I just wanted to pass along a warning to fellow Bonneville owners that you really need to get your transmission fluid changed if you have not done so and are over 40,000 miles. I just had my 2001 Aurora with the 4t65E transmission done today and was real surprised on the difference that it made. My 2001 has 45,500 miles on it and the fluid was surprisingly dark. I think a large source of the problem is that there is not an external transmission cooler on the 65E besides the one inside the radiator. Because of the lack of the cooler the transmission reaches higher temperatures than it really should. I remember that the previous tranmission to the 65E was the 60 E and those had external transmission coolers from the factory.

I had the transmission flush done which replaced over 90% of the original transmission fluid. Typical pan-drops+ filter changes only change about 40% of the original fluid. The shop I took my Aurora to was called Marathon Auto service and the transmission service they performed on my car was a BG transmission flush. What they do is they disconnect the lines going to the transmission cooler located inside the radiator and connect it to a machine. the car is started and the machine allows the transmission'* own pump to pump out the old fluid. There is a piston that measures the rate in which the fluid is leaving the vehicle and a pump from within the machine pumps new fluid into the transmission until the fluid is totally clean. I opted for the cleaner and conditioner as well instead of just the fluid change. The difference is they put a cleaner into the transmission then drive the car for about 5 miles. Then they change the fluid out, then put a conditioner into the transmission. They'll then take it for another five mile drive to make sure everything is alright. It was.

I just really have to recommend you 4t65E transmission owners get your fluid flushed if you have over 40,000 miles because of what mine looked like! I think I'll get it done once a year to be safe. THe total cost for me was $113.04 for the flush, cleaner, and conditioner. The price with just the flush was $88.

On the right is my transmission fluid before the service. The fluid on the left is my fluid after the flush. This is with 45,000 miles remember on this 4t65E!



the fluid on the right is my mom'* 2000 SSEi'* fluid at 58,000 miles before a flush. the transmission is the 4t65E-HD.

The fluid on the left is after the flush.

I had my 97 done with just a filter, the 40% method. Fluid wasn't burned at 135K but it needed to be changed. I'll probably get on a yearly regiment as well, but usually the higher mileage tranny'* aren't recommended by most for the 100% flush.

Did you feel any difference or is the fluid coloration your only noticable improvement?

I haven't driven the Bonneville since it got done yesterday, and my Aurora was done today. The Aurora seems to shift quite a bit better. Before you felt every shift. now I only feel about half of them. It'* always shifted too firm at low speeds but if you let it shift over 3,000 RPM you never feel it shift unless you're going WOT. Real odd. :?

EchoSSEi'* is starting to look nasty. He'* flushing this week with his trans cooler install.

I'm at 121,000 miles and not one flush!

Me...I'm not into flushing. I'm not convinced that it will make the tranny last THAT much longer.

I did a fluid exchange (not flush) at 180,000 miles on the 65HD. Dropped the pan, replaced filter, replaced fluid. Hopefully good for another 200,000.

you should check the trans fluid and the oil every time you get gas. We get our trans flushed whenever the fluid is not red anymore. It firms up the shifts a little.

Lookin good dan. I love my external tranny cooler and engine oil coolers. Just one more thing to replace, but for how much I floor the gas and street race its still nice and pink since marh when pan was dropped.

I think if my car had the 65e i wouldve blown the tranny by now.

I should prolly change mine because of something I did last week. I thought I was going to loose my parking spot in the woods so I tried to hustle in it. I came to a complete stop before shifting from D to R but I hit the gas before it engaged. Didn't sound too good. :(

i think if you had done regular flushing from a low mileage point onward, such as Custom88 at 40,000, then yes you could improve the life and performance of your transmission, but i think starting flushing at high mileage...such as me....could be asking for trouble wouldnt you agree?