Last post on Sep 29, 2013 at 11:13 PM
You are in the Jeep Cherokee and Jeep Grand Cherokee
What is this discussion about?
Jeep Grand Cherokee, Jeep Grand Cherokee SRT-8, Jeep Commander SRT-8, SUV
#154 of 202 Re: Jeep Grand Cherokee Hemi Vibration
Mar 19, 2008 (5:21 pm)
Just to give you some insight from a technicians perspective....yes, there is a vibration on "rkbintx" vehicle (I am the tech working on it) but there is much more that goes on behind the scenes that is written here.
(1) It's a 21Hz "vibration" at 72mph that i've found (40Hz is out of the driveline range)
(2) It's been a process of elimination with this vehicle - transfer case shield (yes, they vibrate), MDS, other body harmonics, exhaust, etc.
(3) Yes, when the MDS turns on, you can feel (and sometimes hear) it. You can feel the surging if you really pay attention. Turning off 4 cylinders WILL cause a change in engine harmonics - there's just no way around that.
(4) Under warranty guidelines, we can't install export driveshafts under an older model TSB that doesn't apply to the vehicle being worked on (Chrysler would just reject the claim and all h*ll breaks loose at the dealership for us)
(5) Star is sometimes of no use to us unless you get a well seasoned "veteran" on the phone
(6) We can't just throw parts at a vehicle in an attempt to fix it.
(7) It's bothering me as well that I can't get a clear answer on what it is and have to take all of these steps to figure it out. However, this forum gave me some better direction with the export TSB post.
With that said....the rear driveshaft part number on the export (2005) WK models is the same up to 2008 models. There is only one revision on it since the TSB came out. So...i've ordered the rear shaft to find out what the difference is and to find out if this actually fixes it or not. Will this fix the issue on all Jeeps in question - there's just too many variables to say yes or no - weight, load, road conditions, tire size/make/model, driveline configuration...they all come into play one can't say for sure that "all" have the same vibration unless you know that all the ones making this vibration are physically the same.
#155 of 202 Vibration with Hemi at 70-75 MPH
Mar 19, 2008 (6:09 pm)
I respsect the fact that you are a technician and I am not. However, It was pretty easy to isolate the problem to the drivetrain for me. In fact, when all was said and done I found out that Star was recommending driveshaft swapouts for the problem. That was interesting because I felt the problem was in this area the entire time. After the rear driveshaft was replaced, there was about a 50% improvement. I took the vehicle back and said close but no cigar. I suggested they change the front driveshaft as well being that there are two driveshafts on the vehicle. Turns out I had to wait over a month to get a front drivesaft because they were on national back order! Coincidental? I doubt it. When my front driveshaft finally came in and got replaced, the improvment went up by about 40% giving me a grand total of 90% improvement.
The saddest part to this blog is that people have to research and surf the internet for answers and help because Chrysler won't acknowledge the problem even though they are aware of it and feel that leaving the lot after paying 43K for a new truck with a shuddering vibration should be acceptable.
#156 of 202 Re: Vibration with Hemi at 70-75 MPH [wholelottahemi]
Mar 19, 2008 (7:18 pm)
Well put (Alan). My fix was simple as well after 6 months of "we already replaced that".....yes the driveshaft(s) were replaced...a few times. But where I received most of my success was replacing the tires. I ditched the POS Goodyear ...they said i had two flat spots on my tires....and went with a beefier tire. BAM!!! (like emeril says) the problem, in my case, was corrected. Do I still have issues with my JEEP....yes! But quite frankly I was tired of dealing with a dealership that I know was feeding me lies to begin with. They got my money.....and it wasn't coming back.
#157 of 202 Re: Vibration with Hemi at 70-75 MPH
Mar 19, 2008 (8:01 pm)
As both posts put it very well...two similar vehicle with a very similar issue - two different "fixes" - one was tires and the other driveshafts. So here is exactly why replacing parts or pointing fingers at one specific part (as was noted on several posts) is not always the correct path to repairing an issue.
As technicians, we not only play "doctor" on these vehicles, but also detective, engineer (sometimes reverse engineering something to find the issue), and even scapegoats for corporate "issues".
#158 of 202 Vibration with Hemi at 70-75 MPH
Mar 20, 2008 (12:24 am)
Hello! I agree with fasstdak - I measured noise and made a spectral analysis and came to 40Hz as well. My Chrysler service (Europe) says the policy is to balance the shaft first, so I am waiting for results. I asked for weight measurement records before and after balancing to see the change.
The repair service also raised the wehicle and checked for vibrations while vehicle was up. They confirmed vibrations - means involvement of tires, road and wind were eliminated.
#159 of 202 Re: Vibration with Hemi at 70-75 MPH [jaybee5]
Mar 20, 2008 (9:52 am)
I must say I appreciate my technician taking the time to look at this discussion thread and reply with his perspective. I hope this (or even another diagnose and replace) takes care of the problem enough to where I feel its no longer an issue; otherwise, Chrysler will probably be hearing from me to take it back. As an Engineer myself, I appreciate the time and trouble you go through to find out the problem on a sophisticated piece of Engineering. And...I also know the first or second wave of technicians at a corporation can feed you useless information...when issues finally get to me at my company, I can't believe some the answers given to customers before me on the product I developed.
#160 of 202 Re: Vibration with Hemi at 70-75 MPH
Mar 21, 2008 (7:13 am)
Well, got the new rear driveshaft today and found out something interesting on the new shaft vs. the old shaft in this particular Jeep (same part number too). The balance weights are VERY different, smaller weights and more of them (looks like someone is paying attention to the driveshaft balancer now). I ran it on the highway with my sirometer (basic frequency meter) and found NO vibrations at 55, 60, 65, 70, and 75mph...looks like this forum put me in the right direction on the repair. Vehicle is going over to Make Ready for a cleaning and will test it one more time before I close up the ticket.
#161 of 202 so is this problem only w/ 4wd vehicles ?
Mar 24, 2008 (7:09 pm)
we plan on leasing a 2008 GCL, rwd. but i'm very concerned after reading all the hardships everyone here is/ has encountered. i did test drive a rwd hemi ltd, but didn't notice any vibrations. it could've been the fact that it was a short highway section (3 miles) or the fact i was so enamored w/ the rest of the vehicle. has anyone here had this problem w/ a rwd vehicle ? tia, for any input.
#162 of 202 Re: Jeep Grand Cherokee Hemi Vibration [jaybee5]
Apr 06, 2008 (4:56 am)
Hello, so I have some more news about vibrations. I had tires balanced and then my repair service took the shaft for rebalancing. Everything was OK and according to standards, no problems found (yes the service confirmed vibrations are problem with my car). If your service claim vibrations are caused by wheels, ask them to raise the vehicle with wheels off and check again.
The repair service then did more detailed vibration analysis and probably took apart transmission and front drive train for tolerances check (if they do warranty fixes they are not obliged to tell you what they did and how they fixed it..). They found no problems again. So the official message is "we found no problems and vibrations you feel may be caused by switching the HEMI cylinders". I dont believe that, because vibrations neither depend on engine revolutions nor switching cylinders. As written before, I believe they depend on actual speed of car, thus are related to parts that are affixed to shaft and wheel axis.
When I got the car back, it seems the problem is partially fixed, so I think it may be improper mounting during manufacturing process - dismounting and remounting may partially fix it.
I am not quite sure what to do next. Either I can take independent court analyst and cooperate with him in court actions against the service, or I can wait until the problem appears in Technical Service Bulletin and then have it fixed under warranty. I would not risk paying by myself to change front or rear drivetrain as I am not 100% sure it is the cause of problem.
#163 of 202 Re: Jeep Grand Cherokee Hemi Vibration [jaybee5]
Apr 06, 2008 (5:28 am)
Vibrations (caused via harmonics) can be caused by changes in engine operation (among other things) - RPM, Exhaust pulses, cylinder changes, accessory pulleys, A/C compressor, etc. There are quite a few things in and on the engine that can easily change the harmonics and cause a vibration. Re-mounting a tire can change the driveline harmonics if one (or more) tires had too much weight - excessive road force can also cause a low frequency harmonic (vibration).
Checking the vehicle in the air changes driveline harmonics as the tires are now free spinning (no friction from the road) and driveline angle is different. It also changes suspension and driveline geometry. Checking for vibrations at a specific speed requires that the vehicle be on the road at ride height. Can it help - if the tire/wheel is severely out of round...you'll see it...but other than that - having it up in the air isn't going to help much.
As for repairs under warranty - the dealership does have to inform you of what was repaired - any parts used for warranty work have to be documented on the work order anyway for warranty claims to be paid. If there was nothing on it, request a copy of the technicians notes on the shop ticket.
I'm not trying to defend the dealership but as a service tech (and dealing with one of these specific issues), it's definitely not an easy one and claiming one fix for every case isn't the correct way about it. I've gone over a vehicle now with a runout gauge on just about every point on the driveline - everything is well within normal limits and now have requested that a Chrysler Engineer/Field Tech come out and look at it with me. I'll post what we find but remember, a fix for one specific case isn't going to necessarily be the one for all.