Mechanic recommended NOT changing transmission fluid?

dbsoundman · 08-02-2021, 08:39 AM

Hi all, I spoke to a local heavy truck shop about getting some work done on my bus, and among the work to be done I asked about getting a transmission fluid change. He asked if it was manual or auto; I said Allison auto. He then went on to say that he highly recommends NOT changing the fluid, and only servicing it if the fluid looks bad. He did say that changing the external filters would be a good thing to do.

My understanding is that these transmissions should be drained and filled at a minimum once a year, at least under regular service. So what's the right thing to do? Bear in mind the bus is still new to me so I haven't done anything to the transmission fluid.

Booyah45828 · 08-02-2021, 08:49 AM

There's a service interval from allison that one would follow based off the transmission, fluid used, time and mileage. Depending on those variables he might be right in that the filter gets changed, but the fluid not. The only thing you'll hurt by changing the fluid too often is your wallet. I'd prefer it be changed early vs waiting on it to get dirty. By the time the fluid appears "dirty" to most people, it's likely well worn and no longer up to the task.

With TES295 fluid, fluid change intervals might be stretched out to 300k miles depending on the variables above, with filter changes occurring annually or every other year. On the 2000's we swap the filters annually because they're cheap and it's easy.

Most of the transmissions in the fleet are "smart" in that they tell us when they want fluid/filter service by illuminating the check trans light.

Mr4btTahoe · 08-02-2021, 09:19 AM

...you want to change the fluid BEFORE it looks bad. Lol.

What you don't want to do is FLUSH the transmission. Just change the fluid that is in the pan and do a filter change. Let the fluid do it's job to keep the transmission clean. Flushing them or doing a "fluid exchange" tends to break free all the stuck dirt and grime... leading to plugged solenoids, valve bodies, etc.

Their "service" may be done by machine which in that case, he'd be right. You don't want to do a full fluid exchange unless you know the transmission has been serviced on a regular basis.

dbsoundman · 08-02-2021, 09:44 AM

Interesting. I don't know what kind of fluid is in there right now but I would assume it's "standard" Dextron III or the like. My bus has about 162k on the clock. Should I just change the filters this year and schedule a fluid drain/refill next year or the year after? I'm trying to catch up on services but I don't see getting the bus done enough to travel this year anyway.

Mr4btTahoe · 08-02-2021, 09:51 AM

Quote:

Originally Posted by dbsoundman

Interesting. I don't know what kind of fluid is in there right now but I would assume it's "standard" Dextron III or the like. My bus has about 162k on the clock. Should I just change the filters this year and schedule a fluid drain/refill next year or the year after? I'm trying to catch up on services but I don't see getting the bus done enough to travel this year anyway.

If the fluid looks relatively clean, I'd go on and change the fluid in the pan while you are at it. There is a filter inside the pan that should be changed too. Drain.. clean the pan.. swap filters... fill it back up. Let it warm up and check fluid levels.

cadillackid · 08-02-2021, 10:12 AM

If the fluid looks really bad you prob don’t want to change it as you will finish off an already dying transmission. Fresh fluid is a cleaner and will finish off the friction discs .. if the fluid looks relatively good then change it..

If your fluid looks really bad then plan on your transmission being rebuilt anyway soon ..

dbsoundman · 08-02-2021, 10:13 AM

So maybe I need to find a new mechanic? Or make sure I understood him. Because it seemed like he was totally against doing anything to automatic transmission fluid beyond topping it up and replacing the external filters.

Mr4btTahoe · 08-02-2021, 10:24 AM

Quote:

Originally Posted by dbsoundman

So maybe I need to find a new mechanic? Or make sure I understood him. Because it seemed like he was totally against doing anything to automatic transmission fluid beyond topping it up and replacing the external filters.

There are a lot of mechanics out there that will not touch an automatic transmission with a 10' pole... mainly because things can go wrong. I've never had a failure come up with just changing the fluid in the pan and filters. I have however had things go wrong when disturbing the valve body on a high mileage unit. It's a liability to most shops which is why they likely don't want to touch it.

I'm sure there is a shop in the area that will drop the pan and change the internal filter... or you can skip it and go with your current mechanic's suggestion.

Booyah45828 · 08-02-2021, 10:53 AM

On a 3060, as with most electronic allisons, the internal filter is only replaced when rebuilt/reman'd. It doesn't need changed on an interval or anything as part of regular service. It's really just a screen and doesn't filter as much as one might think it does/should.

If your worried about it, and it was my bus, I'd swap the external filter, drain the pan, refill with transynd and call it a day. On buses we replace the trans fluid at 100k, so at 160k it should have been done at least once, and wouldn't hurt to have it done again.

Mr4btTahoe · 08-02-2021, 11:15 AM

Quote:

Originally Posted by Booyah45828

On a 3060, as with most electronic allisons, the internal filter is only replaced when rebuilt/reman'd. It doesn't need changed on an interval or anything as part of regular service. It's really just a screen and doesn't filter as much as one might think it does/should.

If your worried about it, and it was my bus, I'd swap the external filter, drain the pan, refill with transynd and call it a day. On buses we replace the trans fluid at 100k, so at 160k it should have been done at least once, and wouldn't hurt to have it done again.

Good info to have. What about on mechanical allisons like the 545 and 643? Is the internal filter just a screen or an actual filter?

Booyah45828 · 08-02-2021, 11:26 AM

Depends on the trans. They've revised it over the years. I've seen a brass/mesh screen, paper, and polyester installed. If it's a paper or poly filter, replace it along with the external filter. If it's the brass screen, there's no need to replace it except during rebuilds. I think the screen style is actually obsolete and was upgraded to the paper/poly version.

I'd have to look in one of the old service manuals for filter/fluid replacement intervals. But it's a lot more often then the new ones.

Mr4btTahoe · 08-02-2021, 11:41 AM

Quote:

Originally Posted by Booyah45828

Depends on the trans. They've revised it over the years. I've seen a brass/mesh screen, paper, and polyester installed. If it's a paper or poly filter, replace it along with the external filter. If it's the brass screen, there's no need to replace it except during rebuilds. I think the screen style is actually obsolete and was upgraded to the paper/poly version.

I'd have to look in one of the old service manuals for filter/fluid replacement intervals. But it's a lot more often then the new ones.

If the paper/poly element was the upgrade, wouldn't the newer transmissions have that instead of the screen?

Sehnsucht · 08-02-2021, 11:55 AM

It goes against my instinct but my experience is as soon as you open the transmission or flush it you cause problems instead of preventing them. Might be like what Mr4btTahoe said and disturbing the status quo is what causes the issue. So in spite of myself my practice with transmissions is to let it be until it experiences issues and then rebuild it.

Booyah45828 · 08-02-2021, 12:30 PM

Quote:

Originally Posted by Mr4btTahoe

If the paper/poly element was the upgrade, wouldn't the newer transmissions have that instead of the screen?

Correct. I'm not sure of the year they did it though. So if yours is old or original, it might have the brass screen, and your replacement filter won't fit without the adapter tube, o ring, and bracket.

So if you go to service a new to you trans, and see it's got the screen vs a filter, don't disturb the screen, just bolt the pan back on and replace the external filter. Or order in the filter and kit and return the kit if it's not needed. You can spray it with some brake cleaner if you'd like, but it really won't make much of a difference.

But again, your regular service from allison doesn't have you dropping the pan and messing with the internal screen/filter.

randydupree · 08-07-2021, 03:27 PM

No pan on the 3060,and no filter in the pan.
There is 2 filters,on the bottom of the trans theres 2 plates that are held on with 5 bolts,the filters are above those plates.

Booyah45828 · 08-09-2021, 07:59 AM

Quote:

Originally Posted by randydupree

No pan on the 3060,and no filter in the pan.
There is 2 filters,on the bottom of the trans theres 2 plates that are held on with 5 bolts,the filters are above those plates.

You're right.

Not sure what I was thinking. Brain fart for sure. Must have been thinking about 2000's.

Mr4btTahoe · 08-09-2021, 08:52 AM

Quote:

Originally Posted by Booyah45828

You're right.

Not sure what I was thinking. Brain fart for sure. Must have been thinking about 2000's.

The 3060 sounds like an oddball. I'm used to the 545 and 643s. Didn't even notice that he had the transmission type listed in his bus details.

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