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Yep. That's it. Or you can check out Jeeperf's site and get some SERIOUS polyurethane ones. Maybe we can talk him into a group buy....hmmmmmmm......
 

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Discussion Starter #5
I definatly would be using the poly ones. The problem im having is deciding whether to pay to get them replaced or tackle them myself. Its more than I want to do on my own and its more than I want to spend if I pay a shop lol.
 

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I definatly would be using the poly ones. The problem im having is deciding whether to pay to get them replaced or tackle them myself. Its more than I want to do on my own and its more than I want to spend if I pay a shop lol.
Well just a couple weeks ago I had the dealer replace mine (under lifetime powertrain warrantee) and it took them 2 days. The front differential has to be removed and what that entails I don't know. My commander was from Detroit as a lease and then me in Ohio for 5 years so the rust was fun for the mechanic. I would take it to a local mechanic instead of dealer and it may not be very expensive.
 

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Discussion Starter #7
So I went ahead and ordered the poly bushing kit for the front differential from Jeep Performance. They better be worth it for the money I paid to get them to Canada...exchange and shipping costs. My mechanic said the Chrysler kit will maybe only last 5 years so i can only assume that these will last longer.
 

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Be careful ordering parts off of eBay, some or just really poor quality. Having said that, this particular auction states they are "Crown" brand, which is know to be quality stuff, so if they seller has a good rating and is being honest in the brand of parts he's offering that might be a good deal.

I have not done the bushing replacement. It does require dropping the front axle which means removing the CV shafts, which means dissembling the suspension quite a bit to do it. But a professional should be able to do it in a day.

The problem is removing the two pressed in bushings, they are a bear to get out and most common tools just won't fit to press them out. There are some youtube videos of folks doing the job, remember the job is exactly the same for the same years Grand Cherokee's, and the fastest way seems to be using an air chisel to chisel the old bushing sleeves out of the axle.
 

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Yep. That's it. Or you can check out Jeeperf's site and get some SERIOUS polyurethane ones. Maybe we can talk him into a group buy....hmmmmmmm......
The Polyurethane versions removes the voids in the bushings, the primary reason the OEM bushings wear out and tear, but also the reason why they provide smoothness and damping.

So logically, the solid poly bushing would last much longer, i.e. you won't have to do the job another time.

But, how do they feel with NVH and smoothness on the driveline? Anyone with some experience can comment?

I have seen plenty of warnings of poly bushings increasing the NVH/Harshness/Roughness and some do and some don't when I've tried them. I guess most do, but its a matter of degree, and some I've found its hardly noticeable and some almost all the time you can't tell a difference at all.

Other problem, they are expensive, compared to if you bargain shop a good quality brand that is direct replacement.
 

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The Polyurethane versions removes the voids in the bushings, the primary reason the OEM bushings wear out and tear, but also the reason why they provide smoothness and damping.

So logically, the solid poly bushing would last much longer, i.e. you won't have to do the job another time.

But, how do they feel with NVH and smoothness on the driveline? Anyone with some experience can comment?

I have seen plenty of warnings of poly bushings increasing the NVH/Harshness/Roughness and some do and some don't when I've tried them. I guess most do, but its a matter of degree, and some I've found its hardly noticeable and some almost all the time you can't tell a difference at all.

Other problem, they are expensive, compared to if you bargain shop a good quality brand that is direct replacement.
polyurethane comes in varying durometer ratings, plus yes, the voids in the oem design help quite a bit to dampen the transfer of sound and harshness as well. I have read comments regarding poly diff mounts in the past on jeepforum saying that while it may be a slightly noticable difference, it isn't a horrendous difference. IMHO it really depends on how long you plan to own the vehicle, and whether you'd like to save a few bucks now with an OEM style or spend twice as much time or labor cost having them installed more than once.
A durometer scale is a type of measurement for rubber material hardness. The rubber durometer chart below gives you an idea of the rubber hardness that you want for your application. Generally, most rubber materials fall under the rubber durometer scale of Shore A. Thus, if you need a rubber or O-ring durometer that feels like a running shoe sole, review our rubber hardness chart below, then pick Shore 70A. A rubber durometer of Shore 70A is the most commonly chosen material hardness for all applications.

a. Shore 20A = Rubber Band
b. Shore 40A = Pencil Eraser
c. Shore 60A = Car Tire Tread
d. Shore 70A* = Running Shoe Sole
e. Shore 80A = Leather Belt
f. Shore 100A = Shopping Cart Wheel
EDIT: of course it was Omelet's build thread that I read about this first... that guy has done everything:

Well great news! My front pinion bushing was starting to fail again..........yippy :brickwall So this time I hit up Wally at JeePerf for a set of his 05-10 Jeep WK/XK Poly Differential Bushing. Then it was time to get to work.




I grabbed a pneumatic chisel thinking that was going to make the job easier. FYI it really didn't. I found the easiest way to get the old bushings out was to use a sawzall and cut the center out, then cut a slit in the outer collar. At that point the collar will just pop out with minimal force. Here's what my first one looked like after using the chisel.






Yes that sucked! But once I popped the new one in it was worth it.






Then it was on to the next bushing which was much easier since I gave up on the chisel and grabbed the sawzal.











Now that I have been driving around with them for a while I can say they do increase road noise a little, but not too much. Just knowing I will never have to replace them again definitely makes the slight increase worth it though! The added noise sounds more like a bearing going out than anything else. So maybe I'm only hearing something starting to fail. I guess we'll see soon enough :pout:
 

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The rest of omelet's pictures

Now time for the front one. You can see the fun I had with this one!




Notice I marked the sleeve so I knew the proper orientation for when the new bushing went in. (the 2 green marks) The new bushing was quite tight. I had to really give it a beating to get it in all the way. It's not coming out easily! Lets hope it never has to.








Then all that was left was putting it all back together.







 

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Oh, I've seen photos of WK/XK front axles disconnected and rotated to expose the bushings, still in the vehicle. But I've never seen any photos of people actually changing the bushings with the axle in that position.

So the photo looks like it would make the bushing change a lot faster and easier, but judging how tough it is to force out the old bushings, it might have to come all the way out and have it laying on the floor.

I'm pretty sure the FSM says to drop the whole axle to the floor to change the bushings. I think it could be very easy to damage the axles or CV shafts if you only half remove it with stuff still attached and have to pound on it with hammers and air chisels to get those bushing out.

[EDIT]
So I was still typing this as lucky posted this how to install, so it looks like at least one person has removed and installed the bushings without dropping the axle out entirely. So I suppose its reasonably possible to do it without doing damage.
 

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My only experience with poly bushings is when I raced SCCA with my Mustang. I upgraded all the bushings in the car with poly and it tightened up the car tremendously. It felt like the car was twice as "stiff" as when I welded in subframe connectors. By "stiff" I mean suspension response, not as a decline or worsening of ride quality. To be perfectly honest, with my exhaust mods I wouldn't have felt any NVH issues as the Bassani high flow cats, x-pipes, and mufflers had some serious rumble and a touch of drone at a few spots in the RPM band. Made it feel like I went from a Pinto to a GT40. There is no doubt that your Commander will handle MUCH better with the poly bushings.

As for the install, I can't imagine it would harm the diff or the CV joints by leaving it bolted in and rotating. The way mafucaturers recommend to effect repairs is not necessarily the quickest or most efficient way, but the way that it WILL enable a repair to be completed in EVERY single situation regardless of how boogered up a car might be. I'd most likely farm this job out to an independent shop rather than have the dealer do it, just for labor time. Remember, the dealers don't make anywhere near the money on selling cars as they do on service and parts!
 

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Discussion Starter #14
Great information guys thank you. I am confident that the poly are going to last.

I am waiting for these to arrive so I schedule the Jeep into a local mechanics. My plan is to have the bushings completly replaced as well as getting both exhaust manifold gaskets done and a split heater hose. About $2000 worth of work :frown2:. Then i need get the rough country lift and then a new tire and wheel combo other than the 22" rims and tires I have on her now. I have some 18's but not sure if I can get an aggresive all terrain tire to go with those rims.
 

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My only experience with poly bushings is when I raced SCCA with my Mustang. I upgraded all the bushings in the car with poly and it tightened up the car tremendously. It felt like the car was twice as "stiff" as when I welded in subframe connectors. By "stiff" I mean suspension response, not as a decline or worsening of ride quality. To be perfectly honest, with my exhaust mods I wouldn't have felt any NVH issues as the Bassani high flow cats, x-pipes, and mufflers had some serious rumble and a touch of drone at a few spots in the RPM band. Made it feel like I went from a Pinto to a GT40. There is no doubt that your Commander will handle MUCH better with the poly bushings.

As for the install, I can't imagine it would harm the diff or the CV joints by leaving it bolted in and rotating. The way mafucaturers recommend to effect repairs is not necessarily the quickest or most efficient way, but the way that it WILL enable a repair to be completed in EVERY single situation regardless of how boogered up a car might be. I'd most likely farm this job out to an independent shop rather than have the dealer do it, just for labor time. Remember, the dealers don't make anywhere near the money on selling cars as they do on service and parts!
I've used Poly Bushings in the Suspension also and have not noticed a difference in ride or smoothness of the suspension in newer cars, older cars, like vintage/antique 60's muscle cars there was some noticeable roughness, but you can't rule out it was other parts of the suspension in poor shape causing it.

I have filled voids in motor mounts with windshield urethane that is very much like polyerathane bushings, probably medium levels on the duro meter. That creates a bit to a lot of NVH from the engine.

The axle is different, an engine has a lot of vibration from so many reciprocating parts, the axle will have some vibrations, more torque reaction from torque being put through it, i.e. it winds to wind-up and un-wind, that creates the noticeable clunks when the oem bushings tear or wear out. My guess would be what some folks seem to be reporting, almost unoticeable increase in NVH, you really have to look for it, you'd probably notice it when you make big torque changes in the driveline, which its probably much less than you notice when you have worn out/broken OEM mounts.

Sometimes going the extra distance to get a part all the way out, so its easier to work on, is worth it and takes less time overall. Judging from some of the videos of guys trying to get the old bushings out of the axle, it looks like its worth to get the axle out and on the floor. But, I haven't done it, and the last round of pictures made it look like that guy got em out no problem with the axle just drop down, tilted and supported by a block of wood.
 

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Mongo, we may be saying the same thing but differently. Hahaha! This just may be a matter of semantics and preference. I think of a car not as harsh or smooth, but rather tight or loose. An early 70's Cadillac is like floating down the road on a marshmallow, to me that's a very loose car. The driver inputs are effortless, the road feel is nonexistent, and the suspension transmits nothing to the driver/passengers. Some might consider that a "smooth" suspension. Whereas a race tuned Corvette is extremely sensitive to driver input, you can feel the road in the steering wheel, and the car tells you exactly what it's doing. To me that car is tight. I guess it depends where you fall on that spectrum. I prefer to have a very tight suspension set up because I can push the car to its absolute limits. A loose or soft suspension may provide ultimate comfort but there's no telling when the car is getting close to its limits. So, I can understand why this is such a subjective issue. For me, I prefer a car that communicates and I like them tight. Someone else may want a plush and isolated ride, which to them might be an ideal set up. You might find poly bushings make the car harsher while I find it more responsive. Either way, it's a driver preference and that is the most important thing: set up your car the way YOU want it.
As for the "best" way to tackle this project, I must confess that I don't know the answer. While I like to bust my knuckles up under the shade of a tree, I'm really not a "mechanic". I just enjoy turning wrenches on my vehicles! As long as the job gets done the way you want it, that's what's important! Cheers!
 

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Great information guys thank you. I am confident that the poly are going to last.

I am waiting for these to arrive so I schedule the Jeep into a local mechanics. My plan is to have the bushings completly replaced as well as getting both exhaust manifold gaskets done and a split heater hose. About $2000 worth of work :frown2:. Then i need get the rough country lift and then a new tire and wheel combo other than the 22" rims and tires I have on her now. I have some 18's but not sure if I can get an aggresive all terrain tire to go with those rims.
The "Safari" edition JK comes with an 18" wheel. There are plenty of more aggressive tire options for 18" rims.
 

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Oh, I've seen photos of WK/XK front axles disconnected and rotated to expose the bushings, still in the vehicle. But I've never seen any photos of people actually changing the bushings with the axle in that position.

So the photo looks like it would make the bushing change a lot faster and easier, but judging how tough it is to force out the old bushings, it might have to come all the way out and have it laying on the floor.

I'm pretty sure the FSM says to drop the whole axle to the floor to change the bushings. I think it could be very easy to damage the axles or CV shafts if you only half remove it with stuff still attached and have to pound on it with hammers and air chisels to get those bushing out.

[EDIT]
So I was still typing this as lucky posted this how to install, so it looks like at least one person has removed and installed the bushings without dropping the axle out entirely. So I suppose its reasonably possible to do it without doing damage.
FIY that is Omelet's Jeep WK. He's running ~6" of lift and 37" trepadors not exactly a stock vehicle, so there may be significantly more clearance to work in his.
 

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N: oise, V:ibration, H:arshness
 
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