vibration on deceleration? (1 Viewer)

[cruisernerd]

i'm trying to diagnos a sound that my truck is making.
when i am travelling at a decent rate of speed and i let off the throttle i get a vibration. don't know if it is possible to know what it is from my description, but appreciate any input.

 

[Degnol]

I've had that problem twice for different reasons. The first was caused by loose bolts on the pinion flange and the second time I had too little spline engagement on my driveshaft after a lift.

GL

Ed

 

[matros]

ujoint or pinion angle if youve recently changed it

 

[cruisernerd]

i'll give you a little more of the story.

i'm a little nervous because i got my t-case rebuilt 2 weeks ago.
before the rebuild, the truck would vibrate at speed in 4wd.
it would make a slight vibration on deceleration from a decent rate of speed.40 mph or so.
i was nervous about the thing leaving me stranded so i took it to a shop(first mistake). got the guy to give it the rubber glove treatment... he tells me the t-case has where.
i already suspected this so i get him to rebuild it.
it makes just as much noise or more than before the rebuild.

wtf!?

i am going to climb under it and have a look just wondering what else it could be.
thanks for the shoulder to cry on

 

[Degnol]

How about even MORE of the story....

Do you have a lift, either spring or shackle? Are you sprung over or under?

The only TC thing that would cause a vibration would be the output bearing having too much play, so get under the truck and wiggle the driveshaft at the parking brake and at the pinion.

If you have a lift of any kind, check the spline engagement....if it looks like this, you have too little engagement and that can cause vibration, especially on decelleration.

GL

Ed

 

[cruisernerd]

i have an '81 bj42 with a split case. ome 2.5 in the rear,with stock shackles. and 2"shackle lift up front, with unknow springs maybe one inch over stock. the case was tight before the rebuild. only 213,000km.
the reason i thought it needed a rebuild was(embarassing) i ran it low on oil, down to about half. you know how a bad seal between the tranny and t-case moves the gear oil into the tranny?
i'm scratching my head...
i'll go climb under it, the 6" of new snow has cooled my motivation to lay on the ground. but you interest has renewed it.
thank- you for the input.

 

[cruisernerd]

the only play that i can find is at the slip yoke. the mechanic i saw said it was normal. i can turn it 1/32 of an inch at the most.
when in neutral, and i turn the drive shaft by hand. the back feels tight, not much room to turn it back and forth, before the tires ingage. but the front can be turned quite a bit more.
is this normal?

 

[Pin_Head]

Worn slip yoke splines can cause this too. Basically any play in the drive shaft other than rotation is not good. Get under there and yank the shaft every which way and see what moves.

 

[cruisernerd]

when idid this the slip yoke was the only thing that moved. the only other movement i could get was to turn the drive shaft, (i am assuming) so the pinion gear would contact the ring gear. turned very little in the back, quite a bit more up front. also front ds had more play than the back.
FWIW i had it balanced.
is it my imagination or is it starting to sound like a drive shaft/third member issue?
i'll go check it again.

 

[cruisernerd]

so i climb under it again... in 2wd with hubs locked, tranny in neutral. rear drive shaft bare turns back and forth before engaging tires.

the front turns almost 45 degrees before turning the tires!

i put it in 4hi tranny in neutral, rear the same. now the front is the same as the rear, almost no back and forth turning before tires are engaged. then i put the t-case in neutral. and it is the same as 4hi.
hope i'm explaining this ok. don't know if any of this means anything, but should there be so much sloop in the front third?

 

[cruisernerd]

thought i would add a pic of the rig in question.

that's custom paint on the bumper, in case you are wondering.lol