Switching to synthetic fluid

[bilzy7]

I want to change my fluid in tranny to full synthetic. Do I need to flush out ALL the old fluid or will I be ok just putting a new filter in and gasket and adding what, 3 quarts I think it is?
I always hear mixed thoughts about fluid flushes. I read if you don't normally get fluid flushed, you shouldn't do it cause it could cause small chunks to get stuck.
I just figured since I'm at 12235x miles now and idk when the last time if at all fluid was changed so I'd like to.

 

[bilzy7]

4.0 sohc 1998 explorer 4x4 auto.

 

[kemo]

If you have no clue whether or not it has been changed in the past, then DO NOT CHANGE IT!!!

Example: If you have a tranny with gunk that is actually KEEPING the tranny functional, flushing the fluid and that gunk out will net you a dead tranny. Flushing the transmission at this point is a terrible idea.

 

[bilzy7]

Ok so I should probably just replace filter and re add non synthetic fluid?

 

[kemo]

Swapping the filter would be a bad idea too.

 

[bilzy7]

Damn... I was just hoping to protect my investment lol. Guess I'll just leave it. Thanks for advice.

 

[kemo]

transmissions are extremely sensitive. The shop I worked at stopped doing any tranny servicing after having one go horribly wrong, even though we did everything right. All that was done was the tranny filter, and the Jeep didn't leave the lift.

This was also one of the things taught in college, "no fluid swaps or filter swaps!" Quick lube shops might try to sell a flush to you... but a shop that specializes in transmissions will almost always refuse the work.

Look at it this way, if the filter becomes clogged, your transmission would die soon after swapping to a new filter anyways (assuming the filter was full of crap at the time of the swap).

 

[Ozwynn]

I got mixed feeling on this. I had the Lincoln hot flushed at a Ford dealership when the transmission was slipping a little and that was 27,xxx miles ago. Several trusted transmission shops told me not to do it and even Ford tried to sell me on a new transmission.

I also did this before on my 91 Explorer and had no issues.

Did this on my aerostar and the transmission failed in days.

A Fluid flush will kill a transmission that has issues. Not so sure it will a hurt a healthy transmission.

Just be prepared to have to rebuilt it if you do flush it.

 

[kemo]

I got mixed feeling on this. I had the Lincoln hot flushed at a Ford dealership when the transmission was slipping a little and that was 27,xxx miles ago. Several trusted transmission shops told me not to do it and even Ford tried to sell me on a new transmission.

I also did this before on my 91 Explorer and had no issues.

Did this on my aerostar and the transmission failed in days.

A Fluid flush will kill a transmission that has issues. Not so sure it will a hurt a healthy transmission.

Just be prepared to have to rebuilt it if you do flush it.

The biggest problem is, you don't know for sure whether or not it is actually healthy. That is where the gamble is, same with the filter. You could do it, and it could work without a problem.

 

[Sasquatch_Ryda]

You guys all crack me up with this stuff

If a transmission is slipping....a fluid change is not going to help it at all.

As for a flush knocking loose 'gunk' holding a transmission together....bullshit. A flush is just simply a fluid exchange machine. Old fluid out via the pump, new fluid in via the return. Nothing involved other than that. No different than the normal flow of fluid through the transmission.

If you are not showing any signs of shifting concerns, by all means change out the fluid and filter in the trans. Use synthetic if you want, mixing fluids will not hurt anything.

 

[kemo]

You guys all crack me up with this stuff

If a transmission is slipping....a fluid change is not going to help it at all.

As for a flush knocking loose 'gunk' holding a transmission together....bullshit. A flush is just simply a fluid exchange machine. Old fluid out via the pump, new fluid in via the return. Nothing involved other than that. No different than the normal flow of fluid through the transmission.

If you are not showing any signs of shifting concerns, by all means change out the fluid and filter in the trans. Use synthetic if you want, mixing fluids will not hurt anything.

Go talk to someone who is actually a tranny specialist, because your information is incredibly wrong. Example: A flush and exchange are two completely different things. Flushes include the use of a chemical to remove deposits and gunk in the transmission.

 

[Sasquatch_Ryda]

Which one of our trans specialists would you like me to ask tomorrow for you?

We have two machines at our dealership, a Wynns TransServe and a MotorVac unit.

You add clean fluid to the machines and they replace the old with the new. No chemicals or voodoo involved.

Anyways....I'm not going to argue with you. To the OP, if your fluid is not burnt and the trans is not slipping of giving you any other issues, please by all means change your fluid and filter.

 

[kemo]

Here's an example from Honda...

http://www.youtube.com/watch?v=Pf6KY6rrqYU&t=220s

 

[Ozwynn]

if it fails after a flush then it was going to fail wether you flushed it or not.

 

[kemo]

if it fails after a flush then it was going to fail wether you flushed it or not.

Amen, but you just can't tell when!