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G0709 gearbox face casting sealing to the quick change gear box?????

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Mike8623

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#1
I've had a leak off and on since I got my G0709 new. The leak is between the Quick Change Gear Box and the gearbox casting plate (cover). When I take the cover off the gearbox and put it back on I just can't seem to get it to seal. I've tried using both a gasket and no gasket , gasket sealer and no gasket sealer. Has anyone else had this problem or any suggestions on how to seal the Gear box. I've got a couple more gaskets coming and am going to try again. It sure would be nice to not have this leak. Anyone out there with any suggestions? Also would anyone venture a torque range and tightening sequence for the screws and does anyone know of a gasket sealer that kinda expands to keep leaks from happening???
 

Ulma Doctor

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#2
my first thought is that there is excessive clearance somewhere, either on the cover plate or on the surface of the gear box
if you were so inclined, you could clean the area of the gearbox and the cover - put a 3/16" bead of Permatex Form-A-Gasket #3 on the cover and install the gasket. wear gloves because the #3 is super sticky and doesn't come off easily unless you have laquer thinner or MEK or Acetone arround.
the #3 doesn't harden and fills small crevices.
it does NOT expand though.
it is used in the aviation industry, but i have used the stuff for many hard to seal components from diesel engines, transmissions, differential covers, gearboxes, hydraulic sumps and flange mount electric motor sealing

the screws should have torque in the 7 ft/lb range (unlubricated)
 

Bob Korves

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#3
#2 Permatex is thicker than the #3 aviation Permatex, and is better for filling larger gaps. #3 was designed for sealing aluminum crankcase halves of aircraft engines without changing dimensions for the crank and cam journals. It is for tightly and closely fitting parts to stop seepage that would occur without sealant. #2 can be used about the same way that silicone sealers and anaerobic "gasket eliminator" type sealants do. They should still have metal to metal seating in at least some places so they do not flex, but will fill also bigger gaps.
Make sure you know where the leak is coming from. It might not be the gasket area, it might be a flaw in the metal, a burr, or a crack, or something else entirely. Try your best to find the "shooting gun" that is causing the leak. Guessing and slathering on more sealant is not the best approach. Once you find the problem, you can work out a solution. When using any sealant, having clean metal to metal surfaces, dry and without oil, remnants of gaskets, and other issues is important to avoid failure of the repair.
 

Mike8623

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#4
Thanks for responding guys. So if I get this right, I use a gasket in addition to the perma-tex and torque to about 7 lbs give or take a bit.

Anyone have any ideas with regards to a sequence for the torquing sequence for the screws?
 

Fabrickator

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#5
When my gearbox cover leaked on my G0602, I lapped the cover to see if it had any low spots it (didn't) and used the black Permatex (#2?) and just bolted it back on. I wouldn't torque the 6mm screws mine had very tight, it just doesn't need any special attention other than ensuring a good seal. There is no oil pressure, heat, etc.. to cause a leak other than it wasn't done right from the factory. i also replaced the oil view window that had crazing cracks in it, with a glass window from McMaster-Carr.
 

Mike8623

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#6
Thanks guys, I think I'll go with the #2 and not use a gasket then torque to 7 lbs. hope this takes care of it.

If anyone else has any ideas get in on this.........I'm looking for information especially from those that have been where I'm at now.
 

mksj

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#7
You could also use some Permatex 82180 Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker, it is made to take up gaps and it will also flex. I generally use their high temp version 81160 and never had an issue with leaks. I would use it with the stock gasket. There are a number of other possible sources for the oil leak, this is also mentioned in other postings on the G0709 gearbox leaks. Often the seals can go around the gear selectors or bearings, also the oil site glass tends to leak over time. Since the leak has been since new might also suggest a possible porosity or a casting flaw. Also do not overfill the gearbox with oil, sometimes the bearings/shafts above the oil level do not have seals. There is also oil based Fluorescent Leak Detection Dye which could be used with a black light that could be used to find a source of the leak.
 

Mike8623

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#8
so guys, I only have a inch pound torque wrench it looks like for a M5 metric cap screw the torque is around 15 inch pounds. Does that seem right to you folks.
 

Silverbullet

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#9
You may need sealant on the bolt threads also. And the black permatex is best it never gets hard . It resists oil much better then the silicone type.
 

Mike8623

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#11
Well good news, I 'm pretty sure I finally found the leak. There are two steel shafts that are in the gearbox on which the cam and shift forks live. They both are positioned so that they are below the sight glass window. Both of these shafts live in two holes both of which are drilled completely through the gear box. Both of those holes on the right side go into a chamber on the right side of the gearbox that you cannot see into unless you take the forward, reverse shaft lever cover off. Upon taking off that cover I could see where the cam shaft "O" ring had been leaking down the side of the casing and out a hole in the bottom of it where electrical wires go. This hole is on the bottom of the gearbox and allows the oil to spread all over the bottom of the gearbox thus being hard to really find the cause of the leak. The oil in the gearbox had leaked to just below the cam shaft thus leaving about an inch of oil in the bottom of the gearbox which was the reason a lot of oil flowed out of the gearbox upon the removal of the gearbox cover. If the leak had been on the bottom of the gearbox cover the reservoir would have been empty upon removing the cover. I took care of the "O" ring leak and will put the cover back one today and refill, we'll see what happens.

I thank all those that replied and helped.

I'm still a little curious about the 15 inch pound torque for the screws if anyone has an opinion
 
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