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756 trans dipstick


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My 756 blows Hytran out the trans dipstick when roaded a short distance. The range cover has been replaced ,I think its off a 1486 etc from junk yard.I had to have a machinist drill the cover and move tube over exactly.  I replaced the orings etc. And still leaks. Anyone have similar troubles . Mite get a different dipstick from a yard and see if oring grooves are worn ...? I don't know..lol. Any help appreciated.  

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Yep, got a 966 and a 756 that will do it...and I don't even run them five gallon over like all the armchair mechanics tell you to do. O-rings are fine, the steel 'baffle' is still on the dipsticks...I'm not sure what it is. Can't just plug the hole, either, as that is also your breather...

Travis

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I've run into that problem a few times and each time it was that someone had replaced the original .900 OD washer on the dipstick, with a larger OD washer which fit tighter in the tube.   I can't really explain why, but that was the problem.  Maybe it caused pressure buildup and then the oil splash from the gears threw oil out as the pressure was released??  When I ground the larger OD washer down to spec, the problem went away.

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I'm going to elaborate a little on sparkys note. 

Is the baffle still on the dipstick? Right below the o rings there should be a washer looking baffle welded to the dipstick. Without this it will blow splashed oil out. My 766 was doing this so I swapped out sticks with my 756 and it quit. I then took my dipstick and spot welded a 1/4"×1 washer on it. Well then it would not do it for a while then start again. Looking at the original baffle it has holes in it. What oil does get past the baffle should be stopped by the o ring and allowed to drain back into trans. So I drilled 2 small holes In the washer and it never leaked again. Hope this helps 

I do believe if you look at the dipstick it vents through the center so tighter o rings shouldnt make a bit of difference. But I'm not staring at it just going off memory 

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Our 1256 did this same thing!! I brazed a washer to the dipstick, and it didn’t help, so I used brake clean on the vent holes, and blew a lot of air through it! Took it for a drive, no change! I needed it to spread urea this spring, so I blew more brake clean around the under part of the dipstick, through the vent holes, and blew everything clean, and through the vent holes from both ways.  It’s fine now?! So I don’t know if it just needed 2 rounds of brake clean and air, or what??? 

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On 9/11/2020 at 5:00 PM, Missouri Mule said:

I'm going to elaborate a little on sparkys note. 

Is the baffle still on the dipstick? Right below the o rings there should be a washer looking baffle welded to the dipstick. Without this it will blow splashed oil out. My 766 was doing this so I swapped out sticks with my 756 and it quit. I then took my dipstick and spot welded a 1/4"×1 washer on it. Well then it would not do it for a while then start again. Looking at the original baffle it has holes in it. What oil does get past the baffle should be stopped by the o ring and allowed to drain back into trans. So I drilled 2 small holes In the washer and it never leaked again. Hope this helps 

I do believe if you look at the dipstick it vents through the center so tighter o rings shouldnt make a bit of difference. But I'm not staring at it just going off memory 

Thank you sir. I did just that yesterday morning after checking the 806,1066,and 706 at the farm . I put 3 washers on it cause I saw several in parts diagrams with 2 from the factory.  And the black stripe 10 had 2 . It gets down the road about 25mph with 38's and a 5.9 Cummins..lol Thanks again to all

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On 9/13/2020 at 6:59 PM, cwinn said:

Thank you sir. I did just that yesterday morning after checking the 806,1066,and 706 at the farm . I put 3 washers on it cause I saw several in parts diagrams with 2 from the factory.  And the black stripe 10 had 2 . It gets down the road about 25mph with 38's and a 5.9 Cummins..lol Thanks again to all

No problem. 

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