skouba

Hello All,
I'm new here. But i recently acquired a 1986 toyota 4runner. There are a couple things that I am unsure of, being a relative newb to all this.
First of, when making lower speed sharper turns the truck rocks pretty bad, almost like a lurching, only when turning. I have read that it could be something to do with (correct me) the steering stops? (little plastic/rubber pads) Because i do know that one is gone and one is pretty worn. But it almost feels like the rear diff is locking up, I can't confirm this, but just a thought.
One other thing, when I am turning down a street, say coasting, there is a clicking noise coming from the rear end, it's very consistent, and almost sounds like a big ratchet being turned. The guy i got it from said something about the rear diff being semi locking if that sounds right, like it actually alternates between locked and unlocked. Is that a thing? I mean i do know he did work on both the diffs sometime before i bought it.

Anyways i would appreciate any insight that anyone may have. I have a good general mechanical understanding its just I've never owned a vehicle before, so still learning lots of the terms.

Thanks,
Shane

blake.nemitz

sounds like its stuck in 4wd or the rear is locked up

RJR

I would say both. You have an automatic (ratcheting) locker in the rear, which accounts for the clicking sounds when turning. That's normal and having the locker is a good thing for offroad use.

It also sounds like you are driving it in 4wd on the pavement. That's a no-no, as it causes drivetrain windup, tire scuffing, lurching, and overall bad behavior and potential damage. You should only use 4wd on low-traction surfaces.

If you're pretty sure you have the transfer case in 2wd, it's probably time to figure out why it's not releasing from 4wd. Jack up the front end and see if the front wheels turn freely and independently. They should when in 2wd.

It's also possible the automatic locker is not releasing properly in turns. Ask the previous owner what's in the rear end.

AKHeathen

a little scrubbing/jumping on sharp turns is expected from any front-steering link setup. only rear linked knuckles turn correctly. even a brand new pickup will do it. as far as your noise, the best method i'v e found, when ou can replicate it this whay, is have someone stand out side and judge exactly where it's coming from and it's relation to the rotation of the rear tire. it could be a u-joint going out, or something else

RJR

That certainly hasn't been my experience. With the front end free-wheeling (i.e., xfer case in 2wd, ADD unlocked) the vehicle turns smoothly on pavement all the way to steering lock. I make a hard U-turn out of my driveway every day, so I'd notice something like that.

skouba

Thanks for the input. I am certain the transfer case is in 2H (jacked it up and front wheels spun freely.
I ran it while jacked up, and I am pretty sure that it's a really bad diff. It's happy in 1st and 2nd, but up from that a terrible knocking/banging noise comes out the rear, just when its idling off the ground in gear.
So hopefully I will be able to find something to replace it with.

Terrys87

iTrader: (1)

Being a stock 86 it should have the end shaft pink and be 4.10s http://www.4crawler.com/4x4/4R_TechI...tml#DiffRatios You will need to pull the driveshaft to see the color. I would count and compare teeth with a replacement.

skouba

I got ahold of the guy I bought it from, he says that he re geared it to 4.56.
If i understand correctly both front and rear diffs need to be the same ratio in order for 4wd to work correctly?
Also what are the advantages/disadvantages of running 4.56?

Terrys87

iTrader: (1)

4.56 you can run a larger tire, I dont think it makes much of a difference going from 4.10 to 4.56s. I think the 4.56 came in trucks that had the automatic transmission. It is geared lower to help with power for the automatics.

With two different gear sizes on each end of the axles, it will bind up the transfer case. One set of gears will spin faster then the other. I have run into issues of getting the exact same tire sizes but from two different brands, one set of tires can be larger or smaller then the other set. Basically causing the same effect. You can drive it but I would not engage the transfer case until you have your gears matched.

tj884Rdlx

The front bump stops grinding at full lock will make an awful creaky groaning, but at full lock only, and they can be greased and silenced. This should be easy to distinguish from Rear end diff sounds.

With the rear end off the ground, you should be able to spin the left wheel by hand and watch the right turn in the opposite direction, if the diff is OPEN. if it's LOCKED the wheels will turn in same direction. This is bad - for a truck driven on pavement. The semi locking Rear should lock only under slippage conditions with high torque force.

You can confirm the gear ratios by counting the revolutions at each axle. Google that for easy instructions if you want to try it.

Bear in mind that some semi lockers are notchy if you accelerate through a curve, vs coasting. Know the difference between functionally noisy and broken.

Good luck.

skouba

Yeah I figured something was wrong, when I spin one wheel, the other one spins in the same direction. So I guess it is indeed locked. Is there anything I can do about it?
Thanks

skouba

Also the guy says he has both original diffs still. He wants $400 for the pair. Is that normal, even when they have 200k on them?

RJR

That's normal operation for an automatic locker and doesn't necessarily mean anything is wrong. It's also normal for them to click when you go around a turn.

Here's how to test if it will unlock properly and ratchet in turns. You'll need a buddy to help you.
- Raise both rear wheels off the ground, and put the transmission in gear or park so the drive shaft can't turn.
- Now have your friend rotate one wheel as far forward as possible and hold it there firmly with a fair amount of force. While he's doing that, try to rotate the other wheel in reverse. With some effort, it should unlock and allow the wheel to turn backwards while making a clicking sound. If you can't budge it, the locker isn't unlocking properly.
- Now have him hold his wheel in reverse, and rotate yours forward. You should get the same ratcheting action.
- Trade wheels and repeat.

Automatic lockers are very effective on the trails, but they can be noisy and annoying on the street. It's your choice as to whether you want to put up with it. Also, ask the PO what kind of locker he put in. Detroits are really strong, but have a reputation for rough street manners. Some of the others like the Aussie are much smoother. Of course, if he tells you he never installed a locker, then the behavior you're seeing means the diff is broke and will have to come out.

If the original diffs haven't been monkeyed with, and have always had clean lubricant in them (no water, etc.), then they'll run long past 200K miles. With proper lubrication, they really don't wear much. You might have to replace a leaky pinion seal sooner or later, however.

AKHeathen

limited slip requires a grwat amount of force before it starts to slip in that manner as well. if anything, it's the open diffs in a gen 2 that is it's weak point stock. the upgrade would be a locker of any sort to keep it handling good but not get stuck as readilyh as an open diff.

AKHeathen

well, larger rubber to rim ratio hides it well. if you want good turning geometry, its only through rear-knuckle actuation..... there is no exception it is plain solid math.

RJR

I'm not sure of your terminology re: "front steering link" vs "rear knuckle" design. I assume you're talking about whether the tie rods run in front or in back of the axle, and how that affects turning the inside wheel at a sharper angle than the outside one, which is required for perfectly smooth steering. I haven't thought that whole problem through, so I can't comment further on that aspect at this point.

AKHeathen

yes, that is what i meant. it's one basic point of steering geometry. the relationship of linear movement to rotational degrees of the steering axis increases to increased rotation bias the further the connection point moves from perpendicular....... so basically, if the tie rod ball joint is strait ahead of the steering knuckle ball-joint pivot, we will call that a factor of 1:1 for arguments sake. if it moves inboard or outboard, say 2", it would be like 1.2:1 and like 1.6 to 1 at 4" linear on the link, giving 1.6x the turning per inch as strait foreward. because of tire and rotor clearance, as well as ball joint/pin load reduction, everything is compact in there and the tie rod ig generally set inboard 1-2.5". what this means is typically when you are, say half way turned in one direction, the inside tire has reduced to 1:1 and the outside tire is turning in at like 1.4:1, essentially giving you a serious toe-in when turning sharp. the outside tire is pushing into the turn and the inside pushing out. a rear linked steering setup is the same with inboard attachment as a front one with outboard attachment in it's effect, and when turning, the inside tire should be turned sharper since it is traveling a smaller radius that the outside tire..... this is just one of the factors you have to concider as a whole.
another that can greatly effect it is sai, or "kingpin angle" it will effect the way the tire tilts and lifts vertically and slighly adjust the steering link ratio. one example would be if your lift springs or shakles twists the axle. (or even an ifs lift that moves the lower control arm foreward or rearward).... you would use wedge shims to fix the angle.

RJR

Thanks for your clarification. That was a good explanation. I understand the principle involved; I've just never crawled under and looked at the specifics of the actual implementation. As you say, if a front steering setup has the tie rod ball joints pointing inboard of the knuckle, that would be exactly wrong for smooth steering. I'm curious now as to the actual geometry on my 4runner. I'll take some measurements one of these evenings and put it all into Mathcad to see what it looks like.