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Discussion Starter · #1 ·
I went to change my front gearcase fluid and the 8mm hex head was badly stripped. I finally got it out by drilling through it and using a bolt extractor, but now I'm confused about the drain plug size. I bought a M18x1.50 and it ended up being a little bit too small. A M20 was too big, and M19 doesn't appear to exist. It finally dawned on me that 3/4" standard bolts are right in between M18 and M20. I found that a 3/4-16 fine thread seems to fit well, but was hoping someone with more background might be able to confirm. I think I'm mostly confused because I always assumed the engine would be all metric, but this one seems standard. Thoughts? Thanks!
 

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2008 800 ho efi, 2019 850 SP premium
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Welcome to the forum
 
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19’ 850SP Camo. MtAiry Maryland
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I went to change my front gearcase fluid and the 8mm hex head was badly stripped. I finally got it out by drilling through it and using a bolt extractor, but now I'm confused about the drain plug size. I bought a M18x1.50 and it ended up being a little bit too small. A M20 was too big, and M19 doesn't appear to exist. It finally dawned on me that 3/4" standard bolts are right in between M18 and M20. I found that a 3/4-16 fine thread seems to fit well, but was hoping someone with more background might be able to confirm. I think I'm mostly confused because I always assumed the engine would be all metric, but this one seems standard. Thoughts? Thanks!
Yes, I’ve found other fasteners that are standard American as well. Now that you’ve experienced that, next time it won’t F with you as much.
 

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Also fits the rear case.
 

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Also fits the rear case.
How far does that protrude from the housing? Any chance it can get knocked off if it comes in contact with anything off the trail? Don't the OEM ones sit flush to avoid getting knocked off?
 
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How far does that protrude from the housing? Any chance it can get knocked off if it comes in contact with anything off the trail? Don't the OEM ones sit flush to avoid getting knocked off?
I think on the 570 at least it would be protected. That’s the original Polaris design!
 

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19’ 850SP Camo. MtAiry Maryland
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How far does that protrude from the housing? Any chance it can get knocked off if it comes in contact with anything off the trail? Don't the OEM ones sit flush to avoid getting knocked off?
^^ That is my question as well, the OEM one doesn’t protrude so can’t be damaged by rock contact
 

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How far does that protrude from the housing? Any chance it can get knocked off if it comes in contact with anything off the trail? Don't the OEM ones sit flush to avoid getting knocked off?

8mm with a 9/16 hex head case harden steel.
 

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I think the plugs being hardened even make the situation worse because all it'll do is break the case which is the softest of the two
 
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I think the plugs being hardened even make the situation worse because all it'll do is break the case which is the softest of the two
FPD, I don’t think that plug will work on our 850’s, looks like it will protrude past the skid plate.
 

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I'll stick with the flush mount plug. I figure I'll gain 2-3 mph top end speed with less mud and wind resistance over the hex head plugs!
 
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Isn’t that the same one that Sprotsman turned you on to a while back?
Yes it is back in July in fact. I ordered the Factory Plug from "Fix My Toys" but decided to go with the hex bolt/plug heavier and more robust attaches with a 9/16 socket seals with a o'ring. I had already completed the fluid change on front differential so drain plug was already in place just waiting on fill plug I went with the Quad Logic plug plus ordered two more for the rear. On my next fluid change I will replace front differential drain plug..
 
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Yes it is back in July in fact. I ordered the Factory Plug from "Fix My Toys" but decided to go with the hex bolt/plug heavier and more robust attaches with a 9/16 socket seals with a o'ring. I had already completed the fluid change on front differential so drain plug was already in place just waiting on fill plug I went with the Quad Logic plug plus ordered two more for the rear. On my next fluid change I will replace front differential drain plug..
Gotcha, yeh the OEM plugs are some of the softest metal I’ve seen. I don’t tighten them that much since they’re O ring sealed. I just changed all my fluids and the only one that gave me grief was the front Diff drain plug, like it got tighter on its own. I’ll be looking into that other steel flush mount plug.
 

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Discussion Starter · #19 ·
The service manual says it only needs 8-10lbs of torque, and mine was torqued down MUCH more than that. I properly torqued the fill and drain, and both remove much easier now.
 
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