Anyone went 4.88 yet?
- Thread starter JMG73072
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Jetboy
New member
I think it kinda depends on what your goal is. Do you want lower than stock gearing? 4.56 will be significantly lower gearing with 34's than stock. When your speedometer reads 75, your actual speed will only be 65mph. With 4.88 gears, when your speedometer reads 75, you'll actually be going 61mph. To maintain highway speed of 80mph - what my local highways are posted at - you'll be spinning 2800rpms. That's neither good nor bad, but your uncorrected speedometer will read just about 100mph to get to the speed limit, and if you drive 90mph like the flow of traffic, your speedometer will be up around 110mph. - and that means your engine and drivetrain through to the drive flange of the differential will be experiencing 110mph equivalent rotational speeds.
Just food for thought. IMO 4.10 gears would be ideal for 34's, but there are none available for the rear axle. A GX460 rear diff 3.909 would be just a hair off of returning to stock gearing. So 4.56 would be my next choice and I'd probably try to find clearance for 35's. For my use, I don't see any reason I'd ever go to 4.88's because I'd be running 38"+ tires and at that point I'd have different axles. OTOH if my 4runner was a dedicated trail rig - sure, I'll almost always go lower gears. My Land Cruiser has 5.29's and I don't think they are low enough at times.
And if you can afford it - a Lefty transfer case with a 4.7 gear set would be my first choice and keep stock gearing for highway use.
Just food for thought. IMO 4.10 gears would be ideal for 34's, but there are none available for the rear axle. A GX460 rear diff 3.909 would be just a hair off of returning to stock gearing. So 4.56 would be my next choice and I'd probably try to find clearance for 35's. For my use, I don't see any reason I'd ever go to 4.88's because I'd be running 38"+ tires and at that point I'd have different axles. OTOH if my 4runner was a dedicated trail rig - sure, I'll almost always go lower gears. My Land Cruiser has 5.29's and I don't think they are low enough at times.
And if you can afford it - a Lefty transfer case with a 4.7 gear set would be my first choice and keep stock gearing for highway use.
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JMG73072
New member
Jetboy-
I could maybe stuff a big 34 like a 34.4 but I think that's about all. Just constantly searches for a gear on the slightest of hills between 4th & 5th. The goal is to correct that, I do dd about 50-60miles a day 50/50 city/hwy. Fuel mileage is already 14ish so whatever on that front, I didn't buy this thing for its stellar economy. Some lower 1st gear in 4lo would be welcome too. Thanks for the thoughts.
Jeremy556
New member
Interestingly, the 5th gen speedometer and odometer readings come from the wheel sensors and not the sensor on the transmission, so regearing does not affect the speedo/odo readings, just tire size. This is the first vehicle I have re-geared that I didn't need a speedohealer.
wfo9
New member
The speedometer will be correct (besides tire size). It reads wheel speed.
Swarty
New member
A nice calculator.
Just so you can calc your revs, etc. free and super useful. GRIMMJEEPER is on the forum somewhere....
Also when comparing a 4runner to a Landcruiser remember that the older Landcruisers transfer case is 1:2 or 1:2.3 depending on year while the 5th gen 4runner is 1:2.57. This allows you to use higher gearing.just an FYI. If you do the math a 4.56 in a 4runner is about equivalent to a 5.29 in a landcruiser. Well sort of. Once you look at the transmission it gets a bit more fuzzy.
http://www.grimmjeeper.com/gears.html
Just so you can calc your revs, etc. free and super useful. GRIMMJEEPER is on the forum somewhere....
Also when comparing a 4runner to a Landcruiser remember that the older Landcruisers transfer case is 1:2 or 1:2.3 depending on year while the 5th gen 4runner is 1:2.57. This allows you to use higher gearing.just an FYI. If you do the math a 4.56 in a 4runner is about equivalent to a 5.29 in a landcruiser. Well sort of. Once you look at the transmission it gets a bit more fuzzy.
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Jetboy
New member
I learn something new every day here. I like the idea. So... how would you re-calibrate it? Are folks using an electronic inline interceptor/signal generator? I imagine you could get custom machined tone rings, but that's a bit more work to install.
Does anyone know how a 4.7 transfer case gear set would impact all the other vehicle speed sensitive functions - like crawl control, KDSS operation, rear locker automatic disengage, etc? The engine rpms wouldn't match up with what the cpu is expecting based on speed readings.
Jeremy556
New member
The speedo error isn't bad up to 34" tire so I don't think anyone has bothered with it.
I haven't seen anyone here that has changed transfer case gearing, but maybe someone on the FJC forums has on a 2010+.
bimrunner
New member
[MENTION=89026]JMG73072[/MENTION] [MENTION=118321]Jetboy[/MENTION] Do the gears and see if it bothers you. According to GPS, my speedo is only off 7-8% all due to tire size. It feels great crawling with the new gears and the stock t-case. I wouldn't mess with it unless you discover you want more out of your rig. I like the 4.56 with 34s myself but only you know how you want it to feel. I think unless you planned to run 35s at the smallest, you will be happier with the 4.56 gears. The pinion head starts getting thin in the 4.88. It might be fine but a lot of FCJ guys were having problems with 4.88. I honestly think 4.56 is the sweet spot for the stock housings.
Jeremy556
New member
Doing some reading in the FSM and looking at the real time data lists on the engine ecu and skid control ecus.
"The skid control ECU converts signals from the speed sensor into 4-pulse signals and sends them to the combination meter. After these signals are converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, they are then transmitted to the power management control ECU. The power management control ECU determines the vehicle speed based on the frequencies of these pulse signals."
The engine ecu has SPD (NT) and SPD (SP2) speed inputs from the transmission, NT being turbine shaft speed and SP2 is output shaft speed
"The skid control ECU converts signals from the speed sensor into 4-pulse signals and sends them to the combination meter. After these signals are converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, they are then transmitted to the power management control ECU. The power management control ECU determines the vehicle speed based on the frequencies of these pulse signals."
The engine ecu has SPD (NT) and SPD (SP2) speed inputs from the transmission, NT being turbine shaft speed and SP2 is output shaft speed
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Jeremy556
New member
Cutting.
For 35s I think you'll need body lift, drop bracket/spindle, or long travel and extended bump stops.
txbonds
Senior Member
Ah. I see. Too much for mine now since its a daily driver first. Thanks.
Jetboy
New member
I'm on stock side tires. Probably won't modify my T4R for a while as I have an FJ40 trail rig with a lot more of everything - tires, suspension, 1,000lbs lighter, etc. But, I keep dreaming of a more comfortable 4runner that's maybe 75% as capable.
My future dream mod set would be maybe 37's with custom a-arms that relocate the front spindle forward 2" and maybe outward 1-2" with longer travel. Once you go past the basics, you'll need to start cutting. And then you're going past a point of no return. And at some point you usually find that having a dedicated trail rig is cheaper than trying to do both daily driving and more difficult offroading with the same vehicle. I really like the 4runner as is and even stock it's quite capable.
My future dream mod set would be maybe 37's with custom a-arms that relocate the front spindle forward 2" and maybe outward 1-2" with longer travel. Once you go past the basics, you'll need to start cutting. And then you're going past a point of no return. And at some point you usually find that having a dedicated trail rig is cheaper than trying to do both daily driving and more difficult offroading with the same vehicle. I really like the 4runner as is and even stock it's quite capable.
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wfo9
New member
My truck just has 33s at the moment, but the spedo is 100% accurate according to GPS @ 80mph...
I purchased my truck used and it had 33s on it. The previous owner had all the work done at Toyota of Dallas, which is trdparts4u. So I assume they might have done something with the ECU to correct the slight error, or maybe the error with 33s is so small that it cannot be measured....
To the OP. I think 4.56 is a better way to go. I really like mine and would not go back to 3.73 for anything, but I do wish I could shift one more gear on the hwy on flat ground. I don't have a stock muffler, so I get a little resonance at about 70mph now. I find it is best at 65 or 75. 70 is noisy, but I think most of that is my exhaust.... I lost about 1.5mpg going to 4.56. I basically get about 16 on the hwy now and 15 around town.
I purchased my truck used and it had 33s on it. The previous owner had all the work done at Toyota of Dallas, which is trdparts4u. So I assume they might have done something with the ECU to correct the slight error, or maybe the error with 33s is so small that it cannot be measured....
To the OP. I think 4.56 is a better way to go. I really like mine and would not go back to 3.73 for anything, but I do wish I could shift one more gear on the hwy on flat ground. I don't have a stock muffler, so I get a little resonance at about 70mph now. I find it is best at 65 or 75. 70 is noisy, but I think most of that is my exhaust.... I lost about 1.5mpg going to 4.56. I basically get about 16 on the hwy now and 15 around town.
JMG73072
New member
It's not much cutting, a little on the bumper cover up front and a good bmc and you too can run 34's. With the MT rear bump stops I can still stuff it all the way to the stops and probably clear each side by maybe as much as 3/8". Mine is my DD too fwiw. I am leaning towards the 4.56's. Thanks to all who have chimed in so far.
txbonds
Senior Member
Good to know. Thanks.
I have brand new 33s right now but on the next tire change down the road I might look at 34s. I'll have a shrockworks front bumper shortly so I'd only need to do the BMC up front I guess.
