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Discussion Starter · #1 ·
Hello tractor gods! We just purchased our 2nd gravely, an 818T w/ 18hp Onan for $300 not running! Got the engine running, as I put it into gear there was a loud screech (gears grinding i presume) and then stopped the engine in its tracks. It ran fine powering the PTO, Hydros and was spinning the idler wheels on the clutches from what I could tell like it does on my 812.

I drained the oil and can see/feel very fine metal shavings, no chunks though. removed the engine to get a peak inside. I can tell that the gears can be shifted with no problems. High/Low range lever was popped off and is very tight but seems to just need some lube. I can shift the high/low range lever with alot of force but I can see it shifts seemingly smoothly inside the trans.

I'm not an expert on transmissions, but it seems there is an issue somewhere between the gears and engaging the clutch. I dont believe it is the final drive or a cracked axle as the wheels spin in the opposite direction no problem and i cant physically pull on the hubs and there is no movement in them.

PLEASE HELP. Im brave enough to tear into this trans, but I really want to know if its necessary. Could this be an issue with the clutches? Or is it realistically a woodruff key or something that will require major surgery?

PS the wheels are totally locked up no matter what gear when I put it in gear and shift the clutch forward or backward.
 

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Old Iron Connoisseur
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Sounds like something in the final pinion to diff locked up. If you have the motor off you are most of the way to opening it up. It can be done on the frame rails but others including myself generally prefer to stand it on it's left side tire to work on it free from the frame and rest of the tractor. Hydraulic lines and transmission controls are all that is left to remove. Once open it should be fairly obvious what is lodged.
 

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Discussion Starter · #3 ·
Hey thanks Jimmy. Quick question, in the 800/8000 shop manual it says to install a spacer on the left axle. I need to remove the hub in order to do that. I read some posts about removing the hub and that it can be difficult. Is it worth removing the hub for that spacer or should I leave it and only wrestle with the right wheel to remove the trans case? I assume you're going to say, "yes put the spacer in" haha.
 

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You don't have to install that spacer, it will just allow the transmission to fall a few inches when the case is opened. I think I stuck some 2x4 pieces in there or something when I opened mine up last time.
 

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It almost sounds like the clutch bearings are gone. Pull the clutches and see if the bearings are OK.
 

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I have done 4 transmissions. The first 3 were done with the transmission off the tractor and on its side. This last one was done with the transmission on the tractor. I will NEVER take a transmission off and lay it on it's side again.


I saved at least 2 hrs of time and bunches of grief. My advice is to download the G series service manual and follow that. I have to admit I was 1/2 way through the disassembly process and thought maybe it was a mistake but it was a huge win. The reason for the huge win is that gravity is working for you, not against you.

With some practice, one could assemble a transmission from a bare case in less than 10 minutes.

I did do one thing that helped a lot and that was to power wash the transmission before I started.
 

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he hardest part in getting the case off is removing a wheel hub that has been loose on the axle for a long time. I got lucky this last time as the hub just tapped off with an 8 oz hammer. The slot in the axle was worn a bit and I needed a new woodruff key, but it wasn't bad.

The reason I had to tear down the transmission was the bearing was gone on the reverse gear.

A few words of advice.

1 - Replace the seals that get disturbed. That means that the right side axle seal, forward direction clutch seals, and the brake shaft seal. As a minimum, replace the direction clutch hub seal and shaft seal. Those are the ones that require disassembly of the transmission to replace.

2 - Do NOT use gasket sealer on the case gasket. The gasket is impregnated with sealant and once it is clamped for a while, it creates it's own seal weather there was grease on the gasket or not. It is pure magic how well the plain gasket seals.

3 - Do use some gasket sealer between the engine and transmission. Many times there is no gasket there.

4 - Never use the cover bolts to seat the transmission cover. If the cover cannot be fully seated with the assistance of some light taps from a soft faced hammer, something is wrong. Take the cover off and figure out what is wrong.

5 - If you lose a woodruff key, buy one from Gravely. The keys are hardened and the local hardware store does NOT stock hardened woodruff keys.

Here are some pictures of my latest transmission repair.



This is what the reverse gear is supposed to look like.


This is what I pulled out.


This is what was left of the direction clutch shaft seal.


Reverse shaft damage.


more of the same.




The ONLY way to work on these transmissions. I could have pulled the other two shaft assemblies out but there was no point. If I had to pull the diff out I would have jacked up the other side and put blocks under the axle housing. The left tire is resting on the ground. Total parts needed for this repair was under $150. That included shaft, bearing, seals, 6 quarts of oil, and gasket.

I am going to tear down my 24G transmission later this year to replace the forward and reverse clutch shafts. It will be done in situ just like this one. The PO never lubricated the clutch splines and as a result, the shaft splines are worn badly.

I still don't know what caused the bearing failure. I think the shaft seal was bad thus allowing water in.
 

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One more thing. If the transmission is left on the tractor, neither the hydraulic pump nor the lines have to be disconnected.

As long as the rear deck is off and the shifter plate is off, now is the perfect time to clean, lubricate and derust the PTO rod and clevis.
 

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Discussion Starter · #10 ·
OK. So I disassembled the clutches and was able to get a good look at the bearings. Everything seemed to move smooth and freely. I decided to examine the trans more closely because I can't help but notice that this trans seems to be working fine! I have one wheel on and can spin the hub on the other and make the gears spin inside.

(I'm not an expert so my vocabulary is off but I understand how automotive transmissions work using a final drive and that its really one wheel drive, not 2. That is why the wheels spin in opposite directions. )

Ok so I decided to re-mount the engine and try things out. I greased, and re-mounted the clutches and started the Onan up.

-everything including the PTO, and hydros were spinning

-I discovered that If I push the clutch handle all the way forward it would put the wheels and trans in neutral. If I put the lever in neutral it would engage the trans into reverse. And then as I shifted the handle into reverse the engine started to bog down

It seems as though the clevis needs adjusting. Putting it into reverse was putting too much pressure against the clutch bogging the engine down?

Let me know what you think.
 

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I thought I'd add this. If you need to remove the transmission cover, do so very slowly, checking to be sure that shafts, spacers, gears, etc. are'nt pulling away from the case as you pull the cover off. You will spend less time trying to figure what goes back where.

Also, before I pulled my cover, I removed the two bolts at the 9, and 3 o'clock positions on the cover. I hand tightened two 6 in. bolts, which I had already prepared by cutting the heads off, in their place. The bolts became threaded guide "rods". They enabled me to slide the cover away from the transmission a little at a time.

When it came time to put everything back together, they made alignment of everything very easy as I slid the cover into place. A few light taps with a rubber mallot, and the cover snugged into place.

You can see the cover guide "rods" threaded into the transmission case just below the metal locator dowels.
 

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If I push the clutch handle all the way forward it would put the wheels and trans in neutral. If I put the lever in neutral it would engage the trans into reverse. And then as I shifted the handle into reverse the engine started to bog down

Let me know what you think.
You need to adjust the clutches per the manual or look for a broken or missing clevis or clevis pin. I have never adjusted the clevis rods on any of my tractors including my 818T.

It sounds like forward and reverse clutches are engaging at the same time.
 

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The application of the two clutches at the same time is usually indicative of clutches that are too tight. What I do is with the tractor off, adjust the forward clutch so it easily locks in place. This is accomplished with the two 1/2" NF nuts that hold the clitch plate on. I also adjust the rear so that it starts engaging near the end of it's travel.

It is possible that the clutch plates were not assembled properly. If the linkage is really worn that could also be an issue.

If have, in the dark, dim past improperly adjusted direction clutches so both were applied simultaneously. I can't remember how I did it.
 

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That is it. That is how I did it. It is easy to use the wrong holes.
 

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Yes, that is the easy way. There is also the possibility that, assuming the right holes were used, the cam/plate assy(s). may have been installed misaligned, or with the rollers in their engaged position (not retracted in the cam detents, or neutral). This would also throw the positons of the clutch cam(s), linkage(s) and shift lever position off when reconnected. It would also alter forward/reverse engagements.
 

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Here's a pic of the clutch cam, and clutch plate on the 814. With the transmission in neutral, both the forward, and reverse clutch cams are positioned with the linkage clevis pin through-bores at the 12 o'clock position. The clutch plate rollers are also set into the deep side of the clutch cam detents.

First, I would check the clutch plates, to be sure that they are mounted properly. The plates should be mounted through the top holes on the forward side of the tractor, and the bottom holes on the rearward side.

Next, I would disconnect the linkages from the clutch cams, and move both cams so the the clevis through- holes are at the 12 o'clock position (neutral). Then look down at the position of the top clutch plate mounted rollers. They should be positioned in the deep side of the clutch cam detents.

If it is'nt, you will need to remove the clutch plate (the 2 retainer/clutch adjustment nuts) and remove and adjust the clutch cam(s) on the shaft so that when you re-install the plate, the cam clevis through-hole is at 12 o'clock, while the rollers are also positioned in the deep side of the clutch cam detents.

You may have to adjust your linkages (depending on what a p/o might have done to "fix" the problem) so that your shift lever is at half of it's range of motion when in neutral.

With the tractor off, and the transmission in nuetral, the clutch gaps should be adjusted (by tightening/loosening the clutch plate retaining/adjustment nuts) to either .20 or .30 thousanths all around. I have seen both.

I just hope that this is your problem.
 

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Just another thought, as anything is possible. You might also check to be sure that the clutch plates are installed right side up, so that the one roller is at TOP center of the clutch plate as installed (pic).
 

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Discussion Starter · #19 ·
EUREKA!! You guys have really made my week.

So I popped off the clutches on both sides. The bearings seemed to roll smoothly. I brushed up the rust and put some grease on those rollers. It was very easy to tell right off the bar that the forward and reverse clutches were in fact engaging at the same time. I never really understood how the clutches really worked on my 812 because it always just worked and I live by, " if it ain't broke dont fix it."

So I adjusted the clutches per everyone's recommendations and she is now smoothly working in both directions!!! I didn't get a chance to try her out in all gears because it was like 8 @ night and I already get funny looks from my neighbors (my garage I'll do what I want!) I will post a video or pics today when I take her for a real test ride. Thanks again for all the info tractor gods! You've answered my prayers and blessed me with loads of info for the 812 and 818T.

ALL HAIL THE TRACTORS. YEIT!
 
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