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Another "Grinding Noise" thread. Please advise.

Muad'Dib

NAXJA Forum User
Location
Bend, Oregon
Ok so a little bit of history first, please bare with me as i like and expect to be as informative as possible.

1990 Jeep Cherokee Laredo with NP231 and Dana 35 rear.

About October / November of last year i hit a Deer with my Jeep. I had to replace the Condenser, radiator, header panel, misc front trim / lighting, ps pump (really needed to only replace the pulley), belt, and electric fan. Other then that, the Jeep seemed fine. After i got most of the parts from a wrecking yard (all but the radiator) i peiced it back together and she ran like before. One thing i did notice that i didnt notice before was that when i accelerated hard from a stop i would get (hard to explain) a clunking \ striping \ grinding noise from almost directly below me (or at least is seemed) just for a second. I lived with it for awhile, and now that i have had more time to put into the Jeep i tried to figure out what could be causing this. After searching here, and just plain google searching, i figured i would see what happens if i were to replace the transmission mount.
About a week ago, i picked up a replacement transmission mount from a local schucks. After searching around, i came to the conclusion (please correct me if i am wrong) that purchasing a poly mount really isnt worth it in the transmission area. They supplied me with a Anchor part # 2625 transmission mount. I inspected it and it looked sound.
Today i finally had the chance to swap this in. After again searching, i came to the conclusion that i shouldnt have to remove the crossmember to do the swap.
I jacked up the vehicle, and supported it on jack stands. I put a 2x4 between the jack and the transmission pan right next to where the mount is, and made sure that it was snug enough to carry the weight of the transmission. I removed the 1/2 inch nuts that attach the crossmember to the transmission mount, and then raised the transmission about 1/2 inch. I then went to remove the 18mm bolts that attach the transmission mount to the bottom of the transfer case / transmission. It was a snug fit, so i decided to go ahead and remove the crossmember which was easily removed. I would recommend doing so for anyone who doesnt live in an area that rust is an issue. The nuts / bolts on the crossmember (according to searches i have done) are prone to breaking, but mine came out just fine. After doing so, it was much much easier to get to the 18mm bolts, but they were torqued down pretty hard core. I had to use a pipe on my ratchet and a heck of alot of human force to break them free, but they did come loose. I removed them, and the old transmission mount came out just fine. After it was out it looked a bit "collapsed" on one side, and had alot of minor tears in it. Here are some pictures:
http://i17.tinypic.com/6bkvh8w.jpg
http://i12.tinypic.com/65z3iwx.jpg
http://i14.tinypic.com/6gtbsm1.jpg
http://i13.tinypic.com/6aj6q6s.jpg
I am pretty sure that it is bad, and i doubt that it has ever been changed.
I then cleaned up all the surfaces that come into contact with others with a towel to clean up grease oil etc, and go to install the 18mm bolts that hold the top portion of the transmission mount. The side that is away from the exhaust "hanger" lined up ok, so i got the bolt started in there first. On the side that is closest to the exhaust hanger, it was off about a half inch towards the front of the vehicle. I took my trusty pipe, and used it for leverage to push the exhaust hanger ( that is attached to the plate that goes between the mount and the transmission / transfer case). With some force i got it to line up better, and got the bolt started. I got it "snug" making sure to keep force on the hanger so that it all lined up correctly, and then snugged up the other side. I then got out my torque wrench and torqued them both to 55 ft pounds. I found the torque specs here:
http://www.naxja.org/forum/showthread.php?t=46879
Please tell me if these are incorrect.
After i got these top bolts torqued down, i lined up the crossmember with the four bolt shafts on the bottom of the transmission mount, and then got the nut on the drivers side started. It was just a bit off, but i got it started just fine. I then went to get the passengers side nut started to hold the crossmember in place, and it was hanging about 1/2 inch below the frame. I had to jack up the transmission about another inch to get the crossmember high enough so that i could get the nut started on the bolt shaft coming out of the frame. I also had to forcibly move the crossmember towards the front of the vehicle to get the holes to line up. Once i did so, i got the nuts / bolts snug and torqued them to 30 ft pounds reffering to the article above. I then got the 1/2 inch nuts and snugged them lightly inside the crossmember attaching it to the bottom of the new transmission mount. Once i did this, i dropped the jack so that the transmission / transfer case would rest like it should, and i then torqued the nuts to 22 NM ( since it was easier then trying to figure out how much 192 inch pounds were on my torque wrench lol). Everything looked great underneath, but i did start to think it was kinda weird that now with this new mount everything had to be raised. I just "assumed" that this was because my old mount was worn, and now the new mount is putting everything where it is supposed to be.
I raised the vehicle, removed the jack stands, and lowered the vehicle. I was on level ground, so i figured it would be a good time to check the gear oil in my differential. (I replaced the oil approx 1 year ago). When i removed the stupid rubber plug, alot of fluid came out. I wasnt too alarmed as when i replaced the oil i didnt know 1/4 as much as i do now, and from my knowledge the oil is only supposed to be level (if not a little lower) with the fill plug. I let it drain, and checked to make sure that it was about level and put the plug back in. (Please tell me if this was a mistake or if i did this correctly)

I cleaned up a bit, got in the Jeep and started her up. It went into all gears much smoother as i was expecting. I then took it for a ride, and it shifted smooth like it always has, possibly a bit smoother. I then tested hard from a stop to see what would happen. What a sound! It makes a horrible sound now. Much louder and more noticible then before. Coming from the same area, its (very hard to explain) kind of like a grinding / slipping. I even does it when giving it a moderate amount of throttle from a stop. I also tested while driving smoothly, and then flooring it (making sure that it downshifted and applied to most torque to everything) and it DID NOT make any noises. If it did, i didnt notice it. If it would help you, i can take a video (with sound) of this happening.
Im pretty sure the motor mounts have never been replaced as well, and i have plans to replace them in the near future.
Ok so after all that, here are my questions:

Do you want me to "film" this so you can hear it?
Besides my motor mounts being shot (taking into account the encounter with the deer) what else could be causing this problem?
Did i torque it all together correctly, or are the torque specs i used way off?
Did i make a mistake by checking / draining the gear oil in the rear differential as i did?

Thank you very much for taking the time to read this post and possibly help me out. As i stated in the begining, i wanted to be as precise as possible to help you help me.
Thanks again soo much. You guys are really the greatest.
 
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Yeah if you park on flat ground and move your drive shaft by hand feel for any cluncking (one hand on yoke and other on shaft, then other side. should be solid.
 
I had a similar hard to describe noise on my jeep and it ended up being a few loose (missing) engine to trany bolts. This caused a misalignment and alot of noise and headaches for me. Your collision may have caused some minor misalignments and and this vibration. Good luck!
 
could be the exhaust mount at the tranny/transfer case crossmember. Mine started to make a noise that I assumed to be a worn u-joint. I crawled under the jeep while it was running and noticed the exhaust was rattling away. It would seem worse when under load. It was bearable for quite a while, just intermittent. Now it rattles alot more, but I still havn't gotten around to fixing it.
 
99XJeeper said:
Any idea what condition your U-joints are in. not really sure what it is a video would probably help though

Not sure really how to check them, or for that mater know where they are. Sounds noobish, but in all honesty this is the first time i have been doing most of the work myself. A little guidence there would be appreciated.
Ill get a video today when i wake up a little more.

Stihl029 said:
Yeah if you park on flat ground and move your drive shaft by hand feel for any cluncking (one hand on yoke and other on shaft, then other side. should be solid.

This seems a little hard to understand for me. Im supposed to move my driveshaft when parked on flat ground. I have "rotated" it before while under the Jeep and it has made a "clunking noise" while doing so. I just figured this was normal clunking that happens when the driveshaft changes direction. Am i wrong? Am i even doing the test correctly. Whats the "yoke"? Sorry for all the noob questions.

my80chevette said:
I had a similar hard to describe noise on my jeep and it ended up being a few loose (missing) engine to trany bolts. This caused a misalignment and alot of noise and headaches for me. Your collision may have caused some minor misalignments and and this vibration. Good luck!

In my case its only when accelerating from a stop. If i had this problem wouldnt the noise be pretty much full time? Ill check them anyway. Thanks.

Jeremy89XJ said:
You also may want to look at your control arm bushings. I hit a deer in my '89 and crushed the lower bushing on the drivers side. Made a horrible noise until replaced.

Same as above. Wouldnt this cause a noise all the time? Another noob question, but what is the control arm? If i could find it, ill inspect its condition.

clunk said:
could be the exhaust mount at the tranny/transfer case crossmember. Mine started to make a noise that I assumed to be a worn u-joint. I crawled under the jeep while it was running and noticed the exhaust was rattling away. It would seem worse when under load. It was bearable for quite a while, just intermittent. Now it rattles alot more, but I still havn't gotten around to fixing it.

I was thinking about this while i was replacing the transmission mount, as others have stated this is what was making a similiar noise. The exhaust hanger that is attached to the metal plate that goes between the transmission mount and the transmission / transfer case seemed to be in great shape. After i got the new transmission mount in correctly, i attempted to move the exhaust system, and it was very very firm. Barly budged at all. I assume then that its not clunking into the crossmember since the hanger holds it firm well above it.

Ill post a video a little later. Thanks all for helping. Any other suggestions?
 
Ok i took a video. Its not really noticable in it, but i think its the noise that sounds like im peeling out.

http://video.tinypic.com/player.php?v=5zcqgwo

After reading my Haynes (yeah i know i need a fsm) i think i understand how to check my u joints.

This morning before i did anything i got under the vehicle, and i attempted to rotate the rear driveshaft. It didnt budge. I held the end that goes into the differential (i believe someone called it the yoke? Correct me if i am wrong) and i attempted to rotate the driveshaft again. I didnt feel any play at all. Did i do this test correctly?

Thanks again
 
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