Should I do a drain and refill or a drain and refill then flush of transmission fluid

Tiny
ROYCAR71
  • MEMBER
  • 1998 GMC JIMMY
  • 6 CYL
  • AUTOMATIC
  • 125,708 MILES
I am near my interval to replace my transmission fluid in both of my vehicles(GMC Jimmy 98 and Ford Expedition 97). My question is should I do a drain and refill and replace filter or drain and refill replace filter than Flush new transmission through cooler lines?
Monday, June 25th, 2012 AT 2:01 AM

3 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Flush first is my recommendation.

Roy
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Monday, June 25th, 2012 AT 2:03 AM
Tiny
ROYCAR71
  • MEMBER
  • 363 POSTS
Disconnect cooler supply line and pour new transmission fluid in. Put pan underneath cooler line and turn on engine. Transmission fluid flows in pan as I continue to add new transmission fluid and old transmission fluid comes out of cooler supply line until new transmission fluid shows coming out stop engine. Then I should drop transmission pan and change filter and gasket and loose some new transmission fluid just poured in to flush out old fluid. Then top off to required level. Is this how it is done? Thanks.

P.S. Both vehicles have over 100,000 miles and never had flush done.
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Monday, June 25th, 2012 AT 2:18 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
No. You need the actual machine that circulates the fluids. When you do it this way, you starve the main shaft of lube with an open cooler line.

Roy
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Monday, June 25th, 2012 AT 2:39 AM

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