Low gear spindle noise

EvansER89 · Jan 17, 2017

Help! Low gear spindle noise

We have an early 90s VF that just "developed" a loud noise in the spindle.

We had an issue with our air compressor leaking, and had fixed that. We went to run our warm up and the machine was running fine when we realized the air was still turned off, run back to the compressor and flipped the switch, and we hear a nasty noise and realize the spindle tried to change gears, while running...
Now it sounds pretty rough running at S500, but fine at S2000.

Would like to point out that the machine was running-with no air-which is weird.
The spindle runs fine in high gear at any speed (S2000-7500), and in high gear at the low speeds (S2000 overridden to 10 or 20%), so high gear seems to be fine, as do the spindle bearings.

Did we toast the low gear cog, or bearing? Is something just loose? Is something jammed, or not seating correctly?
How do we check?

Any help would be much appreciated!

ewlsey · Jan 17, 2017

I wonder if that is a sliding gear or there is some kind of sliding dog/collar arrangement. It might be academic though. Haas is notorious for not selling parts for their gear boxes. They want you to buy the whole thing.

Sounds like your low air pressure switch is bad. I'd get that sorted before you lose the spindle bearings.

SIM · Jan 18, 2017

Sounds like you may have removed a chunk of low speed gear tooth. Slow it jumps but fast it slides by...till you take a cut.

I'd put in low gear and turn spindle by hand real slow so you feel resistance...if it binds in one spot, tooth may be deformed...but if you have a gap with no contact or more backlash then normal, I'd say missing tooth.

Guys have rebuilt themselves...don't expect to much Haas Help as they are replace Tranny if you have a problem.

EvansER89 · Jan 18, 2017

Were going to pull the motor off and take a look inside, I assume on an older machine Haas won't be dealing just the bits and pieces we'd need. I'll start looking into rebuilding it after I talk to Selway.
We also tried running it in reverse to see if it was different, or maybe not engaging properly. It sounded "better", but still not good. Its always sounded different, which I assume is from the additional miles is has running forward vs backwards, or...?

@ewlsey Is the low pressure switch how it may have been running without air and not alarming out?

@SIM Just to make sure I understand, you suggest try spinning it to see if there is slop (missing tooth), or binding (bent tooth), by hand while it is shifted into low gear?

haastec · Jan 18, 2017

SIM said:
Sounds like you may have removed a chunk of low speed gear tooth. Slow it jumps but fast it slides by...till you take a cut.

I'd put in low gear and turn spindle by hand real slow so you feel resistance...if it binds in one spot, tooth may be deformed...but if you have a gap with no contact or more backlash then normal, I'd say missing tooth.

Guys have rebuilt themselves...don't expect to much Haas Help as they are replace Tranny if you have a problem.

I agree with this. There are a couple of good threads about rebuilding old machines that have good write ups about what they did to rebuild the gearboxes.

My guess is that you chipped a tooth on the low gear side. Drain the oil and see if you can find any chunks. The drain plug should have a magnet on the end also to help catch any metal.

With regards to running with no air, check parameter 76. I think most older machines have this set at 500 or newer ones have it set to 1500. This is a time delay telling the machine how long to wait before triggering the low air alarm. Sometimes, the techs (guilty myself sometimes) will leave this set at 999999999. We set it high at times to allow us to jog and move the machine around without triggering an alarm. If yours is not set high like this, then suspect the pressure switch.

EvansER89 · Jan 18, 2017

The low air alarm showed up when we first powered up earlier that day, and is what keyed me into the compressor leak in the first place. After we fixed that and turned on the compressor (but the line was still closed to the machine) I was able to clear the alarm; it was working before we ran the warm up, then somehow it apparently wasn't working anymore.

Most of the rebuild threads I see detail replacing bearings, and not replacing gears, *hopefully* that's all we are going to need...

SIM · Jan 18, 2017

EvansER89 said:
@SIM Just to make sure I understand, you suggest try spinning it to see if there is slop (missing tooth), or binding (bent tooth), by hand while it is shifted into low gear?

No, check when in low gear.

EvansER89 · Jan 18, 2017

What material would those gears be made from typically? Cast iron, or steel?

EvansER89 · Jan 18, 2017

Looking through other posts, I don't see how to actually remove the gearbox to access the gears.
There are a lot of hoses and some copper tubes attached to the gearbox housing, its a bit intimidating just pulling stuff off, is there a manual for actually removing the gearbox somewhere?

ewlsey · Jan 18, 2017

The copper lines are air lines for the shift fork. There will be two prox switches for the fork as well. Then there is an oil fill tube. I dunno what else. Just mark things before you pull them apart.

I'd leave the spindle motor on the machine if it was me. Just hang it off to the side or put it on top of the cabinet.

EvansER89 · Jan 19, 2017

Spun the spindle around while in low gear as suggested, no binding, or extra loose spots, checked again in high gear to see if it felt significantly different aside from gear ratios but it felt good, so we went ahead with the disassembly. Managed to get everything apart in some fashion with only one bloodied knuckle, and poke around in the gearbox. No signs of catastrophic damage, no teeth were broken off, but there was signs of grinding from the gear shift with the spindle turning, as seen in the pictures.

There are burrs along the tapered faces where the gears engage axially as they shift; would those burrs be enough to keep the gears from meshing properly and create the noise? It definitely doesn't look as bad as it sounds... We're going to try hand filing them, maybe hit them with a wire wheel, and then pop it all back together.

We could hear the noise while turning in low gear with the gearbox just sitting on the table, so luckily we don't have to completely reassemble everything to decide if it sounds any better.

machineit2 · Jan 19, 2017

EvansER89 said:
Spun the spindle around while in low gear as suggested, no binding, or extra loose spots, checked again in high gear to see if it felt significantly different aside from gear ratios but it felt good, so we went ahead with the disassembly. Managed to get everything apart in some fashion with only one bloodied knuckle, and poke around in the gearbox. No signs of catastrophic damage, no teeth were broken off, but there was signs of grinding from the gear shift with the spindle turning, as seen in the pictures.

There are burrs along the tapered faces where the gears engage axially as they shift; would those burrs be enough to keep the gears from meshing properly and create the noise? It definitely doesn't look as bad as it sounds... We're going to try hand filing them, maybe hit them with a wire wheel, and then pop it all back together.

We could hear the noise while turning in low gear with the gearbox just sitting on the table, so luckily we don't have to completely reassemble everything to decide if it sounds any better.

View attachment 188989 View attachment 188990 View attachment 188991

I was going to post yesterday but got busy, sorry. I have a 96 that had a little noise in low gear when I got it in the first place. Not bad at all, but you knew when you were in first gear. I have had it for about 7 years now.

About 6 months ago I went on a short vacation and when I returned it did a power up on my machines. The 96 did not want to change gears and alarmed out a few times. Finally it tried to make the change and it did not complete it properly, but no alarm. When I started the warm-up program it was not in gear properly and did some good grinding before I hit E-Stop. I worked it back and forth and got it making the changes good again then ran it in low gear. It was considerably noisier and I was sure I was going to have to work on the box.

I decided to run it in low gear forward and reverse for a while. I ran it several hours back and forth and the noise mostly went away. Now after many more hours of usage, it is no more noisy than it was when I got it and works perfectly. These are straight cut gears and what happened is the some burrs were put on the engagement edges. They simply get reshaped and worn off in use.

I support your effort to clean up the teeth, clean and reassemble the gear box and see how it works. Your accuracy and such will not be negatively affected and you can save a bundle of money.

Best of luck----Mike

EvansER89 · Jan 19, 2017

That is encouraging!
I did run it in reverse briefly, probably should have gone longer but I was concerned about blowing something up...
Tearing it apart and then resetting everything will probably end up being a huge PITA, I hope it works!

EvansER89 · Jan 20, 2017

We got it cleaned up, greased, topped off the oil and its back together. Fired it up and I hear an air leak I swear wasn't there before. Ran the spindle at S1250 and it sounds better than before, tried to shift to low at S500 and nothing... Alarm 118 low gear fault. Track down the leak, its from the cluster of valves behind the gearbox which control the gear shift. Have a couple of questions for you guys:

These were working just fine before, never had a problem shifting until the accident the other day, and even after that it was able to shift fine, so I'm not convinced anything is broken. I'm wondering if its possible the shift mechanism is stuck in between gears and holding a switch open?

Should/can we try shifting "manually" with a pair of bent pliers pulling on the shifter, or try blowing air into the copper lines at high pressure to force a shift?

The other thing it that we missed labeling the wires for the switches that tell it high or low gear. I would assume these would alarm out if installed incorrectly, but we switched them around when the gear change didn't work and it still worked the same. How do we tell which is which?

I'm hoping someone will chime in with a solution that doesn't require removing everything again before we get back to it today!

EvansER89 · Jan 20, 2017

We were able to shift gears by blowing into the copper air lines, so the shifter is not stuck, and the lines arent clogged.
Next we put it into low gear by hand, but as soon as we put air to the machine it shifted into high gear, so I think somehow air is not sealing in the shifter.
Were going to order a solenoid just as some insurance but are thinking the top-hat shaped seal in the shifter may have been installed upside down allowing air around the seal. We oriented this part based on pictures from other threads on gearbox teardowns, so this seems unlikely, but more likely than our solenoid going out during this process...

Any other thoughts?!?

ewlsey · Jan 20, 2017

Failure is always an option. I'd pull the shift cylinder back apart.

EvansER89 · Jan 20, 2017

After flipping the sealhead around it shifts fine. Running in low gear still sounds a little rough, but improved. We will try running it for a while and see if we cant knock down any remaining burrs and help it seat itself.

ewlsey · Jan 20, 2017

What was the old scam for noisy transmissions? Sawdust? Maybe oatmeal? Ask a used car dealer.

If you inspected it and the bearings are free and the gears are intact, I say run it. It'll self correct...

magno_grail · Jan 20, 2017

Sawdust.
The diagnostic page should show the position of the switches. You can manually work the switches and watch the numbers change.
The open side of the seal faces the pressure.

EvansER89 · Jan 21, 2017

The picture we were looking at was a little misleading, but after taking the shifter apart and looking at the picture we figured out we had it upside down.
Fortunately we also saw a picture that had the gear switches and could figure out which was which.
It shifts fine again, but its still a bit noisier in low gear than high. We've been running it CW/CCW/CW/CCW at various low gear speeds for a few hours in hopes of seating the gears better. If we ever actually cut in low gear it would probably fix itself pretty quick, but the closest way we can simulate some low gear load on it is to just spin the heaviest tool we have.
I had been thinning for a while that the spindle bearings were on their way out because of noise I'd hear during warmup, but now I'm thinking its actually been the low gear noise all along. Makes me feel a bit more confident about the condition of the machine for now.

Thanks for everybody's help! Maybe if some other poor soul has the same problem they can save themselves some smashed knuckles, and will just try rev-honing their gears instead of taking it all apart!

Low gear spindle noise

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