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Transmission clunks at 20mph

23K views 40 replies 25 participants last post by  jeepjeep06 
#1 ·
Does anyone else experience this:

As I gently slow down to a stop sign, etc. the commander clunks at 20mph.

My jeep dealer says it is normal the the chip has learned how I drive. If you have experience have you been able to fix

Greg
06 Limited 4.7 4x2
 
#3 ·
Mine does the same thing. I actually notice it when I slow down going down hill in my neighborhood. Never thought about bringing it in and asking about it.
 
#4 ·
I picked up my new Jeep a little over a week ago. I noticed right from the dealer that when I was slowing below 20mph I heard a loud clunk from the transmission. I thought perhaps it was break in...it continued for 300 miles. I checked the trans fluid and it was low...had it filled and it was almost a quart low. I hoped that would fix it...no go..I also noticed that around 45-50mph the Jeep seemed to be "searching" for the gear. It seamed to drop off and serge. Took it to the dealer...they checked the trans, looked for TSB's and finally just "relearned the transmission". I assume that is resetting the computer? It improved the 45-50mph problem and the "clunking" when downshifting is greatly improved. Not gone completely, I still think it downshifts a little hard sometimes.

At this point I guess I'll just live the with the occassional hard downshift. DH reminds me that I'm used to his Ram 1500 Hemi with a "Mercedes" transmission and my old Stratus Coupe with it's Japanese transmission. That's a pretty sad commentary...Germany and Japan can make smooth trans...buy US and you get clunking! :rolleyes:
 
#9 ·
Well looks like I will have to be the bearer of bad news. Clearing out computer will only resolve the clunk for a short period of time. It will eventually return. Having the dealer clear the ECM (Computer) will only resolve for a short period of time.

Even having the dealer replace the ECM will not resolve and chrylser will give you BS line that its is learning how you drive. Then they will tell you all their RFE545 transmissions make the clunk.

I am starting to wonder if may be it is the rear axle because it feels more like the clunk is coming from the rear of the vehicle.

greg
 
#10 ·
Had the same problem for the first thousand miles or two. But it seems to have stopped, as I haven't hear it in about the last 10,000.
 
#11 ·
Haags said:
Had the same problem for the first thousand miles or two. But it seems to have stopped, as I haven't hear it in about the last 10,000.
Same here, I totally forgot about it, would drive me crazy. Havent felt it in at least 10K miles. I am at 18K now.
 
#15 ·
csamos2 said:
Get the exact same thing on occasion, but its very subtle. Almost no noise, and just a subtle bump. Doesnt really bother me at all
Same here. It's so minor that it doesn't even bother me. In my previous cars I had poly mounts for the engine and transmission and that would knock hard because they are so stiff and a lot stronger than the cheap rubber that is used in oem mounts. So this little thud is nothing compared to what I used to have.
 
#16 ·
mine between 20-25MPH slowing down

my 07 4.7 started doing it around 4000miles. Now at 8K it still does it which is very annoying. I always watch my speedo everytime I come to a stop and when it hits 20-25MPH, CLUNK!, I must do this at least 20 times a day. Gives me something to look forward to while commuting.
 
#18 ·
Its the same for me at 10-15mph but only ever so slight. I had a similar knock with the CRD Engined XH which has a different gearbox all together.

All my Auto Land Rovers did the same and my wifes ML55 has a similar knock also....I'm not worried by it and I cover some huge milage week on week! :)

I think we all like our trucks to be perfect and give them the love they deserve, and when we hear a knock we worry about them as if they were our loved ones! :)
 
#19 ·
Phew, this is making me feel better, I've had my XK for 3000 miles now, (has 21000 on it) and it's been doing the same thing... just when I am in stop and go traffic, so about 10-15 mph... and I have been concerned.

I have had stick shift cars previously, so I was getting concerned when I was hearing this clunk from the transmission.
 
#20 ·
My mom's '06 Limited QTII did the same thing for about one year. I drove her Jeep a few times last month and the "clunk" on the downshift is gone. It may be that the ECM is sorting things out.
 
#21 ·
I just had my tranny rebuilt a couple weeks ago. Now, I get a hard clunk from undrneath every now and again. Does anyone know if this is "something" being relearned? Is it something that will go away, possibly?
 
#23 ·
Danny,
Once you have verified fluid levels, consider a forced computer relearn.
Remove the negative cable, turn key to on.....wait a minute or so.....key off (and removed) re-attach cable and go for a drive.....some around town, some highway, maybe 20 miles worth.
If it settles down, thats all it wanted.
If it still clunks and you can reproduce it for the trans shop during a road test.....do so.

Rob
 
#24 ·
Sorry, didn't read the whole thread, has anyone mentioned "bump" shift?

The earlier Chrysler electronic transmission, this happened from time to time. Like the engine controllers the transmission controllers are "ADAPTIVE", meaning they monitor performance and make adjustments according to the feedback. The feedback sometime can be wrong and bad correction can be set, that will cause poor performance for a while, while the controller re-adjusts back to better settings during operation.

Dumping volatile memory of the controllers would dump the bad setting stored there, but disconnecting power doesn't usually dump the shift schedule of the trans controller, maybe that isn't stored in volatile memory, but its worth a try.

Usually 'bump' shifts are the result of doing something you should NOT during servicing, like with the vehicle up in the air, running the engine and trans spinning wheels with no load on them. I created a 'bump' shift on my mini-van doing this, and it took about a 100 miles of driving normally to have it gradually go away.

The Dealer can put your transmission into quick learn mode with the proprietary scan tool. It only takes 30 seconds, but most dealers will charge you more than $100 to do it. So maybe, if the bump shift is minor enough, the service manager was trying to save you money instead of overcharging you because the manufacturers design in anti-competitive designs into their vehicles now.
 
#26 ·
As long as your somewhere in between those holes (read in nuetral with the trans. near a normal temp) your in good shape...so if that means adding approx. 1/4 to 1/2 quart then I'd recommend doing that asap. :)
 
#27 · (Edited)
Ok, between the holes :)(I added 1/4 quart) and did the reset and test drive like Robbie had instructed. Nothing really changed at all:icon_confused: I still have a shudder/hard shift right around the time I'm hitting 38-40 mph. It doesn't do it every time---depends on how much throttle I'm giving it.
 
#29 ·
I too have lived w/this transmission "dump/clunk" when slowing to a stop. From my experience over the last 1.5 years w/ the SuperChips tuner I'd have to say it appears to be 100% programming related. Using the Shift Schedule app (along w/the torque management) I've spent a lot of time "building" my trans to suit my driving style (umm, "spirited"). The first thing I noticed when I uploaded the shift modifications (using the "SuperChips" provided schedule) was a total LACK of the dump/clunk. Over the course of a couple months, I ended up w/a customized scheduled which significantly modified the 1-3 up/down gear selection settings (all of which are set based on speed and throttle position), and also reduced the torque management down to about 15% - this provided a much quicker shift - I can't stand how the default trans settings seem to "mush" through the gears.
Now that I've got things how I want them, the dump/clunk is back.
I dropped the pan a couple of weeks ago. Used Wix filters and AMSOIL. That really *seems* to have improved the feel of the trans, but the dump/clunk still remains.
Excruciatingly long story a bit longer...
I re-programmed with the "SuperChips" schedule - dump/clunk gone. And by gone I mean It NEVER happens. I can usually get it to reproduce easily w/in 30mins of driving. Swap back to mine or the stock settings, and it returns. You get the picture. I actually spent a Saturday swapping back and forth (takes about 10 minutes each time to program) dependably reproducing the same outcomes.
I've now managed to get my shift schedule tweaked in the lower ranges. Much improved over stock (IMO) and no more dump/clunk.
Just my .02
 
#30 · (Edited)
I'm not sure he owns the Superchips Flashpaq, if he does its not listed in his signature there. I was a bit stunned, after paying $339 for mine that the implied ability to get trans. shift gains really were only going to be achieved by giving them a further $40 to download that specific tune...needless to say, I didn't do so yet because I got a bit miffed off about this (reading advertisement by Superchips they imply things that don't actually occur after you buy the unit)...long story short, I've changed trans. fluid and have added 2 qts. of Synthetic Trick Shift to my trans. That has dramatically cleaned up the shifts and cost me only an extra $16. Either way is fine, and I am sure I could get more outta my trans. by giving Superchips another $40 but I hesitate doing so because I'm still not very happy about the companies claims then finding out after you spend lots of money with them that you need to spend even more to get what they actually claimed initially (including fan temp. settings). Pretty shady of Superchips to have done this...and I told that (nicely) to one of their reps on the phone last week. :) He told me: "Sir, you are not the first Jeep owner that has said that to me, and I apologize." By the way, just as a side note, I've never experienced the hard shifts or any clunking in my '08....thankfully!
 
#36 ·
Ok...forgive me...but what are the difference between ECM, PCM, and TCM?:ugh2:
 
#37 · (Edited)
I believe the ECM and PCM terms are used interchangeably and are the same thing, not sure though.
ECM = engine control module
PCM = powertrain control module
TCM = transmission control module
 
#39 ·
Ok, so I discovered another problem today. After I put the truck into drive, from park, with my foot still on the brake, my RPM's surged up and down two or three times, and the truck felt like it was trying to lunge forward and backward a little bit....but couldn't because my foot was on the brake. It did this two or three different times when shifted into drive from park throughout the day. Sheesh, I am sure glad the trans. shop "fixed" my transmission, lol. I've checked my fluid level....it's perfect. I am sure not looking forward to having to drop off my truck again. I am no mechanic, so my question is this: What can the even actually DO to remedy this? I mean, they gutted my tranny and re-built pretty much everything....what COULD they do to fix this?
 
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