I very recently purchased a used 2007 Durango: 128K miles, 5.7 L, SLT. Overall it seems to run well with the exception of an occasional clunk (both felt and heard) from the transmission. The dealer told me there is nothing wrong with it. A transmission shop drove it and noticed a clunk sound when shifting from 3rd to 4th gear. They also said they couldn't fix it because there were no diagnostic codes and all electrical tests, rear end inspections, etc were fine and didn't know what to fix. Being an amateur at repairing vehicles I am trying to figure out what is causing the clunk.

The clunk seems to occur when shifting from 3rd to 4th and when there is basically no load on the transmission. For example, when driving down a street with a very slight decline and slightly (very lightly) accelerating to approach 40 MPH when I reach 38 MPH the transmission will shift into 4th gear and there will be a clunk from the transmission - or I guess it could be from the drive train somewhere. This is repeatable but can be difficult to get just the right speeds and throttle position.

The other time I noticed it is when towing a small pop-up trailer in tow/haul mode. Cruise control was set at 65 MPH. There was a section of rolling hills where upon going down a hill the transmission would shift to 3rd gear to slow the vehicle down. Upon reaching the bottom of the hill where it flattens out before going back up the hill the vehicle would then up-shift into 4th gear and a clunk would be heard/felt. The speed generally stayed between 60-65 MPH during this time.This repeated on many occasions during our trip.

These two situations are similar in that at the time the clunk is heard the transmission is not really subjected to a hard/heavy load. I had read MDS issues could cause this type of problem but seeing that tow/haul mode shuts off MDS I have eliminated a PCM software issue (the dealer said I had the latest PCM update)

The transmission shifts fine (almost unnoticeable) at all other times. If I drive a little more aggressively shifting is fine through all gears both up and down.

The differentials, transmission, and transfer case had fluids changed by a dealer 35k miles ago. It is due for an fluid change for the transfer case. Transmission fluid looks really good (no burning, discoloration, or smell).

Does anyone have any suggestions as to what may be causing this problem and how to test any faulty components? Is the transmission on its way out - should I just sell the Durango now? Would something like Lubegard help? I have read various opinions as to the use of additives - especially with ATF+4 fluid. I still don't know what to do in that regard.

Thanks for any suggestions.
John

 

4 wheel drive? All wheel drive? It might be just drivetrain slop, which would be considered 'normal' in a 4x4. There is a little bit of slop in all the parts, collectively, it can be quite a bit.... (as these things go.) since it only does it under specific, light-load conditions, I wouldn't be surprised if that wasn't all it was.

 

Yes it is a 4x4. I hope it is just slack in the drivetrain. I just found it interesting that it only happens in shifting from 3-4. Thanks for your input - it is much appreciated.

 

Yeah, that sounds a lot like it's just driveline slop. There probably isn't a fix for it...... (at least, not something that would be what I consider 'cost effective'...... )