1996 V6 Automatic with OME and 285/75 16 BFG AT's on factory 16" alloys. I've seen a significant decrease in performance. Around town driving is okay, but highway driving has suffered. Hills on the interstate cause the 4Runner to slow down.

What can I do?

 

Since you did not ask why you lost performance, I will leave that alone.

To truly get the performance back, you will need to re-gear or go with a SC'r. Both are expensive options. You can take the bite out of the power loss by doing the deckplate mod, ISR mod, exhaust, and headers.

We can help you get started on any of those mods. Just say the word!

 

If you want to get the performance back to stock then you need to re-gear.

EDIT: Christian beat me to it.

 

or just put the smaller tires back on

 

You need to regear.........then you can do lockers at the same time

 

By adding a larger diameter tire (285) you have made it harder for your drivetrain to generate and maintain momentum. The easiest way to alleviate this is to change the gear ratios in your front and rear differentials to a ratio that will more closely mimic the tire size/gear size relationship you had from the factory. If you measure the actual diameter of your stock tire size and the actual diameter of your new tire, then figure out the difference in a percentage. That is the approximate percentage you need to compensate for with new gears. If your stock tire was a 29" and the new size is 33" that is approx. a 14% difference. So if you have 4.10:1 gears stock you need to go to 4.56:1 gears (the closest match available) Some of us chose to go up to 4.88;1 or even 5.29:1 for even better performance off-road but the higher you go, the lower your gas mileage and max possible top speed will be. If you plan to spend most of your time on-road and want your stock acceleration back I would recommend 4.56:1 gears. If you plan to go off-road a lot, I would recommend 4.88:1 and since you need to open up the differentials to put the new gears in I would recommend installing locking differentials at the same time to avoid paying double labor later. If you have a factory locking differential in the rear already then adding an ARB air locker to the front would really be nice, but totally optional. If you don't already have a locker in the rear then I would highly recommend adding one to the rear at least and also front if money permits. You can tell if you have a factory locker by looking for a button on your dash that says "RR DIFF LOCK" it will be below your steering wheel to the left, beneath your instrument cluster. Use these links to decipher from your VIN#, what your factory gear ratio is. The second link will help you calculate what gears you should have judging from what gears you had and what tires you want to run etc.

http://www.brian894x4.com/Gearratiosanddiffs.html

http://www.4crawler.com/4x4/4LoCalc.shtml

Feel free to ask anything else!

-Sean

 

Very informative post Sean!
I've called a offroad mechanic and they quoted me around $1500 to do both, front and rear. I decided to keep everything stock for now. You might want to consider a cold air intake to get some of the power back.

 

That's a good idea, but I think he wheels his rig, so he may not want to become a Sears Shop Vac in his next stream crossing.

 

True, true. If you're in muddy/wet terrain, it wouldn't be advisable.

 

Best shot for increased power would be to S/C it and add headers.
Otherwise at least do the cheap deckplate mod and Amsoil filter.

 

You need to regear.

Most of the mods that have to do with better breathing, excluding maybe the SC, are going to allow the engine to maintain torque at higher rpms. The SC might build up lower end torque too, I don't have one so I can't speak from experience. In order to take advantage of a better breathing motor, lower gearing is best. It gives you the benefits of the lower gear, which equals higher acceleration, but at higher speeds.

Basically the motor is at a mechanical disadvantage. The correct fix is lower gearing to compensate for the larger tires. The other mods are great but more like bandaids when gears are the real fix. Lower gearing will allow the engine to work less hard and things like the tranny will last longer down the road. It'll wheel way better too.

Frank

 

Was that quote just for gears or was one or both lockers included?

Here is some sample pricing:

•$600 ARB rear locker
•$300 pair of Yukon 4.88:1 ring&pinion
•$200 pair of Yukon Master install kits
•$350 Installation charge per diff. w/o locker
•$450 Installation charge per diff. w/locker
(price quotes for labor from Rockstar Trux in San Jose. http://www.rockstartrux.com , price quotes for parts taken from google search)

That comes to $1,200 installed w/o a locker, and $1,900 installed with one ARB locker. You could use less expensive gears, a detroit locker and a less niche shop for quite a bit less money. A lot of shops will also give you a price break if you buy everything from them and have them do the installation. To do the job correctly, it isn't always cheap. I would rather have proper gears than a super charger, luckily I don't have to choose, 'cause I already have both!