turbo86yota

So yesterday while 4wheeling I noticed a potential problem and figured i'd get sum input. When I would engage the truck into hi4 or low4, the entire truck would shake VERY NOTICEABLY. It would get worse the faster I'd go. Then when i'd get off the gas the entire front end would shake until the truck came to a halt. But with the front hubs not locked, none of this would happen. ONLY WHEN THE FRONT HUBS ARE LOCKED does this happen. I can put the truck in 4hi or 4low (for the gearing) and nothing abnormal will happen. I ran it shaking like this the whole day like this and it really killed part of the fun.

My best explanation on to how the shaking is speed dependant (not made to scale lol)

ACCELERATION:
MPH: ......0..........10..........20..........30
SHAKING: x x x xxxxxXXXXXXXXXetc...

DEACCELERATION:
MPH: .....30..........20..........10..........0
SHAKING: XXXXXXXXXxxxxx x ...x .....x

Sorry about the crude table but you get the picture... SO any1 have any idea wtf is wrong with my front end. Oh keep in mind that this is an sas 86 toyota, stock gears and open diffs front and back.

Tacoclimber

Well, initially I would have suggested the front driveshaft, but if it's only when it's locked, that would suggest something wrong inside the axle perhaps? Is it possible that you damaged a birf or something?

It's been a few years since I had a SA rig. I'm sure someone more knowledgeable will chime in soon. Good luck!

turbo86yota

Yeah honestly, I'm not too knowledgable when it comes to the differentials. I just wanna know where to begin looking as far as the front axle. At this point I miss my IFS lol. 1st SAS rig and its given me problems up the yang...

Tacoclimber

Another question:

Did it "just start", or is it possible wheeling damage?

That might help us with diagnosing the possibles.

turbo86yota

Well, i just purchased this truck and it only happens with the above conditions. Keep in mind that this was light wheeling too.

Just_Me69

Sorry to be so direct. If the front and rear are spinning at the same speed, your problem lies in the tires. Think of how a differential works. I don't care if they're the same size, minute variations in the circumference of the tire will cause the transfer case to bind. Resulting in these vibrations. Next thing you know, you will have to buy a new case. If you're going 30 with the hubs locked and the case in 4, you're looking for trouble. Again, my deepest regards for not hurting your feelings.

4Crawler

iTrader: (3)

What sort of road surface are you on when doing this test? If on pavement, generally not a good idea to do that in a part time 4WD system. For some additional testing, do this on gravel or dirt. And, you can try locking the front hubs and leave the transfer case in 2H and see what happens. And see if that is different than 4H with the front hubs unlocked. Maybe have someone walk or drive beside the truck when you have the shaking problem and see if they can look at the front driveshaft or anything else that may be out of whack. And try lifting the front axle in the air and lock the hubs and try spinning the front wheels and driiveshaft by hand and feel for any binding.

Kaleb

Are your differential gear ratios the same? When I SAS'd my rig I had 4.56s in the rear and 4.10s up front. I took it out for a test drive, and it did the same thing that you described.

924runner

does it do it in 2H with the hubs locked?
if so try taking thae front shaft out and trying again.
process of elimination.

ulfr

I've had this problem before, did take a f...ng while to get rid of it.
Do you have leaf spring or coil spring suspension?
Do you have a panhard bar? If so, it could be the bushings in the bar, try switching them for new if you haven't got new ones.
The weight on the shuckle bearings? Is that measure okay and the bolts tight with pressuremeter? If not, you should check these two things out.
Are the tires ballanced? If not, it might cause a problem.
The steering machine could also be a problem, if it's not 100% in the center it might start to shake.

Keener

my truck used to do that to, as long as the hubs were locked,(2wd or 4wd). it was slop(alot) in my driveshaft spline was was guilty.

have you got steep a front driveline angle? could be u-joints binding a bit