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-   -   Clunk in Rear Differential (http://www.jeepgarage.org/f203/clunk-in-rear-differential-58468.html)

redhawks2 04-15-2013 06:40 PM

Clunk in Rear Differential
 
I have a '99 WJ with only 56K miles on it. bought it last week. I have noticed that there is a definite clunk from the rear after stopping while still in drive. I have the 4.7 V8 and Quadra TracII. I am new to this system. The clunk occurs after being stopped for about 5 seconds but the time lapse varies from two seconds to about 20 seconds. The clunk doesn't happen at any other time. When it does happen I can feel it as well as hear it.
Any info would be appreciated.
Thanks

redhawks2 04-16-2013 07:36 PM

Re: Clunk in Read Differential
 
I'm rethinking the noise and it may be the transfer case I suppose and My hearing is not that great. I just can't figure out what could be making the clunk noise after the car has come to a complete stop and has been idling at a stop light for several seconds since nothing should be moving. Makes no sense to me. The clunk noise does not happen if I shift into neutral before I come to a complete stop and doesn't happen when I put the trans back into gear.

Frango100 04-16-2013 09:50 PM

Re: Clunk in Read Differential
 
Thinking about it, i had something alike happening after my transmission rebuild. It was finally the transmission shifting from 1st gear into 2nd gear with the jeep standing still.
There are 5 pressure switches in the TRS/solenoid assy which are used as a feedback signal to the TCM. When the TCM selects a gear, the pressure switch shows the TCM that the pressure is there.
If the signal is not received, the TCM thinks that 1st gear (in this case) is not selected and it will take 2nd gear instead. This shift is felt as a clunk, due to the releasing of one clutch and then applying of an other clutch. On my jeep the fault was with one of the pressure switches.
Did you check if a DTC is set? To do so, do the key dance: switch ignition switch off/on three times and leave it in on at the third time. The odometer will show " DONE" when all ok, or any fault code.

redhawks2 04-16-2013 10:18 PM

Re: Clunk in Read Differential
 
Thanks for the info I'll give that a try!

dudefromflorida 04-17-2013 11:26 AM

Re: Clunk in Read Differential
 
I too have been thinking... If you were to do a "stop and go" and take off again before the clunk decided to say hello how does the jeep feel?
Does it take off in first, or does it seem to be bogged down and possibly in second?

redhawks2 04-17-2013 12:43 PM

Re: Clunk in Rear Differential or T-case
 
I tried doing the key dance but nothing showed up on the speedo. I have an OBD-II scanner but it is not showing any codes. I'll try the stop and go before the clunk happens to see what happens and let you know.
Thanks for the replies.

Frango100 04-17-2013 05:26 PM

Re: Clunk in Read Differential
 
When i had this problem before and it went into 2nd gear, i didn't realise it at first. The torque converter let it all go fluently and the engine has power enough to take off in 2nd. I only had a fault code set, which made me start trouble shooting and find out what was going on.
You should try to compare the acceleration after a stop without the clunk with one with the clunk, to see if you will feel any differences, which could confirm the "being in 2nd" gear theory.

redhawks2 04-18-2013 09:20 AM

Re: Clunk in Read Differential
 
I did the stop and go several times, with and without the clunk and it always took off in first gear. I'm going to get under it this weekend just confirm that nothing is loose. I get a lot of noise out of moaning out of the rear brakes, the sound is that which is made when you don't have your foot on the brake pedal hard enough and the car wants to pull ahead. Probably totally unrelated but will check it out.
Is the transmission sensor that you mentioned something that can be changed easily and if so I might change it out just for peace of mind.
Thanks for any info.

dudefromflorida 04-18-2013 10:10 AM

Re: Clunk in Read Differential
 
Mine moans like crazy as well. Frango100 will have to answer the sensor question, I am unsure what sensor he was hinting at. There is a transmission speed sensors that are on top of the trans driver side accessible from the ground. One in the front (input), and one towards the rear (output) and both SHOULD be the same part number.
Usually with the sensor you will get a code if it is failing or has failed like what happen to Frango100
Does this clunk happen every time? If you roll forward at an idle and stop again does it clunk again?

redhawks2 04-18-2013 06:14 PM

Re: Clunk in Read Differential
 
No codes wih my scanner and no check engine light. Did the key dance again and it worked this time and the word DONE came on the speedo. I does not clunk on the first few stops and seems to be a bit more pronounced if I stop harder. If I slow the car to a gentle stop it does not clunk. I does not clunk again if I roll forward at idle. It always starts in low. I'm thinking more and more that something is loose.
I really appeciate all the replys and suggestions.

Frango100 04-18-2013 07:14 PM

Re: Clunk in Read Differential
 
The TRS/solenoid assy is not a sensor, its in fact the electric/hydraulic heart for the transmission shifting. It has 5 clutch control solenoids,1 pressure control solenoid, 5 pressure switches and several switches which are actuated depending on the shift lever position. Its inside of the tranny, mounted on top of the valve body. Not a very cheap item to change (approx. USD300 + filters + fluid + rtv), so you need to be sure that the problem is in there. When you have a speed sensor problem, you probably get a code set and for sure the shifting will be harsh.
Can it be that you release a bit the pressure on the brake pedal and that then the clunk shows up? I would indeed check the rear brake components and especially the 4 nuts which hold the brake backing plate on the back side, those nuts tend to come loose sometimes.

redhawks2 04-19-2013 07:18 AM

Re: Clunk in Rear Differential
 
Thanks for the info Frango...I'll be under the car this weekend, pulling the back wheels off, etc.


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