Transmission Fluid. To change or not to change.

[paflyboy55]

I decided to change my transmission filter. I also thought about changing the fluid. I've heard from several people that after they changed fluid they started having transmission problems. Thought is "if it's working fine don't mess with it" and mine has been working fine. Any thoughts out there?

[1984Lodge]

I am in the change the fluid camp. Here is my thoughts... You can keep running the old fluid and it will continue to work. I think that it is just delaying a potential problem. If you change the fluid and a problem shows up, it does not mean the new fluid caused the problem, it just means the problem was already there and the new fluid uncovered the problem. So its really a decision on whether you want to deal with potential problems now, or wait to see if they show up later. And in my mind the problems are only going to get worse by delaying them. A lot of people think that I am crazy for putting transynd in my transmission, but I have already noticed cooler transmission temps and better performance out of the transmission. Yes the fluid is expensive, but not as expensive as rebuilding the transmission. Just some of my thoughts, everyone has their own way and none of them are right or wrong, just have to decide what is the best way for you and your use.

[NH Bill]

Respected Allison shop put me on the synthetic path a while back. Recommend service at 12,000 mile intervals..Stated by the third 12,000 mile service (filter and synthetic fluid), all the residual old fluid will be cleaned out.

Really put it through her paces after the first round without issue during very hot summer and some long pulls. Seem to recall temps never moving above 185. So far, so good. Been parked for a while, Will go through it again before we head out.

Mike H reported to know a LOT about this subject. Hope he comments..

NH Bill

[nbedinger]

Originally Posted by paflyboy55

I decided to change my transmission filter. I also thought about changing the fluid. I've heard from several people that after they changed fluid they started having transmission problems. Thought is "if it's working fine don't mess with it" and mine has been working fine. Any thoughts out there?

I have the same vague notion about fluid changes, for instance changing rear end oil--seems like there's a right way (involving raising one rear side, then the other side, to make sure fresh lube flows well into axle tubes) and a wrong way (just drain and refill to the plug level). Consequences of not getting it completely right are bad.

Trans fluid change--I've heard so many things about automatic fluid change, like how important it is to back flush to flow all wear sediment out, flush torque converter, ... NH Bill's 3-stage process sounds like a way to get all the old fluid replaced by diluting it with fresh fluid. Drain it three times??

Probably all of it is true! Wish it was all pulled together in one place so I could know exactly what is a complete job of fluid change, to do or have done.

[Steelwheels]

Originally Posted by nbedinger

I have the same vague notion about fluid changes, for instance changing rear end oil--seems like there's a right way (involving raising one rear side, then the other side, to make sure fresh lube flows well into axle tubes) and a wrong way (just drain and refill to the plug level). Consequences of not getting it completely right are bad.

Trans fluid change--I've heard so many things about automatic fluid change, like how important it is to back flush to flow all wear sediment out, flush torque converter, ... NH Bill's 3-stage process sounds like a way to get all the old fluid replaced by diluting it with fresh fluid. Drain it three times??

Probably all of it is true! Wish it was all pulled together in one place so I could know exactly what is a complete job of fluid change, to do or have done.

I had my transmission fluid changed and the transmission checked out when I first bought my coach. I took it to ZF they drained changed the filter and refilled nothing special.
The person who changed the fluid, said never change the fluid in a automatic car, but the tranny is the bus is different.

[Mike Hohnstein]

Fluid changes get a bad rap due to pumps used in oil change shops. Trans flushing is a bad plan, on the other hand draining the pan, changing the filter and refilling with Dextron or equivalent dino oil isn't a scary proposition. Engine oil can work in the ZF or Allisons, wouldn't mess with it for a passenger car, particularly late models, most have very specific fluid requirements. Using syn oil in any experienced engine, trans or rear axle can result in leaks due to vintage seals. I've used Mobile One 10/30 in my new cars since 1998, but from new, wouldn't do that with a used vehicle.

[Randy Dupree]

Mike is right about the fluids in an old trans.
Its been proven many times..

[Crit Bliss]

I change every 2 years since replacing my transmission in 2010

[badandy]

Would you rather run Walmart Dexron instead of switching to synthetic in an old trans? That's basically the choice now since Dexron is dead.

[Rick]

Originally Posted by badandy

Would you rather run Walmart Dexron instead of switching to synthetic in an old trans? That's basically the choice now since Dexron is dead.

Yes