# Plugs and Injectors **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** cherokee, jeep\ **Created:** [October 25, 2022, 11:57am UTC](https://community.cartalk.com/t/plugs-and-injectors/187076 "2022-10-25T11:57:30Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [October 30, 2022, 12:30am UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/21 "2022-10-30T00:30:27Z")
> [@George\_San\_Jose1](#): > > ask shop if they tried just re-filling the axle w/fresh axle oil. Might work. The offending noise is believed to be from the differential assembly, not the axle shafts. This is a rear axle assembly, no oil; ![image](https://global.discourse-cdn.com/cartalk/original/3X/7/1/71234400cd3746d6b0f8984649303c2ba9a01483.jpeg) ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [October 30, 2022, 10:24am UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/22 "2022-10-30T10:24:16Z")
When George said rear axle, I believe he was referring to the rear differential, AKA rear drive unit in Jeep-speak, which does have fluid. ---
**Author:** ![mstrlucky74](https://avatars.discourse-cdn.com/v4/letter/m/74df32/32.png) [@mstrlucky74](https://community.cartalk.com/u/mstrlucky74)\ **Post date:** [October 30, 2022, 1:05pm UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/23 "2022-10-30T13:05:54Z")
Are you saying oil will fix it? Maybe . ---
**Author:** ![mstrlucky74](https://avatars.discourse-cdn.com/v4/letter/m/74df32/32.png) [@mstrlucky74](https://community.cartalk.com/u/mstrlucky74)\ **Post date:** [October 30, 2022, 3:35pm UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/24 "2022-10-30T15:35:24Z")
So I looked at the owners manual. It says to replace the spark plugs every 10 years 100,000 miles the jeep has 80,000 miles on it. I got to be honest I feel like replacing the plugs and the fuel injection cleaning which was over $1000 was a complete upsell and not necessary I could be wrong ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [October 30, 2022, 4:04pm UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/25 "2022-10-30T16:04:22Z")
Some dealerships do engage in upselling. You took it in for drive train noises, they changed a power transfer unit, but, as I understand it, noise is still present. I my opinion, focus on the drive train noises. Suggest you call local, non-chain, independent mechanic, find one that can locate the source of the noise and provide a diagnosis. Expect to pay a diagnostic fee. After the drive train is fixed, then using any of the previously mentioned fuel treatments, get some Highway or interstate runs on the engine. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 30, 2022, 10:18pm UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/26 "2022-10-30T22:18:41Z")
> [@mstrlucky74](#): > > Curious if it’s the rear differential why so I hear the noise on the front ? That’s a very good question. Ask your shop to justify the rear differential diagnosis. > [@mstrlucky74](#): > > Are you saying oil will fix it? If the rear differential oil level is below spec or dirty, that can cause untoward noises. > [@mstrlucky74](#): > > feel like replacing the plugs and the fuel injection cleaning which was over $1000 was a complete upsell and not necessary Replacing plugs at 80 K vs 100 K seems like a common sense good idea to me. No harm done, good bang for the buck. Me, I wouldn’t go longer than 50 K before replacing spark plugs, irrespective of what owner’s manual says. New spark plugs can only help. The fuel injector cleaning, that could have been an upsell, would have to know the more about the shop’s justification to make a judgement. ---
**Author:** ![mstrlucky74](https://avatars.discourse-cdn.com/v4/letter/m/74df32/32.png) [@mstrlucky74](https://community.cartalk.com/u/mstrlucky74)\ **Post date:** [October 31, 2022, 12:49am UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/27 "2022-10-31T00:49:32Z")
If it is the rear differential are you suppose to hear noise in the front? ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 31, 2022, 11:03pm UTC](https://community.cartalk.com/t/plugs-and-injectors/187076/28 "2022-10-31T23:03:01Z")
Might depend on the vehicle design, but on my prior rear-wheel drive cars and current daily-driver 4WD truck, if problem is at the rear, the sound clearly comes from the rear, not the front. [Previous page](https://community.cartalk.com/t/plugs-and-injectors/187076.md?page=1)