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Ever since the dealer did the center diff recall the transmission makes this humming growling sound when it is about to shift under load IE going up a hill. It also has shake in the driveline as it is about to shift, Other than that it runs and drives great ...NO codes. Anyone have any expierence with this?? TIA --Rob
 
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Re: Dealer did the center diff warraty work and now transmission

What center diff recall? Post details please.
 

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Re: Dealer did the center diff warraty work and now transmission

awdbiturboRR said:
Ever since the dealer did the center diff recall the transmission makes this humming growling sound when it is about to shift under load IE going up a hill. It also has shake in the driveline as it is about to shift, Other than that it runs and drives great ...NO codes. Anyone have any expierence with this?? TIA --Rob
Mine does the same thing, I have a 2003. But I don't know WHY or WHEN it started to make that noise because I bought it used. Does it make the humming noise when using manual sport mode? (I've been driving mine using the manual sport mode and it doesn't make that noise). No codes. Does it hum when you take the foot off the gas pedal? (Mine stops when I take the foot off the gas).

I tried changing the trans fluid several times, changed the trans filter, changed differential fluids, and it still makes the noise. I was suspecting the front differential, but the techs can't figure it out either. :doh:
 

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Re: Dealer did the center diff warraty work and now transmission

I have this same problem, and mine started after my tranny was remanufactured 6 weeks ago. I had the diff recall done two years ago and did not experience the noise at all until the reamanned tranny was installed. There are posts all over this forum with various iterations of this problem, but I haven't seen one concrete solution posted yet. We really need to put our collective heads together and see if we can nail this down.

Mine happens mainly from 1500 to 2000 RPM's. It does not happen in Sport or Manual mode. My noise used to be much worse and more consistent, but the reman company paid to have another remanned torque converter installed on my Range (the original rebuild included a remanned torque converter). After the second torque converter was installed, my noise was much less noticeable and does it less than before. But I still get the noise in certain RPM conditions.

The fact that the noise doesn't happen in Sport Mode or Manual Mode really seems to point to the torque converter if you read when and how the lock up clutch works. But I can't see two remanned torque converters in a row being bad, so I'm thinking something else is playing into it. But if it were a diff alignment problem, then putting the tranny in Manual Mode shouldn't abate the noise.

I really want to get this figured out! Thanks for any help anyone can provide.

-Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

If I could ask a question?

Does the speed of 53mph (85km/h) have any significance to the noise? i.e. does the noise
a) appear at speeds below 53mph but often disappears above this
b) never appear below 53mph, only ever above this speed
c) appear to have no dependence on this speed whatsoever

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

RRPhil said:
If I could ask a question?

Does the speed of 53mph (85km/h) have any significance to the noise? i.e. does the noise
a) appear at speeds below 53mph but often disappears above this
b) never appear below 53mph, only ever above this speed
c) appear to have no dependence on this speed whatsoever

Phil
Phil, thanks so much for jumping in to help here. I've read most of your epic posts on how the transmission and torque converter operate to try to understand/pinpoint this issue.

It most often happens below 53 mph. Rarely if ever has it happened above this speed. The two speed zones that it seems to most often do it in are around 30 MPH and then again around 50 MPH. The issue was much more consistent as far as it when it made the noise on my first remanned torque converter. With the new one in, the issue is much more sporadic. Because the noise was so consistent before, I could get it to repeat every time say at 50 MPH. When maintaining that speed manually, the noise would occur upon the slightest accelerator input. Simply by switching over to cruise control at that same speed would make the noise go away, even if the cruise had to call for more acceleration to maintain speed to go up a slight incline. The noise mostly occurs only under light acceleration, I can't remember a time that it did it under heavy acceleration. The noise happens almost exclusively in 5th gear, thought I think it might have happened in 4th. It does not happen at all when in manual mode 5th gear.

Thanks for any help you can provide!

-Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

So selecting Sport mode - which allows the transmission to automatically shift between 1st, 2nd, 3rd & 4th gears but not 5th - eliminates the noise, which maybe incriminates 5th gear as being the culprit, but you can select 5th gear manually (with ‘5’ displayed on the instrument panel) and not be able to produce the noise. Is this correct?

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

RRPhil said:
So selecting Sport mode - which allows the transmission to automatically shift between 1st, 2nd, 3rd & 4th gears but not 5th - eliminates the noise, which maybe incriminates 5th gear as being the culprit, but you can select 5th gear manually (with ‘5’ displayed on the instrument panel) and not be able to produce the noise. Is this correct?

Phil
Yes - that is exactly correct. I did some of these type isolation tests on reman TC #1, so I will rerun them just to confirm on TC#2. Little harder to run them now since the noise is less predictable (but it is the exact same noise as before as far as the sound it makes).

Thanks,
Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

Hmmm :think: , the symptoms certainly seem to point toward the torque converter lock up clutch.

Because of the vehicle speeds involved it seems to indicate that the noise occurs while the LUC is in its ‘partially activated’ mode i.e. when it’s supposed to be operating under controlled slip conditions to isolate driveline torsional vibration.

Maybe it might be possible for one of you suffering from this problem to try to tie the noise up more specifically to the engagement of the LUC? The graphs below show how the LUC behaves during constant throttle acceleration for a couple of very light throttle openings.

If you found a quiet, flat, straight piece of road and accelerated with the throttle pedal held at one fixed position to see if the noise tied up with the LUC engagement? Obviously you’re unlikely to have a calibrated right foot so I’ve given an idea of how long the acceleration period takes for the two throttle openings :


25% throttle is very, very light on the accelerator pedal. It takes 40 seconds to accelerate from rest to 43mph at this setting.



35% throttle is also pretty light on the accelerator pedal. It takes 45 seconds to accelerate from 15mph to 60mph.

You can see that the partial LUC engagement point occurs immediately after the 2-3 upshift so, if you’re listening to & counting the upshifts while you’re doing this, you should be able to identify the point where it’s applied.

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

Phil,will LUC wait till 57mph or engage earlier because of the lesser throttle shown in first graph ?
 

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Re: Dealer did the center diff warraty work and now transmission

From all the measurements that I’ve made so far (several hours of data capture) the LUC never fully engages below 53mph (i.e. full pressure = locked solid), whether in 4th or 5th gear, even on the lightest throttle openings.

At wider throttle openings this speed is higher.

I should emphasise that all my measurements are taken from a ZF 5HP24 control system. The GM 5L40-E ('02-'05 diesel) and later 6HP26 (’06MY onwards) transmission control systems may well be quite different.

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

Could it be something as simple as the drive shaft being out of balance?

I have not looked to see if they have any counter weights. If it does maybe they got knocked off during removal installation?
 

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Re: Dealer did the center diff warraty work and now transmission

It seems like if there were a physical issue with the transmission you'd notice issues regardless of sport/manual/cruise control/normal modes. Is there some way to disable the LUC so that the problem might be isolated without causing faults which would trigger failsafe? Personally, I'm betting its a software issue, and it may not even be the transmission software. I'm not a transmission guy though, so you can take this with a grain of salt.
 

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Re: Dealer did the center diff warraty work and now transmission

Thanks for all of the help here guys.

I haven't yet had a chance to try the experiment outlined in Phil's post using light throttle. I'm going to have to search out a place to do that when I get some time.

I have been really trying to pay attention to speed/RPM's when the noise occurs. The two most common times are right at 30MPH/1250 RPM's and then again at 40MPH/1750 RPM's. This is when under fairly light acceleration. I believe I heard the noise yesterday at 60MPH under heavy acceleration getting on the interstate.

I really think it has to do with the LUC's controlled slip as well, especially considering that engaging cruise control immediately eliminates the noise at speed/RMP conditions that would otherwise produce the noise. My understanding is that in cruise, the LUC is fully locked.

I agree that it doesn't sound like it is in the tranny itself b/c putting it in manual or cruise modes eliminates the noise. Also, I don't think it could be a driveshaft balance issue since the noise can be eliminated with these other modes. Unless perhaps something is out of balance that is sensitive to the controlled slip function. Just grasping at staws with this thought - but maybe something in the driveline is out of balance and it makes this noise only when the controlled slip function is occurring. That would explain why I'm still having this problem on my 2nd TC.

If I wasn't already on my second remanned torque converter, I would say it absolutely is the TC. But what are the chances of 2 TC's in a row being bad? The symptoms and functionality we are all posting here pointed strongly enough for the reman company (Auto Sports Unlimited) in Michigan to send a replacement TC to Mississippi at their expense and pay $800 in labor to have it installed. So we really thought that was it. I don't think they are going to be as willing to do it a third time, and I don't blame them. As I said originally, on the second TC, when the noise occurs it is quieter than before though of the same quality, and it occurs less frequently. So we know that pulling the tranny and putting in a second TC did affect the noise.

Thanks again,
Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

Regarding de-activating the LUC, as one solenoid (EDS4) in the valve block is entirely responsible for controlling the lock-up clutch (and nothing else) it’s tempting to suggest just temporarily pulling its connector off. However I suspect the transmission ECU would then throw up a P0743 error (open circuit).

An alternative might be to swap over the LUC solenoid with one of the other three identical solenoids in the valve block (labelled A, B & C in the photo) and see if that makes any difference (i.e. eliminate a possibly faulty solenoid)?

Regarding the LUC activation with cruise control, if the cruise control is engaged at any vehicle speed above 53mph then the LUC will be applied fully (i.e. locked solid). At speeds below this it will be engaged in controlled-slip mode (i.e. partial engagement). So does the noise disappear if cruise control is engaged below 53mph?

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

RRPhil said:
So does the noise disappear if cruise control is engaged below 53mph?

Phil
Yes, I did this test on the first remanned TC at 50MPH and at 30MPH. On the first TC, the noise was consistent enough and broad enough (as far as the conditions in which it would occur) for me to confidently say that the act of engaging the cruise was alone enough to cause the noise to go away. On my second remanned TC, the conditions the noise happens in are much narrower; therefore, it could be that I am outside the noise producing conditions at the times I have cruise engaged.

Thanks,
Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

Hey, Phil, one other thing on the LUC when cruise is engaged. Dan posted this up from Rave:

Cruise Mode
When cruise control is activated, the EAT ECU receives a cruise active message on the CAN. The EAT ECU activates
a cruise control map which prevents locking and unlocking of the torque converter clutch and minimises up and down
shifts. If cruise control is operative and the vehicle speed increases due to coasting downhill, the ECM can request a
down shift via a CAN message if the vehicle speed exceeds the set cruise limit.

If you take this for what it says, then the limited slip function would be disabled at all speeds without reference to 53MPH. Is this the whole story, or is there more to it?

-Cliff
 

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Re: Dealer did the center diff warraty work and now transmission

In ‘cruise mode’ the cruise control map certainly prevents the LUC from locking & unlocking while a particular speed is being maintained, and this can be seen in the measurements I’ve taken below. At 60mph cruise and 70mph cruise (i.e. >53mph) you can see that the LUC is 100% engaged (locked solid) and although the throttle is being continually adjusted to maintain vehicle speed the LUC stays locked.

However if you look at the LUC at 30mph, 40mph and 50mph cruise speeds (i.e. <53mph) you can see that it is operating in controlled-slip mode where the LUC pressure is being adjusted to match the throttle opening (or more accurately engine torque) to maintain a constant slip rate.

Phil
 

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Re: Dealer did the center diff warraty work and now transmission

awdbiturboRR what model year Range do you have ...

to all of you in this post you have no idea how great it feels to have come across this. I thought I was the only one having this issue.

I have a 2006 4.2 S/C RR and have the EXACT same problem. I have searched high and low of other combinations of posts but nothing concrete has been found. I get the exact same grumble-strain type noise mainly in 5th accompanied by vibrations at the exact same RPM range as noted in the previous posts. Would love love love to find a solution to this problem as I am about to schedule with the dealer but strongly feel they wont be able to suggest anything concrete. I have been able to "hone" in on the phenomenon with careful accelerator peddle control to the point you can see the headlight beam bounce at night.

If I notice anything more that may be of help I will be sure to post. Together hopefully this can be rectified.
 

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Re: Dealer did the center diff warraty work and now transmission

Sorry one more thing I thought to say which kind of seems like a moot point with all the expertise thats being brought to this discussion. If so much of this is controlled by the ECU etc is it possible to reflash or update the computers with different mapping programs?
 
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