Tranmission Questions for 95 Bonnevuille

[JJ052653]

I have 95 Bonneville and would like to change the transmission oil. The car has 173,000 miles. The transmission was last change about 90,000 miles ago.
Question:

1) Should I have the transmission flush and oil change with filter
2) Just change the Oil and filter
3) Change the Oil and filter and bleed the remaining oil disconneting the transmission output coolent line until I visual see that the new oil has cycle through

I am also having another problem, were the transmission will not shift out of 2nd gear sometimes. When this happens, I shift to OD and then back to D. My mechanic has read the code reading torgue converter issue, but the mechanic mention it might be either the Pringle swith, shift lever contact go back or PCM.

I would appreciate any advise some has

[richtazz]

with that many miles, do not do a fluid exchange. I suggest just changing the filter and whatever fluid drains when you drop the pan. Try an additive like Trans-x or Lucas trans treatment to help clean any deposits that may have developed. If the fluid is dark brown, or smells burnt, it may be too late.

[JJ052653]

Talk to a few transmission place. Their method for fully changing/replacing the transmission fluid, is to hook up to a fluid exchanger machine that will remove all the old transmission and replace it with new fluid. In addtion to dropping the pan and replacing the filer. Is this a good process or is there a better method.

[ChemMan]

I think what richtazz is getting at is that a transmission with that many miles on it can actually be negatively affected by a fluid change. The way my father put it is that the old oil is thicker and less slippery, and that replacing the fluid with new, thin, slippery oil could possibly cause the transmission to have more problems. Your best bet would be to probably drop the pan and replace the filter and any fluid in the pan. Or you could be like me and not mess with it as long as the fluid looks good and is not burnt or turning brown.

[richtazz]

Actually, the new fluid is grippier than the old fluid, and can cause the clutch friction material to be torn from the metal backing plates, effectively ruining the transmission. If the car/trans has over 70k, DO NOT do a fluid flush/exchange, unless you want a new trans again. Only do the filter, and the fluid lost while dropping the pan.