TH-400 Trans question

[dieselcrawler]

Hello all,
I have been noticeing a vibration in my '84 K-30. It started about a year ago, faint as first, and has gotten worse a little at a time, till now, it is quite bad. It is an occilating vibration, seems to be at drive shaft speed, and has caused me to change bearrings in the rearend (pinion and diff case side bearrings), and change the transfer case (I knew it needed changed, I did run it out of lube for a while). The drive shaft has new u-joints in it, and it has been ballanced.
I was speaking to a friend of mine, he said he had a truck that made a simular sound, and he was told by his machanic that is was in the trans. Is this possible? Has anyone ever heard of this? If it is the case, it must be something damaged in the Drive parts, or the output shaft. I only get his vibration at 45+ MPH, and it almost goes away when under hard acceleration, is most noticable when coasting/slight accel.
Please help, this is driving me nuts. I do have a spare trans, out of a gasser truck, but it's alot of work to change if this is not the problem.
Thanks....
Greg

[Peter J. Bierman]

How about the balance of your wheels?
45 is a typical speed for imbalance vibrations.

Peter

[85-m1028]

I'd also check the pinoin angle on the rear some times the spring can get a little worn and throw the angle out of allignment

[dieselcrawler]

Thanks for the sugjustions guys, but no, it's not the tires, and not the driveshaft angle. Tires have all been checked recently, and would have the same vibration at all power loads, this one changes with the ammount of power applied, less under full power/acceleration, more noticeable at light, crusing throttle. Driveshaft angle can't have changed, I have about 12 leafs in the spring packs, there is no give to them! (but man oh man, will the ol' truck carry a load! Had over 6000# of gravel in it before) I at one point thought it might be wheel berrings, but it doesn't change going straight vs. right or left hand turns, it's always there. The sound of it all even seems to come from up front, in the trans area, but the dang diesel is so loud at highway speeds, it's hard to tell. No sound proofing or floor mats in my truck at all... (the junk and trash on the floor boards doesn't count)

Thanks for your input... any other ideas?

Greg

[jaymanaa]

I had a weird vibration that sounds simalar, and it turned out to be the harmonic damper on the engine. I changed it and it was like putting a new engine in and letting off a stuck parking brake! Unbeleivable differance!!!! My truck had about 115,000 and the damper didn't really look bad? Just a thought, good luck.

[doncannon]

Hello all,
DieselCrawler: Is the noise there if you put the trans in nuetral? Does it change at all with speed? or is it more like you said...only changes with amount of power?
let us know,
Don

[john8662]

I had a groaning problem on my '86 6.2 that I could never troubleshoot.

It occurred about the same RPM you're describing. I didn't really get a vibration, just an annoying sound.

My current theory is that it was the Torque converter to flexplate bolts, as one of them wasn't secure and was loose (I only had three) because of of a burred thread didn't let the bolt bottom out properly.

So was this a problem you had before you did your engine work?

[85-m1028]

you know I noticed that I have the same occilating vibration, but mine doesn't happen till about 60-65mph, I have new u-joints just rebuilt the trans with new converter too, so I just assumed it was in the pinion angle, also have new tires and rims all lugs torqued to spec, but my springs and shocks are OEM! so I should eliminate springs as soon as I get new ones, I remember the vibration being there before drivetrain rebuild!!

[dieselcrawler]

Yes, the vibration is there when you pop the trans in neutral, but it is not the same as when it's in drive, and the drive train is under a load.

Also noticed what seems to be the water pump leaking yesterday... I'll be out of town all next week, maybe the truck will heal it's self if let to sit in the garage, kept nice and warm with the block heater... wishful thinking, I know...

I'll keep you posted, thanks for the input....

Greg

[NH2112]

Check the pinion yoke nut, I had one back off a little bit and cause vibrations at certain road speeds, both in neutral and in gear. I tightened the nut down and it went away. I should have replaced the crush collar but didn't, but it never gave me any problems afterward. A little while later I drained the rear diff and saw that the vibrations had been caused by the heel of the pinion sliding back and grinding on the diff carrier - there was a nice sawtooth pattern "machined" into the carrier LOL

[dieselcrawler]

Hey all...

As to the pinion, nope, I replaced the pinion berrings a few weeks ago also. No change. The sound/vibration does not seem to be in the motor, 'cause it's still there if I put the truck in neutral going down a hill, so it will maintain speed. It changes intensity, of course, but is still there. I am still thinking that it's in the trans... it's just NOISY up there... I dunno...

Water pump is still leaking... Grrrrr. Darn truck is just falling apart. First things first, I need 4WD, will be working on the frontend gears, axles, and ball joints this weekend.

Later....
Greg

[Robyn]

OK
You most likely have either a torque converter going south or possibly a bad flex plate.
if the converter was replaced during a rebuild and the unit was not done right the hubs can be welded back on out of spec and they will cause the converter to wobble after a while the front pump bushing wears out and the thing will shake real bad.
I have also seen water pumps on these beasts cause some nasty vibrations too.
Food for thought. Pop the belts off and run it in Nuetral and see if its gone, if not be looking at the converter. Been there done that.
Robyn

[Robyn]

Just a thought
I see you said the water pump is leaking.
If that pump is bad the weight of the fan clutch and the fan can really shake things up.
My 84 Blazer had a bad pump and it was shaking the whole truck at road speed.

[dieselcrawler]

While I agree that the water pump may cause some noise/vibration, it would be at engine speed. The problem I seem to be having is still noticeable while coasting down a long hill, with the trans in neutral and the motor idleing. The sound/vibration changes, but doesn't go away. This leads me to beleave it may be in the tail of the trans, or input of the transfer case. However, I changed the transfer case a few weeks/month or so ago, and no change what so ever. That would limit it to the output shaft on the trans... is that even likly?
Just to make sure it's not in the rear end, I may slide the axles out a little, and let the drive shaft, and rear gears spin up to speed... see what happens. If I still have it, then I know it's in front of that... Drive shaft, transfer case, trans...
I replaced the flexplate in June when I had the motor out to install the turbo. The vibration was there before that, only slight, and was there after, just the same.
Thanks for the ideas... hope everyone had a good Christmas...

Greg

[Robyn]

You may have a drive shaft that has taken a twist and has become "Out of Phase"
Check your drive line and be sure that the joints front and back are in alignment. If the slip yoke was taken off to replace a cross and put back on one or more splines off of phase it will shake you right out of the cab. A drive shaft speeds up and slows down 4 times per revolution and if the joint are out of phase they fight each other and will really shake things up. also if this is a 4X4 and has been romped about some you may have a shaft that is tweeked???
Good luck
Robyn

[Robyn]

With the wheels off the ground let the rig Idle in gear and carefuly watch the drive shaft. I should run true without any wobble. If it wobbles you got trouble with the shaft. If it is a multi piece shaft be sure the front and back shafts have the joints aligned. Remember any misalignment spells SHAKE

[Robyn]

Just one more thing
Check the carrier bearing if it has one. If that thing is toast it will shake as the shafts will whip around. If the rubber is all wallowed out it can cause this too.

[doncannon]

Hello All,

DieselCrawler: I agree with Robyn C52 it could be a carrier bearing. mine vibrated when i first bought it then went away after we replaced it. Well now for finding the source, I am guessing that you are not running with the hubs engaged so that eliminates the front (if they are disengage them and see if it makes a difference). If the transfer case is also not in 4wd that should eliminate the f driveshaft. So you could (be careful here)remove the rear driveshaft. Next you will need to lock-in the hubs then hop in put the stick in 4wd hi and run it around a little to see if it still has the vibration (of course unbolting the carrier bearing). I did the same with my p-time to get some parts once and DO NOT recommend driving it like that for long. It may point you in the right direction. If it is full time this will NOT work. Hope this helps, Don

[dieselcrawler]

By carrier, you are talking about the berring suporting the middle universal joint in a two pc rear drive shaft, right? I have a single pc drive shaft, custom made for the truck when I did the dually conversion, that was, come to think of it, at the same time the vibration became noticeable. Keep in mind that prior to that, the truck had 40" boggers on it too... kinda made the diesel sound quiet, and vibrations were at a whole new leval... **grin**
The question I am left with, after pondering on it here for a few minutes, is this: Can the ballance of a drive shaft change with normal use?This drive shaft was custom made, and a rather long one, by the standards of the guy who made it for me. He liked to keep them to max of 60", this one needed to be about 61", he made it up for me anyway, with out his normal warrenty. Ran smooth at first, after the whole truck was together, with ballanced, stock size tires.
I also have the NP208 transfer case, and the slip-type tail shaft. So, if I pull the rear drive shaft, the fluid will leak out the back of the transfer case. I do know it is not in the front driveline, I have not used it much at all in the past 6 mos. Frontend diff berrings were trashed, changed it out last week, used corp 10 bolt went in, with new ball joints, axle joints. Reused all my old spindles and outters. Yee ha, I have 6wd again....
I have thought about changeing to the 2 pc rear drive shaft, but need to find the parts to do it. I only have one truck with that type of rear shaft, and part of it is already missing! Grrr.

Greg

[arveetek]

Greg,

I'm fighting a drive-line vibration too. Mine doesn't make noise, but feels just like a bad u-joint. It's real noticeable at slower speeds, but is worse around 45 mph. Above that and it goes away until above 65 mph. I've replaced all the u-joints, some of them twice, trying to isolate the problem. I've finally decided it must be a bad bearing/bushing on the output shaft of the tranny.

I can grab the slip yoke and and it will move up and down a bit. Plus, I've replaced the rear oil seal twice, and it keeps leaking, making me think the yoke is moving around and wearing the seal out.

I need a new torque convertor, so the tranny will be coming out for some maintenance soon anyway. I'll take care of it then.

You might check the slip yoke on the TC and see if moves around up and down and side to side. It ought to be pretty tight.

Casey