'85 4-runner pulls in 4WD??!?

DanS HJ-45

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So, the Chica bought an '85 4-runner. In 2WD it drives straight and all. In 4WD it pulls pretty hard to the right. So, to try to remedy it a bit (and because it needed it), we pulled the birfs and did the cleaning proper (with beno's help). That's a drain of the 3rd, new gear oil, plus all the knuckles cleaned and reassembled. We found a wheel bearing on the right that was a bit buggered, so a new Koyo was put in there (I love have multiple sets of new ones in the shop). The trunion bearings were also replaced with new ones. At the same time, I rebuilt the lockout hubs to make sure they were engaging and disengaging correctly.

Anyway, it now seems to drive straight on gravel, but not on pavement when in 4WD. Still pulls to the right quite a bit (5-10 pounds maybe?). It is much worse when you're on the throttle, but it's still noticeable with the truck coasting.

The only other issue is that I need to rebuild the brake calipers, as they are nasty rusty ugly, plus on the right side at least one of the pistons is binding (presumably from rust), so might that have something to do with it?

Anything I'm missing?

Dan
 

KLF

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You do know you're not supposed to be in 4WD on dry pavement, right? Binds up the drivetrain.

Ya, I'd fix the calipers, see if that helps. Might as well do the vented rotor upgrade, get rid of those solid rotors.
 

DanS HJ-45

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You do know you're not supposed to be in 4WD on dry pavement, right? Binds up the drivetrain.

Ya, I'd fix the calipers, see if that helps. Might as well do the vented rotor upgrade, get rid of those solid rotors.
How can driving straight on pavement bind up the drivetrain (unless tires are worn to severely undersize)?

This pull is totally different than driveline binding by the feel of it. It's nothing like driving the 40, the faux-lux, the '95 pickup, or any of the Power Wagons on the same stretch of road--none of them "bind up" or pull to the side.

Before this it pulled even on icy roads, and that's obviously a pretty big concern. So getting all of the pull out of it just seems to be a really good idea to me. Especially since it's not mine, it's the chica's. We're going to stick with the solid rotors for the time being I think, unless it is cheaper for me to use the "V6" IFS calipers I have lying around and just buy new rotors. No real need for an upgrade here, just to have safe, reliable brakes.

Dan
 

2ndGenToyotaFan

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Are you sure the front and rear diffs are geared the same? The bottom line is, the brakes and wheel bearings are all working the same in 2wd, or 4wd.... If it's pulling only in 4wd, then it's got to be something diff/axle related....
 
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How can driving straight on pavement bind up the drivetrain (unless tires are worn to severely undersize)?


Dan

Oh God....


Dan, you just can't do it. Get over it.

AWDs have center diffs. Diffs allow for a "differentiation" of SHAFT rotations.

(Standard TCs are not really transfer cases, they are more like PTOs.)


The PTO in your 4WD is not allowing front to back differentiation.

You don't know it, but unless the tires are EXACTLY the same OD, and the rotations are EXACTLY the same, it will create binding.


PTO 4WDs are a no-no on the street, or hard packed, tractable surfaces. And don't give me that, "when I go rock crawling" stuff either (MUD). The rocks are usually dirt/ dust covered and think about how much you're using it. It's not a lot of the service life, whereas DDing in 4WD would be.


Can't do it, so get over it. Sorry.


EDIT: Jeep has a AWD, 4WD and 2WD TC (So do the new 4Runners, but I doubt you can get any for a 5speed) that sits behind an (IIRC) Asin transmission. I created thread on if it could be swapped in, but it gained no interest. I wish I could do it. I love AWD in some instances, but truth be told it's not needed 99% of the time. That's why I don't do 80s. 15mpg highway gets REAL old, REAL quick.
 
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2ndGenToyotaFan

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Driving straight on pavement in 4wd will not cause pulling. I've done it, yes there is some binding, there's just too many variables for a straight line to work.
 

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If it's pulling only in 4wd, then it's got to be something diff/axle related....
Or tire size... 4runners of that era don't have a transfer case differential. My bet is one tire is larger than the others. Likely the spare tire is in use cos one of the others got a flat. Check tread depth carefully for all tires.
 
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Oh God....


Dan, you just can't do it. Get over it.

AWDs have center diffs. Diffs allow for a "differentiation" of SHAFT rotations.

(Standard TCs are not really transfer cases, they are more like PTOs.)


The PTO in your 4WD is not allowing front to back differentiation.
Hey dude. what are you smoking here??? center diff, PTO... this is an 85' toyota truck not a series 80 and up Land Cruiser yuppie wagon... There is NO CENTER DIFF.

To the guy with the truck. make sure all tires are the same size, the brake calipers are replaced and properly bleed and the diffs are the same ratio. There should be no pull if the truck tires, diff, brakes are right and the work to the birfs was done correctly.
 

DanS HJ-45

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The more I think about it, it's got to be either tires or brakes. The two front tires appear the same, but different than the two in the back (don't get me started--it's high on MY list of things that need to be done, but it may take a while before she can pony up the cash to replace all 4 tires).

But, with the whole front axle gone through, I can only see it being the brakes or tires. I'm tempted to pull the wheels off of the faux-lux to see if it makes any difference there (since I buy tires in sets of 5, I KNOW those have worn evenly). Or, I might put my HJ-45 up on blocks and give her those wheels and tires, as they are at least all the same (even if they are a pretty lame AT mall tire). They'd also be better wheels than the 80's-tacular ones the PO put on there, that also happen to be nearly impossible to get a socket into for the lugs...

Diff ratios being mismatched would cause a driveline bind, not a pull to one side though, correct? Or would the open diff in the front cause it to bind, but come across to me as a pull to the side? If that were the case, couldn't I put the transmission in neutral and have it still bind.pull? It only really does it when I'm pushing the throttle down.

Either way.... I'm off to try rebuilding the calipers tomorrow! no time to learn like the present. I'll post pictures or something one of these days.

Dan
 
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The more I think about it, it's got to be either tires or brakes. The two front tires appear the same, but different than the two in the back (don't get me started--it's high on MY list of things that need to be done, but it may take a while before she can pony up the cash to replace all 4 tires).
EDIT: All shafts lead to the TC. And in order for there not to be any bind, they must be the same. Having a slight under drive on the rear axle is gonna make bind.


Run a tape on the OD of all the tires. Also, you say the back two don't look the same. How are the rear axle and front axle rotations gonna be the EXACT same as they rotate again? :confused: The transfer case has NO WAY of allowing slip or differentiation, remember?

BIND! All four tires, on all 6 shafts MUST BE THE EXACT SAME in order to have no bind. Hard to do but possible in a straight line, but as soon as you turn, there go the exact rotations.

Other things that could effect O.D. Manufacturers defects, tread depth and air pressure.



Diff ratios being mismatched would cause a driveline bind, not a pull to one side though, correct? Or would the open diff in the front cause it to bind, but come across to me as a pull to the side? If that were the case, couldn't I put the transmission in neutral and have it still bind.pull? It only really does it when I'm pushing the throttle down.



Dan


Whatever the shortest way is for the bind to escape, is going to be it.

It's a buildup of pressure (since there is NO way for it to escape) until it dissipates through its weakest point. Whatever that is.


I'd say through the shortest shaft on the weakest axle.
 
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There is NO CENTER DIFF.

Something I had HOPED everyone in this tech would know. Thanks Sherlock.

Read the post again, only this time realize there was no AWD option for trucks of our vintage, if you want to know WHY 4WD will not work on a hard surface.


4WD is not, nor can it ever be, AWD. The two are completely different.

You can, in an emergency situation use 4WD on a road, but should be as soon as possible returned to hi 2.


If anyone doubts me, it's right there plain as day on the sun visor in your truck.

I'm just explaining to you why it won't work.


Want to see and feel gear bind?

Run down the road in your 5speed. Get down to about 40mph in 5th gear and floor it. You won't be able to, without force, get the lever to neutral without the use of the clutch.

It works two ways.

Find a hill. Put it in 3rd and compression brake down. You won't be able to, without force, get the lever to neutral without the use of the clutch.


The only way to move the lever is if there is NO pressure on the gears. With miss-matched tires and rotations your TC is doing the same thing in one of the two above situations. It must have a way to allow the differences in rotation in order NOT to bind. And a standard TC does not have a way to do that.
 
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leave the solid rotors on and up grade the booster to the 1 inch, if you want really good brakes.

second since it sounds like you looked it over.

1. caliper dragging, is the right one hotter then the left? you have to coast to a stop to check it.

2. measure the rear axle to the same spot on the frame and see if the rear axle is at an angle to the front.
Check the front axle the same way. make sure your measurements are right on.

change the front and rear tires from one side to the other.
check your spring bushings also.

that is all I can think of.
 

DanS HJ-45

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Well I still don't know what the fix is. Rebuilding the brakes didn't work. Putting on a set of 4 tires that have all worn uniformly didn't work.

But somehow the combination of those two things fixed it. I just took it for a little drive and it tracks straight all the time. Including in 4WD on pavement. :flipoff2:

Pics of the now blingy calipers when I get home from pizza!

Dan
 
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leave the solid rotors on and up grade the booster to the 1 inch, if you want really good brakes.
Dan,

Glad you got it fixed and apologies for the hijack. Missouriman, I have been contemplating installing this Marlin 1" master without changing to the front vented rotors:

Brake Master Cylinder | Marlin Crawler, Inc.

My concern has been that the brakes might not have enough travel due to the larger bore size. Have you done this upgrade with everything else more or less stock?
 
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Dan,

Glad you got it fixed and apologies for the hijack. Missouriman, I have been contemplating installing this Marlin 1" master without changing to the front vented rotors:

Brake Master Cylinder | Marlin Crawler, Inc.

My concern has been that the brakes might not have enough travel due to the larger bore size. Have you done this upgrade with everything else more or less stock?

Yes, running it on my wifes truck, her brakes are every bit as good as mine.
and she doesn't have to worry about different calipers or if we shear a knuckle off we can just grab one from the garage with out having to change the rotors out.
the vented seem to fade less on huge long down hills but I don't see that they are much better.

when I need new rotors again I will most likely go back to stock.
less parts and can inter change things between the two trucks.
and any junk yard will have the stock parts. but not the modified parts.

hope that makes sense.

edit.
I replaced her master and the later larger booster as well.
it is tight but fits, some bending of the stock lines to get them mounted.
when bolting it up push it up and away from the steering shaft as you tighten it down.
or it can contact the steering shaft.
 

DanS HJ-45

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So, just another quick update.

I ended up rebuilding or replacing everything in the brake system except the master cylinder.

1)Rebuilding calipers is easy and fun! I can't wait to do them for my 45 and Dad's 40 (not to mention when I SAS the faux-lux)
2)I hate rust
3)Even with a ruptured diaphragm in the booster, the truck with new brakes will stop better than you think.
4)I love junkyards. $60 for a used booster, sure beats NAPA or Toyota prices....
5)I love my HJ-45. It provided a few odds and ends that would have been expensive or time consuming to get. Wheels and Tires (check out the new ones I put on it!!! :eek:), lug nuts, and maybe a few other bits...
6)Silver/Grey caliper paint is awesome. It doesn't look blingy, but it fits a truck nicely.

With about 100 miles since all this was done, the truck drives like it's brand new! Tracks perfectly straight, stops with gusto (and straight too--as in: hands off the wheel straight), and all around clean steering. Wow!

When I get home: Timing Chain needs replaced, since we don't know if it's been done, probably water pump while I'm in there. Also will swap in a new (used) set of front springs, as these ones are crap. They are already an upward arch on flat ground. (They cost all of $40 at the junkyard, plus new bushings which are on the way...)

Dan
knuckle rebuilt 1.jpg
drums.jpg
45 wheels.jpg
 
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