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-   -   Gear change to O/D occasionaly with a thud (http://www.jeepgarage.org/f203/gear-change-to-o-d-occasionaly-with-a-thud-42304.html)

mfour 05-19-2012 02:50 AM

Gear change to O/D occasionaly with a thud
 
Hi All

I have only had my WG for a couple of months, and it is also the first Jeep that I have driven. A brilliant vehicle for the most part, except for one annoying gear change. I have no idea whether it is considered normal or not, hence my post here.

My Jeep:
2004 V8 4.7L Laredo
Transmission: 545 RFE
Transfer case: NV247 - Quadra-Drive
Mileage: 88 000 miles

The thing:
So after the Jeep has done about 20 minutes worth of town driving (so at running temp) and at random, the up change to O/D comes with a hard thud. It almost feels like the vehicle is tripping over the front diff for a second, something like I have just driven into a curb. Accompanied by a loud thud from the tranny, which only last for a second. After that all is well again.

Now this only happens sporadically and it would never happen under acceleration. It seems more prone to happen when lifting off the accelerator just before it would have changed up to O/D. For instance, accelerating from stop to stop and backing off the accelerator before reaching a constant speed. Another example would be after pulling off and reaching a decline in the road (before top gear has been reached) and releasing the accelerator.

I say O/D, because it seems to not happen when I switch the O/D off. I have tried to duplicate the problem with O/D off but have not succeeded. The tranny fluids all check out right with no obvious problems.

Some advise would be very much appreciated, even if it is just to calm my nerves :D I so badly don't want my baby to out a lemon :p

01grand 05-19-2012 02:53 PM

Check the transfer case fluid, maybe replace it if you don't know if it's ever been changed. This sounds like what was going on with my old boss's jeep. The nv247 takes either mopar tcase fluid, or mobil 424 or amsoil hydraulic fluid.


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mfour 05-20-2012 07:03 AM

Re: Gear change to O/D occasionaly with a thud
 
Quote:

Originally Posted by 01grand (Post 631946)
Check the transfer case fluid, maybe replace it if you don't know if it's ever been changed. This sounds like what was going on with my old boss's jeep. The nv247 takes either mopar tcase fluid, or mobil 424 or amsoil hydraulic fluid.


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Thanks for the reply!

Did the fluid change sort out your boss's problem?

The fluid on the dipstick still looks very clean, but of course it might well have previously been filled with the incorrect grade fluid. I think I'll have to look into the service history a bit more, try and get hold of the service agents.

Frango100 05-20-2012 07:34 AM

Re: Gear change to O/D occasionaly with a thud
 
With O/D in off, the tranny can shift until 3rd gear, but not to 4th or 5th gear.
My jeep also behaves a bit like yours, accelerating its shifts nice, but when you, when accelerating, take your foot of the accelerator, you feel a bump and it shifts at that point into an other gear. I also feel it when i go over a traffic bump with a little over 20 Km/h and then accelerate, it shifts suddenly and you can feel a bump. When the speed is below 20Km/h, it doesnīt happen. Not sure if it has anything to do with an electrical input to the TCM or something else. Just for trouble shooting i will change the TPS sensor and see if that will change anything.
I wonder what the T-case fluid would do in this case, or the bump should come from the progressive coupler inside the T-case which activates, but still donīt see the relation.:confused:

01grand 05-20-2012 11:05 AM

It did fix his problem but I really don't understand how unless it was something in the progressive coupler and the bad fluid.


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mfour 05-20-2012 04:20 PM

Re: Gear change to O/D occasionaly with a thud
 
Interesting thanks for the replies.

Well it will be due for a proper service in a couple of months, so the fluid might as well be replaced then. If that does not solve anything I'll replace the TPS and take it from there. I believe the vehicle was used for towing, maybe something got stressed in the box due to incorrect driving, or something like that. I'll also do some reading on the progressive coupler, I don't really know much about it yet, so thanks for the heads-up on that.

From your comments I don't think I need to panic just yet, this is always a good thing :D

Thanks again :thumbsup:

hamilton5 06-17-2012 01:43 AM

Re: Gear change to O/D occasionaly with a thud
 
Ive read posts about a bent plate on the valve body with these O/D clunks/thuds.. might be worth noting..

mfour 06-19-2012 02:33 AM

Re: Gear change to O/D occasionaly with a thud
 
Quote:

Originally Posted by hamilton5 (Post 644208)
Ive read posts about a bent plate on the valve body with these O/D clunks/thuds.. might be worth noting..

Yes thanks, something to look at if/when it gets to the point where I can't live with it. At the moment I've learnt how to avoid the harsh change, which is not getting worse (or better for that matter). That said, I will take it in to have the box looked at at some point (when time is on my side), and it always helps to give some direction for things to look at.


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