Knock in 4high: Diagnosis help

[Cheever3]

Was out in the snow today. We got a few inches today so I had the jeep in 4 high. On turns there was an obvious and repeated knock throughout the turn and the vibration was also noticeable. The ground was slick enough where there should not have been any binding or skipping.

Driving in a straight line it drove just fine. However, after rolling the window down I could tell there was a ticking during accelerating.

When I put it in 2WD no ticking, no knocks.

U-Joints on front ds???

Thanks

Billy

[BlackNBlue-ISH]

Don’t U-joints naturally bind and release while spinning? The rear driveshaft has two or three joints oriented so that you don’t get that vibration. Driving down the street straight, or just taking a normal corner you may not notice, but if you are sliding the back end around, or getting them spinning without traction, you would definitely notice em. My guess is the ujoints may not be bad, just complaining.

[Cheever3]

Thanks Dan. I noticed it turning into a parking lot at very slow speed. It was most noticeable on tight turns. I will say that the feel and noise I got were pretty significant.

[MDSRACING398]

U joints in front axle shafts

[Kurt]

U joints in front axle shafts

Ditto

[Cheever3]

Thank you gentlemen. Might take this as an opportunity to upgrade the drive shafts.

[Frank]

Cheever : The driveshafts only rotate , The guys are telling you to look at the front axle U-Joints just behind the front wheels. Those U-Joints not only rotate but they do so a compound angles . The more you turn , the more they flex in two directions. Hence the noise is there when you turn. Probably the non-serviceable factory ones, you cant always tell just grabbing them and moving them up and down and side to side. They could be freezing up from lack of grease and when turned , they bind up and make the noise. Put it on 4 jack stands in 4 wheel drive. Put it in gear at idle and straight ahead. Walk around the Jeep to listen. Then turn the wheel and listen to which side it comes from. Youll find it. Change them both. FjR68

[Yipjeep]

Trying to get a better understanding of diagnosing noises. Are the axle u-joints under stress when in 4wd versus 2wd? Curious why the noise would disappear when driving the Jeep in 2WD, but return when 4WD is engaged.

[MDSRACING398]

Load vs no load

[BlackNBlue-ISH]

If you've ever driven a vehicle with a large enough lift and no drive line correction, the vibrations only happen during acceleration or deceleration. Not while coasting. Like Mark said, load vs no load.

[Cheever3]

Thank you all for checking my understanding and for the idea Frank.

Much appreciated.

[Frank]

YipJeep Good question . Without having lockout hubs on the front axle you dont really have 2 wheel drive , just no power being supplied to the front axle. Therefore everything is still rotating at the same speed as the rear . DS and axles are still rotating . On an open diff in this mode you dont feel the front end when you turn but if in 4WD you feel the resistance of the front end because the front being powered now has pull and wants the Jeep to go straight. The more you turn , the more the axle u-joints have to work. The drive shafts on the road pretty much just revolve . Off road would compound their dutys by rotating and moving up and down compounding their rotation. Now while a u-joint may make noise in a DS , it probably would do so all the time or at least more on accelerate or decelerate but it would be there. The axle u-joints will probably only start to talk to you during a turn. Hope this helps. FjR68

[Frank]

Welllllllllllllllllllllll ? What did you find out ????????? Dont let a 12* day you from crawlin around under her . FjR68

[Cheever3]

Sorry to say but I haven’t had the time to put the Jeep on the jack stands and try out your advice Frank. I’m off for the week starting Friday and I’ll be able to check it out then. I’ll let you know what I hear from either side.

If it is the axle u joints I would like to take a crack at changing them out. I’ve never done that so I’d be looking for some help if anyone was available. Will repost when the time comes.

[BlackNBlue-ISH]

Axle ujoints were the first ujoints I ever replaced. Be sure to look up how to do all the different methods on YouTube. Find the one that works for your tools available.