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That horrible feeling in your stomach
During a chassis inspection after returning from AZ I discovered I had a little bit of transmission fluid collecting around one of the trans filter housing plates; figured the gasket may have failed. I decided, 2 years/40,000 I might as well do the whole transmission service and not have to mess with it for a while after that. I was going to lose a couple gallons taking down the filter anyway.
I did not think much of it at the time but the 12 bolts holding the filters on were rather tight loosening them with a 1/2″ ratchet, so was the drain plug.
New filters and seals arrived and I got to work. I snugged up the filter bolts and adjusted the torque wrench to 40 lb/ft. FIVE OF THE TWELVE M10 bolts just spun around and around. After taking the damaged bolts back off it was clear somebody used an impact during the last service and ran them tight as can be into the aluminum housing. The bolt threads were flush with aluminum and the holes were smooth as can be. That’s the feeling Im talking about!! By the way, the drain plug had been tightened WAY over 25 lb/ft.
I spent the rest of the day tapping new threads, cussing, getting metal shavings in my eyes, more cussing, and thinking this should have been so routine. I went with M12 bolts rather than helicoils since there was plenty of room and one less step. Allison, wherever she is, must have been looking out for guys like me when she designed that beauty. Thankfully everything worked right and was able to torque the new bolts correctly.
During all this my wife calls and asks if we are still leaving on time this weekend. I told her we are never leaving again if I dont figure this out.
If you ever look at the filter/O-ring/gasket set up Allison uses, it is highly unlikely fluid should ever leak or the gasket ever fail, the bolts were clearly failing and that is what had started this whole thing.
I’m sure I am not the first person this have ever happened to but if I ever meet the person who did that I will happily Hi-Five them in the face with a chair and as a note to the next person who owns this coach you will need a 15mm socket and a 19mm socket to change the filters but please know there was extra care and attention given with every bolt holding them in!
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4 Replies
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That is a common problem when people servicing the transmission fluid and filters do not pay close attention to the torque specs which are clearly stated on the paperwork that comes with the filters. I believe later transmissions have inserts so they are more forgiving of sloppy mechanics and Allison has a tool specific to the problem for repairing it. Jeff has one and I’ll bet he has put it to work numerous times.
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Patrick: Is there room to placard the socket size, the required torque setting, and a warning to NOT use an impact?
An impact wrench should NEVER be used on aluminum or magnesium. If you can’t thread the bolt or nut by hand or with a socket on the end of a screwdriver until is well on … STOP and figure out why.
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Yes, this is one of the jobs you better do yourself if you do not want your transmission pan threads stripped.
Another one is oil filter change on the 3.6l Jeep engines which many of us have in our toads. The oil filter is integral with the oil cooler housing and made out of plastic. The oil filter housing is cantilevered off the cooler between the two heads. It takes very little to crack the oil filter/cooler housing if one is not careful when tightening the oil filter cap. Common issue.
Gerald
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The filter kit comes with very clear instructions on the torque specs that you cannot miss when you open it up. It will be pretty obvious to the next guy which bolt will go in which hole, and if not, that would be the last guy I would want working on my transmission!
Dick is dead on about being able to thread into aluminum by hand. If you start this job and cannot back all the bolts out by hand after breaking them loose….start to worry! I had not serviced this transmission in the past and cant believe I did not know the moment I started to take the bolts down. It wouldnt have changed anything but given me that stomach feeling a day earlier!
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