I read a few things about NOT changing the fluid on a high mileage automatic transmission if it hasn't been done before. Any truth to this? If false what fluid does it take?

When changing the gaskets on the valve covers should the gasket be installed dry, no oil like an oil filter gasket?

Thanks!

 

I actually always oil the oil filter gasket before I put on the filter. When I did my valve cover gasket I used a blue Felpro. I just cleaned the mating surfaces and installed it. No leaks 3 years later.

 

Yes, I didn't word that very good. I always oil the filter gasket. So no oil on the valve cover gasket? Thanks!

 

I have also read about this advice, from many seemingly creditable sources, but I don't have the back ground to interpret it as advice I could pass on.

As I understand the thinking, it is kind of along the lines of, if it isn't broken , don't fix it. In this case, the type of fluid effects how the seals swell, and as things get old and go through many cycles, the internals and the fluid that transmits power them take a set, a working alignment developed after years of use, with that particular fluid, with the characteristics developed over the years, forming a working match.

You replace one old worn component, the fluid, and the new stuff is no longer compatible with the old seals, it doesn't effect them the same, and the swell changes in the seals. One might compare the situation to a bicycle chain, where the chain cog wear over the years has worn to where only the old chain that wore into the cogs a they aged will fit, A new chain will not fit the worn gears correctly enough to shift without skipping. So bicyclist change the chain when it returns a bad measurement, before it starts creating out of specification wear patterns on the gear teeth. A casual rider just buys a bike and considers the chain as a life time non consumable part.

I don't know if this old advice applies to modern designs. As you might have experienced, a lot of old time repair advice no longer applies to modern designs. I have been reading here long enough to see the old thinking about engine temperatures , with a lot of nonsense about changing thermostats to lower temperatures (!) as beneficial, come and go, finally.

I would look at the old fluid, smell it, feel it, compare it to new fluid, and make a judgement call, much depends on known milage, and you might have some old repair records to check. If the fluid seemed in good shape, I would swap it out as needed maintenance, as called for in the schedule. If it seemed burnt or worn, I would let it go, for street use, and start saving up for the day things finally break. the thinking is that with the new fluid, you get instant breakage, instead of through wear over time. sort of like what happened to me when the wrong fluid was installed in an old transmission. It was the cornerstone to the downfall of the car, much like a broken hip is often pull rope that starts the course to broken health in the elderly.

I never install a dry gasket, unless specifically noted as part of the instructions. I think the slight lubrication helps prevent any binding that might happen as the surfaces are brought together.

 

How many miles on the transmission? Any service records. Any slipping of odd behavior? If any concerns, it's a roll of the dice.

I changed mine on my 04 at 100k. I could find one record of a change at 30K. Fluid was pristine when I dropped it and changed the filter.

Unfortunately there is no dipstick, so the only way to check the fluid condition would be to have it level and running while you pull the plug. Otherwise, you're committed to at least a fluid change when you pull the plug (with it not running)

 

Mine has 91k and my dads has 60k. No records to show if they have been changed.

 

Like Ed, I changed mine at slightly over 100k miles. No issues before, none since. BUT.....I have been advised by a guy that does tranny FLUSHES that FLUSHING a tranny at over 100k miles is NOT RECOMMENDED. I haven't heard anything negative from him about fluid CHANGES. Why the following advice he gave me is OK,, when machine flushing isn't, I don't know.. He recommended I change the filter, then change the fluid several times to get most of the old fluid out. The converter can't be drained, so this method will eventually flush most of the old fluid out. This type of 'flushing', though a PITA, is apparently preferable to flushing by machine when your tranny is, uh, a senior citizen!!

 

Personally if the car looks like it was well kept, I would change the fluid in the pan and filter and not worry.

 

Both cars shift like butter now, so I’m guessing we shouldn’t have any issues. Thanks.