225 70 R14 to 235 75 R15 issue

[Grubb44]

I’ve got a 97 2.3 5 speed. I decided to upgrade the tires and wheels a few years back to 235 75 R15 from the factory 225 70 R14. Now it seems like I’m always going between 4th and 5th gear on the highway at about 60-70 mph to keep up with traffic. I use to not drive with these on the interstate that much until a recent job change.

I hear of so many people making the swap but never hear of this issue. Is this normal? Has anyone else experienced this?

Drive train is all new with less the 30k on it. With the exception of the rear end. Currently it has an open 3.73 rear gear.

Any advice on this would be greatly appreciated. Weather I need to go with different tires? Or a different rear gear?

Thanks

 

[Dirtman]

The larger you go up in tire size the more top end speed you gain at the cost of loosing low end torque. So a re-gear to 4.10 ratio would help get your final drive ratio back close to what it was. Or go back to the tiny tires...

 

[Grubb44]

What if I went to a 3.55 or even a 3.45 rear gear? With these same tires, I know I would lose some low end torque, but would I gain top end speed for interstate driving?

 

[Dirtman]

You're already doing 70 in fourth gear, how much more speed do you need?

You should be in fifth gear by 55mph...

 

[Grubb44]

It’s difficult to stay at 70 in 5th gear. Constantly going between 4 gear and 5 gear. I hit a slight incline and it’s back to 4th gear to get back up to 70mph then finally into 5th.

 

[Dirtman]

Yes because the larger tires gave you a higher final drive ratio leaving you with no power in fifth gear. You need to lower the ratio not increase it. If you switch to 3.55 you most likely won't ever be able to get to fifth gear.

 

[Grubb44]

Ok. So lowering the ratio will in the end help get me where it should be in a “back to almost normal” driving state. Correct?

Any idea on what 4.10 gears came in? Model or year?

Thank you for your help BTW. I haven’t ever done rear end gearing so studying it all and learning now.

 

[pjtoledo]

verify your speedometer readings. with the increase in tire size you may be going faster than the speed-o reads.
how many RPMs at 70? (in 5th)

 

[Grubb44]

Will check this weekend or maybe after work tomorrow. Supposed to be nice so will be on the HD tomorrow.

I do remember my speedo is roughly 8-10mph fast now. Which makes no sense why if the Speedo reads 65 means I’m running 75 and have a hard time staying in 5th without dropping down to 4th. Does that make sense??

 

[Grubb44]

My bad 8-10 mph slow. I got backwards. Lol

Larger tires on a factory setup will cause the Speedo to show a slower then actual speed. Speed I am saying in the post is speed on the Speedo. If that makes any sense?

 

[Jay11]

I’ve got a 97 2.3 5 speed.

Been following this and now I have to ask...your 97 2.3 is a 4 gear, no? 5? I have a 98 XLT 2.4 autom. I always thought was a 4 gear after reading around that's it's a 4 gear tranny. Now am confused ?? Please someone clarify.

 

[Uncle Gump]

5 speed...

 

[Grubb44]

My 97 is a 5 speed manual. With 3.77 gears if I remember correctly. Currently I pulled the factory 14in wheels and factory spec tires off my 96 parts truck and am running on my 97 until I can save the money for a 4.11 gear for my 97 then put these tires back onto the truck.

 

[scotts90ranger]

as far as what to get an axle out of, a 4x4 2.3L Ranger will have 4.10's, to get the same thing look for a '93-97, a '90-92 will bolt in as well but be a little narrower.

For the record I shift a lot at speed on my Ranger wtih 35" tires and 5.13 gears and a turbo engine, but it never goes freeway speed and actually does better in 5th above 60mph

 

[Denisefwd93]

I'd get a complete rear axle assembly you can usually find them for less than $300 which oddly close...to the cost of tires.

your factory size to your current size is quite a difference I was actually surprised when I looked it up

225/70-R14 vs 235/75-R15 Tire Comparison - Tire Size Calculator | Tacoma World

235/75-R15 tires are 2.48 inches (62.9 mm) larger in diameter than 225/70-R14 tires and the speedometer difference is 8.6%

www.tacomaworld.com

I recently took 31s ones off my truck and had the original 235 size put on, HUGE difference in gas mileage!