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I have a 2006 713 with a 10 spd mack t310m and I am starting to have trouble going from low to high.

It feels like I am not getting full air psi for the shift. Does this trans have an air filter? 

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Sounds like the syncronizer is worn. There usually is an air filter, but on your truck I can't tell you where to look.

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Check for a loose or broken yoke bolt 

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Posted (edited)

Maybe a screen somewhere in the valve, but nothing set up to be serviceable access. Just did the synchro in the 05’ CV713, T318 though. In our case we lost range shift instantly when the main shaft snap ring shattered and let the synchro do what it wanted. He was less than one mile from home. Limped back in low and stopped using it. All I had to replace was 3 snap rings and the shifting soft parts w/gaskets. In chassis repair, bought the plate tool. Got away pretty cheap, main synchro was pristine, no damage. 

Is it getting the grind on......?

Edited by Mack Technician

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The yoke bolt isn't loose I checked. I had that happen two times so far.  When I go to make the low to high shift I get the zzzzz  when I get back into the gas peddle . To make it drop it I have to tap the gas peddle two times lightly . This started last week one to two times a day  now its all day except for the first 20 mins of driving in the am.

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Posted (edited)

I’d stop so as not to release any more hard metals than you have so far since the synchro is a rear case only repair and not a bearing kit job. Metal will attract to magnets, but it’s still going to roll itself around in places you don’t want it before it’s trapped. Drop the oil, with a cup set aside to check for metal fleck. Pull the big window at the rear and check the synchro. If you don’t know exactly what your looking for have someone stroke the range shift. When you see it operate internally you can identify the engagement clutch center and check it in both positions. Make sure your stroking full travel and nothings bent or loose or worn in shift mechanism (fork, set screws, etc). You will see one side of the center plate has more tooth wear than the adjacent side. 

Best thing to do first.....Go to Mack E-Media. They have a great step by step diagnostics packet to diagnose-for-repair or condemn the 300 series range for shift issues. Free download. Ignore the $20 list price and click on the manual shortcut. You could buy a copy, or they offer a download if you have a printer.  Note the PV776-blahblah number in the left lower corner, that’s the publication ID w/description. 

 

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Edited by Mack Technician
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15 hours ago, nelm1994 said:

The yoke bolt isn't loose I checked. I had that happen two times so far.  When I go to make the low to high shift I get the zzzzz  when I get back into the gas peddle . To make it drop it I have to tap the gas peddle two times lightly . This started last week one to two times a day  now its all day except for the first 20 mins of driving in the am.

I would suspect if you've had the yoke come loose several times that its about time to do syncro plates as Rob mentioned ! Having said that Have you checked the the oil yet If the truck is equipped with a trans  cooler coolant can get into and contaminate trans oil and cause the same issue!

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