four cylinder automatic. 159000 miles unknown fluid change history. I just bought this truck so havent driven it long. The tranny is shifting perfect. The fluid is full smells alright maybe a smidge dark. I dont plan to tow anything, or haul any thing heavy. I take it easy on the gas. Now my question, should i change the fluid and filter? I am leaning towards if it isnt broke dont fix it. I am leaning this way because it is working perfect, and a fluid change could make it worse, and make it not want to shift, or make it slip. So what do you all think? leave it alone till it gives trouble? or what??

later!! chris

 

I'd change it.

 

+1 definately worth the preventive maintence. Its not like you will not have to do it eventually...and now will help stop problems ahead of time. I think the stuff you should be more worried about is the additives and solvents. Stay away from them and you are good!

 

I agree with the guys, change the fluid.

I'd consider doing a drop the pan, to change the filter, inspect the residue in the bottom of the pan & on the magnet, as this could give you some good insite on how the tranny is doing.

Then clean the pan & magnet, replace the pan gasket with a good Fel-Pro type & continue on & do a complete fluid exchange/pump-out, by removing the tranny return line at the cooler.

This way you'll have a clean pan with a new gasket, new filter & all new fluid in the system.

If we wait until we begin to have problems, we've waited too long, the damage is done. Maybe it can be righted, maybe not !!!!!

I always expierence a positive change in shift quality, when I do a full fluid pump out.

In fact I have the fluid, filters, & the pan gaskets will be here this morning,, to do a full fluid pump-out on my 94 Taurus & 99 Ranger this week.

Both get a full fluid pump-out/exchange, every 25-30K miles!!!!

Let us know what you decide to do & how it goes.

 

Let me tell you how to do this procedure. You start by disconnecting the cooler return line. You run the engine with the tranny in park. This causes the fluid pump to operate. You drain the fluid that comes out and keep adding new fluid until you see new clean fluid coming out the drain. This takes about 11 or 12 quarts. This method cleans out at least 95% of the old fluid without the harmful effects of the profesional flush machines. This method will not hurt your transmission. Once you have finished flushing the tranny, this way, drop the pan, and inspect for any abnormal wear or particles. Replace the filter, clean the pan, and put it all back together, top the fluid of and you are done. If you just drop the pan, you are replacing less than half of your old fluid, which while it is better than nothing, it is not much better. It is similar to only replacing half of your oil at each oil change. It just doesn't get the job done.

You now have two votes for what the guys on the Aero forum call the gentle flush.

 

but with this many miles, and not knowing how many miles are on the fluid, could changing the fluid cause problems??? Could fresh fluid make it worse if the old fluid had been in there say 90000 miles or more?? I had heard from many people who were probably referring to older trannies, that new fluid in a high mileage tranny could would make the clutches slip. Any truth to this? One side of my mind really wants to change it, but the other says this is high mileage tranny, what if new fluid makes it slip??

later!! chris

 

Well how is old worn out, oxidized, dirty fluid, thats varnishing & sludging things up & clogging the filter & reducing fluid flow, going to cause a tranny to work real good & last longer?????

When you get the pan off, you'll more likely know how things are inside.

From the description you've given of the fluids condition & how well the tranny is working & the miles on it, seems to me someone has been looking after it at least fairly well.

If it's all sludged & varnished up inside, you'd likely be having shifting problems & the fluid would likely not look or smell right.

If you want to get a feel for the solids suspended in the fluid, put a drop from the dipstick onto a clean white paper napkin & tell us what you see.

If the spot is clear red, the fluid is rather clean. If it forms a dirty black or brown ring, the fluid needs to be changed. The more off color the spot is, the more degraded the fluids condition.

I think I know what your troubled about. If it's dirty inside, that the new fluids detergents will loosen up enough crud to cause problems, but imo if the deposits were that bad, you'd likely be having some shifting problems.

If the previous seller replaced the fluid just before you purchsed it, then by your reasoning it's already too late, but by my reasoning, it'll be like a flush, that'll slowly soften & remove any varnish & sludge, hold it in suspension & the filter will have latched onto the larger particles.

So why not consider dropping the pan to check things out, replace the filter & fluid & continue on with the full fluid replacement/pump out until the systems full capacity has been removed & replaced with new fluid & start things off with a clean sheet.

I suppose you could call the previous owner & inquire about it's past maintenance history, if your loosing sleep over this. The previous owners name should be on the vehicles title.