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Discussion Starter #1
How much trans oil is lost when replacing the Allison transmission external spin-on filter? The manual says to replace it once before draining and replacing the trans fluid and internal filter.
 

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It might be a cup whenever I do them I never top it off and all is well. Can double check and make sure its not low or wasn't to begin with Make sure you clean and reinstall the magnet. I change my personal one every 15k Miles.
 

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How much trans oil is lost when replacing the Allison transmission external spin-on filter? The manual says to replace it once before draining and replacing the trans fluid and internal filter.
Which manual says that?
 

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I have been driving Dmax/Allison GMC pickups since 2001 and for the filter change I pre-fill the new filter, clean the magnet, and put it all back in place. Very little fluid drips out but if you never pre-fill the filter after a few changes you will be down a little. BUT never overfill the Allison because it will run much warmer indicating its displeasure. Make sure when checking the level that you follow the instructions about having it at normal operating temperature for an accurate check.

Or buy one of the next generation GM HD twins with the "pseudo-Allison" which doesn't have a spin on external filter :(
 

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Discussion Starter #6
the owner's manual and the supplement manual indicate that the external filter be changed about 45,000 miles and the transmission fully serviced at about 97,500.
 
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