Transmission overfill issues?

[FLtractor 23]

Recently got a new to me 1966 Wheelhorse 856. Runs good, stops. Deck needs some parts. But I’ll be using it to tow a yard wagon. Seller I bought it from for $400.00 and 330 miles roundtrip with trailer rental. Seller told me he hasent changed oil or transmission fluid in the 4 years he owned it. So today I got around to draining the transmission fluid, posted a picture. Somewhat milky. I refilled it with about 3/4 quart of 70 wt oil I had laying around, according to manual it holds 1 1/2 quart transmission fluid… I drove it around a bit then l drained that and was able to get about 1 quart of 80-90 wt marine gear lube oil. When it came out the fill hole… my question is can it be too full? Should I drain some out to better help the splashing and prevent the seals from leaking due to too much gear lube? Having driven it with that much fluid in it already, did i already do damage?

[Racinbob 11,702]

I haven't bothered to even remove that 'fill' plug for decades. The 'fill until it comes out the hole' thing is wrong. Simply put use 1.5 quarts in the 3 and 4 speeds, 2 quarts in the 6 and 8 speeds. I use a nozzle on the jugs of lube and remove one of the seat bolts to fill. Some folks remove the shifter. Here's a chart they put out. Ignore the highlighted part. 

 

[ri702bill 8,933]

Fluid still show signs of having water in it?? 

May be time (probably is) for a new shifter boot..... the shifter acts like a wick in the rain & water gets by the boot.

[oliver2-44 10,298]

These transmissions have a "hump" in the middle of the bottom.  

They won't completely drain unless you lift the front of the tractor up as high as you safety can.

Many of us like to flush the transmission on new to me horses with diesel or kerosene.

I usually do two flushes. you've already did one.

sometimes I put 2 quarts of diesel in and drive it on the gravel or paved road.

Don't drive in the grass as the seals may leak with this thin fluid.

Sometimes I just put it on jack stands and run it in each gear for about 10 minutes .

Then, as Racinbob said, just fill with the recommended amount, forget the fill hole level measurement. 

As you've mentioned, get a new shifter boot. 

While it's jacked up to drain, grease the front end since it has no weight on it. 

Edited Thursday at 10:38 AM by oliver2-44

[ebinmaine 70,495]

7 minutes ago, oliver2-44 said:

These transmissions have a "hump" in the middle of the bottom.  

They won't completely drain unless you lift the front of the tractor up as high as you safety can.

 

[Ed Kennell 40,373]

Check your PM.

On 4/3/2025 at 8:06 AM, Ed Kennell said:

If your transmission shows any sign of water (a tan milky look) or dark thick oil, you should definitely flush it with kerosene or diesel.

Raise the front of the tractor as high as safely possible when draining to get the oil over the center hump to the drain hole.

 

1. Drain the old oil

2. Fill with kero or diesel

3. If it is running, drive it slowly in tight figure 8s using all forward and reverse gears. If it is not running, jack up one wheel and rotate that wheel by hand both directions while using all the gears.  Repeat this with the other wheel raised.  The goal is to rotate and wash all the gears and bearings.

4. Raise the front and drain the kero.  If it is really black and dirty, I would repeat steps 2. and 3. till the kero comes out clean.

5. Then I like to fill with cheap low viscosity motor oil and repeat step 3.

6. Drain the light oil and fill with 90 wt rear oil.

 

BTW, I save the drained kero for washing parts.  And the drained motor oil for rubbing down to preserve the patina on the tins.

 

While each wheel is jacked up, this is a good time to check the axle bearings for movement.  There should be no up/down or front/back movement.   In and out movement is normal up to about 1/16".    The axle seals may leak some of the thin kero.,but should stop with the 90wt oil.  If the bearings check OK and the axle seals do leak oil, the seals can easily be replaced.

 

 

 

 

Edited Thursday at 05:21 PM by Ed Kennell

[kpinnc 13,627]

8 hours ago, Racinbob said:

I haven't bothered to even remove that 'fill' plug for decades. The 'fill until it comes out the hole' thing is wrong. Simply put use 1.5 quarts in the 3 and 4 speeds, 2 quarts in the 6 and 8 speeds

 

I've always used 2 full quarts of gear oil whether it's a 4 or 8 speed. 

 

 

[ebinmaine 70,495]

Just now, kpinnc said:

 

I've always used 2 full quarts of gear oil whether it's a 4 or 8 speed. 

 

 

 

 

Same

[Racinbob 11,702]

2 hours ago, kpinnc said:

 

I've always used 2 full quarts of gear oil whether it's a 4 or 8 speed. 

 

 

 

2 hours ago, ebinmaine said:

 

 

Same

 

I do the same but I didn't want to muddy the tranny fluid by differing from the chart.