New KM3 Tires and 4.88 Re-Gear: Pics, Charts, and Video w/ In-Cabin Sound

[Gear Up]

I recently swapped out the tires on my 2016 Trail edition from Cooper AT3 275/70 to BF Goodrich KM3 33x12.5. I also had a re-gear done at the same time from the OEM to 4.88. This thread is to share info about the new setup.

The work was scheduled for two days at the shop, but they were down one employee so it took three and still needs a body mount chop. These are wide tires with rubbing. They are mounted on Fuel Vector wheels with a -12 offset. I am looking forward to an off-road test and some rock crawling after the chop! :rockon:

Pics:

New vs. Old - The AT3 looks taller, but it's just the perspective.

The new gears are awesome! Shifting is so much smoother than before. What about the specs? I captured a bit of data on a ride around town and on the interstate. Data capture was done with an OBDLink LX reader and the Torque app.

This chart shows the engine RPM and speed for a wide range. I cut out the top and bottom ends of both RPM and torque figures. The torque levels for the data are between 14.360 and 39.518 lb/ft.

And this chart displays the difference from GPS measured speed and reported speed from the OBD.

How is the noise? It's definitely louder and has a noticeable whine. The audio for this video was captured with an Olympus LS-14 digital recorder positioned on top of a couple of towels on the passenger seat. For a reference point, I start it with the radio on a sports-talk station and volume at 25 of the OEM head unit.


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Happy to answer any questions.


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[Dave 41079]

Looks good. I'm really happy with my KM3s, and I've put them through some pretty righteous abuse between Turkey Bay and AOP. The 4.88s must be awesome offroad with the 33s, how are they on the interstate? What's your RPM at 70-80? I tried looking on your graph but couldn't really get it accurately.

 

[Tejas]

I am having a hard time picking up on any gear whine in that clip but you can definitely notice the roar of the tires which is to be expected.

I'll be interested to hear your thoughts once you've done a road trip as well as how they perform off-road.

 

[mteolus]

Some guy on YouTube went with 5.29 on the gearing as some were saying 4.88 isn't enough, but that's probably with a 6 inch lift and a lot of other weight on his Taco. I think he said the gas mileage was a little better even with higher RPM because with stock gearing even with lower RPM the gas pedal was down further.

https://www.youtube.com/watch?v=3auo58-kXaQ

A pic of your rig with the 12.5 inch wide tires would be cool.

What was the cost?

 

[beachtaco]

The 4.88s must be awesome offroad with the 33s, how are they on the interstate? What's your RPM at 70-80? I tried looking on your graph but couldn't really get it accurately.

What made you decided on the 4.88 versus 4.56 or higher? 4.88 is great for offroading and if you have a heavy T4R. But I would imagine mileage would suffer at highway speeds. I'm guessing you're around 2500 rpm at 70.

Some guy on YouTube went with 5.29 on the gearing as some were saying 4.88 isn't enough, but that's probably with a 6 inch lift and a lot of other weight on his Taco. I think he said the gas mileage was a little better even with higher RPM because with stock gearing even with lower RPM the gas pedal was down further.

I remember watching this video. Definitely worth watching but IIRC the tech said that the newer 3.5L loved to rev.

 

[Bumbo]

He might be in-between gears with a 33… it might just be user preference at that point but with a 32.1” tire the 4.56 would have been perfect for me.

 

[Gear Up]

What's your RPM at 70-80? I tried looking on your graph but couldn't really get it accurately.

These are at GPS recorded speeds:

• 55 MPH: ~ 2053
• 65 MPH: ~ 2439
• 70 MPH: ~ 2800

Some guy on YouTube went with 5.29 on the gearing as some were saying 4.88 isn't enough, but that's probably with a 6 inch lift and a lot of other weight on his Taco. I think he said the gas mileage was a little better even with higher RPM because with stock gearing even with lower RPM the gas pedal was down further.

A pic of your rig with the 12.5 inch wide tires would be cool.

What was the cost?

I'll get a picture and the costs from the receipt posted later.

What made you decided on the 4.88 versus 4.56 or higher? 4.88 is great for offroading and if you have a heavy T4R. But I would imagine mileage would suffer at highway speeds.

I went with the 4.88 because I do very little highway driving and have a lot of weight on the truck with Shrockworks front and rear, winch, swing-out tire carrier, sliders, skids, etc. I think the 5.29 gearing is too fragile. Also, if (when...) I do bump up to 35s, no need to re-re-gear.

 

[Dave 41079]

These are at GPS recorded speeds:

• 55 MPH: ~ 2053
• 65 MPH: ~ 2439
• 70 MPH: ~ 2800

I'll get a picture and the costs from the receipt posted later.





I went with the 4.88 because I do very little highway driving and have a lot of weight on the truck with Shrockworks front and rear, winch, swing-out tire carrier, sliders, skids, etc. I think the 5.29 gearing is too fragile. Also, if (when...) I do bump up to 35s, no need to re-re-gear.

My next set of tires will be 35s, and I'm trying to decide between 4.56s and 4.88s for gears. I still do a lot of highway driving, so that plays a factor for me. I had 4.56s with 35s on my Tacoma, and that felt pretty good. I've been wary of 4.88s because of the weaker pinion, but have a buddy that's been wheeling pretty hard on them that's starting to convince me. We also don't play around...pretty much everyone I wheel with has some kind of body damage, including myself with 7200 miles on my 18. Right now my biggest gripe is how low and forward the KDSS skid sits. It is really hindering me off road.

 

[Gear Up]

A couple more pictures:

And here is the cost info:

• Nitro 4.88 gear package: $1,445
• Wheels: $210 ea.
• Tires: $290 ea.
• Regear labor: $500

 

[beachtaco]

These are at GPS recorded speeds:

• 55 MPH: ~ 2053
• 65 MPH: ~ 2439
• 70 MPH: ~ 2800

I went with the 4.88 because I do very little highway driving and have a lot of weight on the truck with Shrockworks front and rear, winch, swing-out tire carrier, sliders, skids, etc. I think the 5.29 gearing is too fragile. Also, if (when...) I do bump up to 35s, no need to re-re-gear.

Makes sense. I wish I could say I do little highway driving. BTW, your 4r looks great!

 

[Dave 41079]

A couple more pictures:

And here is the cost info:

• Nitro 4.88 gear package: $1,445
• Wheels: $210 ea.
• Tires: $290 ea.
• Regear labor: $500

Looks fantastic, prices seem fair too. Any plans for skids? Ever do any wheeling in the area?

 

[Gear Up]

... Any plans for skids? Ever do any wheeling in the area?

I have full skids, I just took them off for the work and left them off until the diff fluid gets changed in two weeks.


I go out at Windrock and Tellico. Looking into a trip in Kentucky at Daniel Boone.

 

[Dave 41079]

I have full skids, I just took them off for the work and left them off until the diff fluid gets changed in two weeks.


I go out at Windrock and Tellico. Looking into a trip in Kentucky at Daniel Boone.

My IFS skid for my KDSS really limits me. It was really pissing me off last weekend at AOP. Just did some Daniel Boone/Black Mountain/KAT about a month ago. Great time.

 

[Gear Up]

Update:


Had the body mount chop and diff fluid change yesterday. The fluid looked great and there were just a few shavings on the plug magnets. One more change in about 500 miles and I'll probably fill with Redline lightweight shockproof.


I also had the ToyTech Superflex HD coils installed in the rear. Got the rake back.


After the first full tank of gas, mileage on the vehicle computer was 15.0; manual calculation was 15.0418. This is a mix of city / highway with mostly city. Highway driving seems to yield about 17-18 MPG.

 

[rochmpr]

My next set of tires will be 35s, and I'm trying to decide between 4.56s and 4.88s for gears. I still do a lot of highway driving, so that plays a factor for me. I had 4.56s with 35s on my Tacoma, and that felt pretty good. I've been wary of 4.88s because of the weaker pinion, but have a buddy that's been wheeling pretty hard on them that's starting to convince me. We also don't play around...pretty much everyone I wheel with has some kind of body damage, including myself with 7200 miles on my 18. Right now my biggest gripe is how low and forward the KDSS skid sits. It is really hindering me off road.

If you plan on going 35's, go with the 4.88. I went to 4.56 and 285/75's and this was a great combo. Earlier this year, I went to 315/70's and noticed more shifting pulling hills. Wishing I had 4.88's now.

Sent from my SM-G965U using Tapatalk

 

[Dave 41079]

If you plan on going 35's, go with the 4.88. I went to 4.56 and 285/75's and this was a great combo. Earlier this year, I went to 315/70's and noticed more shifting pulling hills. Wishing I had 4.88's now.

Sent from my SM-G965U using Tapatalk

Thanks for the info. Did you notice a big difference going from 33s to 35s as far as approach angle is concerned?