I see threads for almost everything except the front 'U' joints

Do they ever go bad, and how would you know?

Axle or drive shaft? Yes to both, usually they will squeak/chirp

The seals can break down and allow water or grit inside - this can destroy the needle bearings. The cross-shaft can break, as can the yoke that holds the u-joint captive.

There are also some u-joints that are greaseable - for these you periodically top them off with a grease gun. "Maintenance free" u-joints usually have a stable lubricant inside the caps, but if the seal breaks the lube can drain out and ruin the bearings as well.

From someone that had to replace my u-joints, because they rusted enough to break...
Yes, they can.
Hehehe...
JJ

If you do discover a bad u-joint, go for good quality non-store brands. Spicer's 5-760x is a great choice for the front axle shafts and Spicer's 5-1310x would be an equally good choice for a non-Rubicon's driveshafts. Both are triple-sealed and usually good for at least 100k miles. Not to mention both are significantly stronger and more durable than what the factory installed, and are direct replacements.

Sealed u-joints are also stronger than typical greasable u-joints are since their bodies are not drilled throughout for the grease channels as those with a grease zerk in the body have been.

I bought mine at O'Reilly Auto Parts.
They had a cheaper version and a more expensive version.
My Jeep mechanic friend said to definitely get the more expensive one.
He said that they are a lot stronger and have a much longer warranty.
JJ

A 1yr vs 3yr warranty. At 150k miles I still have OEM u joints but would replace with spicers if need be instead of the auto part brand.

Yep, I have had rear "U" joints go bad, you hear them squeak, or grumble on take off, I have even had them not make noise but vibrate on the highway.

But how do you know when the front "U" joints go bad, I seldom use the 4 wheel drive, and the front drive shaft always spin with no load. How do you know when they go bad?

I recently replaced my rear joint from Auto Zone, bought their best joints with grease fitting on the end of the bearing cap.......Mistake! the grease fitting don't have the common zerk fitting. I might as well bought the standard with out fittings.

I believe he means his axle u joints

Car quest sells spicer. They are great.

No, I was referring to the front drive shaft not front axles.

If I am in 2 wheel drive mode, the front shaft still spins, with no load it will still wear out/grease will still dry up. U Joints can still go bad, How would you know?

yes the front driveshaft u-joints do go bad. search Angry Sparrows. You'll get a lot more results.

when the front u-joints in the driveshaft go bad, if you do not listen to the angry sparrows....and wait too long to fix the problem, the increased friction inside the Double Cardan joint will actually cause the transfer case to split in half catastrophically on the road...some call it "exploding". The driveshaft will often shear in half and whip around, busting up other stuff too....like the exhaust, transmission, oil pan, wiring, etc.

Thanks Unlimited for your reply, I have replace the main drive shaft "U" joints twice and figure maybe it's time to drop the front shaft and just replace them.

This is a "high mileage Jeep' (270,000 miles) and there really aren't any rules or good guide lines on preventative maintenance that I know of. Low mileage Jeeps, you just fix what brakes and replace in pairs.

Thanks again.

And what do you think of this: http://www.rcvperformance.com/produc...aspx?sku=CVJ30
I bought and put on. We'll see how it will be. Wheels 33 "12.5 - Cooper Discoverer STT.

I have them and have been impressed by them. Probably overkill but I'm good with that.

I don't think that the Vanco big brake kit will work with RCV's, in case that matters to anyone else.

I just want another 30,000 miles, about 1 more year, with this Jeep and she will be sold off.
I think with 300,000 miles I will have gotten my money's worth. I'll let it be someone else's project and I'll look for a clean low mileage 06 Sahara.

Number 1 cause of u joint failure is over greasing displacing seals letting water or crud in and thus damaging bearing

That is what the man I most trusted and respected in mechanical matters told me and I believe it

Consistent with Jerry's advice on sealed non greaseable units

Mine are going bad and my mechanic told me it'd be 2 or 3 grand to fix, but I also thing they are bending me over with that estimate. How much is it to fix? Mine is chirping and it's driving me insane

He's raping you. It's 50 bucks for axles a hundred for 3 in driveshaft and the cv. Not sure which your talking about. Driveshaft is less than an hour job axles less than 2 for sure. But could go over one if your like me and don't do this daily Totally ripping you off. Write reviews everywhere you can find to warn others.

Edit. That's part prices. I quoted.

Do you drive on rough terrain? Here in Poland we have a lot of areas to ride but the most interesting areas are in Ukraine and Romania in the Carpathians and the Balkans, Albania and Montenegro. These distances from 1000 to 2000 km. On the trip 7-10 days is enough.
A very long video of the fight in the Ukrainian Carpathians:
https://www.youtube.com/watch?v=i5aB-FudVMk

Other videos from the Carpathian expeditions:

https://www.youtube.com/watch?v=yq76ZabqkI4

https://www.youtube.com/watch?v=xQLpj4LdY6I

Thank you that helps so much. He also mentioned that I cannot put it in 4 wheel anymore or they will break completely due to extra torque. Is that true? I'm really a newbie at axles and engine work

Wow... Run fast from that place.

I wouldn't off road heavy in 4Wd but just driving around town .. Meh. Guess it depends on how bad the joint is.

I would guess if the joint is that bad in the time this posting has been in the Forum, you would be looking at your drive shaft laying on the ground under your Jeep.

"U" joints almost always give a lot of notice as they go bad, and they're easy to replace. I can't say for the front axles, I haven't done them before, but I have never heard it took a Brain Surgeon to do them.

The number 1 is not greasing,

Your mechanic is right about over greasing, it can damage the grease boots and allow water, dirt and crud in. I'd say that is number 2.

Ok well I 100% have the angry sparrows, iv had it for about a week, what parts do I need to buy? Anyone want to give me a recommendation on where to buy? Thank you!

Meet Stu:
TJ Front Drive Shaft CV Overhaul

or take the driveshaft out and drop it off at a local driveline shop and have them rebuild it.

You need 1 of these Moog 617 CV Ball Repair Kit : Amazon.com : Automotive

And 3 of these
Spicer 5-1310X U-Joint Kit : Amazon.com : Automotive

Buy 5 if you want to do back shaft to. You don't need a vice but it's nice to have. The press can be borrowed for free at O'Reillys auto. Once pressed out you can use a pair of pliers or vise grips to pull the caps off. Stu's write up is really nice. Have fun.

Also please update your profile. I'm assuming you don't have a Rubicon due to your avatar.

Sub'd