05/30 Q/A Session - 2005 - 2007 Grand Cherokee - Page 8 - JeepForum.com
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post #106 of 150 Old 05-30-2007, 04:33 PM
TRZ
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CRD fuel economy

Car and Driver tested the CRD WK and got 17 MPG overall. This seems pretty low compared to the 20/24 EPA estimates. Does the CRD engine require a long break-in period, during which optimum fuel economy should not be expected?

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post #107 of 150 Old 05-30-2007, 04:33 PM Thread Starter
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Quote:
Originally Posted by MacAttack
I like to keep "overdrive" off at all times when city driving.

Any harm in doing this?
Am I shortening the life of the tranny by doing this?
This won't hurt anything, but just keep in mind, your fuel mileage may be slightly lower because of it.
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post #108 of 150 Old 05-30-2007, 04:35 PM Thread Starter
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Quote:
Originally Posted by Muddy Cherokee
Why was the decision made to use IFS instead of a solid front axle? I heard rumors of Jeep testing an IFS/IRS GC before the WK was released, but they couldn't make it handle as well as a GC on solid axles. Is this true? Are there any chances of a return to solid front axles or is car-like ride more important than off road ability to too many people?
IFS was chosen for the improved steering feel and the improved ride and comfort that it provides.

Unfortunately, we can't discuss the specifics of our future products.

Thanks for participating!
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post #109 of 150 Old 05-30-2007, 04:35 PM
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Quote:
Originally Posted by MacAttack
I like to keep "overdrive" off at all times when city driving.

Any harm in doing this?
Am I shortening the life of the tranny by doing this?
Quote:
Originally Posted by JeepEngineers
I assume you're driving a WJ. Manually shifting the transmission won't harm it, as long as you're running the engine at resonable RPM levels(ie. not reving it too high). Often times, if you're driving in hilly terrain and you find the transmission "hunting" for gears, it's better to lock out overdrive so you elliminate unecessary shifting. As far as driving with overdrive off all the time, it's not really going to do much for you other than decrease your fuel mileage.

Mitch

2000 WJ Limited - 4.7l, 4x4, pioneer HU w/ ipod interface, upgraded front calipers, yakima lowrider system, uniden cb w/ 4 ft firestick, 3.5" tweeter upgrade
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post #110 of 150 Old 05-30-2007, 04:37 PM Thread Starter
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Quote:
Originally Posted by blankster
Is there a specific mileage range when one would consider a 5.7 fully broken in? Do synthetics effect (extend) break-in. Is there a mileage point for the drive train? I remember the first 100 miles on my '07 Overland the drive train seemed very stiff.
It's really totally dependent on duty cycle. For example, towing will accelerate the break-in process. Synthetics by nature of their composition and the wear reducing effects can extend this interval. Most gasoline engines if driven normally will break in within a few thousand miles.

Remember, we don't have any specific oil type (other than weight and API certification) requirments, but we also don't recommend extending your change intervals just because you're using synthetic.
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post #111 of 150 Old 05-30-2007, 04:37 PM Thread Starter
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Quote:
Originally Posted by Colo.kid
Do the clutches in the ELSDs require any maintenance after extensive use? The reason I ask is my '05 "bucked" a far amount in low range with making tight turns offroad. At 35,000 miles it no longer does this and I wonder if the ELSDs are still engaged properly?
For severe off-roading, Schedule B recommends axle service every 12,000 miles. Be sure to use the recommended lube as well as the friction modifier. Also be careful to clean the old RTV from the housing and cover plate and don't allow any stray bits to fall into the sump. Also, when reassembling, don't use an excessive amount of RTV on the rear cover plate. In both circumstances, small pieces of hardened RTV can easily clog the small oil passages of the ELSD system, preventing proper operation.

The Final Drive Control Module (FDCM) does detect situations in which the T-Case or ELSD does not appear to be functioning properly. In this situation, a fault code would be stored and the "Service 4WD System" indicator would turn on.

Thanks for your question!
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post #112 of 150 Old 05-30-2007, 04:37 PM Thread Starter
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Quote:
Originally Posted by TRZ
In the past Jeep has installed stronger front axles to accomodate local conditions (i.e. Venezuela ZJs had D44 front axles). Did Jeep ever produce a WK with a solid front axle? Any thoughts on level of difficulty of replacing the WK's IFS frontend with a JK D44?
No, there has never been a WK built with a solid front axle. If no one else has done it already, a creative fabricator/welder can do anything. I've seen pictures of KJs significantly lifted and fitted with a solid front axle.
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post #113 of 150 Old 05-30-2007, 04:39 PM
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Why is it that it seems that the WK's are being plagued with bad axle bearings again, my previous ZJ and WJ's all had the front and rear differentials rebuilt because of noise, and now my WK is going down the same road.
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post #114 of 150 Old 05-30-2007, 04:41 PM
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Quote:
Originally Posted by JeepEngineers
No, there has never been a WK built with a solid front axle. If no one else has done it already, a creative fabricator/welder can do anything. I've seen pictures of KJs significantly lifted and fitted with a solid front axle.
There is a guy at LOST that did so to a KJ. Very cool, but I recall he spent something like close to 10k to do it.


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post #115 of 150 Old 05-30-2007, 04:41 PM
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Is friction modifier required for either of the axles on the Jeep SRT8?
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post #116 of 150 Old 05-30-2007, 04:43 PM Thread Starter
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Quote:
Originally Posted by TRZ
Car and Driver tested the CRD WK and got 17 MPG overall. This seems pretty low compared to the 20/24 EPA estimates. Does the CRD engine require a long break-in period, during which optimum fuel economy should not be expected?
The only break-in we recommend for the vehicle is to drive moderately for the first 300 miles. As with any engine, average fuel economy does tend to increase with mileage. I can say from experience the EPA ratings for this engine are pretty realistic.
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post #117 of 150 Old 05-30-2007, 04:44 PM
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On the WJ you can retrieve CEL codes vai the key on/off/on/off/on method, is there a reason that you cannot do this on the WK?
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post #118 of 150 Old 05-30-2007, 04:44 PM Thread Starter
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SRT-8 Axles

Quote:
Originally Posted by oH2o
Is friction modifier required for either of the axles on the Jeep SRT8?
There is no limited slip device in the SRT-8 front or rear axles therefore no friction modifier is required.

The transfer case uses a special lube that also doen't require any additional friction modifier.

Thanks for your question!
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post #119 of 150 Old 05-30-2007, 04:46 PM
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The Trailhawk is a kick-*** design, how has the feedback/interest level been so far, say compared to the popular 1999/2000 Commander concept?
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post #120 of 150 Old 05-30-2007, 04:47 PM Thread Starter
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Quote:
Originally Posted by CDN WK
Why is it that it seems that the WK's are being plagued with bad axle bearings again, my previous ZJ and WJ's all had the front and rear differentials rebuilt because of noise, and now my WK is going down the same road.
We typically don't see many bearing failures on WK axles. However, we do regularly monitor warranty repairs for purposes of continuous quality improvement.
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