Topic: another vibration question

[kauaikid]

I just read a grip of posts regarding vibrations and still need some advice. 

My story:  While driving at about 50 mph in 4th my crawl box needle bearing seized which brought my tires to a dead stop and caused me to slide at least 50 ft.  What I found was that the needle bearing on the coupler was seized and 5 of my ring gear teeth were torn off.

I rebuilt another crawl box(didn't mess with the rear t-case because input and output shafts rotated fine), had a shop install a new set of 5.29 gears  and had them reuse my solid spacer(which are still being broken in). 

Only at 40-45 mph in 4th gear under load only, I get a bouncing vibration. When I push in the clutch it goes away. I had my drive-shaft balance checked and it was fine, my output shaft nut seems fine, backlash on diff seems ok, no leaks on tcase or diff, t-case mounts are okay, motor doesn't look like it contacted anything and motor mounts looked okay visually.  What's next??

I would like to know if losing a rear tire balance weight could cause this, could it possibly be just 4th gear in my trans due to the stress, does anyone think the the rear t-case could run smoothly(shifting,no noise) and be the problem, or could it be a bad gearing install, stress on rear axles, etc. I realize there are numerous possibilities just wondering what some of you gurus would check next.

I'm running a 4 inch all-pro lift with one inch longer rear shackles, my truck is an 84 longbed with a single piece drive-shaft, 35 inch tires, air lockers, and dual cases with 4.7's in the rear if that helps. And before the accident it never vibrated. 

[Burl Earl]

what i have learned in my schooling is that a missing wheel weight could not do that. it is slightly possible that you warped your flywheel or trans input shaft, in the accident, and that could be why the vibration goes away when you disengage the clutch. since your gears are brand new and were pro installed i wouldn't worry about that being the problem. it most likely is from the trans, clutch assembly or one of your t-cases. i hope that may help you.

[79coyotefrg]

I just read a grip of posts regarding vibrations and still need some advice. 

My story:  While driving at about 50 mph in 4th my crawl box needle bearing seized which brought my tires to a dead stop and caused me to slide at least 50 ft.  What I found was that the needle bearing on the coupler was seized and 5 of my ring gear teeth were torn off.

.............., had a shop install a new set of 5.29 gears  and had them reuse my solid spacer(which are still being broken in). 

when you installed your tcases  did you dump 1 qt of lube  into the front case shifter hole??
if not thats why your needle bearing locked up

.............. and were pro installed i wouldn't worry about that being the problem. it most likely is from the trans, clutch assembly or one of your t-cases. i hope that may help you.

being installed by a "local shop" does NOT = a professional installation,   there's a "offroad shop" near me that does gear installs for customers, i recently found out they dont have a bearing press and never have,  they  just "eyeball" the pinion  and  install what looks good 

so what im saying is,  CHECK YOUR PINION
make sure its not sloppy,  also make sure your drive shaft is in phase,  the  bouncing you discribes  sounds like a busted u joint or a  badly out of phase shaft

[kauaikid [OP]]

yes the t-case needle bearing failure was due to lack of oil.  However that has been a lesson learned.  I did check my pinion prior to reinstalling my third as well as it installed for excess play and found it had no more play than it did when it was setup from marlin.  I thought about the drive shaft phase but figured since it was on the balance machine yesterday and was nearly perfectly balanced and I didn't pull it apart it would be balanced when I reinstalled it.  Is that incorrect?

[KDXSR5]

The warped flywheel or clutch idea sounds plausable especially since it is only in 4th gear. When in 4th gear, the transmission is sending power 1:1 and that would probably be where you would get a vibe from the flywheel/clutch stuff. When my clutch was going out a couple years ago, it would only slip in 4th gear or when in low.

[kauaikid [OP]]

thanks, I'll pull it and try to take a look.  I'm getting pretty good at pulling the tranny and t-cases at this point by myself so if anything good is coming out of this its practice I guess

[kauaikid [OP]]

What are the odds of it being my 4th gear in my trans?  I was in 4th at around the same speed when it locked up.  I also don't have the problem when i'm going through that speed in third gear.  Any thoughts?  Also wouldn't I notice it in my clutch if the fly wheel was warped?

[Burl Earl]

What are the odds of it being my 4th gear in my trans?  I was in 4th at around the same speed when it locked up.  I also don't have the problem when i'm going through that speed in third gear.  Any thoughts?  Also wouldn't I notice it in my clutch if the fly wheel was warped?

if it is 4th gear your going to need a new main shaft in your transmission because 4th gear is 1:1. which means your crank speed is the same as your transmission, output & driveline speed. also, replacing your main in the transmission means replacing all the helical gears in th transmission. it would be a lot easier to get a new trans or upgrade to the 23 spline turbo trans. as for the flywheel/clutch warpage. if you have a dial indicator you can use that to check the out of round and warpage. otherwise use a straight edge and feeler gauges. put feeler gauge on a part of the flywheel put straight edge on top. then try to pull out the feeler gauge. if it moves the straight edge then it is smaller than that feeler gauge. check about 6 places around the flywheel.