Transmission has no gear oil

[JimSraj 429]

The 312-8 that I acquired a while back came with a snowblower which is the real reason for buying it. The blower is in decent shape and I'm making a lift tube and flag for it. Actually, the tube is made just need to find a 3/4” rod or bolt to make the flag. 
I couldn’t resist finding out if the  M12S would run so I checked it out and she’s up and running with just a new; starter solenoid, rinsed out fuel tank, new fuel lines, and fuel and air filters. Motor oil was clean and spark plug fired well. Well that’s all great but on to the transmission. No oil registers on the dipstick at all. I had rolled it around to get it on the trailer and off into the shed. Didn’t hear any suspicious sounds so after I got the engine running a jacked up the rear end and spun the wheels. No noises and the opposite wheel spins opposite of the one I’m spinning in every gear with no nasty noises. Started the engine and VERY briefly engaged each gear both hi and low range. Same thing, smooth, no noises. 
I’m going to take the drain plug out before anything else just to see if there is any gear oil at all in there. 
My question to you all with more experience than I have is, would you fill it with gear oil and see what happens or just go ahead and tear it down to see why there is no oil in it and check for other damage?  I’m pretty sure seals need to be replaced. Oh yeah, while it was jacked up I checked to see what movement I might find in the axle bearings. Absolutely no slack top to bottom or side to side. The other strange thing is the axles look reasonably clean. No signs of leaking seals. 
What do you think?

[wallfish 16,996]

Drain what's there in it now and give it a look see. If it's clean and not milky just fill'er back up with new gear oil and watch for leaks around all of the shafts. Milky means water and you can fill some diesel into it and run it. Then drain that out and fill with gear oil. 

[ebinmaine 67,471]

1 minute ago, wallfish said:

Drain what's there in it now and give it a look see. If it's clean and not milky just fill'er back up with new gear oil and watch for leaks around all of the shafts. Milky means water and you can fill some diesel into it and run it. Then drain that out and fill with gear oil. 

 

Seconded. 

 

The diesel will show leaks easier than gear oil too. 

[Skwerl58 704]

Get the front end high and drain it. Make certain you are removing the drain plug and do as stated earlier. 

[leabassett@sbcglobal.net 149]

I say drain it and put 1/2 the gear oil it needs in it. Let it set a few days with cardboard under it, If it has a big wet spot than tear it down. If not fill all the way and run it. It may take 10 years to leak all the oil out. 

[Brockport Bill 1,661]

i had a C165 we rescued that had been outdoors for years with bad gear shift boot so lots of rain got into tranny -- the tranny oil was VERY milky -- i did 3 flushes with kerosene before it was pure again to put in final 80-90 gear oil. As noted above important to jack up front -- also to drive for 5-10 minutes between flushes to get warm  - - use all gears including reverse and hi-low -- then drain again - that should remove corrosion and sediment -- Enjoy !!

[Bill D 1,920]

Dumb question, does it have the correct dipstick in it.  If it had a dipstick for a hydro it wouldn't show as having any oil.  Also, any chance the dipstick snapped off.  I've seen that as well.  Looks like there isn't any oil until you realize what happened.  

 

If it's not making any weird noises, and everything seems to be working, then I say fill it and run it.

[ri702bill 8,318]

8 hours ago, ebinmaine said:

The diesel will show leaks easier than gear oil too. 

 

Boy, will it ever!! Could be time for a new shifter boot when done....

A rare problem, but a showstopper.... check the underside middle of the Unidrive case for "impact" damage, as the castings are thin there.

Oil capacity in a 8 speed is 2 quarts, as I recall...  Someone else will either verify or say different...

Edited October 1 by ri702bill

[953 nut 55,218]

10 hours ago, JimSraj said:

Absolutely no slack top to bottom or side to side. The other strange thing is the axles look reasonably clean. No signs of leaking seals.

If it ain't broke don't fix it.      If the transmission had been operates with no oil for very long the outer axle bearings and seals would have suffered a great deal of damage. Like @Bill D said, chances are you have oil in there, just need to confirm what is there. If you have another 8 speed check the two dipsticks side by side.  

Use a piece of wire in place of the dipstick and go all the way to the bottom to see what, if anything is actually in there.

[peter lena 8,624]

@JimSraj  , sounds like a very common  recovery . hopefully , first question , any drive around areas in your  neighborhood ?  a lighter flushing / cleaning fluid , is very good , for initial motion , like hi mileage ATF fluid , for sling ease , on open gearing , diesel is also good . once its filled , like to pit some road time on it , use every gear / range , that slinging  cleaning / flushing effect is what you want , get a new shift boot , might easily have axel seal leaks , would wait on that , cleaning is more important , now . having done this recovery on a number of  neglected horses , get after the worst issues first , also like to run in an unknown  engine on a seperate gallon of heavily treated fresh gas . drop carb bowl , many opportunities  as you go along , might  hang a tag with issue , and move on , easy to get back to it . good lick with it , pete 

[Ed Kennell 38,170]

5 hours ago, Bill D said:

.  Also, any chance the dipstick snapped off.  I've seen that as well.  

 

 

                                I've seen that also.  If they are bent, they can wear thru rubbing on a gear.

  If it is empty, I would take the opportunity to flush with diesel before filling with gear oil.   Be sure to raise the front of the tractor as high as possible to get the drainings over the hump.

Edited October 1 by Ed Kennell

[Bill D 1,920]

Any updates on this?

 

[JimSraj 429]

10 hours ago, Bill D said:

Any updates on this?

 

Checked the dipstick against another from a 1991 8 speed. Same length. Then I did as 953nut suggested and checked with a wire and found that there was about an inch of oil on it after touching bottom. The oil was a little cloudy so I got the front end well up off the ground and drained the trans. Replaced the plug and put 2 qts. of diesel in and went through all the gears and ranges with the rear end jacked up and over cardboard starting in low range and ending in 3rd hi. Started to notice a very slight seep at axle seals once in hi range. By the time I got to 3rd hi it was a pretty steady drip. I’m gonna let it sit for a while the run it again before draining and replacing the seals. Hoping the hubs will cooperate. 
There was a noticeable metallic sound coming from either the input or the idler. I’m hoping idler but won’t have time to get back to that for better than a week. The sound seemed a little too hi pitched to be coming from the input shaft bearing. Maybe I’m just letting my hopes influence my judgement.  Hope not. 

[ebinmaine 67,471]

8 hours ago, JimSraj said:

Hoping the hubs will cooperate. 

 

Given patience, heat, good penetrant, and most of all, TIME, they'll come off. 

 

 

8 hours ago, JimSraj said:

The sound seemed a little too hi pitched to be coming from the input shaft bearing. Maybe I’m just letting my hopes influence my judgement.  Hope not. 

 

A higher pitch noise is more likely to be in the outside of the oil bath. 

Not foolproof but more likely. 

 

Hopes vs judgement is only a matter of time to change an outside bearing vs time to open the transmission. 

Quite different, yes. But both very repairable. 

[JimSraj 429]

13 hours ago, ebinmaine said:

 

Given patience, heat, good penetrant, and most of all, TIME, they'll come off. 

 

 

 

A higher pitch noise is more likely to be in the outside of the oil bath. 

Not foolproof but more likely. 

 

Hopes vs judgement is only a matter of time to change an outside bearing vs time to open the transmission. 

Quite different, yes. But both very repairable. 

Thanks Eric, I ran through the gears agin today with the diesel in there and then pulled up the front end and drained it. It’ll stay ‘reared up’ until I’m back in a week or so. Then I’ll see about that squealing and replace the axle seals. 🤞on the hubs. 

[kpinnc 12,017]

On 10/2/2024 at 9:51 PM, JimSraj said:

There was a noticeable metallic sound coming from either the input or the idler.

I would think that the thin diesel would make for a bit of whine coming from the higher speed small gears and needle bearings. 90-140W oil may be a little more quiet. 

[oliver2-44 9,743]

If the area around the axle seals is all oil caked dirt the seals may be OK.  Diesel will leak where 80w90 wont.

If it was me I'd put gear oil in it and run it awhile and only fight the hubs when I knew for sure I had to.

[JimSraj 429]

11 hours ago, kpinnc said:

I would think that the thin diesel would make for a bit of whine coming from the higher speed small gears and needle bearings. 90-140W oil may be a little more quiet. 

The sound really seems to be coming from either the input shaft bearing or the idler not from deep inside the case. 

[JimSraj 429]

11 hours ago, oliver2-44 said:

If the area around the axle seals is all oil caked dirt the seals may be OK.  Diesel will leak where 80w90 wont.

If it was me I'd put gear oil in it and run it awhile and only fight the hubs when I knew for sure I had to.

Yeah, I was thinking that way too. I’m going to see if the hubs come off easily and then decide. As you say I can fight the hubs later if need be. Thing is the oil level was at least a quart low initially. No telling how long I took to leak down to that though. 
I’m pretty happy to have gotten it running and only found this little leak in a $100 tractor , blower and deck, even though the deck is shot. 

[Ed Kennell 38,170]

2 hours ago, JimSraj said:

’m pretty happy to have gotten it running and only found this little leak in a $100 tractor

Any $100 wheel horse purchase is a win.    

[kpinnc 12,017]

9 hours ago, JimSraj said:

The sound really seems to be coming from either the input shaft bearing or the idler not from deep inside the case. 

Makes sense. That is the highest speed portion, and the small gears are directly behind it. 
 

I think you’ve done this right. After draining the diesel and adding gear oil, you should be good. Maybe a shaft seal or two will need replacing, but that’s not unusual. 

Edited October 4 by kpinnc

[ebinmaine 67,471]

3 hours ago, kpinnc said:

After draining the diesel and adding heat oil

Ehhhhh.....?

[kpinnc 12,017]

1 hour ago, ebinmaine said:

Ehhhhh.....?

I really hate this new phone. If I typo, it comes up with its own interpretation… I’m gonna have to proofread more. 

 

I fixed the post. 
 

The old saying is true: Never give a smartphone to a dumba$$… 

Edited October 4 by kpinnc

[ebinmaine 67,471]

35 minutes ago, kpinnc said:

I really hate this new phone. If I typo, it comes up with its own interpretation… I’m gonna have to proofread more. 

 

I fixed the post. 
 

The old saying is true: Never give a smartphone to a dumba$$… 

 

I figured that's what youzz meant to write but I was hoping to glean some super useful new learnin'    

 

My phone will "autocorrect" things that AREN'T EVEN WRONG!!!

 

Like I need help screwing up????

 

 

 

[MainelyWheelhorse 435]

@kpinnc @ebinmaine Minor… It would just be a double flush of almost the same thing. Extra clean! 😁