Lower gearing to stop down shifting?

[techno1154]

My 2001 XJ has had three sets of gears, the stock 3.55s, 4.10s and 4.56s.
I ran 10.50 X 31s, with a AW4 for several years, first with 3.55s and then 4.10s.
The 3.55s did not do well going up grades, which is much of the time in the West, with the engine spinning too slow in overdrive.
Re-gearing, I found that 4.10s and 31"s were perfect for both highway driving and off roading. Driving became more enjoyable and my mileage didn't change.
If you can afford it, you will not regret it.

Over the years there have been many discussions here on about the perfect gearing to tire size combination. Many of us have differing opinions as to what is perfect. I must agree though that what is perfect for some is absolutely impossible to work with for others. Opinions here is as different and varied as,....well snowflakes.

I agree 100% with the comment of Lazyxj. I ran 31" BFG's on 3.55 gears. Using cruise control on the highway with about 300lbs of cargo and just myself the AW4 would do a gear hunt on every incline. The fuel consumption would also go down the tubes if I selected 3rd gear manually. Going to 4.10 gears was the perfect(in my opinion) solution. Yes, there difference between my XJ and yours, namely,...mine have an AW4 and yours 5 speed manual. However, for highway driving both transmissions have just about the same ratio in the top gear/over drive. The differences are so miniscule they are not worth mentioning.

In conclusion, I would say choose your tire size, your driving terrain be it crawling or highway and gear accordingly. My XJ give best fuel economy between 2300 and 2800 RPM which is between 60 and 75 MPH on the highway.

 

[IslanderOffRoad]

People, you are confusing the guy, the dude is only running 31s with a 5speed. I have a 93 with a 5 speed and 33s. I swapped in 3.55 axles from an automatic and the gearing is perfect. GPS shows my speedo reading 52.5 when I'm actually going 50. Close enough!

I have a 5 speed and I disagree.

 

[Sub Zero]

Over the years there have been many discussions here on about the perfect gearing to tire size combination. Many of us have differing opinions as to what is perfect. I must agree though that what is perfect for some is absolutely impossible to work with for others. Opinions here is as different and varied as,....well snowflakes.

I agree 100% with the comment of Lazyxj. I ran 31" BFG's on 3.55 gears. Using cruise control on the highway with about 300lbs of cargo and just myself the AW4 would do a gear hunt on every incline. The fuel consumption would also go down the tubes if I selected 3rd gear manually. Going to 4.10 gears was the perfect(in my opinion) solution. Yes, there difference between my XJ and yours, namely,...mine have an AW4 and yours 5 speed manual. However, for highway driving both transmissions have just about the same ratio in the top gear/over drive. The differences are so miniscule they are not worth mentioning.

In conclusion, I would say choose your tire size, your driving terrain be it crawling or highway and gear accordingly. My XJ give best fuel economy between 2300 and 2800 RPM which is between 60 and 75 MPH on the highway.

Yeah, 4.10s seem like they're perfect after more research. I used a few RPM calculators and with my 31s and 4.10 gears it would put me at 2,666 at 75mph and 2,844 at 80mph. I figure as long as I stay under 3k it's not too bad

 

[josh9mile]

I have a 5 speed and I disagree.

well the math doesnt lie.

 

[IslanderOffRoad]

well the math doesnt lie.

It doesn't, however with the terrain he's dealing with he will be much happier with 4.10's

 

[dan1977p]

I run 80mph at 3k and the motor just purrs. That's on 33's with 4.88's so the gears will need to be different but just letting you know 3k isn't a huge deal.

 

[Sub Zero]

I run 80mph at 3k and the motor just purrs. That's on 33's with 4.88's so the gears will need to be different but just letting you know 3k isn't a huge deal.

I know 3k isn't a super big deal, just trying to stay under 3k for the small gain in fuel economy. I should be right in the power too, so I shouldn't have to downshift from 5th anymore

 

[Sub Zero]

Here's some pics just to confirm that I have a d30hp and a Chrysler 8.25, am I right?

 

[IslanderOffRoad]

Yup that's an 8.25

Fairly sure it's an hp30 as well though that angle is a bit tough to confirm

 

[Sub Zero]

I'll try to snap a pic from the front and the other side this evening

 

[Sub Zero]

Here's a better angle

 

[iluv83vettes]

That's high pinion

 

[Sub Zero]

That's what I thought, just wanted to confirm

 

[Crawler]

Dude...

Just start gathering what you need to do the 4.10 swap with locker(s).
I did that on a 5-speed '93 on 31s that I drove all over the back roads of Arizona, southern California,
southern & eastern Nevada, Utah, and even northern Baja as far south as the observatory.

You will be very happy with that combination in all but the most demanding aspects.

:cheers:

 

[Sub Zero]

Dude...

Just start gathering what you need to do the 4.10 swap with locker(s).
I did that on a 5-speed '93 on 31s that I drove all over the back roads of Arizona, southern California,
southern & eastern Nevada, Utah, and even northern Baja as far south as the observatory.

You will be very happy with that combination in all but the most demanding aspects.

:cheers:

That's the plan

 

[Crawler]

I'm moving (early retiring) to the Benson/Sierra Vista area this Summer.
See ya' out around the Pinalenos sometime... :sunshine:

 

[Sub Zero]

I drive through Benson all the time, hopefully my xj will be looking good by then

 

[DieselSJ]

Yeah, 4.10s seem like they're perfect after more research. I used a few RPM calculators and with my 31s and 4.10 gears it would put me at 2,666 at 75mph and 2,844 at 80mph. I figure as long as I stay under 3k it's not too bad

That would be for a 1:1 final drive, which is not OD. Multiply the gear ratio by .75 to get the equivalent ratio. A 4.10 with a AW4 in overdrive would relate to about a 3.08 on those charts.

My old '88 had 4.10 with 31's and I thought it was spot on for something that was a dual purpose rig.

 

[Sub Zero]

Yeah, the overdrive on the ax-15 is 0.79. I calculated accordingly