Rob Posted January 11, 2009 Share Posted January 11, 2009 I have rebuilt the top cover to this Mack air shift transmission, (TRDL 107) three times and it still passes air into the transmission case. The rails measure good, (.0003 down in wear area) and are clean and smooth. All "O" rings are new on all sealing areas. The transmission works and shifts fine but the truck depletes all stored air within three minutes when the engine is shut down. Tonight I could hear air leakage with the engine shut down, center floor panel removed, and shop air applied to one of the wet tanks. Soap bubbles traced the leak coming from the transmission vent. When a single bolt that retains the top cover was removed with shop air applied, a real tornado was unleashed! Tomorrow, I plan to remove the top cover again, and place a regulated 60 psi to the air ports for the shift cylinders to find out which one is not sealing properly. There are no other air connections to the transmission itself so this should isolate the area.I was thinking of looking at a reman unit but cannot find what is wrong with this one. Strange thing as the shafts are not worn enough to cause any leakage with new sealing rings.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/ Share on other sites More sharing options...
LocomotiveBreath Posted January 11, 2009 Share Posted January 11, 2009 Maybe a crack or pinhole in an air port. Quote Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-28985 Share on other sites More sharing options...
Rob Posted January 11, 2009 Author Share Posted January 11, 2009 Maybe a crack or pinhole in an air port. With the cover inverted and air applied, I can probably get a closer idea with the soap bubbles. Sure is frustrating cause it is not real easy to get to in the truck. Before the rebuild, I had no idea where the air was going cause everything was buried in grease/dirt, and access was not opened up.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-28987 Share on other sites More sharing options...
theakerstwo Posted January 11, 2009 Share Posted January 11, 2009 Has it got a air controled PTO on it. That is some times were air gets in side. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-28993 Share on other sites More sharing options...
Rob Posted January 11, 2009 Author Share Posted January 11, 2009 Has it got a air controled PTO on it. That is some times were air gets in side.Hi Glenn, it does not have an air shift pto.Thanks,Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-28994 Share on other sites More sharing options...
Rob Posted January 12, 2009 Author Share Posted January 12, 2009 Well, I got this one figgered out finally. The service manual that I have does not cover the actual air shift top cover that I have. It is very close, but the one I have has an extra set of "O" rings in the range selector section and the later production ones do not. These have to be looked for to find, as they are way down deep in the bore the piston slides though. Can't really believe that I've looked over it so many times. With the cover inverted on the bench, and all the air lines connected to a regulated 60psi pressure, soap bubbles readily revealed the leak when in the low range of the transmission selector.I'll have it back together tomorrow as I'm just about a fucking expert on this damn thing now.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-29047 Share on other sites More sharing options...
LocomotiveBreath Posted January 12, 2009 Share Posted January 12, 2009 Well now I know who send one to if the need ever arises. Quote Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-29058 Share on other sites More sharing options...
BulldogVision Posted January 12, 2009 Share Posted January 12, 2009 You see what happens when you spend so much time trying to seal leaks in your vast collection of, shall we say, lady friends.......Tends to fog over the 'ol brain don't it!!!!!!!!! Quote My 'ol dog has a bite worse than it's bark!!!!!!!! Ummmmm....Is this the number I dialed???????? Link to comment https://www.bigmacktrucks.com/topic/7920-cant-quite-figger-this-one-out/#findComment-29062 Share on other sites More sharing options...
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