5.13's check out northridge 4x4 i got mine there and came right away ,i was told to talk to dave there and i did and he is very friendly and knows what you need to know,goodluck,mine are getting installed this week so hopefully i will be very happy with them

 

Cool. I missed the commute part.

 

I currently have 373's w/automatic(dog) and I bought 488's from Northridge. I am supposed to get them installed Friday or Saturday. I will let you know how it is. Anybody know how long I should break in the gears before I change the fluid? Should I drive it like normal? and what about the frt ones?

 

The shop that put my 5.13's in wanted it back for an inspection and new fluid in 500 miles.

If the OP hadn't said 34's I'd say 5.13's are the way to go in an automatic. As long as there is no likelihood of going larger I'd imagine 4.88's would be a good bet. As to the cost it's more like 1300.00 for parts and labor on both axles.

 

Did you buy the gears from the shop or buy them somewhere else and have them do the install? Just curious since I'm looking to upgrade gears as well.

 

The shop provided the gears. Their price was the same as I could buy them online. In this situation I prefer to get the parts from the same shop that will be doing the service. If there is a problem I don't want to hear from the shop "the gears were defective" and from the gear supplier "the shop installed them wrong". They supplid them and installed them and are on the hook 100% if there is a problem.

 

I have been thinking about regearing myself. I am currently in Iraq and have been thinking about doing a few things to the Jeep. I have a 6sp w/ the shitty 3.21 gears. Light off road use sometimes pull small trailer w/ dirtbikes or harley. Any sugestion on gearing/price and where to get from that is military friendly $?


Thanks,

SSG P
Iraq

 

When you get back you'll just have to call around in your area. I paid 1300 for mine but had other qutes of 1800 to 2200!. The shop that did it was the local 4x4 shop and they probably do more gears than everyone else combined. I'd be sure to get some referals if possible.

 

I'm waiting for now to see the best proven combo for the 35's and a auto. It's a toss up between 488's and 513's it seems. Some say 513's and others say 488's with 35's. It's a hard decision at this point.

 

I believe you are wrong on this. There have been enough gears done on JK's now that we know what works. With a stick and it's .85 OD the 4.88's work just fine. But the OD on the auto is .69 so 5.13's work better.

Before I did gears I asked everybody I came across with a lifted JK if they had done gears and if so what they thought. I'm 90 miles from Moab and 95 miles from the Ouray/Silverton/ Telluride area so there are lots of modifyed JK's. I did not come across a single person with 35"'s or 37"'s and 5.13's that regretted the 5.13's. Most with auto's and 4.88's regretted the 4.88's and wished they had done 5.13's. I also encountered people with 37's and 5.13's who wished 5.38's had been available.

The key is the rpms. My stock Rubi 32/4.10 spun 2250 at 75 mph. The Cruise Control was marginal, it went in and out of OD all the time and fuel economy was 18.0. (The factory Rubi gears should be 4.56).

With 35/4.10 it was 2050 at 75mph. It was impossible to keep it in OD unless going downhill, the cruise was unusable and fuel economy fell to 14.

With 35's and 5.13's my rpm at 75 is 2600 rpm. It stays in OD very well and the cruise works well. My fuel economy is essentially unchanged from stock. Driveability is MUCH improved; to the point where I'm no longer unhappy with this engine and it vastly outperforms my 98 TJ automatic even though my JK is a lot heavier due to being a 4dr with lots of RockHard stuff on it and a Tuffy Drawer loaded with tools, recovery gear and supplies. I am in Colrado at 4600 ft and have been as high as 13185 ft and am quite happy with it's performance. Off road the performance is excellent and I can not recall ever needing to floor it. I'm going to drag it to 60 mph against my Chev 3/4 ton Duramax diesel; my gut feeling is that my JK is faster.

The 3.8 is not a 4.0 straight 6. The 3.8 V6 likes to rev; 2600 rpm is nothing. I think the engine is happiest in the 2500-2700 rpm range and gears should be chosen so that you are in that range when driving down the road. My understanding is that the sweet spot for power and economy is 2500 to a bit below 3000 rpm. Over 3000 rpm fuel economy suffers.

I think you should get the 5.13's. I doubt the 4.88's would give you any better fuel economy and the performance, both on and off road, wold be better with the 5.13's. It's really not a hard decision; 5.13's just plain work with an automatic.