bad vibrations in 4wd..

[sityslkrbj70]

so bombing round town today in the snow i decided to throw the truck in 4wd after one of my stops.. locked the hubs and plopped it into 4wd.. now it was fine untill i got onto a relatively clear road and my speed went up to bout 40km/h @ 2000 rpm and it seems to happen in all gears.. and is worse on decel.. noise is gone above or below the speeds listed above. took it out of 4wd and the truck is fine. now i suspect the following.. sounds like a driveshaft issue.. also my springs in the rear are clapped out and i think the angle has to do with it also... so my question is;

would the angle of the driveshafts give a vibration?
would that noise be from extra strain on the u-joints?
don't think it's an internal issue with the diffs or anything?

mb.

 

[_Walker_]

Did you check the forward drive shaft for any obvious problems? I had the bolts connecting the rear universal to the transfer case 1/2 work themselves loose on the 60 a few years back, very similar to what you are describing. Not noticeable at low speed, upon attaining velocity the vibration grew. Just a few turns of the wrench and the world was back in order...

When the truck is under acceleration does the vibration increase or decrease compared to when you are coasting?
On deceleration is it worse or better when downshifting vs clutch in & braking?

 

[crushers]

unlock hubs
put in two wheel drive
crawl under and grab the front driveshaft at the diff end
wiggle up/down/side/other side/into the diff
there should be NO movement.

while grabbing and wiggling hold the diff end at the diff end of the front u/joint turn the diff one way and the drive shaft the other, you should not be able to move it at all. if you can then hold the pinion end and move the driveshaft up and down and side to side... there should be NO movement.

now go to the transfer case end of the driveshaft and check that out with the above proceedure
there should be NO movement in any direction...

now lock front hubs and retest front diff end by turning the driveshaft, there should be no more than 1/64th of a turn in either direction, this is your backlash, if you have more then report back how much.

 

[Rigpig]

both front d-shats on my BJ70's for some reason had sloppy splines and that's where the vibs on mine came from. I've seen others with the same issue also. Have a look at your u-joints while your at it.
Cheers!

 

[Natty]

and check that your front driveshaft is "in-phase" with the diff end - ie. the end of the shaft where the u-joint goes looks like a "C"... make sure it matches the "C" coming off the front diff, have the "C" ends in-line with one another or it will cause vibration... sometimes previous owners or people that didn't realize will put them on without having them in phase with one another...

I hope this makes sense, I'm not sure of the proper terminology... this is the ghetto explaination...

 

[sityslkrbj70]

i'll check 2morrow.. just helped a buddy install a new fuel tank in his 60.. below 0.. in the snow.. on the ground.. lol.. thanks for the info.. very appreciated!

 

[micruz60]

similar problem on fj60...

Sorry, to 'hijack' this thread, but it is sounding right along the lines of something I've been experiencing, some strange 4hi activity, it feels like the rear end wants to pass the front end... I did what crushers recommended, and have no movement in driveline into diff or transf (sideways, up/down front/back), but when i lock the hubs (not shift into 4 hi) and then rotate the driveline, i get about an 1/8 th turn. I've consulted my FSM, says 20mm backlash is spec, sooo somethings up. Earlier this fall, I replaced both front brake rotors and calipers, repacked the hub bearings etc., so I'm pretty confident it isn't in the wheel area. Another clue: after driving 25 or so miles in blizzz and snow/ice road mountain pass, I checked the hubs for any heat - none, then threw some snow on the front diff... it melted right away. Whaddya think?

I'm sorta new to this forum, just haven't posted any.
My stable:
'77 FJ40 quietly waiting for action, 190,xxx miles some mods
'87 FJ60 daily driver, 284,xxx miles custom tree wrinkles some mods

 

[crushers]

same diff ratios front and back?
diff fluid in front end?
water contamination in front diff?
1/8th turn is quite a bit so back lash needs setting up sooner or later...

the front diff should get slightly warm but shoudl not melt snow, something is not right inside, check fluid level

 

[Eric Winkworth]

I have very little experience with diffs so not to jump on your toes Wayne but 1/64th of an inch? seems really really tight.... if the FSM says 20mm thats about 3/4 of an inch, 25mm is a full inch.

I know I have some INSANE backlash in my diffs if they are supposed the be 1/64th... I attribute my 4wd vibs to my driveshaft angle since my 3 inch lift.... I was thinking of dropping my t-case an inch...

this is basically why my rear diff is like.... and I don't get any vibs from it at all, even when lugging the engine low
http://www.youtube.com/watch?v=KxIpXVMMrM8&feature=related

is that too much hahahah?

 

[crushers]

umm, reread the original post. 1/16th of a turn...
take a circle, cut it into quarters, that is a quater turn
cut it into eigths and that is an eight of a turn
cut it into 16ths and that is a 16th of a turn which is still a lot but acceptable in real life...

you have about 1/8th of a turn in the video...

 

[Eric Winkworth]

"there should be no more than 1/64th of a turn in either direction" this is the post

ohhh and I wasn't at all understanding your method of measure... I thought we were talking inches... makes much more sense..

cheers

 

[scuirer]

BJ70 Vibration in 4-wheel drive

Reading this thread prompted me to investigate the exact same symptoms described by MB. I followed the diagnostic in the thread, found diff. fluid low, topped-off, then drove it for 2KM each in 2/locked hubs/H4/L4, all without unusual vibration. When I unlocked the hubs I did notice that the passenger's side made a distinct click when operated. It makes me consider that the hub is not engaging/disengaging properly.

1985 Canadian spec. BJ70 283,000Km, 2.5OME lift