Even though you may be running at the same RPM, remember, you have a lower ratio in the rear end, which means more torque multiplication. So, at that given RPM, you have to put a little less throttle into it to maintain speed, as air resistance is the biggest factor to maintaining speed, and that pretty much stays constant.

There are some other factors, like the fact that larger tires weigh more. But, that affects acceleration more than maintaining a constant RPM, as the rotation inertia of the larger tire is higher.

Trust me on this one, if you can trust someone on a board in the age of the internet. I drive a rig with this exact setup, and I don't want to go up, I don't want to go down. 5.29's with the auto gearing is just right, it accelerates OK (it is the 3.slow) and once that steep OD kicks in, it purrs down the freeway at 65.

I found both my diffs on Craigslist, with lockers. I paid $325 for the front diff, 5.29's, Lockright. It has Genuine gears, kind of cheap gears, but it is the front. I paid $425 for a complete rear V6 axle assy with 5.29 Yukon gears and a Lockright. I looked for 18 months. So, if you have time, start searching the boards and Craigslist, the deals do pop up.

 

I have been looking forever it seems and I need it pretty much within the next month. I dont need front and back or a locker just a rear will do perfectly fine for now.

School is starting back up which means I have to leave my full time job and try and find a part time job in this ty economy.With school starting back up I will drive roughly 400 miles a week and with the mpg I am getting I just can't do that.However I can't justify purchasing 1000 dollar gear set already made I will be calling around tomorrow and getting some price quotes on installing gears.I have looked on craigslist for awhile It would be extremely helpful if you could look in your region for me aswell.

 

Take a look at this chart, gives you rpm's you will be turning at 65mph with different gears and tire size. I have a 4runner 3.0 31" tires and 4:56 gears, on the hwy i get just over 20mpg. I'm planning on going to 33" w/o a gear swap. IMHO I think this will be a nice compromise. And try the boneyard for the differentials, save a few bucks and will be a POC to change in an afternoon.

http://www.4lo.com/calc/geartable.htm

 

I hear ya, but I'm running 31's with a 22RE and an auto. Should I take the gearing up one step further????

 

Just a few thoughts...

92 pickup 22re 5spd 4.10 on 31X10.5 she does well and I'm not complaining about her. I can run the highways and still have enough to play in the mud and haul wood as well.

95 4runner 3.0 auto 4.88 33X12.5 A bit sluggish, I think it's due to the fact that she needs some work and the tranny in not the best. Going to keep the gearing will do 5spd swap in a year or two. Does well on the trails though.

 

For 33" tires and 5.29's, this chart says 3501 RPM's, assuming a 1:1 gear ratio. Given the Automatic's deep overdrive, .705:1, he would be running 2470 RPM at 65 mph, which is actually a little low. My 33's don't measure exactly 33", and with the tire bulge, a little less. I spin at about 2550 at 65. Right in the "good mileage" range.

The OD in the auto is just too damn high.

 

My OD runs at 0.688 on my 31's, and I have a 22RE. Should I go to 4.88's???

 

well I found a guy who said he would install them for 150 a pop.He is a Toyota guru supposedly and builds all kinds of toyota machines.Im pretty sure Im gonna go with him he sounded really legit and knew exactly what I was talking about.He even went as far as making sure they were the right gears for me asking about my trans, and tire size.


Now I am about to purchase gears,do you have to get a master install kit?

 

Man, I'm confused!

My axle code is G252 (supposed to be 4.56 gearing for an AT with 31's), but the door sill sticker only lists 225/15's. I thought those came with 4.30s???

 

my truck has the stock gears and i run 33x12.50 i get around fine but i think my 4 banger could use some more power so i called the local 4x4 center and they told me that 4.88s would bring me almost dead back to stock feel and driving condition and would improve my offroad ability. i was mostly lookin for gas mileage though.

 

Well if you have the stock 4.10 then yes the 4.88's will make a bit of difference. She will not have to work as hard turning all that rubber.

 

It would put you slightly over stock. Your speedo would read a bit fast.

 

I would believe the door sticker for the ratio, mine still has the listing for small tires also. But by speedo,tach and tire size. Mine works out correctly to match the sticker. my axle code is G254, 4.56 4 pinion.

 

I'm actually thinking my sticker might be wrong. When cruising next to a Civic with those BIG speedo readouts, I'm about 5-6 mph slow on my speedometer. When I bought the truck two years ago, it had the 225's, but also had aftermarket rims, so I didn't know if a PO had gone down in size from 31's. With 0.68 OD on my auto, I'm thinking I'm rolling around on 31's and 4.30 gears.

Tough to say. I don't want to crack it open to "count splines" to verify, but I don't want to spend $$ on 4.88's if I'm already close at 4.56. If I were coming up from 4.30's, that to me would be enough difference to be worth it.

Crystal ball, anyone??

 

Better question: Can someone with a 4.56/31" combo tell me what rpm they're running at a given speed???

I'd like to compare.

 

What spped do ya want? I'll check it on the way home tonite. I'll check it in 4th since I have a stick and that will eliminate the O.D. difference between us.

 

60 and/or 70 maybe??

Thanks!

 

If you don't trust the sticker on the door, you can get a good idea by jacking the rear tires off the ground, marking the driveshaft and tire with a piece of chalk and counting how many times the driveshaft spins for one rotation of a tire.

This will give you a much better idea what ratio you have than comparing RPMs at a given speed.

 

Will that be accurate enough to tell the difference between 4.30s and 4.56s?

 

Far more accurate than using RPMs. If the driveshaft spins 4 1/4 times its 4.30. If is spins 4 1/2 its 4.56. 4 3/4 = 4.88.