H55 Over-run "Humm" (1 Viewer)

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EasternYeti

EasternYeti

Joined
Jun 10, 2015
Threads
97
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Location
Franklin, Massachusetts
Good Morning Gentlemen,

On my way to work today, i noticed a distinct hum coming from what appears to be my H55 when costing (In gear, no power applied ) If i maul the knob i can feel the hum through the shifter.

This hum disappears once i step on the gas, and i'm concerned this could be a larger issue. Throw-out Bearings? Input Shaft Bearing? Simple Oil Change?

The H55 itself is relatively new (30K miles), and after something is so well known for its durability, i'm surprised that it would have an issue so early into its life. I'm not aware when the oil was last changed, or what it was

Any advice is appreciated, really don't need this right now, but I'd rather not have the truck acting up while i'm at the Solid Axle Summit in August, so if something needs to be done i'm going to iron it out beforehand. If im overreacting please let me know, its easy to get caught up in the different sounds our trucks make, i'm just overly cautious

Thanks,
James
 
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I have a similar noise and I've narrowed it down to the driveshaft splines, coasting a minor but noticeable vibration and noise. This shaft has ca. 375k miles on it and I guess it has developed some worn spots.

Add the d-shaft to the list of things to check to rule out the H55F
 
Godwin said:
I have a similar noise and I've narrowed it down to the driveshaft splines, coasting a minor but noticeable vibration and noise. This shaft has ca. 375k miles on it and I guess it has developed some worn spots.

Add the d-shaft to the list of things to check to rule out the H55F
Click to expand...

I didn't think of that, the drivetrain in my cruiser is pushing 250k. is there anything I should look for specifically on the drive shaft itself?
 
Have you at least checked the oil?
 
Haha!
 
If I recall the fill is on the drivers side up close to the floor. Someone correct me if I'm wrong :)
 
It will never leak externally. It can leak internally into the transfer case. Check the transfer case oil level too.

image.jpeg
 
Dam OS...you are one prepared dude. Incredible feedback and as always spot on. We are lucky to have you surfing MUD as much as you do :)
 
EasternYeti said:
It's never leaked oil of any kind (strange I know) but I'll ckeck today

Where's the fill on a H55?
Click to expand...

Output Shaft said:
It will never leak externally. It can leak internally into the transfer case. Check the transfer case oil level too.

View attachment 1448012
Click to expand...


My BJ74/H55 does not leak externally untill the transmission is ~3 quarts low and the transfer case is ~3 quarts over-full and barfing out the breather vent.....:doh:
 
Ok guys, the wining is more pronounced without a doubt.

Figures It'd be pouring after work, but I did check the fluids. Roughly an inch below the fill hole on the H55...so low but not "that low"

Rather than waste money on oil what are ways I can identify a bad input shaft bearing vs a throwout bearing? Or something else that might be going

As I inherited this truck as a vortec swap, if i end up having to take this to a shop, are there any special parts (gaskets / seals ) that are unique which I'd have to specify to them to get the job done?

I simply don't have the facilities to drop the transmission currently, otherwise I'd attempt it myself. Trying not to get ripped off, and more importantly trying to understand why I have a failure at 30k miles of city driving
 
Funny, my transmission actually shifts better cold when it is half bled-to-death.....:lol:

"Oh boy, it's starting to shift nice. It has to be low."
 
Output Shaft said:
First thing to do is see how fast the oil is migrating from the TMS to the TFR case. It could be a very slow weep that only requires oil level adjustments every so often. All cruisers will eventually develop a leak between the cases and most guys just keep an eye on it (or should) & top off/drain occasionally.
The problem is the rubber seal. Not a bearing. The seal wears out over time.

My transmission weeped into the transfer case for over 15 years before I got around to replacing the seal. Every month I would check the oil levels, or more frequently when I was driving long distances. After a while you get a feel for how fast it weeps.

If the oil in the transmission is 1/2 quart low, (and maybe even 1 quart low) it won't harm the transmission. It just won't shift as well. I could always tell when the TMS oil level was little low (& transfer a little high) because shifting wouldn't be as smooth & the transfer case shift lever would rattle a bit at highway speeds.
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Even with the oil level where it is, I didn't notice difficulty in shifting between gears, just a noticeable difference in the sound of the hum when I didn't apply the throttle.

One thing I did notice last month was after I thrawed through a large mud hole with a running start (15 mph ). the gears became difficult to change , and required some more help to get in, Typically it's smooth as butter. Went back to normal after some driving around town

And maybe 6 months ago, when I greased the driveshaft I saw the T-case move an inch or two toward the front of the truck. I was never able to find how or why it moved, as the mounts are solid, but I can't help thinking this hum has something to do with that movement or is a result of it.

When the rain stops this week I'm going to pull the skid plate and top it off, we'll see if the hum continues then
 
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Is it possible that maybe you saw the yoke/transfer case output flange move forward when you greased the ds? I can't see the TC moving forward. It is possible that there is too much grease in the slip joint of the ds that isn't allowing the slip joint to slip and creating a little extra tension on the drivetrain. Just spitballing here.

If it was the Yoke that moved that much, it's something that needs to be tended to but I would think you would be feeling big vibrations and clunks if one of the flange nuts were that loose.
 
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The transfer was shoved forward by over-greasing the slip-yoke. That also puts excessive thrust pressure on the bearings in the transfer and the differential. If the transfer case mount is broken it would be even easier to shove it forward.
 
Can you move the driveshaft up, down or around - slop, at the transfer case?
 
cruiserdan said:
The transfer was shoved forward by over-greasing the slip-yoke. That also puts excessive thrust pressure on the bearings in the transfer and the differential. If the transfer case mount is broken it would be even easier to shove it forward.
Click to expand...

Tomorrow I'll try to determine if this was the case. When it happened, I did check the mounts, and everything was solid. Unless something let go after that point I may be wrong

I know that I over greased it, but it wasn't to the point where I imagine anyone else hadn't done the same thing in 30+ years. The yoke was in desperate need of it, and I hoped a monkey with a grease gun wouldn't be too determential to it's components
 
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