gear ratio in axle. Want change to low gear to get faster

[Milwaukee]

Well i start drive on highway lot. It suck to stay 55 mph to keep rpm under 3,500 is get old for me.

I want change like example it have 4.10 but want drop to like 3.55 or 3.73.


Would it affect fuel mpg if I change gear too low? How much I could go low and able to get 65-70 mph with rpm at 3,500 rpm.

How can I identify what gear I have in my tracker?

It 94 geo tracker 4x4 5 speed

I don't use 4x4 on that anymore due bad hub lock out.

[95 Tracker]

3,500 rpm is really high for 55mph

i'm at around 28-29 hundred rpm for 55mph
3,500rpm for me is around 67mph
i don't know if tire size would change the rpm but i'm on the next size up from stock 215/75/r15

[Milwaukee]

Hey I could get cheap bigger tires.

What size tire it would fit in geo?

[rcherolis]

You want to change the outside diameter of the tire. That would be the number before the R 215/75R/15 would be about the max without a lift. Theb higher the number the taller the side wall. You give up lateral stability though as the sidewall has more flex as it get taller.

[Bex]

Although some here have 235/75/15, they also advise there might be rubbing at full extension of tire. I put on 225/75/15, runs great, although can feel a slight difference in cornering. Anyway, at 3500 I'm doing about 65mph.
(For pinheads, rather than gearheads, this site may calculate speedo difference with larger tire in an easier way to understand:
Tire Size Calculator - tire & wheel plus sizing


btw 3500 is not fast for the motor. its designed to run way faster.
they run at this point for 2 reasons

So, what would you cruise at? If you constantly keep engine above 3500 (even though gas mileage gets much worse...) would your engine wear out faster?

[SlimJim16v]

Found an online calculator that tells you any one of the following, just enter the three known figure, to get the missing one -

RPM
Tyre dia.
Speed
Diff ratio

Stegath Coachcraft: Rear End Ratio calculator

I think it assumes that the gear you're in is 1:1 which is 4th gear on Zuks.
I would also say GPS speed reading is a must.

Hopefully find out what mine is, hope it's not 4.3:1

[SlimJim16v]

Originally Posted by kick-fix

really thousands of sites have calc. (lazy way really)


why use 4th gear, no one drives 60mph in 4th do they? well at least on the flat.

i gave the overall ratio in 5th , why not use it?
and why use a non 4wd site that dont have the tranny and xfr case included.
odd.

Thanks for the maths, didn't know it so looked for an easy calculator, the "lazy way"

I'm sure you know all this, but 4th gear is used as it's 1:1, so the diff sees engine RPM with no change, easier (lazier) way to work things out. I don't actually drive around in 4th all the time.

Found several sites that do include the XFR case ratios, but once again, it's easier (lazier) without, especially as high is 1:1 and nobody drives around in 4wd low on the road.

[ack]

Three points that I have:

1. Running at 3800-4000 PRM on a 1.6 is very doable! I have run at 3900-4000 for the better part of 400 miles a number of time without any engine problems. They are designed to do this.

2. Try this gear calculator:

Ack's Generic Gear Ratio/Speed Calulator

Just plug in all the gear ratios, the engine RPM and the tire diameter and poof! MPH at a given RPM. If you don't know your transmission/tcase/dif ratios, this document has most all of them:

Ack's FAQ: Your 4X4 Portal To All Things Suzuki/Geo

3. Brevity and clarity are signs of good communication skills.

I hope that this helps!

[SlimJim16v]

Thanks again for all the info on your site Ack, not seen this pdf.

I needed a calc to work out my final drive, as the info from Zuk says mine has a 4.3:1 final drive, so I want to check it and hope it's not.

[ack]

Reading your post, SlimJim16v, I noticed you are from London, UK.

I imagine that you are slightly ahead of us USAens in the Metric Useage department...

I wonder if ther is any interest in a metric gear calculator that spits out KPH instead of MPH...

Comments?

(sorry for the HiJack...)