35's on gladiator...regear?

[PuddleJumper]

Cool that your opinion is the only one that matters.

Anyway, i'll full of it too apparently. 6MT, 37lb steel wheels, 63lb Kenda Klever 315/70r17s. i see 6th gear just fine above 65 for cruising. a double downshift into 4th is required for any passing situation, but that's not crazy for a double overdrive manual.

naw man if it can't pull and pass in 8th gear at 60mph. You gotta get the deepest tallest gearset you can in there. cus 3500 rpm @ 60mph 8th outta do it. ?

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[Hootbro]

I am with the others. MT tires and if you did not adjust for the tire size, you have a lot of rolling resistance to not be seeing 8th gear on 4:10 gearing.

 

[Secretariat]

Ok..tire and wheel 109 lbs on the corner...I have positive 34 offset...so they tucked under nicely...I am not driving around like a wild ass with my tires in the on coming lane...I'm 64 y.o.....adjusting speedometer should have nothing to do with this....and oh by the way it is only off by 2 mph...so any other thoughts?

 

[Lunentucker]

Ok..tire and wheel 109 lbs on the corner...I have positive 34 offset...so they tucked under nicely...I am not driving around like a wild ass with my tires in the on coming lane...I'm 64 y.o.....adjusting speedometer should have nothing to do with this....and oh by the way it is only off by 2 mph...so any other thoughts?

The computer needs to be updated with the correct tire size.

 

[Rahkmalla]

adjusting speedometer should have nothing to do with this

it absolutely does since you have an automatic. Your transmission doesn't know when to shift because it's seeing loads it's not expecting at the speeds it thinks you are traveling at.

I have a manual, so this doesn't affect me, but it absolutely will for you.

and oh by the way it is only off by 2 mph

That's not how tire size adjustments work, you'll be a percentage off, so that 2mph will be variable. coming from a rubicon to 35s (34.5 assumed) you'll be 5.5% off, so traveling 20 when speedo reads 19, and 80 when speedo reads 76

 

[ShrimpHappens]

adjusting speedometer should have nothing to do with this

But it does.

Using a programmer to tell the computer you've changed tire sizes affects speedometer accuracy, odometer accuracy, AND transmission programming.

It was a noticeable difference for me just going from 31's to 33's. 100% necessary when going to 35's.

 

[Idlethunder]

Ok..tire and wheel 109 lbs on the corner...I have positive 34 offset...so they tucked under nicely...I am not driving around like a wild ass with my tires in the on coming lane...I'm 64 y.o.....adjusting speedometer should have nothing to do with this....and oh by the way it is only off by 2 mph...so any other thoughts?

I just came from light 35s to heavy 37" tires. My current setup is Baja Boss AT 37x12.50r17 on Fuel Kicker 17x9 -12mm offset wheels, approx 110 pounds per corner. After updating the computer to the proper size for the 37s, my Rubicon with 4.10 drives and shifts better than it did with both the stock 33s and the 35s. Updating the computer for the proper size tires is more about the trans shifting correctly than keeping the speed accurate. I don't see 8th as often now as I did with either of the smaller tires but on level ground I'm in 8th at 65mph. At some point I'll regear because I tow, but for now, mine does fine and I average around 15 mpg with 50/50 in town and highway driving.

 

[InvertedLogic]

You need to reprogram the tire size for the shift points to adjust.

I run 35x11.50x17s all over CO and don't feel the need to regear and see 8th often on even up at attitude.

 

[Gladiatorx2]

You need to reprogram the tire size for the shift points to adjust.

I run 35x11.50x17s all over CO and don't feel the need to regear and see 8th often on even up at attitude.

I have 37's with the same brand of wheels on 4.10 gears and for over 5,000 miles I have averaged over 29 mpg. It was programmed for the tire change.

 

[Gladiatorx2]

I have 37's with the same brand of wheels on 4.10 gears and for over 5,000 miles I have averaged over 29 mpg. It was programmed for the tire change.

 

[Gladiatorx2]

I am at 19.8 right now. That is an older picture. The current true pencil is 19.1 but shows 19.8

 

[EgulAye]

I can chime in my agreement with most; I've got a 2020 Rubicon running the stock wheels and gearing. I put 35x11.50 Nitto Ridge Grappler's on last fall, programmed the new tire size with my Tazer, and have had no issues finding 8th gear. If I drive carefully I can get up to 19mpg average but I'm usually in the high 17's and low 18's.

 

[49Gramps]

I'm running 285/70 18 (34") Ridge Grapplers on 18 x 8" +30 wheels with 4.56 gears. Highway mileage is generally 18-19, town 15-16 mpg. Automatic trans, cruises at 65 at about 2000 rpm in 8th gear.

 

[Great Offender]

Just curious if anyone has had their tire shop adjust the new size. I only ask because I have NEVER been able to get the cables out of the security module and I have had tried too many times to count and several attempts have had a good grip and pressure on the clip. Doesn't even pretend to move. I'm a stubborn bastard and this one has me beat.

Wires are frayed (second owner) so someone else got crazy in there before me and I'm afraid to get too rough.

 

[DailyMoparGuy]

OP, definitely check the tire size calibration and go from there. I don’t know where you live, but it’s pretty hilly where I am and I regularly see 8th gear on the highway (central Massachusetts). That includes trips to New Hampshire’s White Mountains, Pennsylvania, Vermont, etc.

That being said, yea it downshifts to 5th on steep grades or 7th sometimes for slight grades. I wouldn’t expect anything less for any vehicle going up steep grades (except EVs obviously). If I set cruise at 75 mph, the transmission does it’s magic up grades and it stays at 75 mph with no issues (no bogging from a speed standpoint).

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