Can I drive my 4WD 4Runner in front wheel only?

Question

I recently had the misfortune of having my 1997 4Runner's rear diff lock up because of a leak and then no gear oil.

Unfortunately to add to that the frame and major members are very rusted/rotted. (I had a new rear end to put in, but would take A LOT of labor) to replace because nothing unbolts and bolts nicely.

So the question is - can I disable the rear end somehow, put it in 4WD and run it as a front wheel drive for awhile?

If so, what needs to be done?

I assume I need to disengage the rear axles from the mangled mess in the rear diff and also disconnect the driveshaft from the mangled mess.

Unfortunately, I think to do those two things requires as much work as swapping out the rear?

Answer 1

I would really question this approach for these reasons:

• The vehicle wasn't designed to run in 4WD full time. This may put extra strain on the frontend and wear out your front drivetrain and other components.
• The vehicle wasn't designed for the front-wheel drive to handle all of the force of moving the vehicle. Again, this may put extra strain on the frontend and prematurely wear out the vehicle.
• The transfer case generally spreads forces between front and rear drivetrains when in 4WD. It may not be designed for the front to handle 100% of the forces.

In short, if you're planning on scrapping the vehicle after this experiment, I'd be interested to hear how it goes. However, if you ever plan to repair the vehicle, you may discover that not only do you need a new rear end, but also you may discover you need a new frontend, as well as a transfer case and possibly other components.

Of course, just because the vehicle wasn't designed to be used in this manner doesn't mean it can't take the abuse.

Answer 2

I have my 1990 Toyota V6 3.0 extra cab running on the front two wheels only, I had the same thing happen. I was told, a friend of mine, drove a similar truck all the way from the desert into San Diego.

I've been driving the truck all morning, the deal is, I have a "High" 4x4 and a "Low" 4x4, right now I have it engaged to be High 4x4, I am not using the vehicle under any heavy strain. It SEEMS like my RPMs are running much lower, under RWD, at 60 to 80 mph, my RPMs are about 4k. Using ONLY the front two wheels, I'm averaging at 2.5k RPMs.

I'm going to keep driving it like this, I'll post here, and let you know if it can take it. This particular Toyota is the most popular 4WD where I live, so I'll find a few owners and ask them about it too.

Answer 3

It sounds like the vehicle is near the end of its life - I'd try removing the drive shaft from the transmission to the rear diff.

Note: I'm basing this advice on the Top Gear South America special, where they ended up turning a jeep into a front wheel drive vehicle. In theory, it should work, as long as there aren't a lot of fancy electronics & safety systems to get in the way.

Answer 4

I have a 1991 Chevy Tracker on which I will be isolating the rear differential. The reason is that the pinion bearings have had extreme lube starvation do to a axle seal leak which lead to catastrophic failure. The vehicle value doesn't compare to the price of a new/used rear end, or the time it would take to pull each component and inspect for wear/damage. Time and money replacing damaged parts and ensuring proper backlash and end play spec is met. I'll just isolate the rear end.

Now a few things to think about. The difference in radius between the front drive shaft and rear drive shaft results in a very different torque load. Plus even if you isolate the rear axle you would still need to keep lubrication in it. (If it moves you need lube) So make sure you don't have any axle seals leaking.

The transfer case might be chain driven meaning that is your torque limit. The chain will break before your front drive shaft will more than likely. Or it has a planetary rear set for the ranges - Which you won't know till you're on the side of the road. Transfer case heat will be higher given the 100% torque flow to the front differential. For in town use I don't see problem with it. Hard acceleration will be a big no,no. Change the transfer case and front diff lube if you decide to proceed.

Answer 5

I have seen an old series 3 Land-Rover used quite successfully in this fashion, however they are a lot more agricultural than a relatively modern Toyota and so are more capable of taking the abuse. A lot of it will be down to the design of the transfer box - in the case of the Land Rover it was a simple mechanical lock, which either drove just the rear axle, or both at the same speed. If the Toyota has a differential transfer box chances are it won't work at all, and if it does it may well ruin the transfer diff.

Disconnecting the rear propshaft should be fairly easy, as most 4x4s I've seen have traditional flanged UJs at either end of it. Removing the axle halfshafts may not be so easy though, depending on their design (in Land Rovers they slide out very easily, some other cars I have seen require a hydraulic press to separate them from the hubs).

You might find that you can remove the rear diff from the axle, which would make replacing it much easier, but from your description I am guessing that this isn't the case...

Like the other answers, I'm going to summarise with "yes, it is probably possible, but it is not recommended" - I suspect that the local authorities in your jurisdiction would probably take a dim view of it as well, especially given the state you suggest the rest of the vehicle is in!