4.56 for 3.8
#11
JK Freak
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I have a 6spd 3.8 with 4:56 gearing. I currently run 33inch nitto trail graps which are heavy. I also have lots of other heavy mods too. At 70 mph in 6th gear I'm turning about 2700ish the power and feel is great in every gear. I'm gonna go with 35's soon and I'll bet I will still be around 2400-2500 rpm @ 70mph. If you wanna go larger than 35's at some point or have an automatic then deeper gearing would be required but 4:56 is perfect for the 6spd 3.8 that is also a daily driver.
#12
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I've got 4.88s in my 11 with 35's and a 6 speed and I think it's too low a gear on the interstate (2750 @ 70 mph just feels like it needs a 7th gear to me) but it's a great ratio for around town, back roads and on the trail. Average 16.4 mpg with it.
My brother has a 10 with 4.10s running 35's and a 6 speed that I've driven a quite a few times and its drivable but not great by any means.
If I was going to do it again I'd still go with the 4.88 for my driving style (less than 10% interstate) if I did more interstate I might do the 4.56 but it would be a tough choice, But I would not do 4.10s, that would be throwing money away, I wouldn't be happy with it.
My brother has a 10 with 4.10s running 35's and a 6 speed that I've driven a quite a few times and its drivable but not great by any means.
If I was going to do it again I'd still go with the 4.88 for my driving style (less than 10% interstate) if I did more interstate I might do the 4.56 but it would be a tough choice, But I would not do 4.10s, that would be throwing money away, I wouldn't be happy with it.
Last edited by slider_68; 08-12-2013 at 05:36 PM.
#13
JK Super Freak
You would probably be happy. I was worried about too much gear too. That's why despite all the 4:88-5:13 recommendations I got I knew 4:56 would be better, stronger too. I didn't want to be cruising at over 3000 rpms all the time. 2500-2800 seems to be the 3.8's sweet spot. By the way in 4 lo it's a tank!
#14
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You would probably be happy. I was worried about too much gear too. That's why despite all the 4:88-5:13 recommendations I got I knew 4:56 would be better, stronger too. I didn't want to be cruising at over 3000 rpms all the time. 2500-2800 seems to be the 3.8's sweet spot. By the way in 4 lo it's a tank!
#15
Forum Tech Advisor
4.56s cost $110 more than 4.88s.
4.88s with master overhaul (bearing) kits are $550 shipped (link below):
JK Non Rubicon 30/44 Gear Package and Master Overhaul Kits
4.88s will turn the engine only about 180 rpm faster at 70-75 mph than 4.56s. 180 rpm will not kill your fuel economy.
4.88s will do better off road.
4.56s would be a waste of money. 4.10s would be worthy of ridicule. Guys with stock Rubi 6 speeds and 4.10s pay good money to regear to 4.88s or 5.13s.
4.88s with master overhaul (bearing) kits are $550 shipped (link below):
JK Non Rubicon 30/44 Gear Package and Master Overhaul Kits
4.88s will turn the engine only about 180 rpm faster at 70-75 mph than 4.56s. 180 rpm will not kill your fuel economy.
4.88s will do better off road.
4.56s would be a waste of money. 4.10s would be worthy of ridicule. Guys with stock Rubi 6 speeds and 4.10s pay good money to regear to 4.88s or 5.13s.
#16
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The thing is I really don't do a enough offroad to get 4.88. I want something that will pull a small tailer good with out killing the motor.
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
#17
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The thing is I really don't do a enough offroad to get 4.88. I want something that will pull a small tailer good with out killing the motor.
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
Offroad the 4.88's made a huge difference. It has a very slow crawl speed, I'm able to idle down steep hills and not even touch the brakes. It crawls way better as well.
This is just my experiences. The best thing for you to do is to find someone in a local Jeep club with the set ups you are thinking about and go for rides with them so you can see what suits you the best.
#18
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I have 4.88's with 35's in my 11 JK and it works very well. Around here we have lots of hills and the 4.88's help pull those hills. When I had the 35's and 3.73's it was misery on the highway. With the 4.88's I can stay in 6th gear through almost any hill I see.
Offroad the 4.88's made a huge difference. It has a very slow crawl speed, I'm able to idle down steep hills and not even touch the brakes. It crawls way better as well.
This is just my experiences. The best thing for you to do is to find someone in a local Jeep club with the set ups you are thinking about and go for rides with them so you can see what suits you the best.
I need to check into a local jeep club
#19
Forum Tech Advisor
The thing is I really don't do a enough offroad to get 4.88. I want something that will pull a small tailer good with out killing the motor.
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
Also I know guys that went with 4.88 an said it was to low of a gear.
I think I'm just going to have to do a lil more research to suit my needs
This isn't opinion or conjecture. It is math and physics.
If you want personal anecdotal experience:
In July 2011, we used our red 4 dr Rubi 6 speed, with 5.13s and 37s to pull a 3500 lbs camper on a 3500+ mile trip through the Rocky Mountains and down to Southern Utah. Most of the miles were on the highway, in 5th gear at 3300-3600 rpm (we could only use 6th gear on the flat or downhill areas). We drove in 100+ degree weather and across 10,000 ft mountain passes. The engine had 72,000 miles on it. It did not use any oil.
#20
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2600-2800 rpm at highway speeds won't kill a 3.8L.
In fact, with a 2,000 trailer, you likely won't need to run in 5th gear like we did with a loaded 4 dr pulling a 3500 lbs trailer. Unless you come to the Rockies, 6th gear with 35s and a small trailer, with 4.88s will work.
In fact, with a 2,000 trailer, you likely won't need to run in 5th gear like we did with a loaded 4 dr pulling a 3500 lbs trailer. Unless you come to the Rockies, 6th gear with 35s and a small trailer, with 4.88s will work.