lectric80

Ok, I've been searching all night trying to find some pics or anything to go off of, but I'm now cross eyed and not really finding exactly what I need to see.

Vehicle is my 94 4Runner 3.0

Here's the deal, yesterday morning I was on my normal commute home when I ran into a freak storm that dumped around an inch of hail on the roads. While the majority of vehicles were wrecking because they failed to slow down, I slowed down and engaged 4x4. The indicator on the dash lit up almost instantly, and the truck immediately started pulling to the left. Since I was sliding around a bit I left it in and just fought the pull. When I got clear of the area that where the hail was piled up, I pushed the shifter back to 2 high and waited around 30-45 seconds before the light on the dash went out. As soon as it did (the ADD unlocked) the pull to the left stopped. About a half mile later I hit another patch and followed the same process, and again it pulled hard left and took an unusually long time to unlock. I also felt a bit of vibration, but my guess is with 251k on the clock it is probably due for some new CV axles up front.

So the questions are, does anyone have any pictures or ideas on where to look to see if I have a bad solenoid or if the ADD sleeve is sticking? Seems odd to engage so fast but take a very long time to disengage. I did slow down a bit by letting off the gas but it didn't make a difference. There was also a noticeable clunk when it finally did unlock. Also, where exactly is the system locking/unlocking from? I know there are the two solenoids on the passenger fender, but where is the actual locking mechanism?

Next up, what would cause a hard pull to the left? I'm thinking spider gears or differential issues, but I've never actually dealt with this ADD system, so maybe there is something I'm not thinking of?

I'm in the process of getting my garage organized so I can pull it in for some minor stuff, and wanted to take a look at this while I have a chance. Since I'm still a day or two from being ready to pull it in, I want to make sure I know what to look for. Thanks in advance for any help.

PS - Yes I know I could pull the manual hubs from my 90 and swap them on, but I don't want to tear apart my 90 yet and I may have a set I can grab from a buddy with an 88 Runner that is being scrapped. However, that may be a while and I want to deal with this before some trips we have planned.

scope103

The ADD is vacuum driven; you can see the actuator on the side of the front differential, with two vacuum lines. http://personal.utulsa.edu/~nathan-b...le/24disas.pdf

One pushes, one pulls, so asymmetric actuation (quick engage, slow release) CAN be due to one leaky vacuum line. Those two solenoids power the two vacuum lines.

A pull to one side or the other could be due to a lot of things, including a low tire. But the first thing I would do is just jack up the front end and spin the tires by hand. You made need to run the engine (to get vacuum) to test the shifting, so be sure the truck is well supported.

vasinvictor

iTrader: (3)

You can unhook the vacuum hose at each VSS and connect it to full engine vacuum manually. That way you can engage, and disengage the ADD system. You can see if it is still slow to disengage. At least might help you narrow down the problem.

Of course, you can hook the "engage" VSS to full engine vacuum, and add manual locking hubs, somewhat bypassing the ADD.

RJR

I'm not so sure you have an ADD problem. The behavior you describe is consistent with something binding up in the drive train when in 4wd. If the drive train is bound up, the ADD (and the transfer case) will have a hard time disengaging until a turn or something relieves the tension. It will engage right away, but be slow to disengage.

The hard pull to the left while in 4wd suggests something is not quite right in your front diff. I'd jack up the front end and rotate the wheels while in 2wd and then while in 4wd. They should turn freely and independently in 2wd, and opposite directions (but still fairly freely) when in 4wd.

How long have you had the vehicle? Are you absolutely sure the PO didn't install an automatic locker in the front? That'll give you behavior somewhat similar to what you're noticing.

lectric80

I thought of a locker, but the po didn't seem like he would have done anything like that. I say that because he was an elderly gentleman that had owned this Runner since new, and nothing was changed from stock really. He took great care of it, but I've only had it for 3 months. I will be checking it out, but right now I just want to go over the basics.

As far as binding in the drivetrain, you may be on to something. By the time I cleared the bad areas and disengaged the road was just a little wet, so maybe not enough slip to disengage. It didn't seem like I saw this problem the first time we ran it in 4 wheel drive, but we were on a dirt road that was fairly wet and had some slip. I'm going to do some testing on the actuator this weekend if I can find the time. Hoping to trade in my Durango, so that will chew up some time, but if I can get out to the garage tomorrow and get it cleared out the rest of the way, I should have time to pull it in and then I can test it at my leisure on Sat or Sun.

I will also put the front end up in the air and test the rotation to see if anything feels odd. Never had a 4x4 pull this way so I needed to verify it was something that could be cause by the ADD or if I need to look at the diff. Hopefully the gearing will be the same as my buddy's Runner if there is a problem with my diff.

Thanks for the tips everyone, I will report back with findings.