Still trying to solve vibration problem - Update Fixed!!!!

[bax]

Driving the truck with out the rear driveshaft installed and still you have the problem? You say you have worked on the rear end, lots of new parts. question: Did you have the problem before you worked on the rear end?
Think back, Did the problem start after any change or repair was done to the truck. Are your pinion angles good? Is it a rotating vibration? Wooshing noise? Doesn't happen under a load, so it only happen on a coast and once it starts you have to come to a complete stop for it to go away. So if your driving and it starts to vibrate, you shift the 435 into N and turn off the engine, it still vibrates. So at that point everything from the clutch forward is not rotating. So take the clutch the fan and the engine out of the loop. What's left. How do we take the front end out of the loop? Pull the drive shaft and unlock the hubs. Nothing is rotating in the front end now except wheel bearings. So that leaves us with transmission , intermediate housing and transfer case. What causes wooshing noises and vibrations in both a gear driven trans and t case? End play,bad bearing,too long of bolt, could be lots of things. I am sure none of this helps but I was just thinking about the situation. Been there done this before. It's frustrating for sure. Good luck. I bet it's your lug nuts.

 

[rhinobuggie]

You said you changed the 3rd member, did you put gear lube back in it ?

 

[thegreatjustino]

Driving the truck with out the rear driveshaft installed and still you have the problem? You say you have worked on the rear end, lots of new parts. question: Did you have the problem before you worked on the rear end?
Think back, Did the problem start after any change or repair was done to the truck. Are your pinion angles good? Is it a rotating vibration? Wooshing noise? Doesn't happen under a load, so it only happen on a coast and once it starts you have to come to a complete stop for it to go away. So if your driving and it starts to vibrate, you shift the 435 into N and turn off the engine, it still vibrates. So at that point everything from the clutch forward is not rotating. So take the clutch the fan and the engine out of the loop. What's left. How do we take the front end out of the loop? Pull the drive shaft and unlock the hubs. Nothing is rotating in the front end now except wheel bearings. So that leaves us with transmission , intermediate housing and transfer case. What causes wooshing noises and vibrations in both a gear driven trans and t case? End play,bad bearing,too long of bolt, could be lots of things. I am sure none of this helps but I was just thinking about the situation. Been there done this before. It's frustrating for sure. Good luck.

The problem occurs with just the rear driveshaft in and with just the front driveshaft in. Last year, when I did all of this work, I went from the stock three speed, three speed adapter, dana 20, and 28 spline third member with 4.11s and detroit locker to an NP435, 435 adapter, dana 20, and 31 spline third member with 4.11s and detroit.

I am using the same clutch, dana 20, and driveshafts as before I had the problem. Swapped in parts are the 435, 435 adapter, and third member.

It doesn't happen under acceleration load, but it does happen under constant load. If I drive around my neighborhood, cruising in third gear, the vibration will start. By shifting everything into neutral, hitting the clutch, turning off the engine, the vibration is still there. Until I come to a complete stop. As I am slowing down, the vibration slows down. It vibrates with wheel speed, not engine speed. I am leaning toward the rear end, but why do I have the same problem when I just have the front driveshaft in? And if it is the rear end, why does the vibration still seem like it is coming from the transmission with the rear driveshaft out? When the engine is off and the transmission is in neutral and you are coasting, is the transmission still rotating?

There is a vibration to it, but the sound is more like a rubbing sound. It kind of sounds like a washing machine on spin cycle, only a lot louder.

 

[broncokak]

When you say you put everything into neutral are you putting the t-case in neutral too? If so the only thing that should be turning is the rear output of the t-case. If it is happening with either the front or rear driveshaft removed and with everything in neutral I'd think it was an axle issue. Oh, when you’re running just the rear drive shaft have you unlocked your front hubs? Make sure you check your breaks. I had a rear shoe come unglued and it made all kinds of noise and kept fetching up.

 

[rhinobuggie]

I know it's out there but lose lug nuts or a wheel weight is missing

 

[bax]

Justin can you post pictures of you drive shaft set up, both front and rear please.

 

[Viperwolf1]

When the engine is off and the transmission is in neutral and you are coasting, is the transmission still rotating?

The output shaft and gears are still rotating. If you want to eliminate it leave it in gear, put the transfercase in neutral, kill the engine and let the clutch out. The clutch will hold the tranny to the engine speed (zero).

 

[bax]

With everything shifted into N the drive shaft is turning, the rear output is turning and the transmission is turning. That is if you shifted into N when you were moving. the d20 has a split input/output shaft but if all of this is rotating when you shift into N it will keep spinning as one piece. This input / output shaft is suspect but it is original, not part of the change so I am hesitant to call it the problem. The intermediate housing bearing could be an issue but I to think about the drive shaft configuration as the main reason for your problems. This is why I want you to post pictures of them installed.

 

[bax]

The output shaft and gears are still rotating. If you want to eliminate it leave it in gear, put the transfercase in neutral, kill the engine and let the clutch out. The clutch will hold the tranny to the engine speed (zero).

Good call , that stops the trans rotation.

 

[broncokak]

Good call , that stops the trans rotation.

And should hold the input side of the t-case from spinning as well.

 

[thegreatjustino]

The output shaft and gears are still rotating. If you want to eliminate it leave it in gear, put the transfercase in neutral, kill the engine and let the clutch out. The clutch will hold the tranny to the engine speed (zero).

OK, here is what I found using this suggestion: Vibrations starts. I hit the clutch, shift the transfer case into neutral, leave the transmission in gear, shut the engine off, and let off the clutch. The vibration still continues as I coast until I come to a dead stop.

Correct me if I am wrong, but it seems that all of this points to the rear end right?

Bax, I am using the same driveshaft that I used for years with the stock 3-speed and never had any kind of driveline vibrations. I really think this has something to do with the third member I swapped in. As I said in a previous post, I also installed brand new out of the box Moser axles, so the bearings are brand new.

 

[DRBRONCO69]

Justin, when I swapped my stock third member for a detroit locker and the new NV 3550 tranny all at once, I had touble shifting the tranny without it grinding the gears. I thought I had a junk trans. Just for kicks, I swapped the original open 3.50 geared third member back into it and the tranny shifted perfect. I have taken my locker apart twice since and reset the gears and stuff both times. Put it back in and the tranny shifts funky and grinds the gears. Can't figure it out. Maybe it is just a characteristic of my locker, but it drives me crazy. I think that I am just going to buy a nice set of 33 spline axles for the rear and spool it since it doesn't see much street use anymore.

Anyway, maybe just swap out the third member and see if it fixes your problem if you have a known good spare lying around. Good Luck.

 

[broncokak]

Bax, I am using the same driveshaft that I used for years with the stock 3-speed and never had any kind of driveline vibrations. I really think this has something to do with the third member I swapped in. As I said in a previous post, I also installed brand new out of the box Moser axles, so the bearings are brand new.

When I swapped to the 435 in my 76 the drive shaft wound up a little shorter than with the 3 speed. That difference was taken up in the slip joint and did cause some problems for me. But I thought you said it did it with just the front drive shaft in and no rear sometime earlier in the thread.

Also, when you just did your test did you have the front drive shaft in? Were for front hubs unlocked?

It has to be in the rear end, driveshaft or front wheels if that is the case.

 

[Viperwolf1]

OK, here is what I found using this suggestion: Vibrations starts. I hit the clutch, shift the transfer case into neutral, leave the transmission in gear, shut the engine off, and let off the clutch. The vibration still continues as I coast until I come to a dead stop.

Correct me if I am wrong, but it seems that all of this points to the rear end right?

Rear axle or output shaft of D20. You can probably just wiggle test the output shaft to ease your mind.

 

[thegreatjustino]

Also, when you just did your test did you have the front drive shaft in? Were for front hubs unlocked?

It has to be in the rear end, driveshaft or front wheels if that is the case.

Front driveshaft was not installed, and the hubs were unlocked

Rear axle or output shaft of D20. You can probably just wiggle test the output shaft to ease your mind.

That Dana 20 has worked perfectly for the last ten years. It is in great shape. At this point I am convinced that it is the rear end. I have another third member here I can swap in. A huge thanks to everyone for your suggestions.

 

[bax]

Rear axle or output shaft of D20. You can probably just wiggle test the output shaft to ease your mind.

I think with the last test we have it down to the Output of the 20 and the rear end.
I wanted to see the drive shaft angles and the u joint set up. it would not hurt to spin the drive shafts and see if they are true.
I was suspecting the input/output of the 20 to have something wrong with it but now I am suspecting the locker or part of the pinion rubbing the case. End play in the pinion setup may be the problem. Coast / no load situation the pinion is being forced forward. Did you set up with a crush sleeve or did you use a solid spacer. Have you changed the yoke on the pinion after the set up?

 

[Larry B]

After all this checking I strongly suspect the 9 inch carrier bearings. I think I would pull it and look.

 

[thegreatjustino]

Planning on checking axle bearings and rear end as soon as I get a chance. I talked with a rear end shop on the phone today and they told me if I brought the third member in they would check all of the tolerances and give it as much of an inspection as they could without taking it apart - all free of charge, so I am going to do that for sure.

 

[DirtDonk]

What about tires? Have you rotated them, or better yet, can you swap another set on temporarily?

Paul

 

[thegreatjustino]

Holy cow, after all of this, it turns out my problem was an incorrect set of lugnuts. The new axles I installed had much longer studs than the ones I replaced, which didn't allow me to use my old lugnuts. Thinking that I would rather try shortening them and putting my old lugnuts back on, I spent today shortening the wheel studs with my sawzall and re-installing the old nuts. Took it for a drive three times, all around my neighborhood, on the freeway twice, under hard acceleration and light, no vibrations whatsoever..... Silly how such a little thing can cause such big headaches. %)

Again a big thanks to everyone who answered all of my questions and gave me suggestions to track down this problem.