Slight Thunk When Shifting from 2nd to First or Starting to Move from Park

[whalensdad]

I'm experiencing a slight "thunk" when I start out in park, put it into first and start to drive OR when I'm at highway speeds and the car shifts from 2nd to 1st as I slow down to a stop. I brought it to a tranny shop, and they said the tranny was fine and that it was coming from the rear diff. They said they can hear a slight whine (which I can't) and said there seems to be some slop in the rear diff. I have a 2005 4.0L V6 AWD with 86K The problem has been going on for quite some time and doesn't seem to be getting any worse. I haven't brought it in to a shop that does rear diff repairs, yet. I'm thinking of getting rid of it sometime in the next 4 years.

1. Is this an issue that can lead to a catastrophic failure or just slowly get worse over time?
2. What are the costs for repairing/replacing the rear diff?
3. Should I repair or replace (or ignore)?

Just looking for thoughts and suggestions.

 

[Ridgeline]

It sounds to me like the shift solenoid pack in the trans I will be doing this repair on my 04. Mine goes away after driving for awhile but it is a down shift the clunk feels a little like the rear end but there is actually nothing in the rear that would clunk at the exact time you downshift.

 

[Number4]

I second Ridgeline, been waiting for someone else with actual experience to pipe in, but from all I've read, it sounds more like a solenoid pack. If it is, don't take to either shop you've already spoken too, they should know that these go out.
The only thing I'm not sure on is the 'thunk coming out of park,' that almost sounds more like a U-Joint. The solenoid as I understand, is a hard down shift thunk.
Now if your thunk out of park included a slow sharp turn, it may be a false 4x engagement, but that wouldn't have anything to do with driving straight and slowing down/coasting.

And PS, if you plan to keep it another 4 years, then I'd say you are planning on keeping it and should maintain it as such.

 

[Ridgeline]

The thunk from park could be delayed engagement from the solenoid.

 

[whalensdad]

So now I'm confused what to do. The transmission shop has never let me down. They are quite reliable. They are a local shop not affilliated with any of those chain shops that just want to rip you off. Do I find another shop for an analysis, have someone do a better investigation of the rear diff or go back and ask him about the solenoid pack? It seems like the solenoid pack repair would have to be done by a transmission shop.

 

[Number4]

You can do the solenoid yourself. The hardest part near as I can tell, is getting fluid back in. The solenoid doesn't just go out. (As far as I know.) so it may not always present itself. Don't know how the codes read for it either. I'm driving with mine acting up. Will do so until I HAVE to replace it. Mention the solenoid to your tranny shop. See what they say. If they've never heard of them going bad on Ex's then you can quietly back away until such time that sufficient distance has been acquired, the turn and run.

 

[Ridgeline]

I agree a lot of shops don't want to just replace parts inside the trans. There are videos on Youtube on how to do all of this. Not too bad but on the ground would be a a little rough. I am doing my own as my normal shop is not able to reproduce the problem as it is intermittent. I have a friend letting me use a lift once I get all the supplies rounded up.
The solenoid is about $150 online with a warranty but these are refurbished and much more from the stealership. aside from that you would need 5-6 quarts of trans fluid and I plan on replacing my filter while I am in there. The gasket is reusable as long as it is not missing pieces.
The website is 800700tran.com