4:88.1 from 4:10.1 Why not?

Maybe the speedo gets info from the driveshaft? That would mean a gear change will throw things way off.

 

I have no idea.
I've heard that the v6 and 4cyl get their speedo reading from different areas. Idk how true that is

 

Numbah 57, or anyone else.

Can you do me a favour and go to the calculator I linked to and punch in your numbers? See what it says your rpms should be at 70 mph?
I hate to spend a bunch of money on this and not get what I am expecting.
If the calculator does not match your numbers then I might email the person who host the calc and see if something is wrong.
Really appreciate it.

http://www.grimmjeeper.com/gears.html

 

I got a 2013 reg cab 4x4 with auto. I switched to 255/75/17s on FJ steelies and it is off by about 1-2 mph. In my honest opinion, that's not enough for a gear change.

 

Tried that calculator thingy.

It said with my 4.88 gears and 255/85-16 tires I am doing 50mph at 2000 rpm in 5th gear.
I'll grab my GPS and test that on my way to work tomorrow morning and let you know what happens. And give you more of my mph/rpm numbers.

 

My speedometer is dead nuts right now with the tire size I am running too.
I am doing the gear change for pulling a trailer.
The head scratcher for me is why some people are reporting 3k rpm at 70mph with 33 inch tires and 488 gears. According to the calculator that I am referencing, I will be doing 2534 rpm at 70mph with my desired setup.

The numbers from the calculator are not matching the reports I am hearing and before I dump cash into the gears I want to be sure.

I appreciate the input everyone.

 

I know my speedo claims 70ish at 3k but gps says I'm going way slower.

I'll get you some gps mph numbers at 2k 2,500k and 3k tomorrow morning.

 

Just did a quick test in town.
30mph on the speedo = 28 via GPS

I'll get higher speed numbers shortly

 

Speedo...GPS
20...16
30...28
40...34
50...43
60...50
70...60
80...68-70 (had a hard time with this one, our highest speed limit here on Maui is 55 so I was dodging other vehicles and reading speedo and GPS)

RPM at true GPS 70mph was just around 3k
I usually cruise at 2k RPM, in 5th gear that's about 45-50 GPS mph

 

Those numbers are from my 2009 a/c 2.7 with G2 4.88 gears and BFG 255/85-16 km2's

 

Good info. Thanks for taking the time to do this. It is appreciated.

 

Welcome man

 

The auto trans v6 and I think 4 banger as well with ABS uses the front wheel sensors and some kinda skid control computer to get the trucks speed. The v6 and 4 banger manual trans 2wd uses a speed sensor on the trans and the 4wd models use a speed sensor on the tcase.

Now I don't know the actual answer to this but the different placements of speed sensors could be the difference of why some trucks speedo's are way off and some are dead on.

My truck is a 2.7 manual 4wd. When I put 285/75/16 on stock 4.10s my speedo was dead on at 40 and only off by 1 mph at 70. When I put in the 4.88s with the same tires, my speedo was 14 off at 70 (I don't remember what it was at 40). Then with 315/75/16 and 4.88s it was off 2mph at 40 and 7mph at 70.

Also I don't know if everyone is comparing apples to apples because a 5speed manual 2.7 has different gears and gear ratios then 4 speed auto 2.7.

 

Mine is a manual

 

Anyway to correct the speedo after gear and tore changes?

 

Thanks for the above info.
I have auto and he has a manual. From further research, I think that is why the numbers I think I will get and what other peoples numbers are so different.

Speedometer reading is something else that I will have to deal with separately.

I have base 4x4 with auto. So my speed sensor should be in the transfer case. I looked last night and did not see it.
I am hoping that it is, AND a few threads I have come across talk of changing the gear of that sensor to correct the speeds. I hope that is the case for me.

 

I hope that is the same for me. But yours in manual, mine is auto. I think that makes a difference.

 

Trucks getting the gears installed in the next two days. Will know for sure what the rpms will be by this weekend. Cant wait.

 

are you sure .........

 

Why? Why did toyota not ship these with 488 gears?

Anyone who has a 4 banger auto 4x4 should run out and do this now.
Best investment yet. As a added bonus, the speedo was not effected. Still right on the money with 32 inch tires.
70mph I am right around 2600 rpm.
Win.