I recently bought a 91 4 runner, and im trying to figure out if the rearend has been changed or modified. making it simple, the door jamb sticker says: g294 so it is an 8" rearend with 4.10 4 pinion open differential. If i am driving in a circle or doing a u turn in 2 wheel drive, it acts like an open differential, if i put it in 4 high or 4 low, it locks up the rearend and the inside tire spins faster than the ground under it. If i try to drive it somewhere a front and a rear tire drop, and dont touch the ground it spins the wheels not touching, and goes nowhere. any ideas, im new to 4wheeling myself but have knowledge in dragracing and such, so differentials are something i understand. From what i have read, it seems that i have a detroit truetrack, the characteristics seem to fit, but the seller said the car was purchased new by his aunt, and was stock. any help here would be appreciated, im going nuts to try to figure out what kind of diff it has. thanks guys.

 

It sounds like they are open.

If you are driving it on a hard or non-slippery surface in 4wd it will bind and act funky when not going in a straight line.

 

x2 ^^^

 

well okay. but why would my inside tire spin at the same speed as the outside tire in four wheel drive but not two wheel? an open diff doesnt care if its in two or four the driveLine spins the same. when im in four wheel 'something is making the rearerd act differentLy. i noticed what appeared to be a vaccuum Line coming from the rearend but i Suppose it could be a sensor or something. Let me know what you guys know, id Like to learn what can cause that, even if it is an open diff.

 

the line you see could be the diff breather or the abs plug. now for how it is acting how you are tellin us it sounds normal if its an open diff that is how it will act when you have it in 4x4 you feel the front diff pull so it makes it seem like there is something wrong

 

no i get that, but the u turn in 4 wheel, the rearend is completeLy locked up. open diff i dont think will do that. ive read that detroit truetracks will act Like a Locker at times the wheels have even traction. if i do a u turn on the pavement in 4 wheel the inside tire skips or squeals cause its Going faster than the ground, the same speed as the outside tire..

 

and yeah i think the Line is probably the abs sensor. my 8.8 in my fairlane came from an explorer and it had one. i was thinking it might be some vacuum line part of the add system.

 

Just a thought, maybe in 4WD the inside rear is actually trying to keep up with the fronts.

 

Huh ??


How in the world is the inside rear going to try and keep up with the fronts in a standard open diff ?


Fred

 

This is correct


It's not the tire in the air that's keeping up, it's the tire on the ground that's keeping up


The only reason this is so is because there is no differential action between the front and rear drive-line when in 4wd; the fron drive shaft and the rear drive shaft are going to turn at the same speed. With both of the front tires firmly planted on the ground, they are going to pull the truck forwad. If you've only got one rear tire on the ground, that one tire is just going to roll along at the same speed that the front tires are pulling the truck, but at the same rate the rear drive line is still trying to turn those rear tires, so the tire in the air is still going to spin, but not just spin wildly out of control as you would think a normal open diff would, because the rest of the drive-line is keeping it from doing so.

Try the same stunt in just 2wd, without the front drive-line engauged, and that tire in the air is just going to spin like crazy.


it's kinda hard to explain, but if you understand, you know what I'm talking about, lol


If you had a locking/locked diff, you'd definately know it, lol. You would either have to engauge it if you had a selectable, or you'd probably hear or feel it engauging or working, but regardless you definately notice it just in daily driving, on wet roads and such.

 

The fronts have to travel farther than the rears, so they have to slip somewhere.

Don't use 4wd on the road.

To tell for sure if you have an open diff, just jack up the rear end and spin a tire. If the other spins backwards then its open, if it goes the same way, then locker.

 

I got a locker in mine, and when I lift the rear and spin 1 tire, the other does nothing, you just hear the click, click, click.... of the lockright.

 

since you said that the tire that is IN the air gets all the power, you have open diff...

as far as it appearing to lock up when in 4wd, i'm not sure what to tell you. Try doing it in a gravel parking lot and see if it does it then.

if you jack up the rear end leaving ONE tire on the ground and ONE in the air, then try to spin it... if it spins, your open... it if cant spin your locked. thats the much easier way of telling.

 

well that would make sense that its open since it spins when lifted off the ground. but if I u turn on gravel it does what I was saying before and totally spins the inside tire. if its on pavement it does the same. I appreciate everyone's help on this. it seems confusing. im almost ready to believe its open but I just can't figure out how the diff seems to lockup while doing a turn. I figure that would be virtually impossible for an open diff.

 

I wouldn't mind having one of these mystical magical locking diffs... might come in handy

 

well that would make sense that its open since it spins when lifted off the ground. but if I u turn on gravel it does what I was saying before and totally spins the inside tire. if its on pavement it does the same. I appreciate everyone's help on this. it seems confusing. im almost ready to believe its open but I just can't figure out how the diff seems to lockup while doing a turn. I figure that would be virtually impossible for an open diff.

 

If you're in 2WD when this is happening it's because the weight is being transferred to the outside of the vehicle giving the inside wheel less traction.

 

no its not that. im not trying to burn out n a circle. i understand how an open diff behaves in an instance like that. but even when going slow inside tire goes the same speed as the outside. pavement or gravel. (yes i know it shouldnt be done on pavement)

 

sorry guys. reading my own posts, ive not been very clear about whats happening.