Okay, so I have had my truck since May of this year, and it has always had a pretty rough clunk going into overdrive. and when the truck is in 4th about to go into overdrive, it seems like it clunks into a 5th gear for like 2 seconds then clunks hard into overdrive, and the clunk is HARD. It shakes my dash. The guy I bought the truck from let it set for 8 months, because the radiator was leaking and he thought it was a big deal, so I got the truck for a steal. I have done a major tune up on it when I bought it since it sat so long. Coil packs, plugs, wires, etc.

So this is my problem. That was just a little background. I had my tranny fluid changed about 2,000 miles ago. just a filter and fluid. Converter wasn't drained. That did nothing for my overdrive clunk. I looked under my truck today, and noticed that my tranny is leaking fluid from around the pan/gasket. So that means I am going to have to drop the pan and let the fluid come back out to take care of that. So should I just put new tranny fluid in it after the gasket problem? or go ahead and have it flushed since we have to open it back up anyways? I don't know if it's ever been flushed, and I'm hoping a flush might help my problem.


98, supercab, 4.6, 4x4, 4R70W

 

Drop the pan and clean it out. Pay attention to what is in the pan. Drain the torque converter this time and get all of the old oil out. The pan gasket is a permanent type gasket. If you don't have that type, go to the dealer and buy one. You will never have to change the gasket again.
This may not fix your problem, but at least you will know it isn't the fluid causing the problem and you will get the leak repaired.

 

NC I see, me too but yes, I will try that. I have heard bad things about flushing these transmissions, but its bound to go anyways with the way its acting.

 

You don't have to flush it - just drop the pan and drain the converter. That will get all but about 1 quart out.

 

4R70W doesn't have 5 gears. Its a 4 speed with a locking convertor.

Harsh gear change going into 4th can mean the fluid is low or the convertor is slipping, or you have hydraulic issues within the valve body

 

I know it doesn't have 5 gears, but when its about to go into overdrive it clunks and the rpms drop then it clunks into overdrive and the rpms drop again so I don't know.

 

Overdrive is fourth gear. The additional RPM drop is the torque converter locking.