Crawdad

Hi, I just bought a 1990 4Runner SR5 4wd, with the v6. It runs great, and everything on it seems solid, except one thing. While testing the 4wd today (to make sure it engaged) on dry pavement (again, I know this is bad - I was just checking to make sure it worked), just driving straight forward 10-20 feet, the drivetrain started to bind. When I say bind, I mean it would buck a little - not enough to keep it from moving. Now, I'm not incredibily familiar with 4wd, but this is my 3rd 4wd vehicle - I used to own a Dodge Durango, and I currently own a Dodge Ramcharger on 36" TSLs. The Durango didn't bind unless at full turning lock, but it had cushy electronically-compensated everything. The Ramcharger I wouldn't be able to feel if it bound anyway.

I took it offroad today and it ran fine, but I noticed that the front wheels seemed to be "slipping" while I was driving - that is, every 10-20 feet they would rotate and slip a little bit, especially while turning. There wasn't really enough of a straight shot to try it out just going forward. It was not noticeable by anything but the sound, though.

Does this sound like normal drivetrain stuff, or should I be checking to see if the differentials have been regeared? I know that you can check them by noting the number of times the wheels turn in relation to the driveshaft, but I'm not too familiar beyond that.

By the way, if it's of any consequence, the front tires are slightly more worn (1/4" or so) than the rear, and I haven't checked tire pressure, but the front tires need more air in them, they "pooch" more than the rear ones.

Matt16

You're on the right track, that is not normal. I can drive on rainy roads for a while in 4wd and it doesn't bind much. I don't do it often unless for some reason I feel I need to.

A quarter inch might be enough, enough but I doubt that a bit. You could eliminate that possibility by rotating one of the front tires to the back.

It is quite possible someone stupid got the wrong ratio if they picked the diff up from a wrecker.

Crawdad

Just checked tire pressures before I turn in for the night - pass side front is at 23ish PSI, the rest are in the neighborhood of 31psi. I didn't add any air yet, as my neighbors LOVE my compressor during the day, and I'm sure they'll love it twice as much at midnight.

Ran it in the grass for a few feet, didn't bind but it "clunked" when I shifted from 4h to 2hi.

Beginning to regret my purchase.

Edit: Is there any way to check the ratios from a stamp or casting on the housing/third members?

thook

There's an axle code on the VIN plate. Search here or google axle codes or Toyota axle codes for deciphering.

The tire slippage could be very normal. The vehicle has open differentials and so one tire will slip.....especially in a turn.

The clunk...I've heard other people report that as being normal on 5spd. I can tell you on my auto V6 there is none. Have you check the fluid levels and inspected the drivetrain for play at all? U-joint, connecting flanges, etc.

The binding, I don't know. I guess I'd have to hear it. Sorry. Neither of my Yota 4wds's (also have a 5spd, 4cyl) bind in a straight path, though.

dirtoyboy

IF someone swapped the diffs the VIN code is useless to determine what they are. Manual verification is the only way. The tires slipping and bucking on road sounds like 2 different ratios to me

Crawdad

What I figured. Aside from pulling the thirds out and counting the teeth on the ring gear, is there any other way to check the ratios front and rear? And assuming that they are mismatched, how difficult of a process is it to swap out the thirds? I'm more familiar with Dodge/Dana axles (familiar enough to know not to touch them, anyway).

dirtoyboy

easy peasy....jack the vehicle up and count the number of driveshaft rotations to wheel rotations.

Crawdad

Let's assume for a minute that the ratios are different and I know which ratio I want. It it possible to switch 3rds relatively easily, and how difficult is it going to be to find one?

dirtoyboy

Switching 3rds is easy! Probably a 3 to 4 beer job at most with common hand tools, no experience and a good service manual. Don't be scared if you have to do this at all

07sbock

Do you have a feeling when you bought your runner that it had been "molested"? On my old 95 4runner it only clunked into 4x4 if you had the engine revved. I dont know about the binding, check you cv shafts. Do you have the matinence history on it?

Crawdad

Ha, a little bit. I bought it from my father in law for next to nothing (under $1k), and I know that he recently had the rear diff replaced because it was noisy. Before that, I'm not sure who owned it, but I don't think that it has ever really been offroad. I'm going to ask my FIL about it tonight and see what info he has.

dirtoyboy

Let us know! I'm willing to bet thats the problem right there!

grant526

Don't assume the worst. The previous owner may not have rotated the tires often enough. So they are worn to different diameters, creating a gearing difference. Try rotating the tires to the other end. Usually the front end wants to be slightly higher geared [a hundreth (.01)or 2 (.02) higher] then the rear, so it pulls instead of getting pushed. Unevenly worn tires can create enough difference to break gears in the diff.
If your ratio's are different, you more-than-likely would have broken the higher ratio gears by running it as much as you have already.

Matt16

Bingo. Thirds are about $150 from a wrecker. It would be easy enough to pick up the wrong ratio.

Crawdad

I'm really hoping that this is the case - the previous owner has been working on Toyotas for many, many years, owns a 4runner and about 4 other Toyotas, so I don't think that the mixup was done by him. The rear suspension is way out of alignment, in that the tires are bald on the inside, and have 1/4" tread on the other side. The front tires are pretty evenly worn, but are nearly bald. And one of them is about 10psi lower than the other three. I'm going to air the tires up better tonight, and then swap them around and see what I can figure out.

It seems to me that if the gears were vastly different ratio, it wouldn't be able to really drive in 4wd. As it is, you can ride the thing down the road in 4hi, it just doesn't sound good. Or feel good.

If they ARE mismatched, I'm going to have fun trying to distinguish 4.1 turns of the wheel from 4.3 or 4.8

GrillmasterP

Yup - gut instinct says gear mismatch

Its pretty easy to tell- even the difference between 3.91, 4.10, 4.30

3.91 - just shy of 4 complete turns
4.10 - more than 4 but less than 4-1/4
4.30 - more than 4-1/4 but less than 4-1/2
4.56 - just over 4-1/2


I always physically, manually verify gear ratios via spin & count method or count.

Here are some stories.
Friend bought a used 4wd Tacoma - THe Orig owner (very meticulous) bought a complete assembled LSD rear diff from the toyota dealership- He gave them VIN # and even told them he had 4.10's.
Dealership sold him a 3.91 Diff.

Even one of the Yotatech sponsors worked out a deal on what he was told were 4.10 E-locker complete rear diff & axles. His Toyota Supplier Sent him about 30 4.30 complete e-locked rear axles.

Crawdad

Here's what I did:

Jacked up the rear end on one side - one tire up, one tire on pavement. Chalked the tire, chalked the pavement. Chalked diff housing, chalked driveshaft. Rotated tire 2 full revolutions. Driveshaft rotated just over 4.5 times. 4.56 gears?

Did the same for the front - rotated tire 2 times, driveshaft rotated just over 4 times. 4.10 gears?

Here is my question: I would LIKE to keep the 4.56 gears, since they are taller and I plan on lifting and going to 33"s. However, it seems to me like the front third member would be an absolute pain in the butt to replace. Also, I remember reading that the 1990 front diff is different (has ADD?) than others. Will I HAVE to replace it with a 1990 3rd?

Anyone have a 4.56 front third they wanna sell?

Also, since I wheeled it very briefly like this (15 minutes or so), and rolled it back and forth on the street a while, what are the odds I blew my transfer case up? Heh.

black diamond

drive shaft revolutions arn't always that accurate.. did u drain the front diff and check for metal? ring gear?

Crawdad

I haven't yet. The PO insists that when he replaced the chunk, he put 4.10s in it, because he matched the gears he bought off the door code. I'm inclined to believe him since he's been doing this for forever, and knows more about Toyotas than anyone I've ever met.

I guess the only way to check is to pull the dang chunk out of the rear and count the teeth on the ring gear.

Would low t-case fluid cause anything like this? I haven't checked yet, just throwing that in the mix.