High RPMs after gear swap: Is this normal?

[B Martin]

I recently had a 4” lift put on my 2016 Jeep, with 35” tires. Today I had a gear swap done going from a 3.21 to 4.56. My RPMs run high. I have a 6 speed, manual transmission. When I get to about 65, 70 mph my RPMs are pushing 3000. Is this normal? Before I added the lift, in 6th gear, even at 75-80, my RPMs were about 2700. Any info/advice helpful.

 

[franka548]

Did you have the speedometer recalibrated for the tire diameter and gear ratio? I would check on the calibration first, someone might have plugged in incorrect numbers, then go from there.
Frank

 

[B Martin]

I’m not aware of any calibration of the speedometer. Who can do this? Any mechanic? Thank you for the response. Much appreciated.

 

[B Martin]

Did you have the speedometer recalibrated for the tire diameter and gear ratio? I would check on the calibration first, someone might have plugged in incorrect numbers, then go from there.
Frank

Also, will it hurt anything for the RPMs to run this high? I’m assuming that if it’s just a matter of recalibration, I’m hoping not.

 

[Chris]

3000 RPMs isn't going to hurt a thing. You could run it at 6000 RPMs and it wouldn't hurt a thing. The rev limiter is there for a reason, to prevent you from blowing up the engine.

The J-Scan app will allow you to recalibrate the speedometer from your smart phone very, very easily. I would do this before anything else.

You'll need one of these along with the J-Scan app to connect to your OBDII port from your phone:

https://www.amazon.com/gp/product/B06XGB4873/?tag=jkforum-20

 

[franka548]

There are a number of different ways to reset your speedometer, from plug in tuners to phone apps with blue tooth adapter plugged onto your obdII port. Do a search on here for jscan and which blue tooth adapter, and you can do it yourself along with setting your tpms along with many other things.
Frank

 

[B Martin]

Thanks!! I’ll check into getting off of these! I appreciate your help.

 

[B Martin]

3000 RPMs isn't going to hurt a thing. You could run it at 6000 RPMs and it wouldn't hurt a thing. The rev limiter is there for a reason, to prevent you from blowing up the engine.

The J-Scan app will allow you to recalibrate the speedometer from your smart phone very, very easily. I would do this before anything else.

You'll need one of these along with the J-Scan app to connect to your OBDII port from your phone:

https://www.amazon.com/gp/product/B06XGB4873/?tag=jkforum-20

Thank you very much. I have 2 posts now suggesting this. I’ll check into one of these and give it a try.

 

[Largehit71]

Use J scan to turn off that pesky TPMS too.

 

[Nebfarmer]

I recently had a 4” lift put on my 2016 Jeep, with 35” tires. Today I had a gear swap done going from a 3.21 to 4.56. My RPMs run high. I have a 6 speed, manual transmission. When I get to about 65, 70 mph my RPMs are pushing 3000. Is this normal? Before I added the lift, in 6th gear, even at 75-80, my RPMs were about 2700. Any info/advice helpful.

That's what putting in that 4.66 does More RPMs @ lower speed what did you expect?

 

[B Martin]

That's what putting in that 4.66 does More RPMs @ lower speed what did you expect?

I don’t have higher RPMs at lower speeds, only at higher speeds. 70+

 

[B Martin]

I don’t have higher RPMs at lower speeds, only at higher speeds. 70+

and I didn’t know what to expect, that’s why I’m asking if it’s normal, or something I should be concerned about. Thanks

 

[BLACKJKU]

Have you verified your speedometer is reading correctly?

 

[B Martin]

Have you verified your speedometer is reading correctly?

No, but I’m going to try and get that done Monday. A few people I work with suggested getting it put on a dyno.

 

[dcooper45]

A dyno is not what you need, just do the scan app as mentioned prior. Sounds like everything is fine and normal, just a good idea to make sure your speedometer is correct.

 

[B Martin]

A dyno is not what you need, just do the scan app as mentioned prior. Sounds like everything is fine and normal, just a good idea to make sure your speedometer is correct.

Ok, will do. Thank you!

 

[Ozzie rubi]

You change diff gears and of cause the engine will rev higher , that's why you did it to get the engine back in it's power range because of the larger diameter tyres .

 

[72c10]

I bet you were really going about 75-80mph at that range. Can you let me know what your RPMs are at 80mph when you get it recalibrated?

I just went from 3.21 to 4.56 on 33s and thinking of going 35s.

 

[72c10]

Any updates? Did you get your speedo/rpms dialed in?

 

[Jermbob28]

I use a jet performance programmer, scanner and tuner. Can do a lot of things including adjust the speedometer. Most likely is just the calibration because your RPMs at 70 for the 3.6l with Manuel with 4:56 gears is supposed to be right around 2443.