calling all internet diagnostics experts!!

[jfz80]

Some of you remember the fate of the pig on the PPR trip. Seeing as how its almost spring already and i aint got no work yet, ive been trying to figure this one out. any and all help is appreciated.

in summary, w/ a new clutch, the pig is still making the horrible knocking noise at speed. I feel ive isolated it to the rear half of drivetrain, but im not going to say w/ certainty that it is. Anyone had similar issues or care to do some creative analysis to help know where to look next?

I will most likely pull diff cover to examine there first, then maybe pop the top off the 4spd.

oops.... i forgot to add the link w/ more information from the national site https://forum.ih8mud.com/40-55-series-tech/214401-knocking-noise-speed-lil-web-diagnostics.html

 

[landtank]

Hey Jason, do these things have the e-brake/drum assembly mounted to the end of the t-case. I've had similar sounds from cars of old but since it was at a wheel it was easy to identify. Usually a spring breaks or a retainer and loose stuff gets jammed in places and makes noise.

 

[Turkeypen]

Rick!

Landtank may be right, but Bill Wright (Bubba) and I (Forrest) will get right on it and come up with a real-simple answer at the next club meeting.

 

[Turkeypen]

seriously . . . have you checked that all the bolts on the drive shaft are tight (need ocassional retorquing) , is the diff full of good oil, etc?

 

[jfz80]

Hey Jason, do these things have the e-brake/drum assembly mounted to the end of the t-case. I've had similar sounds from cars of old but since it was at a wheel it was easy to identify. Usually a spring breaks or a retainer and loose stuff gets jammed in places and makes noise.

yup this has the p-brake assembly on the end of the t-case. I removed and cleaned it up, adjusted to the point it works fantastic now . It was my first time inside one of these, but all looked normal and after cleaning up, parts moved freely

seriously . . . have you checked that all the bolts on the drive shaft are tight (need ocassional retorquing) , is the diff full of good oil, etc?

Yup replaced all fluids before the pig run, but just checked em all this past weekend too. All Drive shaft bolts are tight. I had to remove both shafts to do the clutch, so i cleaned, relubed, and reinstalled them one at a time. Thats when i noticed it did not make the noise w/ the front shaft only in place. I also noted how sketchy 50 in front wheel drive is in one of these Both shafts are in and i tried to get a video to capture the noise but drivin a SOA pig on 36's w/out a tranny tunnel pretty much rules this method innefective due to background noise.

thanks guys

 

[landtank]

Rick!

Landtank may be right, but Bill Wright (Bubba) and I (Forrest) will get right on it and come up with a real-simple answer at the next club meeting.

I'm still waiting for you two to prognosticate me some lottery numbers. I'm serious! You two spit out a set of numbers for the mega millions game and I'll play it.

 

[landtank]

Jason, it seems to me that the noise is in the rear drive shaft. Even though that is removed everything else is still turning in the axle. Have you checked the slip yoke and made sure the phasing is correct.

 

[jfz80]

Hey what happened to my post?

Rick im still not on top of the in-phase/out of phase concept. Not totally ignorant, but cant say i fully get it. SOOOOO i marked my flanges when i removed the shafts and put them back just as they were. I also marked the slip yoke before removing/cleaning and inserted the splines in the same location.

This is the frustrating point, when you form one conclusion, seems there is a new way to shoot it down as well. My ? to you is then why would it drive fine for 5-6 trips, and then go 5 out of 7 hours before developing this knock on the way to the mtns. I could see a u-joint failing on a trip. Unless the PO installed out of phase and it took 300 miles to wear it to the point of knocking? I have/had not ever changed the driveshaft position previous to this incident, but i did notice that they were in backwards. However this is the only way the flange bolt patterns line up so its not possible to reverse them w/out swapping flange ends (if thats even possible) I think this is a result of the hodge podge F/4spd tranny/3spd t-case.

this knocking problem started before the clutch install and remains afterwards.

 

[jfz80]

hell of a day to lose silver star status....trying to get some pics up of the u-joints if it will help.

 

[landtank]

Check the slip yoke, do you know how to? This is where you could grease the yoke and the grease would take up the play but with use the grease would ooze out and the play would return.

Phasing has to do with the orientation of the ends of the shaft where the u-joints press into. In phase they are orientated the same or parallel, out of phase the ends are at 90* to each other.

 

[jfz80]

I packed them full of grease via the zerks before the PPR trip, and when i separated them fresh grease was in the splines as well as packed in the end void past the splined shaft. There is no torsional play at the splines and when i feel the ujoints they rotate smoothly and have no lateral play in any direction.

again please excuse the ignorance, but are you to compare the front half of a shaft to the back half? ( and not compare the shaft to the flange arrangement). IF this is so the adjustment from in phase to out of phase would be made by separating the halfs and sliding the splines back in w/ ''U'' at end of shaft 90* offset from previously.

if thats the case mine is "almost'' out of phase when the rear of my driveshaft is parallel w/ the ground the t-case end is almost vertical but definately a few splines off from being 90*. Again its weird it drove fine for so long and then started.

 

[jfz80]

d'oh.....i got it. SO it should be and now is in phase (at least one of the possible two positions) i put zirks on same side but looks like these have been tinkered w/ before to accomadate the 4spd tranny pattern as well as 3spd pinion pattern. Who knows what i got here but unfortunately the splines are towards the axles instead of tc which is "ok" but not ideal. Ill see if this doesnt help and then try the 180* if it doesnt.
If thats not it i think im gonna crack the diff cover next. Is a bad ujoint obvious to the touch/test spin?

 

[GXO]

You can usually hear a bad ujoint but not see or feel it unless it is about to let go.

Another possibility is a chipped tooth on the ring gear...DOH.

 

[landtank]

Been thinking about this and just wanted to point out that unlike our 80s a leaf sprung truck compresses the drive shaft when going over a bump. Have you check the length of the shaft to make sure it's got enough compression travel? Also there should be a hole located behind the u-joint on the slip yoke side to prevent the shaft from hydro locking . If this is a made up shaft they might not have done that and it would put pressure on the pinion and t-case output bearings.

 

[krzyabncanuck]

Have you drained / dropped the rear cover yet to see what it looks like back there yet. Even if you do not find anything back there you can use this time to make sure it all is GTG in there.

 

[jfz80]

Been thinking about this and just wanted to point out that unlike our 80s a leaf sprung truck compresses the drive shaft when going over a bump. Have you check the length of the shaft to make sure it's got enough compression travel? Also there should be a hole located behind the u-joint on the slip yoke side to prevent the shaft from hydro locking . If this is a made up shaft they might not have done that and it would put pressure on the pinion and t-case output bearings.

I believe it has plenty of compression travel b/c if anything id worry about dropping the splines out upon drooping, there is not a whole lot of engagement but the splines look to be wearing fine. Ill go double check for outlet hole, i did not notice it.

Have you drained / dropped the rear cover yet to see what it looks like back there yet. Even if you do not find anything back there you can use this time to make sure it all is GTG in there.

it stopped raining and i opened the diff cover only to make the project grow longer, most of the studs backed out of the housing . the teeth look good on the ring gear and feel fine on the "other gear" it meshes with at the pinion. I did not notice any large metal pieces, a few shavings and in the very bottom of diff there were some granules, none of them as large as a bb. The welds look sloppy but i dont see any cracks, ill load some pics next.

 

[jfz80]

Rick, i did feel the output shaft when i had the tranny and t-case pulled and it felt great. BUT i did pump a bunch of grease into the shafts right before the trip, i wonder about pressure on the pinion instead?

couple pics if it helps, and yes thats fresh gear oil??? less than 500 miles w/ factory breather caps in place and moving freely.

 

[Trollhole]

Someone went a little crazy with the welder.

I hope you never break an axle. Cause they will never come out without precision grinding. You need to find a new diff and put a rachet locker in. Thats a trailer queen setup you have there.


Pull the PTO cover on the T-case and take a peek. Chunks on the drain plugs for trans and tranfer?


How much slop do you have in the rear pinion?

 

[jfz80]

Someone went a little crazy with the welder.

Just a little

When i changed before the PPR there were no metal pieces on the plug to tranny or t-case, but since that was before this noise showed up ill go drain those now and look.

How would one measure this said pinion slop? thanks

 

[jfz80]

i pulled the pto cover and all looks good, oil in good shape, all teeth present and accounted for w/ no abnormal wear. THere is no debris on either drain plug for tranny or tcase. I am about to pull the transmission top plate, but was trying to figure out for sure if i need to remove the gear sifter (the push and turn trick i hear is a SOB) Ive read you do and then i read you dont; can anyone confirm before i pull the cover as i cant seem to get the selector out and dont want to if i dont have too.