Interested in swapping from my 4.56 gears to something larger. I'm running 32" tires on a 3zve with an AT in a 1994 pickup, so under-performing is an under-statement. It is brutal on the mpg's. With the stock 225 75/R15's, it runs great and gets over 16 mpg and the speedometer is dead on with the gps speed. As is, no power and gets about 8 mpg. The theoretical gear size that would provide the same performance as stock with the 32" tires would be a 5.16, which obviously is not available.

2 Questions for those knowledgeable on the subject: 1. Which gear would be best for this setup, the 4.88 or 5.29? (5.16 is about right in the middle of the two gears) I do about 50/50 highway and offroad based on running time, so more highway mileage than offroad; and 2. This is probably outside of my experience level and time availability, so what could I expect to pay a shop for this swap?

Thanks,

 

If a shop provides all the parts and R&Rs the 3rds as well as does the gear setting, I'd think you are looking at $2000 give or take a few hundred.

I'm so glad that I can do this kind of work myself.

As to the best gear ratio, I don't know. Hard to believe that mileage could go from 16 to 8 with just that tire change. Pretty extreme.

I run 4.56s on very near a 32 inch tire on my manual tranny 3vz Runner and I get 17mpg under the worst conditions and near 20mpg highway if I hold to 60mph.

 

Would love to have that mileage with 32's. I agree, never would've thought it would make that big of a difference in my mileage. The automatic tranny struggles with it. Almost never in overdrive. I don't think the transmission is slipping or anything I think it just can't handle the gearing. I believe most manual transmission trucks come stock with the 4.29 gears, so the 4.56 is probably perfect for your setup. Also, with a manual tranny the driver has much more control over when to shift. When on a mild grade and try to maintain 40 mph, my transmission shifts down and I will be running 4000 rpm just to maintain speed. With the 225 75/R15's it just cruises, only downshifting on the steepest grades.

I don't know, maybe I should just sell the truck to someone interested in keeping the stock size tires, and buy myself one with the manual tranny. Other than this problem, the truck is in great shape (not the body necessarily, but who cares about that). The engine was completely rebuilt, bearings, steering, suspension all tight, awesome ac, even the dang cruise control and power windows still work.

 

I thought that most automatic V6 4Runners came with 4.88s from factory, maybe I'm wrong there. Can you tell us your axle code just to verify? G144 is 4.88, I don't know what 4.56 is but google can tell us. I'd get at least 4.88s if you don't already have them.

 

Form the door, the axle code is G254, Transmission code is A340H

 

Ok, G254 is 4.56 according to google, so I guess your truck came that way. Your factory tire size is roughly 28" tire, other reading I did suggest that trucks with 31" tires, automatic, V6, and possibly tow package got the 4.88s. One option you have is to find factory 4.88s from junkyard and swap those complete 3rds in, that would be probably the cheapest option, however 4.88 thirds would be used, of questionable condition, and are unique ring gears with an offset in the housing that cannot be re-geared if that matters to you. If you are going to have someone set you up with different gears, check ZUK at www.gearinstalls.com, he is the best.

 

seems to me that you have another issue that you need to look into besides gears.
I am getting 14-15 combined MPG with 35's and 5.29 gears, seems hard to believe that 32" tires would have impacted your mpg that much.
are you measuring your distance traveled with a GPS so you know for sure that you are calculating gas mileage correctly?

 

Yes, distance traveled, fuel used, etc. I've reconfirmed many times. I get right at 7.1 mpg per the odometer and with the tire size conversion it comes to 8.0 mpg based on distance traveled. I've also checked this versus a 95 mile highway trip based on both gps distance traveled and the converted odometer distance. I use the truck about 10-12 weekends per year and this has been a steady problem for about 6 years. I've replaced or checked everything I could think of or was recommended to me on this site. The one thing I hadn't done was put stock size tires on it. I did that recently and the truck drove wonderful and got over 16 mpg. The transmission only shifted down from overdrive on the steepest of grades, just like my daily driver. I believe the fuel consumption is nothing more than the difference in the rpm's I'm turning with the 32" tires as oppose to the 28.3" tires. The transmission lives in 2nd or 3rd gear with the 32's.

 

OK, that is pretty weird than...

 

I have 4.56 gears and been thinking to swap them for 4.88 or larger as well. But after some research and labor quotes, I'm considering that the cost is not much cheaper than installing a MC dual transfer case. Wouldn't that give way more lower gearing options with 4.56 than swapping the actual gears?

 

Only when you are using low range. Doesn't change anything when running high speed road conditions.

 

True. I'm after more low end torque. In Hi-2wd only way to change rpm would be larger gears.

OP, 32" with 4.56 gears should only affect rpm by -3% . If you are trying to fix the low mpg, I don't think that's where the problem is. Something else is quite off in the engine.
https://www.roundforge.com/articles/...t-your-toyota/

 

OP have you thrown the stock pizza cutters on recently and had your mileage go up to normal?

 

No the dual cases will help you off road with the second split for extra low gears. But not really intended to lower your on road gearing. That is typically done with differential gearing.

 

i had an 88 runner for several years with 4.30 gears and 35s and although it was way underpowered i got much better mileage than you.. id say you have another issue as well. i had the 3.0 with automatic as well. i did have some lce headers on it but that wouldn't make the changes your noticing.

 

Yes, it went up to almost 17 mpg.

 

I felt like there was another issue also, but I get almost 17mpg with the stock 225/75 R15's. Could it be transmission issues?

 

Are there any stored codes?

 

No codes.

 

You have pulled them or are just looking for the engine light? Often the ECU will store a code but you wont get a flash.

If you tried to pull them and they aren't any then I would start looking for vacuum leaks. Carb cleaner or starter fluid sprayed around vacuum lines while running. If the engine races at all you found one.

What is your timing set at?

Take a noid light and make sure all injectors are firing. Pull plug wires one at a time while running and see if you get one that does not affect it running.

What about fuel filter?

What do your plugs look like? Post pictures.