dom_poli

Hey guys, new to posting here. Y'all have helped me a lot over the years by reading through the threads but I can't seem to find the answer to my problem on here yet! I've had this 1994 XJ Country auto for a few years now and a few months ago I started noticing a metal grinding/clunking noise when I tap the accelerator. Sounds metallic. This ONLY happens after I've gotten into 2nd or 3rd gear. It almost sounds like loose linkage or something with some play in it. So the first thing I checked were my Ujoints and those have no play. I put a new transmission mount in maybe 6 months ago and that still looks good. I dont see my exhaust rubbing on anything. I did have new leaf springs put on sometime last year so im not sure if that has anything to do with it, I've read about axle wrap on here but don't know much about that. I definitely feel it in the floorboards and hear it coming from the rear end. The transmission doesn't feel like it's slipping and shifts great. Any thoughts? Thanks in advance!

agreen

You didn't say you replaced the motor mounts. I did the exact same thing. New trans mount, started hearing a noise while accelerating. It seemed to stop once the torque converter locked up and I'd cruise. I swear I thought the torque converter was coming apart. Turns out, the motor mounts were just plain blown out. They were metal on metal and I didn't even know it. It doesn't take much to pull the air box out. I think it's like 2 bolts and it's free. Take a look at the driver's side mount. It's usually the first to go.

dom_poli

Thanks for the heads up, I will check those out tomorrow. But if it were the motor mounts, wouldn't I be hearing the noise more from the front than the rear though? Before you replaced yours were you hearing a similar noise? I'm suspicious that it's a trans issue since I only hear it in certain gears.

EZEARL

How long has it been since you've greased the slip yoke? Higher the gear your in the more slack in the driveline. Also did replacing the leaf springs lift the rear end any?

agreen

Yep. Blew my mind. I swore it was the transmission or torque converter.

Short story:
Was going to Disney World in 2016. Decided to take my XJ. Not sure why. The day before I did some maintenance. This included (among other stuff) dropping the pan, changing the filter and fluid, and while I was there, I replaced the trans mount. I drove it that night and all was well. The next day was the 6 hour drive, and that's when it started. Had me sh***ing bricks the whole ride. I thought the new filter was bad or the fresh trans fluid dislodged something in the transmission, or something generally bad was about to happen. Once I got back, I crawled underneath and inspected everything. That's when I noticed the motor mounts. I couldn't believe it. I'd only had it for a short period of time at that point, so I really hadn't looked at everything quite yet. It was weird too, that in gear it idled so smooth, even with blown engine mounts.

Morat

Gotta love the inline six, it's a smooth unit!
But all torque twists the mounts, so they do wear.

dom_poli

I've never greased the slip yoke since I've had the jeep - will do that this afternoon! Good to know, thanks. And yes, the rear leaf springs were heavy duty ones from quadratec and lifted the rear end maybe an inch or so.

dom_poli

Thanks for the info! Will check this later today and keep you posted. Hoping it's something like this and not something internally in the tranny or diff that I'll have to take in to the shop for.

dom_poli

Okay, I looked at the motor mounts and I don't see any visual damage from the top. It's pouring here today so I wasn't able to look from underneath or try to mess with the slip yoke. Hopefully I can get to it later this afternoon if it clears up.

I did want to mention that the noise will go away if I bump it into neutral. ie: get up to speed where I usually hear it but bump it into neutral to try to replicate the problem. I know I shouldn't make it a habit of doing that but I just wanted to test that theory to rule anything out.

I also hear it not only when I barely tap the gas pedal like I said earlier, but when I let off the gas pedal as well. It could be other instances too, but I seem to hear it most prominently when I feather the gas pedal ever so slightly. If it's worth anything, when I say "tap the gas pedal" I'm not quickly slamming on it, I'm barely letting on/off the gas as if you would normally if you were going down a hill and then slowly getting back on it for the ascent. The car isn't torquing or jumping forward when I do this. Not sure if this helps pin point the problem but just thought I'd add that. Thanks guys

EZEARL

Sure sounds like a slip yoke issue to me. With the leaf springs giving the rear end a lift the pinion angle may be off enough to cause a binding of the slip yoke plus it can shorten the amount of transfer case output shaft that's in the driveshaft. To find out for sure if it's a slip yoke issue simply remove the rear driveshaft and after putting the t/c in 4H drive the vehicle. Yours should look like the bottom one.

dom_poli

Thanks for that @EZEARL . And if it doesn't look like that?... or, what happens when I remove the rear driveshaft and drive it in 4H? Should the noise just disappear? And if it does, what part(s) should I replace? Thanks

EZEARL

Removing the rear driveshaft simply eliminates the slip yoke influence from the driveline. It will eliminate your problem IF it's the slip yoke that's causing it.
As far as how to remedy the situation the cheapest routes would be to lower transfer case or install the proper shims under the leaf springs to get the proper pinion angle like in the diagram above. These ways may not work. Didn't for me but has for many here. So then we get in to slip yoke eliminator (sye's) kits. The links below are for references.

https://www.roughcountry.com/jeep-tr...-kit-1072.html
https://www.ironrockoffroad.com/prod...ring-pins.html

Search "sye kits" at ironrock offroad

dom_poli

Thanks @EZEARL , I was able to get up underneath this morning to check it out and my geometry does "look like" the bottom photo, with the diff and trans just about horizontal to the ground. I didnt have time to take the rear drive shaft off though. Is there anything I should check out next before taking it apart? I did notice that the rear driveshaft does have a bit of rotational play - maybe a 1/4". It does not have any back and forth or up/down play at the U-Joints. Just rotational. Is this normal or no? Thanks again.

EZEARL

I just noticed your XJ is a '94 which means your transfer case rear output shaft has an external seal. If you remove the rear driveshaft you'll lose fluid so that won't work. Maybe someone here knows of a temporary fix.

Some rotational play is normal. With no tension on the rear driveline you could check for vertical play at the slip joint. Have you greased it?

Even though the driveline geometry looks good you should measure the angles. Put the vehicle on a level surface:
https://www.cherokeetalk.com/threads...-angles.13941/