QuestionEd,
First of all, thanks for taking the time to address my question. My son purchased a 1999 Cadillac Seville with 133,000 miles. The car seemed to be in great shape and ran real smooth. Two weeks after purchase, he took it to a quick lube station to have the oil changed. The technician suggested that he have his transmission flushed and fluid replaced. My son had the work done. Sometime in the next couple of days, on a road trip out of town, he started having transmission problems. He checked under the hood and the cap with the dip stick for replacing transmission fluid was loose. He tigntened the cap and for a while it seemed to run better. It wasn't long when it started to slip again and the speed sensor also started going wacko (engine started shifting between third and fourth gear). When he returned to town, he took it back to the quick lube place to have them check it. The transmission was low on fluid so they added fluid. He explained what had happened and they asked him to take the car to AAMCO to have his transmission diagnosed. The transmission place did a diagnostic test and told him his speed (external)sensor was bad. He replaced the speed sensor but now he has no fourth gear (drive). The first three gears seem to run ok but he cannot take it on the highway. My son seems to think the quick lube place did not put enough transmission fluid in which subsequently burned up his transmission. The transmission place told him they cannot give him a difinitive answer until he pays the money to have it taken apart for observation. The quick lube place is claiming no fault. My questions are: 1. If the quick lube place did not fill the transmission properly, could that result in the failure of the transmission? 2. Would the speed sensor be a coincidence or could that have failed due to excessive heat from the transmission? 3. Would losing fourth gear be the result of mainly driving highway miles? 4. Is there anything we could do to further investigate and identify the most likely cause for the transmission failure?
AnswerHi,Mike
Yes it sounds like the trans has failed,low fluid level and at hwy speed will cause it to fail,though i havent seen the internal componants of your sons trans i cant give a you an answer on the failed part,i maybe able to give you a few causes of why there is no 4th gear,there is a GM bulliten that states if there is no reverse,second and or 4th gear engagement the likely cause is a failed reaction sun shell and there is an updated more robust part availible from GM parts,the Bullien number is 1577111,this updated part is heat treated and made to resist damage,another cause is that the 4th gear apply band is scored or burned due to lack of fluid,it also uses an apply servo that can fail due to lack of fluid,the trans is a 4T80E its a very strong transmission,the strongest GM trans and was designed to handle high horsepower and torque demands,highway driving with normal fluid level and fluid change intervals will make this trans live for a long time.
The speed sensor probably was a normal failure and not due to extreme temps or low fluid level,so i couldnt say they caused that problem.
The only real way of identifying the main reason for the 4th gear failure is to have the trans componants visually inspected,meaning a complete teardown,it is up to you on who should do this operation,i would recommend that a cadillac dealership do this for you,i have had many trans failures that came from an independant trans shop,only to cost the customer more money and greef later on,but that is only my opinion,let me know what happens and if i can help you further,Thanks
ED
