be the drive shaft hitting something,or maybe the CV joints are shot,but just feel "tight",or it may be the T-case...weird it drives fine in 2wd though,I'd think if something failed in it,it would make noises in both 2WD and 4WD..

I try not to whale on the truck while plowing,knowing the items listed above could fail pretty easily --its had some whippings in the past though..

Been searching online for an exploded view of those style hubs,haven't found a good one yet..

You have something wrong here.
All hubs have room to put a c clip at the end of the shaft.
If you don't, the shaft tends to walk in and the joint will not be centered in the knuckle and when turning in 4wd it will do exactly what you described

 

[imiceman44]

My second guess is the ball in the cv has rusted since last year and now is binding and it will also have the symptoms you have.
Both cases happened to me

 

[eric67camino]

I would definitely inspect the hubs, but it sounds like the t-case chain slipping to me. Had a chain stretch on me once and it sounds like that. Fine in 2wd because its not doing anything. Was actually ok in 4wd with no load, too. Put a load on it and the chain would jump teeth on the gears.

My suspicion would be low fluid that caused the chain to stretch. It could also explain it appearing to not shift out of 4wd. Low fluid could also cause shifter to wear and not actually be disengaging the front driveshaft.

Hopefully I'm wrong and it's something simple. Good luck.

 

[imiceman44]

I would definitely inspect the hubs, but it sounds like the t-case chain slipping to me. Had a chain stretch on me once and it sounds like that. Fine in 2wd because its not doing anything. Was actually ok in 4wd with no load, too. Put a load on it and the chain would jump teeth on the gears.

My suspicion would be low fluid that caused the chain to stretch. It could also explain it appearing to not shift out of 4wd. Low fluid could also cause shifter to wear and not actually be disengaging the front driveshaft.

Hopefully I'm wrong and it's something simple. Good luck.

Didn't think about this, could tie in all the symptoms except the no c clip on the shaft is still no good

 

[eric67camino]

I agree. Need to make sure all clips, caps, etc are in place first. Always check the easiest stuff before going in deep.

 

[diesel4me]

I've been driving it 16 years on the street by shifting it into 2WD and unlocking the hubs...the front drive shaft & axles all spin still,like the transfer case is still in 4WD,but they aren't driving the front wheels because the hubs are unlocked..it drives normally,never had any issues driving it that way all that time--and still dont, as long as it is in 2WD and the hubs are not locked in..
T-case is quiet and makes no unusual noises in street driving..

I've tried turning the front drive shaft by hand with the front end jacked up like Eousa suggested,you cant budge it--been that way since I got the truck..--so I assume the T-case has some internal issue preventing it from coming out of 4WD--weird thing is,the shifter feels normal,it shifts into 4 LO ok,so I'm assuming it isn't the shift forks not taking it out of 4WD..usually when those go sour,you have troubles getting it into 4 LO or neutral,or 4WD..

I have no idea if anyone ever had the t-case apart--maybe they welded something together in there,I don't know,or it has some weird issue..
Doesn't appear to have been opened up,I don't see any RTV on the case halves..but who knows ?..

The T-case leaks ever so slightly ever since I've owned the truck,I have to add about a quart every 6 months or so..I use dexron ATF in it..

Imiceman may be right about the CV portion of the front drive shaft--I have never taken the shaft completely out of it,to see if its got any slop at the ball seats or the u-joints,but they seem tight while it is installed when you try shaking it by hand..

Seeing the shaft has been spinning every mile I've driven it,I suppose it is possible the CV portion is worn now,and my attempts to grease it were not successful,I couldn't get the needle tip even near it to try and pump any grease in the CV ball or the 2 u-joints..the shaft looked brand new when I got the truck too,and I've only put about 10,000 miles on it..

I rather doubt it is rusted up,or it's u-joints are bad though,seeing its been spinning every mile I've driven it,I'd think I'd be hearing noises while driving it on the street to,if that were the case..

Only the U-joint at the front diff was wasted, so I replaced it as I described previously--while I had the drive shaft dangling, I did try shaking it ,and the CV part felt tight ,like it always had..but I know that isn't a true "test" either..

If I remember right,the stub shafts didn't have a snap ring groove,but it's been months since I had the hubs out of it,they might have one--but there was no "inner" snap ring on either hub,just the big circlip on the outer edge of the rotor hub,and it worked fine in 4WD all the time I've owned it that way,so I assume it's correct ...

Fordum posted a link about these hubs about a year ago,when I had trouble taking them out--I'll have to see if I can find that thread,and see if the pictures in the link show the correct order of assembly..

But I assume the hubs are assembled correctly,or they wouldn't unlock or lock in properly.. I did assemble one wrong ,and it wouldn't unlock,so I had to take it apart and flip one of the gears around..then it would lock & unlock properly,and I've been driving it ever since..

I guess I should have tried 4WD right after I was done installing the axle U-joints,but it was last July,and I didn't try that--being a part time 4x4 it does tend to bind and wobble while cornering on dry tar,like all my other trucks,so I didn't bother "testing" it..wish I had now!..

I have no helper to stand near it and try to determine where the noise comes from,sitting in the truck it is tough to tell--sometimes it feels like its coming from the drivers side front,other times it feels more like the transfer case area--if I put my hand on the t-case shifter,when it bangs,to me it doesn't feel like it originates from the t-case,but you can feel the shock in the front driveline..

It almost sounds like a ball bearing or roller getting caught in a ring & pinion.....

If the sagging springs allowed the front shaft to collapse completely I would think I'd hear it banging while driving it on the street over a bumpy road..the front shaft slip yoke has less than 1" of travel left with just the weight of the truck on the front springs--with the plow on it and raised,even less,but it hasn't ever bottomed out far as I know,the bump stops should prevent it from doing that..

It could use some help in the front spring department though,they are only 2 leaf stockers and are sagged bad..
But I tend to think its not that causing this problem..

I'm hoping it is just one of the hubs,or the front drive shaft that's the cause--I'm in no condition to be attempting a t-case swap,I've been sick as hell since Sunday and vomiting,sneezing,chills,fever,I'm not sure if its a cold or the flu,but its a bad case,whatever I have..

I'm also not even sure the spare t-case I have IS good,all I have is the sellers word it was,he claimed he removed it from a truck that rotted to death that had only 70K on it..

I paid only $30 for it,with a TH400 adapter--you don't pass up a 32 spline NP-208 for that price,the adapter and input alone is well worth that!..it "feels" OK spinning it by hand in all the ranges..it is probably OK..

I do have two like new rebuilt front drive shafts,but they are not the correct ones for the truck--both have the "old style" CV joint yoke ,that has the 4 threaded holes in the CV part,to bolt it to the t-case yoke,not the big "round ring" with 4 bolts ..not sure if they will be the right length either..

I screwed myself--I had a brand new front shaft for this truck,but a friend was in a bind years ago,he had a brand new shaft with the "old style" yoke ,and needed the big round ring one--so I traded him for mine--at that time I had a '77 GMC that used the old style yoke,so it was a good deal for both of us then--but now I need the other style....
I'm not sure if you can swap the CV section from the front shaft in my truck with the round ring,onto the old style shaft,if the shafts happen to be the same length..I hate assembling a CV joint,don't even think I could do one any more,if that was possible..a rebuilt front shaft is like $280..

I'm glad the snow coming tonight is supposed to be under 2" before it turns to rain,and its expected to warm into the high 40's for several days,otherwise I'd really be boned..

I just hope I can use the truck to get around town to go pay some bills and get some food in 2WD without the dam diesel crapping out--I have not replaced the fuel filter yet,I added a few bottles of "HEET" and so far that seems to have had some positive effect--I think it had water or "summer" diesel in it..but it only has the stock lift pump on it now,and its been on it since I bought the truck 16 years ago..
Last thing I need is to be stranded when I feel like I'm on deaths doorstep..