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mackr1989

18 speed gear split problems

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mack 18 speed in a 2000 rd with a 400 doesnt always fully engage when splitting between underdrive and direct. it will happen wether the transmission is in high or low range. when this occurs, it will seem to just neutralize and grind. what is going on?

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Sounds like the sycromesh clutches are shot . Coming problem with Mack 18 spd I’ve had a few do it . 

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I had the same problem. I rebuilt the air cylinder that is on the back of the transmission. It was leaking internally. 

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If its the splitter, its the top cover on the back box that possibly needs to have the air cylinder rebuilt (new o-rings, maybe new brass air fittings) and check the air lines and other fittings on top of the transmission.

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The shift fork set screw can come loose as well all of the above pertain most odvious check to make righ now is that the yoke bolt is tight ! if not it can get pricey

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This is not related to your problem but had a 18 speed that had a switch on the dash that would put the hi/low range in neutral for pto work.I have never seen one untill i found this truck.

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how much can any one of these scenarios cost to repair? i was expecting far worse cases and these possible issues dont seem to bad.

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