75 Lesabre 99,000 miles. Has audible whine in first gear. It increases or decreases in pitch with acceleration or decel. Goes away on shift into second. Trans operates normal. Except for the whine. Whats up?
I have heard of some of the dacron filters causing noise. Maybe change the filter to a brass screen type filter. https://www.ebay.com/itm/271192119209
A whine, or a rattling sound? A whine is typically hydraulic related.. a rattle is often the planetary gear set, in those later transmissions. I have a 4L80 that has the rattle in first gear.. been that way all summer since I started driving it (new to me) and for who knows how long before that.. I have all stuff to rebuild the trans, and am going to do that once I put that vehicle away for winter.. but it has not been an issue, and I did do some medium duty towing this summer. JW
It's a whine. Not a rattle. I'm guessing it might be the pump. I've owned multiple vehicles over the years with TH400's. None of those ever made this noise. Or any noise at all for that matter.
Mine was rebuilt last summer and has a whine in 1st as well. Mostly happens when it’s cold, so I think it’s a pump clearance issue or slight fluid cavitation through the filter, everything else works fine.
