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Diagnosis? Front Driveline Clunking

xdarrows

NAXJA Forum User
Location
North Carolina
As I progress slowly through my build, I'm now at the point where I had to drive my '99 XJ home from the garage with the NP242 (Selec-Trac) TC in "4 Full Time" with no rear driveshaft installed (i.e., in "front wheel drive").

As I made my way home through city traffic, there was a loud and distinct "CLUNK-CLUNK" sound from somewhere in the front end under hard acceleration and under hard braking.

This noise was NOT present before the vehicle went in for the SYE.

The mechanic did note that he had found some play in the left front wheel u-joint, but given that the noise hadn't been present earlier, I'm somewhat dubious that the wheel is suddenly making that noise (and it sounds more like it's coming from a central location, rather than outboard).

Any ideas of what or how to check?
 
Check driveshaft and axle shaft u-joints, Check driveshaft slip yoke. Check suspension bushings. Check ball joints. Check motor and transmission mounts.
 
Check driveshaft and axle shaft u-joints, Check driveshaft slip yoke. Check suspension bushings. Check ball joints. Check motor and transmission mounts.

Tim_MN, thanks!

Is there an additional slip yoke? My understanding was that the front drive shaft is a CV shaft like what I'll wind up installing in the rear (just gave my measurement to Rusty's over the phone).

Are there checks I can make in my driveway on these components?
 
Check driveshaft and axle shaft u-joints, Check driveshaft slip yoke. Check suspension bushings. Check ball joints. Check motor and transmission mounts.

Haven't driven the XJ since I took it home and noticed these issues. Just drove it back to the shop for the installation of the Tom Wood drive shaft.

Update to observations:

- Started up, no issues and backed it out of the driveway

- Noticed the shifter was in 4PT and pulled it to 4FT and got ZERO driveline engagement (like it was in neutral)

- Tried pushing it back to 4PT and got "GRINDING NOISE" from the NP242

- Put the auto trans into Neutral and shifted to all the way to 2WD, which resulted in the NP242 engaging and allowing me to drive with the front wheels

- Still getting the "Clunk Clunk" sound as I left off the gas at about 25mph
 
So let me get this straight. You put the trans in neutral, then put the NP242 in 2WD, then trans in drive, and it let you move with the front wheels? I'm no expert but I don't think that's supposed to happen...:dunno:
 
So let me get this straight. You put the trans in neutral, then put the NP242 in 2WD, then trans in drive, and it let you move with the front wheels? I'm no expert but I don't think that's supposed to happen...:dunno:

That's exactly what happened ... WEIRD!!

I got it back to the garage and they looked at and said that it's working fine now. They still have it awaiting installation of my rear axle shims and welding on the new JKS shock mounts.

I'll report once I get it back.
 
Don't mean to be a debbie downer but it kinda sounds like this shop isn't 100% correct in what they do... although i'm not the one that that's been dealing with them so.
 
Don't mean to be a debbie downer but it kinda sounds like this shop isn't 100% correct in what they do... although i'm not the one that that's been dealing with them so.

German shop that's never lifted a vehicle like this ... so, yeah, there's a learning curve.

But, they're German mechanics and take this stuff seriously ... and do good work.
 
The 242 transfer case often is slow to change modes when shifted. The stock transfer case shifter mechanism is not the best design and can be misadjusted, and/or suffer from worn bushings, either of which could cause the t-case to operate between modes or only partially engaged in a specific mode.

I addition to the driveline inspection, check the calipers and caliper mounts for poor fit up and/or excessive wear.
 
The 242 transfer case often is slow to change modes when shifted. The stock transfer case shifter mechanism is not the best design and can be misadjusted, and/or suffer from worn bushings, either of which could cause the t-case to operate between modes or only partially engaged in a specific mode.

I addition to the driveline inspection, check the calipers and caliper mounts for poor fit up and/or excessive wear.

Thanks!
 
As a clarification, the car should not move in 4Full Time with on of the drive shafts missing. 4Full Time utilizes a differential between front and rear output shafts...this is why you can use it full time (all the time, even on dry roads). 4Part Time should not be used on drive pavement, but could be used to engage the front drive shaft if the rear is missing/removed.

I'd also check linkage for adjustment (transfer case) and shift per the manual (while moving).
 
I’ve had a few front end clunks in my Jeep over the years.

One was the frameside trackbar bracket flexing, or more appropriately the frame flexing. First iteration fixing that was RE trackbar and brace. When I did the WJ swap, had a new TB and bracket, clunk (and DW) came back. Frame stiffeners and a new brace fixed that.

Worn out lower control arm bushing, fixed with new JJs

Currently have a worn out UCA bushing. Do that by have my wife roll the Jeep and mash the brakes while I walked along side. Can visibly see movement at the joints.

Had a lose brake caliper that clunked every time I stepped on the brakes

Bolt fell out of the bumpstop extensions and those can rattle on bumps or hard braking/accel.

Springs have clanged/clunked on the frame side trackbar bracket. Just had to cut the corner off that one.

I’ve not had any issues with loose ujoints or anything like that but look there too.

No help on the xfer case, I have the np231, but as others have said a few places make nice linkage kits. Boostwerks comes to mind for the 231, don’t know if he does the 242.


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