GEARS

[JeepDreamer26]

Ok, i have never changed gearing in any of my vehicles before, so with that said here's my question. My mj is a 4cyl 5spd with 3.55s and 35inch tires yes it is a dog! So now that my money is getting to a point were i can start to work on my truck again it's time for gears. What i want to know or get suggestions on is should i go with 4.88s or 5.13s. i plan on staying with my current engine and tire size possibly 33s next time but anyways, so what would you guys suggest? Dose anyone have or had the same set up before? what did you go with? My truck is my daily and every so often gets id say light to medium wheeling. So should i go with 4.88s or 5.13s i want the truck to be able to still cruise at 60 at least but still want to be able to get out of 3rd gear and pull out on hills. Any feedback is appreciated like i previously stated ive never changed my gearing so i don't know how noticeable the gear change will be I'm hoping to get what I'm after with 4.88s cuz I'm thinking 5.13s will give me the power i need but will be a pain on the highway. Thanks again in advance! Hope to see club members at the up coming bantam jeep festival!!!!

[Smokeyyank]

Guessing you're sticking with stock axles? If so what rear are you running? First check out grimmjeeper gear calculator. It will give you a good idea of rpms at speed, etc. 5.13s will give you the most umph by at the sacrafice of highway speed. Also you're putting a lot of strain on the r&p with that deep of gear and tire size. It can be done though. Just no mashing the skinny pedal. Since you're missing 2 cylinders 5.13 s might be the best for 35 s. 33s 4.88 s would work great. 

[JeepDreamer26]

Front axle is a hp dana 30 the rear is the junk of all junks the dana 35, however bfore everyone starts telling me not to waste my money on the dana 35... I'm not! K i have a ford 8.8 posi out of a 01 explorer sport. No it is not in the truck yet but id like to regear b4 i put it in the truck that way i only have to do the front axle gearing while in the truck. Thanks for the feedback!

[Smokeyyank]

Good choice ditching the turdy5. I was just looking at the gear calc. With 5.13's you'll be around 2700rpm trying to hit 65. 4.88's you'll be about 2500rpm. Obviously 5.13's are going to get you the low end grunt but you'll be howling on the highway. 

 

Another idea 

 

http://www.northwestfab.com/NWF-BlackBox-Underdrive_c_7.html

 

More money but you can run less gear in the axles and get a nice crawl ratio. 

 

 

[Pete M]

howling?  stock 2.5L/autos came with 4.56 gears and, what, 26" tires?  that's 3800rpms at 65mph.  I think you'll be juuuust fine at a thousand rpms less than stock.  

[dasbulliwagen]

My 2.5 has 4:10 and 32's and I'm horribly underpowered. I can't imagine running the 2.5 with 3:55 and 35's! How is it even drivable???

[Smokeyyank]

2 hours ago, Pete M said:

howling?  stock 2.5L/autos came with 4.56 gears and, what, 26" tires?  that's 3800rpms at 65mph.  I think you'll be juuuust fine at a thousand rpms less than stock.  

 

Really?! I thought 4.10's where the deepest, but I'll definitely differ to the Jeep gurus on that one. 

[Pete M]

yup.  4.56    apparently the aw4 sucked too much power from the 2.5 and it needed the extra oomph.  (that ratio only applies to 2.5L/aw4 jeeps, not the earlier ones with the non-OD auto trans).  It wasn't very popular and Jeep eventually did away with it as an option.

[Eagle]

8 hours ago, dasbulliwagen said:

My 2.5 has 4:10 and 32's and I'm horribly underpowered. I can't imagine running the 2.5 with 3:55 and 35's! How is it even drivable???

 

More to the point, how is it even possible? 2.5L 5-speeds came with 4.10 gears. It was the 2.5L 4-speeds that came with 3.55 gearing.

[mnkyboy]

I ran 33s and 3.55s for a while, i went to 4.88s which was much better but still could have went deeper, 5.13s weren't available back when i geared it.

Even with the 4.88s gears a 5th gear wasn't really needed, 5.13s would have been better.

 

I would go to at least 5.13s or swap axles and go 5.38, 5.38s and 35s would be pretty nice. I currently run 5.38s and 37s with a built 2.5l and an AX15.

[Swampy]

Well I might through this same issue. I have a hp d30 and a c8.25 rear axle. I originally had a 4spd and was geared 3.55. I swapped in an ax15 and keep the 3.55 while I saved money for gears. I drove it a bit with 36" tsl swampers. It sucked terribly to drive it. I could not go past 3rd with the set up it had. 2.5+ax15+3.55s+36s= no Bueno.

But I personally went with the revolution gear and axle 5.13 set and let me just say it is great in comparison. Don't expect it to be a rocket ship either though, the jeep still like to take its sweet time to get up into highway speeds (60mph) but it is much better to drive in general and offroad its one of the greatest things you could do to help our little engines.