Forgive me if this thread was already brought up. Last year I purchased an 03 with 94000 miles or 155000 Km. I don't have any service records to check if the ATF was changed or not. Should I go ahead and get it done or is it too late and I can make things worse?Thank you in advance.PS. Same question applies for rear diff as well.

 

If you don't know how old it is or if it's the correct stuff, seems to me like you'd want to ascertain both. And since the trans and diff are both done from the bottom, I'd say get it to a competent shop and have both units serviced with fresh, correct fluid.

 

Thank you for your reply. My only concern was that when the fluids get that old I have read that it would be better to leave it in there or you would probably be asking for problems.

 

That's an old wives tale. Have you ever known a transmission or differential to fail because they had fresh, clean, appropriate lubrication?

 

Thank you OregonDan. I will set up an appointment.

 

Yes I have.

 

I have not but my go to mechanic for my DD says it is a roll of the dice if you change fluid in an auto-trans if it has not been changed per manufacturer maintenance schedule. He opined this when I bought my used Maxima and wanted the fluid changed. He did not go into any detail why. I gambled but luckily everything was OK.

 

It is absolutely an old wive's tale that changing transmission fluid will cause problems. I bought my car almost 11 years ago with 75,000 miles on it and had the dealer change transmission fluid before I took possession.

I track my car and have changed fluid and filter myself four more times since then and am ready to change them for a fifth time. The car is now approaching 115,000 miles. I use only Red Line D4 full synthetic fluid.

Keep in mind that a fluid and filter change only removes about half the fluid in the transmission. The other half stays in the torque converter and other transmission works.

 

 

Thank you to all for your replies.I will be going for a change but not a flush. The rear diff fluid will get changed as well.

 

Yes, go ahead and change the fluids if you do not have a record of when, or if, it was ever done.

 

If I am not mistaken the automatic trans fluid in a C5 is good for 100,000 miles anyway. According to the schedule.

 

It's absolutely not an old wives tale, just poorly explained. I owned several transmission shops in the past and have seen many times when a car would totally fail to even move off the lift after a fluid change, to the point where I would refuse to perform the fluid change if there was an indication of existing damage in the transmission.

If the transmission clutches and the torque converter are in good condition you're correct, changing the fluid will not only not cause problems but is advisable; the fluid acts not only hydraulically to transfer power but also is what lubricates everything inside the unit, and the additives that promote that lubrication break down over time. It's also highly recommended to change the filter as well; in addition to filtering the fluid it acts as the pickup from the pan and the internal materials can get hardened with heat/pressure/age to a point where fluid flow can be inhibited.

If, on the other hand, there is damage to the clutch plates then putting fresh fluid into the unit can absolutely cause failure. Transmission fluid is caustic - if you don't believe that let some sit on your car's paint for awhile and see what happens. Fresh fluid in a badly worn transmission can and in some cases does wash the rest of the clutch material off the steel plates in which case the car would simply not move.

Before putting fresh fluid in, it would be wise to check the condition of the fluid. If it appears "clean" i.e. good and red or even slightly toward clear then it's likely the transmission is good to go. If it's brown or blackish i.e. "dirty" then a fluid change is not recommended unless you're prepared for a rebuild. An automatic transmission is a sealed hydraulic system so the fluid doesn't get dirty, if it appears that way it's because it contains clutch material suspended in the fluid. While some amount of this is normal wear, it's really not that hard to differentiate between normal and abnormal just by looking at the fluid on the dipstick, and that's a wise thing to check on any car of this age and mileage before deciding to change the fluid.

 

[QUOTE=Grandpa1;1601465464]If I am not mistaken the automatic trans fluid in a C5 is good for 100,000 miles anyway. According to the schedule.[/QUOT
The manual specifically states that if the tranny is operated in dusty or hi heat conditions to replace auto tranny fluid at 50k miles, Our C5s are old now...anyone with an auto tranny should replace fluid and filter with correct spec'd fluid. I just purchased a mint '01 with 40k miles...auto tranny fluid's getting changed pronto...I should add, I passed on one where the owner had the transmission fluid Flushed at Johnnys auto care with no filter change....I passed on that 29k car...
Do not Flush the transmission.......................simpl y drop the pan, change the filter and add the correct amount of Dex fluid...approx 6 qts.