Clark transmission 1st gear problems

[Ronan]

hey guys I have a Fiat Allis FG95 motor grader (Serial 45M00145) with a Brazilian made Clark transmission (model R28421-503). I just finished replacing all the filters and oils in the machine as well as fixing all the leaks. The last thing left to do is get the first gear to work again. It sorta engages and rolls forward for a second but never really engages. Ever since I bought it in 2006 I've ran in 2nd gear and have sorta babied it cutting hard ground. I spoke with a couple of knowledgeable guys about the problem and they said the rear bearing cap may be worn and a bad O-ring on the backside of the cap causing the fluid to bypass. Well, tonight I took it off and inspected the cap and it looked fine other than some very minor grooves maybe .01 of an inch from the clutch shaft piston ring and the end of the shaft itself, so I replaced the O-ring which was bad and reinstalled the cap thinking I had solved the problem. As soon as I put it in gear it hit a little harder but then it acted the same as before. So I took it off again to make sure the O-ring wasn't damaged and put it back on. Again it made the machine start to roll but acted the same as before a few seconds later. So I'm reaching out to you guys to see if anyone is a Clark gooroo and can steer me in the right direction to get my first gear working. Ive attached a couple of photos to show you the cap and how it looks inside. thanks

 

[Vetech63]

Does your 1st gear work in reverse? If so then the problem is not your first gear clutch pack. Does your other gears in forward work without slipping? What is the condition of the oil you drained? Was it dis colored or burned? Was there any metal or contaminants in the drain oil, or on the drain plug?

 

[Ronan]

It does the same thing in reverse as well and the other gears all work fine forward and reverse. I drain the oil and check the filters and there was very little shavings.

 

[Ronan]

Do you think it may be a weak or worn ring seal on the end of the clutch shaft that’s causing a blow by issue?

 

[Vetech63]

The cap you removed, was it the 5 bolt cap at the top left of the drop box on the back of the transmission? There is a test port plug in the end of the raised boss on that cap. Plug a gauge in there and put it in 1st gear and see if you have around 400 psi. It sounds more like your 1st gear (low) range clutch or drum has failed mechanically. If you haven't removed this 5 bolt cover, then do so and check the seal ring and housing for wear.

 

[Ronan]

Hi Vetech63,

I removed the cover replaced the o-ring and seal ring, no wear inside the housing where the seal ring rides. Just got my gauges in today and I’m gonna check the pressure next week. Right now I’ve got another problem on a different machine. It’s a Komatsu Pc-220Lc-3 excavator. The serial is a 208168 I think. Anyway the engine model is S6D105. Basically I had finish a complete change of fluids, filters and fixed all the leaks and wear items about 2 months ago and parked it until today I went to use it and checked the oil and water just to be sure before I cranked it and I had milk for oil! So I immediately checked the radiator and sure enough it was low. So now after talking to a few heavy equipment buddies they said it could either be an oil cooler, head gasket, water pump or bad liner seals. They said to take the oil pan off and pressure up the radiator to about 15lbs and look with a flash light where the water is coming from. Do you have any idea what it could be or recommend doing a different diagnostic before I remove the pan?

 

[rondig]

Hoe could be oil cooler...headgasket..injector cup....or worse case....dropped liner or cracked block or crack head if it froze

 

[Vetech63]

Hi Vetech63,

I removed the cover replaced the o-ring and seal ring, no wear inside the housing where the seal ring rides. Just got my gauges in today and I’m gonna check the pressure next week. Right now I’ve got another problem on a different machine. It’s a Komatsu Pc-220Lc-3 excavator. The serial is a 208168 I think. Anyway the engine model is S6D105. Basically I had finish a complete change of fluids, filters and fixed all the leaks and wear items about 2 months ago and parked it until today I went to use it and checked the oil and water just to be sure before I cranked it and I had milk for oil! So I immediately checked the radiator and sure enough it was low. So now after talking to a few heavy equipment buddies they said it could either be an oil cooler, head gasket, water pump or bad liner seals. They said to take the oil pan off and pressure up the radiator to about 15lbs and look with a flash light where the water is coming from. Do you have any idea what it could be or recommend doing a different diagnostic before I remove the pan?

Your going to have to remove the pan to narrow down the location. On the excavators, removing the oil pan is usually pretty simple, as to blocking off the oil cooler or other components. You need to know at what rate the leak is at a 15 psi pressure build up. If its small, I'm personally would try some stop leak, but that depends on the location. You could refill the radiator with water, run the engine to operating temperature, and check for any air bubbles coming up in the radiator. That is a normal sign of a head gasket leak. If you don't want to remove the pan yet, then drain the engine oil, refill the system with water, and pressure it to 15 psi. It wont tell you where its coming from, but it will tell you how bad the leak is.

 

[bigrus]

Re grader trans issue- I lost the low gears on my Clark trans a while back, long story of errant diagnosis, so I will cut to the chase. The gasket between the convertor housing & transmission case was thicker than the O rings in that clutch pack area. Doing a pressure check with air in the three ports, low range just hissed air while the other two "clunked" & locked in. To repair, we separated the the two housings, disposed of the gasket, measured up some thicker O rings & installed but deleted the gasket, instead using "master gasket" a loctite type cement. Testing again, all 3 clutch packs, clunk, clunk ,clunk. The transmission had 8500 hrs since rebuild, no idea why this occurred. Hope this helps solve the mystery

 

[clearprop]

https://www.google.com/url?sa=t&sou...FjAAegQIBRAC&usg=AOvVaw1I3mxcyruyJt6njjPibbGZOld thead here.... I have a FG85 with the same problem.

Removed the rear cover of the low gear bearing and the bearing locator as it is called in the service manual is missing. Can anyone tell me, is this just an external snap ring?

Should be able to identify it figure E on about page 13. Item 32.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.numeralkod.com/cross/archivemanuals/clark/32000%20transmission.pdf&ved=2ahUKEwjVs5Pz3frpAhUiTTABHQCDAvAQFjAAegQIBRAC&usg=AOvVaw1I3mxcyruyJt6njjPibbGZ

Anywhere I can lookup a part number?

Thanks in advance