Topic: 31's and Gearing for a Trailer

[Oilsmoke]

I am saving for new gears next early spring.

Here are my thought.
After regearing I plan on a small camp trailer Like a 13' Scamp or I will make my old ATV trailer in a Hybrid Tear Drop  Benroy style.

So I'm thinking I need 4.88. I plan on using BFG 31x10.5x15 KM's. I don't drive over 65 Mph very offend and I still have 5th gear to use. Is this too much Gear for 31's? What do you guys think?

[VA_YJ]

Hey smoke,

4.56 gears will give you "same a stock" ratio with 31s.  I've always heard that the 4.56 is stronger than the 4.88 due to the larger pinion gear (more tooth engagement).

A few things to consider:  How much will the fully loaded trailer weigh? How often and how far will you pull the trailer? Will you be pulling the trailer up steep hills in the mountains?  If you get on a really steep hill, you can always use low range - a cable disconnect on the front axle might help in that situation if you want 2wd.

[jfrabat]

I am saving for new gears next early spring.

Here are my thought.
After regearing I plan on a small camp trailer Like a 13' Scamp or I will make my old ATV trailer in a Hybrid Tear Drop  Benroy style.

So I'm thinking I need 4.88. I plan on using BFG 31x10.5x15 KM's. I don't drive over 65 Mph very offend and I still have 5th gear to use. Is this too much Gear for 31's? What do you guys think?

I am running 4.88 with 31" Bridgeston tires (mine are street tires, so they are a tiny bit smaller than MT's) and I am fine.  At 70 mph, the Jeep is just a touch above 3K rpm's.  This setup allows you not to have to downshift on slight uphills at highway speed (I used to have to downshift to 4th before to get over the top).  So if you are planning on trailering, I recommend this setup.

Hey smoke,

4.56 gears will give you "same a stock" ratio with 31s.  I've always heard that the 4.56 is stronger than the 4.88 due to the larger pinion gear (more tooth engagement).

Just my 2 cents (not trying to offend anyone): regearing for 4.56 is a waste of money (it's jsut TOO close to 4.10 for it to be worth it).  Besides, stock does not give you the most torque.  True, you will probably loose some mpg with 4.88, but it will give you more torque.

Felipe

[Oilsmoke]

I am running 4.88 with 31" Bridgeston tires (mine are street tires, so they are a tiny bit smaller than MT's) and I am fine.  At 70 mph, the Jeep is just a touch above 3K rpm's. 

Felipe

Felipe Is this in 5th gear if so That's would be prefect.

Oilsmoke.

Oh  I will be in the Utah Mountians.  Pretty Steep in places.

[Bounty Hunter]

Go with 4.88, a little lower than what will put you in the stock powerband is nice.  4.10 to 4.56 isn't enough of a change to justify the cost and time.

As for the pinion size of the 4.88, it's a 4cyl on 31" tires, it is very unlikely to be the weak link.  4.88 pinion breakage is rare.

[jfrabat]

Felipe Is this in 5th gear if so That's would be prefect.

Oilsmoke.

Oh  I will be in the Utah Mountians.  Pretty Steep in places.

Well, I am talking about SLIGHT uphills...  I DO live in Miami after all (read: FLAT!), but yes, it WILL go uphill at highway speeds without having to downshift.  And it WILL go against headwind in 5th without having to drop to 4th.  I dont think it will go up Utah hills in 5th, but it will give you more torque.

Go with 4.88, a little lower than what will put you in the stock powerband is nice.  4.10 to 4.56 isn't enough of a change to justify the cost and time.

As for the pinion size of the 4.88, it's a 4cyl on 31" tires, it is very unlikely to be the weak link.  4.88 pinion breakage is rare.

Totally agree!

[VA_YJ]

I agree with the 4.88 setup in the Utah mountains.  Make sure you get the right speedo gear to ensure that your computer is getting the correct VSS reading.  Not only does this make your speedo correct, but can affect performance.

[jfrabat]

I agree with the 4.88 setup in the Utah mountains.  Make sure you get the right speedo gear to ensure that your computer is getting the correct VSS reading.  Not only does this make your speedo correct, but can affect performance.

Oh, yeah, that's a good point; you should need a 44T speedo gear, but that is not available unless you have it custom made.  I am using a 43T gear, and the speedo shows about 69 mph when I am doing 65.

By the way, with 4.88, the engine is doing about 2K at around 60 mph...

Felipe

[Oilsmoke]

Well One good thing about 4.88 is I lost the D35 and Have a Ford 8.8 taking the 4 cyl power most of the time.

I swapped out the stock Speed O gear when I switched to 31's  So I need a 43 tooth Is that the biggest Jeep brand gear they make?

Thx for input Guys 

[VA_YJ]

Here's a place that will custom cut speedo gears for Jeeps:

http://www.transmissioncenter.org/speedometer_gears_for_dodge_and_jeep.htm

The cheapest place to buy Jeep speedo gears is usually the dealer (hard to believe, huh?), where they sell for $12 - $13.

[DodgeMudder]

I used to tow a 13' Scotty behind my 4banger on 31" Uniroyal MT's, I never had an issue running through the PA mountains or running 65mph down the interstate, I just left it in fourth and downshifted more if needed, but then again after stripping the teeth off overdrive before I started towing I would never tow in overdrive anyway, the gear itself just isn't string enough for it.  Heck I now tow with a V-8 Dakota 5spd, and I won't tow with it in 5th because I don't feel it's a strong enough gear, if you read the owners manual there is very few 5/6 speed tranny's capable of towing in 5th gear.

Personally I would save the cash, slow down a little, and keep the stock gearing.

[Oilsmoke]

Mudder Thx for you piont of View, Never enter my mind about 5 th being weak.

I had a Banshee hill shooter and it was all about tranny gears and after I built up the motor I blow out 2nd gear. It was too week.

Hmm? now i am back where i started.

[Jeffy]

Mudder Thx for you piont of View, Never enter my mind about 5 th being weak.

I had a Banshee hill shooter and it was all about tranny gears and after I built up the motor I blow out 2nd gear. It was too week.

Hmm? now i am back where i started.

Yes, 5th is actually OD meaning it's not just another gear.  For towing you'll want to stay in 4th or less.

[Oilsmoke]

OK I have One Last Question.
With 4.88 and In 4th gear with 31's what RPM will i be at 60 MPH?
Thx Inadvance.

Oilsmoke

[jfrabat]

IIRC less than 3K in my case...  I'll check tomorrow when I go out.