transmission flush question
Cargo Master
Joined: Oct 2009
Posts: 2,283
Likes: 0
From: missouri
[QUOTE=Mark Kovalsky;13989983]I keep seeing people talk about backflushing a transmission. I must not know enough about transmissions because I don't know how one would backflush a transmission. Since you seem to know about it, can you explain to me how it's done.
Unhook trans lines. Hook a pump to the line that runs to the cooler. Pump in new transmission fluid and catch the old coming out of the other line. Its pumping fluid in reverse and when they do that they say they do not have to change the internal filter because it flushes the crap the filter has caught out of the filter. Ive had done once and will not do it again. Now that was from the ford dealership here in town. Since you are an expert at transmission repair maybe you can shed some light on the subject. I may of been misled.
Unhook trans lines. Hook a pump to the line that runs to the cooler. Pump in new transmission fluid and catch the old coming out of the other line. Its pumping fluid in reverse and when they do that they say they do not have to change the internal filter because it flushes the crap the filter has caught out of the filter. Ive had done once and will not do it again. Now that was from the ford dealership here in town. Since you are an expert at transmission repair maybe you can shed some light on the subject. I may of been misled.
Senior User
Joined: Mar 2013
Posts: 436
Likes: 1
Originally Posted by 05F250DSL View Post
IMO there has to be a problem already existing for a flush to make it worse.
IMO there has to be a problem already existing for a flush to make it worse.
Perhaps my transmission had issues before the flush, however, if it did it never gave a moments problem until after the flush. Gota love that timing.
That said, if you have your transmission flushed, please let us know and document the mileage and let us know how it works out. Such will be a good test. Be sure to document the flushing method and technology also if you will.
I have heard some say transmissions have check valves in them and only allow fluid flow in one direction. If true, they cannot be back flushed.
As for changing engine oil verses flushing transmission oil; two totally different technologies.
Fleet Mechanic
Joined: Sep 2013
Posts: 1,303
Likes: 84
[QUOTE="Mark Kovalsky I don't buy that for a second. I've been inside some high mileage, very neglected transmissions. I've never seen this varnish that you talk about. [/QUOTE] Mark I have never rebuilt a trans. I have been told that flushing a trans would loosen the varnish built up and cause problems. I don't buy it either. In fact beside lowering a trans pan or replacing solenoids on gm fwd cars I don't have a lot if experience inside a trans. It was more than guys excuse of why a flush is a bad idea.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,714
Likes: 2,639
From: SE Florida
Unhook trans lines. Hook a pump to the line that runs to the cooler. Pump in new transmission fluid and catch the old coming out of the other line. Its pumping fluid in reverse and when they do that they say they do not have to change the internal filter because it flushes the crap the filter has caught out of the filter. Ive had done once and will not do it again. Now that was from the ford dealership here in town. Since you are an expert at transmission repair maybe you can shed some light on the subject. I may of been misled.
It is impossible to backflush a transmission. If you try to pump fluid in the opposite direction to normal flow the pump will act as a check valve and prevent any reverse flow. The only way around that would be to run the engine backwards. Engines do not like that.
The only way that a transmission can be flushed is in the normal direction. The machines that connect in the cooler lines remove the old fluid from the line as the transmission pumps it out and replaces that fluid with new fluid right back into the other end of the line that was disconnected. It does not stir up any more junk than running the engine does.
They are right that the internal filter doesn't need to be changed (unless you have a 2008 Job #2 or newer) because it is a lifetime filter. If that filter needs changing it is because the trans has already failed. But they are NOT flushing the crud out of the filter. The crud isn't there to begin with.
Fleet Owner
Joined: Nov 2003
Posts: 27,893
Likes: 3,611
The DIY method of flushing is exactly like changing your oil - you just have to do it multiple times to get the majority of the old fluid out since there is so much old fluid retained in the transmission.
Most people drain and refill at least 3 -4 times for the at-home flush. Be sure to drive it in between drains and get the fluid fully up to temp so the fluid mixes well. IIRC you are looking for 170 degrees as the target temp. It is not hard to get 85 - 90% of the old fluid out this way.
Be sure to change the external filter also. It is not any cheaper to do it this way, but sometimes you can't find anyone with a hot flush machine. I do it 4 times (apprx 7-8 quarts each time at $6.50 per quart)
Most people drain and refill at least 3 -4 times for the at-home flush. Be sure to drive it in between drains and get the fluid fully up to temp so the fluid mixes well. IIRC you are looking for 170 degrees as the target temp. It is not hard to get 85 - 90% of the old fluid out this way.
Be sure to change the external filter also. It is not any cheaper to do it this way, but sometimes you can't find anyone with a hot flush machine. I do it 4 times (apprx 7-8 quarts each time at $6.50 per quart)
Thread
Thread Starter
Forum
Replies
Last Post
miichael
Explorer, Sport Trac, Mountaineer & Aviator
6
Mar 24, 2006 01:21 PM
